Service Manual

SUBGROUP - INDEX

Section Group Type

Hydraulic pumps - dismantling, installation 7.01.1 A 900 C-LI EDC 24677-

and initial operation A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Variable-displacement pump DPVO 165 7.05.1 A 900 C-LI EDC 24677-

DPVO 165 variable-displacement pump 7.06.1 A 900 C-LI EDC 39762-

DPVP 108 double variable-displacement pump 7.07.1 A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

FMF hydraulic fixed displacement motor 7.20.1 A 900 C-LI EDC 24677-
A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

HMF 75-02P hydraulic fixed-displacement motor7.22.1 A 914 C-LI 35112-

A 924 C-LI 34519-

DMVA regulating motor (travel drive) 7.27.1 A 900 C-LI EDC 24677-
A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

DMVA regulating motor (travel drive) 7.28.1 A 900 C-LI EDC 48070-
A 904 C-LI EDC 51328-
A 914 C-LI 51833-
A 924 C-LI 51833-

Hydraulic cylinder 7.30.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-
LHB/en/Edition: 11/2010

Extension and retraction times of 7.31.1 A 900 C-LI EDC 24677-

hydraulic cylinders A 904 C-LI EDC 30580-
A 914 C-LI
A 924 C-LI

7.1

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 Service Manual

Hydraulic double plunger cylinder 7.32.1 A 900 C-LI EDC

A 904 C-LI EDC
A 914 C-LI
A 924 C-LI

Control oil and regulating unit 7.41.1 A 900 C-LI EDC 24677-
A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Pilot control unit 1x (travelling foot pedal) 7.42.1 A 900 C-LI EDC 24677-
A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Pilot control valve 2 x 7.44.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Pilot control valve 2 x 7.46.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Pilot control unit 4x 7.49.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

LSC control valve block 7.51.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-

LSC pilot plate 7.55.1 A 914 C-LI 35112-

A 924 C-LI 34519-

Cooling unit 7.60.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-

Cooling unit 7.61.1 A 914 C-LI 35112-

A 924 C-LI 34519-
LHB/en/Edition: 11/2010

Leak oil check at control valve blocks 7.68.1 A 900 C-LI EDC 24677-
A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

7.2

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 Service Manual

SUBGROUP - INDEX

Section Group Type

Rotary connection 6 x 7.70.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Rotary connection 7 x 7.75.1 A 900 C-LI EDC 24677-

A 904 C-LI EDC 30580-
A 914 C-LI 35112-
A 924 C-LI 34519-

Accumulator 7.95.1 A 900 C-LI EDC

A 904 C-LI EDC
A 914 C-LI
A 924 C-LI
LHB/en/Edition: 11/2010

7.3

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 Service Manual

LHB/en/Edition: 11/2010

7.4

MJFCIFSS
 Service Manual Hydraulic pumps - dismantling, installation and initial
Opening and closing suction hose

Hydraulic pumps - dismantling, installation and

initial operation
Caution!
Unsecured hydraulic pumps can cause serious injury from crushing!
X Always secure hydraulic pumps with suitable lifting tackle and hoisting gear.

Note!
For a clean and nearly oil-free assembly and disassembly of the hydraulic pumps, we recommend
the use of a vacuum pump (tool no. 180 - 187 in group 2.05).
This pump can also be used as a compressor with a controlled low pressure of 300 - 500 mbar for
ventilating the equipment.
See also service information no. 06 - 03 - 22 / 2003

1 Opening and closing suction hose

Caution!
Risk of damage to hydraulic pump by dry run (complete destruction).
If the machine is started while the stop valve is closed, the hydraulic pumps are running dry and can
thus be severely damaged.
X Before starting the engine, open the stop valve.

The shut-off valve of the suction hose has two positions:

– a open
– b closed

Fig. 1 Stop valve

LHB/en/Edition: 09/2006

X If the suction hose is to be disconnected at the variable-displacement pump or at the hydraulic

tank, close the stop valve b.
X Remove the cover 1.
X Place a suitable oil pan to collect the hydraulic oil under the bleed point.
X Depressurise the hydraulic system.
X Release the hydraulic oil from the pump and the suction hose.

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Hydraulic pumps - dismantling, installation and initial Service Manual
Variable-displacement pump 20 / working hydraulics

X After completion of the repair, turn the stop valve to its initial position a and engage it.

2 Variable-displacement pump 20 / working hydraulics

Fig. 2 Hydraulic pumps

a = A 900 C from serial no. 14675 - 24676

b = A 900 C from serial no. 24677
A 904 C from serial no. 16000 - 30579
c = A 904 C from serial no. 30580

2.1 Dismantling
X Close the stop valve at the hydraulic tank (position b), see Fig. 1
X Place a suitable oil pan under the hydraulic pump.
X Always secure hydraulic pump 20 with suitable lifting tackle and hoisting gear.
X Disconnect hoses / lines at pump 20. Collect the hydraulic oil.
X Loosen and remove the Allen head and hex head screws 12.
X Remove the hydraulic pump 20.

2.2 installation
LHB/en/Edition: 09/2006

X Install hydraulic pump 20.

X Insert the Allen head and hex head screws 12 and tighten them with the prescribed torque, see
Fig. 2.
X Connect all hoses / lines to the hydraulic pump 20.
X Remove the oil pan.

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 Service Manual Hydraulic pumps - dismantling, installation and initial
Gear pumps

2.3 Start-up
X Before starting the system, fill the hydraulic tank all the way to the full mark at the top. Open the
stop valve 3 at the hydraulic tank (position a).
X Unscrew the leak oil lines T1 at the pump 20 until hydraulic oil escapes without foam.
X Screw the leak oil lines T1 tight again.
X Check the screw fittings and lines for tightness.
X Test the suction hose for air-tightness. (Re-tighten the connection and/or the pipe clamps.)

3 Gear pumps

Fig. 3 Gear pumps 31 / 32 and 33

a = A 900 C from serial no. 14675 - 24676

A 904 C from serial no. 16000 - 30579
b = A 900 C from serial no. 24677
A 904 C from serial no. 30580

– Gear pump 30 for pilot control, (see “Hydraulic pumps” on page 2)

– Gear pump 31 for steering
– Gear pump 32 for brake system
– Gear pump 33 hydraulic fan drive
LHB/en/Edition: 09/2006

3.1 Dismantling
X Close the stop valve at the hydraulic tank (position b).
X Place suitable oil pan under hydraulic pumps.
X Disconnect the hoses / lines at the pumps. Collect the hydraulic oil.
X Loosen and remove the Allen head and hex head screws.
X Remove the hydraulic pumps.

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Hydraulic pumps - dismantling, installation and initial Service Manual
Adjustment after pump replacement

3.2 installation
X Install the hydraulic pumps.
X Insert the Allen head and hex head screws and tighten them with the prescribed torque, see Fig. 3.
X Connect all hoses / lines at the pumps.
X Check the screw fittings and lines for tightness.

3.3 Start-up

Note!
Gear pumps do not require initial oil filling.

X Check the oil level the in hydraulic tank. Fill up, if necessary.
X Open the stop valve at the hydraulic tank (position a).
X Loosen the screwed connections of the respective pressures hose (P.
X Start the machine.
X Bleed the pumps with the diesel engine running at low idle speed.
until the oil runs out of the pressure connection (liquid, no oil foam).
X Re-tighten the connections. Check for tightness.
X Remove the oil pan.

4 Adjustment after pump replacement

Note!
If the variable-displacement pump settings must be adjusted after a replacement, proceed as de-
scribed in the adjustment protocol, see group 3.

LHB/en/Edition: 09/2006

7.01.4
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MJFCIFSS
 Service Manual Variable-displacement pump DPVO 165
Function/design

Variable-displacement pump DPVO 165

1 Function/design

The DPVO variable-displacement pump is of the axial piston swash-plate type. Powertrain and inte-
grated pilot-control gear pump are powered by the diesel engine via the flexible coupling (torsion
damper).
The variable-displacement pump regulates its flow rate according to current requirements (load sen-
sing principle) and supplies the required quantities of oil to the various consumers , (lifting / bucket /
stick / travel / support / slewing gear / pivot grapple).
The variable-displacement pump consists of the following main components:
– Powertrain 21
– Pump casing 40
– Mounting plate 46
– Connecting flange 47
– Regulator housing 49
The DPVO variable-displacement pump is flanged to the diesel engine with connection flange 47.
The powertrain consists of drive shaft, cylinder and piston. It can be adjusted by means of the swivel
yoke.
The regulator housing 49 in mounted to the pump casing 40. The performance regulator 25 (for re-
gulating and adjusting the pump performance) is screw-mounted in the regulator housing 49. It ob-
tains feedback on the pivot angle by means of a pin.
Flow regulator 26 sits right on mounting plate 46. It controls the volumetric flow and the adjustment
of the differential pressure Up.
The gear pump 30 (pilot control) is mounted to the mounting plate 46. It is driven by means of an in-
ternal drive shaft. There is an opening in the mounting plate for the installation of an additional gear
pump, if required.
LHB/en/Edition: 07/2008

7.05.1
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Variable-displacement pump DPVO 165 Service Manual
Function/design

Fig. 1 Components of the DPVO

25 Performance regulator (LR) 48 Qmin stop screw

26 Flow regulator (LS) 49 Regulator housing
27 Shuttle valve A1 Pressure connection
28 Check valve AX Pressure connection sealed
29 Restrictor FE Pressure connection of control oil pump
30 Gear pump / pilot control S Suction connection
40 Pump casing 7 Leak oil connection
44 Measuring point pSK (control chamber X2 Measuring point / LS pressure
pressure)
46 Mounting plate X3 Connection of control oil unit LR
47 Connecting flange X4 Connection U-p reduction

Note!
In order to prevent damage to the pump, observe the torque (87 Nm) for the Allen head screws 41
when installing the gear pump 30, see Fig. 1.
LHB/en/Edition: 07/2008

7.05.2
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 Service Manual Variable-displacement pump DPVO 165
Function/design

Fig. 2 Hydraulic diagram of DPVO

1 to hydraulic tank 25 Performance regulator

3 from stop cock / tank 26 Flow regulator
4 Pressure spring / Up 27 Shuttle valve
10 Pressure spring / begin of regulation 28 Check valve
15 Connecting pin (swivel yoke) 29 Restrictor
16 Return piston 30 Gear pump / pilot control
20 DPVO pump unit 44 Measuring point / actuating pressure
21 Powertrain 45 Measuring point / LS pressure
22 Control piston 50 from/to control oil unit
23 Measuring cylinder 100 to control valve block
24 Lever (rocker)
LHB/en/Edition: 07/2008

7.05.3
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Variable-displacement pump DPVO 165 Service Manual
Technical data

2 Technical data

Machine A 900 C Litronic A 904 C Litronic

from serial number 24677 16000
Pump type DPVO 165 DPVO 165
Input speed 1800 rpm 2000 rpm
Drive power of diesel engine 95 kW 99 kW
(nominal power) = Pmax
Volumetric delivery
max. 300 l/min 330 l/min
min. 40 l/min 40 l/min
Hydraulic performance (basic performance) 27 kW 27 kW
Begin of regulation (with basic settings) 50 ± 2 bar 50 ± 2 bar
Control oil pump / pilot control 40 l/min 40 l/min
Check measurement X (Q min. stop) 15.6 mm 15.6 mm

Current from solenoid valve Y50, see setting protocols in group 3

For parameters and reference values, see adjustment protocol in group 3.

Tab. 1 Technical data

3 Functional description of variable-displacement pump

3.1 Powertrain 21, (see “Sectional drawing of DPVO” on page 11)

The drive shaft 5 is borne in the mounting plate 46 and the mounting flange 47 with a cylindrical roller
bearing 8 and a sliding bearing 10. The shaft drives the cylinder 16 and the nine pistons with slipper
19 via the gearing. The toothing on the drive shaft drives the flange-mounted gear pump 30 (pilot con-
trol).
The pistons 19 with slippers are held by means of the return plate 34 and the return ball 33 on the
swivel yoke 7 with the sliding disc 31.
The hydrostatic bearing by means of bores in the pistons 19 reduces the high surface pressure bet-
ween the rotating slippers and the sliding disc 31.
If there is no pressure, the pressure springs 35 / 36 press the cylinder 16 and the return ball 33
against the pilot plate 17. As soon as the pressure rises, the hydraulic forces add to the spring force
LHB/en/Edition: 07/2008

so that an oil film is maintained, while the amount of leak oil is small.
The leak oil lubricates all the moving parts of the powertrain, and is then fed to the tank.
For every rotary motion of the cylinder 16, the pistons 19 execute a double stroke. The length of the
stroke depends on the inclination of swivel yoke 7. The swivel yoke is borne on the rotary roller bea-
ring 14. The rotary motion of the swivel yoke 7 is effected by means of a connection between the con-
trol piston 22 and the connecting link 37 at every axial motion of the piston.
The volumetric delivery of the pump per time interval is determined by the piston capacity (piston di-
ameter x stroke) and the speed of drive shaft 5.

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 Service Manual Variable-displacement pump DPVO 165
Functional description of variable-displacement pump

The pilot plate 17 separates the pressure side from the suction side of the powertrain. The pilot plate
17 has kidney-shaped openings on the suction side, and three smaller kidney-shaped openings on
the pressure side.

Fig. 3 Section of powertrain

16 Cylinder 33 Return ball

17 Pilot plate 34 Return plate
18 Pin 35 Pressure spring
19 Piston 36 Pressure spring

3.1.1 Adjusting the pivot angle of the pump

The connecting link 37 provides a mechanical connection between the swivel yoke 7 and the control
piston 22. The connecting link engages in the opening on the control piston 22. It is secured by means
of the pin 12 and the roll pin 11. The axial motion of the control piston 22 (and thus the rotary motion,
i.e. the change of the angle of swivel yoke 7) is determined by way of the performance regulator and/
or flow regulator.
The LS signal generated by the consumer moves the flow regulator into the actuating position so that
the pump pressure can reach the control chamber. As a result, the pump is swivelled out. The pump
pivots back as soon as the control chamber is connected by the flow regulator (no LS signal) or by
the performance regulator (output too high) to the tank.
In standby mode (i.e. all pilot control valves in neutral position), the pump delivers only min. flow vo-
lumes (about 40 l/min - pre-set in the factory by means of the stop screw 48).

3.1.2 Min. and max. pivoting angle of the pump

The max. pivot angle of the powertrain of the pump is determined by the dead stop (collar 39) of the
control piston 22 in the control cylinder. The stop cannot be adjusted.
LHB/en/Edition: 07/2008

The min. pivot angle of the powertrain is determined by the stop screw 48 (with lock nut 38). It is fac-
tory-set. It is recommended not to tamper with these angle settings.

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Variable-displacement pump DPVO 165 Service Manual
Pump regulation

Fig. 4 Adjusting the swivel yoke

7 Swivel yoke 37 Connecting link

11 Roll pin 38 Lock nut
12 Pin 39 Sleeve
22 Control piston 48 Qmin stop screw

4 Pump regulation

4.1 Performance regulator 25 (LR) hyperbolic regulator

The purpose of the performance regulator is to adapt the flow rates from the pump with respect to the
pump pressure (decreasing output) to the performance curve of the diesel engine. As a result, the
pump performance is regulated along a hyperbolic line. The pump delivers larger volumes at low
pressure and smaller volumes at high pressures. The basic setting of the regulating spring 90 /91 cor-
responds to the mechanical begin of basic regulation. It can be switched up to load limit control via
the control pressure pMLR at the connection X3.
The pressure springs 90 / 91 push the spool 97 to the right against the lever 24. This opens the control
edge S1; the control chamber of the control cylinder 22 receives pump pressure pP. The pump pivots
to Qmax. The return piston 16 has a mechanical connection with the swivel yoke in the connecting
pin 15.

4.1.1 Begin of pump regulation

When the working pressure pP in the system rises to the value of the begin of regulation, the force
LHB/en/Edition: 07/2008

from the measuring cylinder 23 to the lever 24 is increased. The spool 97 is shifted against the pres-
sure spring 90 and opens, through the control edge S2, the connection from the control chamber (SK)
to the tank (T). The pump pivots back. The pump pivoting back results in an axial movement of the
return piston 96 against the pressure spring 83 by means of the connecting pin 95 with the bearing
pin of the swivel yoke. As a consequence, the line of force of the measuring cylinder 98 against the
lever 99 is shifted in the direction of the fulcrum. The force exercised by the lever 94 onto the spool
97 is reduced so that the pressure spring 90 moves the spool 97 back into its neutral position. The
connection between the control chamber (SK) and the tank (T) is closed. The pump remains at a con-
stant flow rate, which results in a constant drop in performance (at the prevailing pP).

7.05.6
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 Service Manual Variable-displacement pump DPVO 165
Pump regulation

4.1.2 Pivoting of the pump (at pressures below the begin of regulation)
As soon as the operating pressure pP in the system drops, the force exercised by the piston 98 onto
the lever 99 is reduced. The spring 90 shifts the spoon 97 against the lever 99. The connection th-
rough the control edge S1 pump pressure (P) in the control chamber (SK) is opened. The pump is
set to a larger pivot angle. The pivoting motion of the pump moves the return piston 96 in the direction
of the screw plug 81. The measuring cylinder 23 is pushed away from the fulcrum by the lever 99.
The resulting force applied by the lever 99 onto the spool 97 is increased, i.e. an equilibrium is re-
established, and the piston 97 is moved to its closing position (S1 and S2 closed).

Fig. 5 Control edges S1 and S2

90 Pressure spring Pp Pump pressure

91 Pressure spring SK Control chamber pressure
97 Spool T Tank pressure
LHB/en/Edition: 07/2008

Fig. 6 Sectional drawing of performance regulator 25

25 Flow regulator, complete 93 Spring plate

49 Regulator housing 94 Ball
81 Screw plug 95 Connecting pin (swivel yoke)
83 Pressure spring 96 Return piston
84 O-ring 97 Spool

7.05.7
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Variable-displacement pump DPVO 165 Service Manual
Pump regulation

85 O-ring 98 Piston with slipper (measuring cylinder)

88 Adjusting screw 99 Lever
89 Screw plug pP Working pressure
90 Pressure spring (begin of regulation) SK Control chamber pressure
91 Pressure spring T Tank pressure
92 Bushing

Note!
Tightening torques: Screw plug 81 / 89 = 35 Nm; sealing nut 87 = 18 Nm.

4.2 Flow regulator 26 (LS regulator)

The flow regulator 26 is used to adapt the flow rates of the pump to the requirements of the consu-
mers.
The flow regulator 26 is screw-mounted to the mounting plate 49. It consists of the following main
components: 3-piece piston 63/64/65 and pressure spring 59 with adjusting screw 52.
The spool 62 is held in its controlling position by the equilibrium of the pressures (pP, pLS) and the
spring force of the pressure spring 59.
When the pressure forces change, the control chamber is connected with the tank, or the pump pres-
sure is applied to the control cylinder. The spring force of the pressure spring 59 and thus the setting
of Up can be adjusted / set by turning the adjusting screw 52.

LHB/en/Edition: 07/2008

Fig. 7 Flow regulator 26

7.05.8
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 Service Manual Variable-displacement pump DPVO 165
Pump regulation

26 Flow regulator, complete 62 Spool

49 Regulator housing 63 Piston
51 Screw plug 64 Control sleeve
52 Adjusting screw 65 Piston
56 Sealing nut 73 O-ring with backing ring
58 Lock nut Pp Pump pressure
59 Pressure spring (adjustment Up) pLS LS pressure
60 Pressure spring T Return channel
61 Seal X2 Connection control block-LS
X4 Connection T to tank

Note!
Screw down the flow regulator 26 all the way to stop. Tighten it with 5 Nm max.
Sealing nut 9 = 8 Nm; nut 3 = 120 Nm.

4.3 Regulation of pressure difference UP LS

4.3.1 Standby
When all consumers are closed, the flow from the pump builds up a backpressure in channel pP. The
backpressure acts on the piston 63. If the pressure exceeds the forces of the pressure springs 59/60,
the control edge S2 is opened, i.e. the connection between SK and T is opened. The powertrain is
swivelled back until the spring forces and the pressure forces on the spool 62 are balanced, or until
the powertrain is set to Qmin.

4.3.2 Pivoting out

The spool 62 is pushed to the right by the pressure spring 59. The control edge S1 is opened, and
the pump pressure pP is applied to the channel SK to the control chamber of the pump. The pump
swivels to the large swivel angle and the pumped volume is increased.
The pressure building up at the connection pLS (by means of operation of a consumer) increases the
sum of the forces acting on the spring side of the spool 62, so that the spool 62 is switched to the
right. The control edge S1 is opened.
– The pump pressure pP is applied through the channel SK to the control camber / control piston.
– The pump swivels to the large swivel angle.
– The pumped volume increases.
The backpressure pP caused by the increasing pump volume is built up and acts on the piston 63.
As soon as it reaches the value set at the pressure spring 59, the spool 62 is moved to the left again
until the control edge S1 closes. The pressure pP ceases to act on the control chamber of the control
piston, but is not released to the tank or the channel T (as the control edge S2 is still closed). As a
result, the powertrain is fixed and the flow rate from the pump is levelled out at a constant value.
LHB/en/Edition: 07/2008

4.3.3 Pivoting back

If the pump pressure pP at the spool 62 exceeds the total value in pLS (consumer pressure at X2)
and the spring force of the pressure spring 59,
– the spool 62 is pushed to the left,
– the control edge S1 is closed,
– the control edge S2 is opened, and
– the spool is relieved through SK to the tank.

7.05.9
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Variable-displacement pump DPVO 165 Service Manual
Adjustment of DPVO variable-displacement pump

– The pump pivots back.

Fig. 8 Sectional drawing of load-sensing regulator

51 Screw plug 68 Backing ring

52 Adjusting screw 72 Backing ring
56 Sealing nut 73 O-ring
58 Nut pP Working pressure
59 Pressure spring(adjustment Up) pLS LS pressure
60 Pressure spring S1 Pump pressure control edge
62 Spool S2 Tank pressure control edge
63 Piston SK Control chamber pressure
64 Bushing T Tank pressure
65 Piston X2 Connection at regulator housing
66 Bushing X4 Connection at regulator housing
67 O-ring

5 Adjustment of DPVO variable-displacement pump

5.1 Adjustment of the differential pressure Up LS and begin of the hydraulic regu-
lation

Note!
The procedure to adjust the differential pressure and begin of regulation of the pump is described
in group 3 "Adjustment protocol" and "Adjustment guideline".
LHB/en/Edition: 07/2008

7.05.10
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 Service Manual Variable-displacement pump DPVO 165
Adjustment of DPVO variable-displacement pump
LHB/en/Edition: 07/2008

Fig. 9 Sectional drawing of DPVO

7.05.11
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Variable-displacement pump DPVO 165 Service Manual
Regulating characteristics

1 Mounting plate 17 Pilot plate

2 Connecting flange 18 Locking pin (against tampering)
3 Stop screw 19 Piston with slipper
4 Locking ring 22 Control piston
5 Drive shaft 30 Gear pump
6 Regulator housing 31 Sliding disc
7 Swivel yoke 32 Set of discs
8 Cylindrical roller bearing 33 Return ball
9 O-ring 34 Return plate
10 Sliding bearing 35 Pressure spring
11 Roll pin 36 Pressure spring
12 Pin 37 Connecting link
13 O-ring 38 Hex nut
14 Cylindrical roller bearing 39 Stop sleeve
15 Pin 40 Pump casing
16 Cylinder with bushing

6 Regulating characteristics

LHB/en/Edition: 07/2008

Fig. 10 Performance curve of DPVO 165

7.05.12
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 Service Manual DPVO 165 variable-displacement pump
Description

DPVO 165 variable-displacement pump

1 Description

The DPVO variable-displacement pump is of the axial piston swash-plate type. The powertrain and
integrated pilot-control gear pump are powered by the diesel engine via the flexible coupling (torsion
damper).
The variable-displacement pump regulates its flow rate according to current requirements (load sen-
sing principle) and supplies the required quantities of oil to the various consumers, (lifting / bucket /
stick / travel / support / slewing gear / pivot grapple).
The variable-displacement pump consists of the following main components:
– Powertrain 21
– Pump casing 40
– Mounting plate 46
– Connecting flange 47
– Regulator housing 49
The DPVO variable-displacement pump is flange-mounted on the diesel engine with the connecting
flange 47.
The powertrain consists of drive shaft, cylinder and piston. It can be adjusted by means of the swivel
yoke.
The regulator housing 49 is mounted on the pump casing 40. The performance regulator 25 (for re-
gulating and adjusting the pump performance) is screw-mounted in the regulator housing 49. It ob-
tains feedback concerning the current pivoting angle by means of a pin.
The flow regulator 26 used to adjust the flow and the differential pressure Up is also screw-mounted
on the regulator housing 49.
The gear pump 30 (pilot control) is mounted to the mounting plate 46. It is driven by means of an in-
ternal drive shaft. There is an opening in the mounting plate for the installation of an additional gear
pump, if required.
LHB/en/Edition: 03/2010

7.06.1
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MJFCIFSS
DPVO 165 variable-displacement pump Service Manual
Description

Fig. 1 Components of the DPVO

25 Performance regulator (LR) 49 Regulator housing

26 Flow regulator (LS) A1 Pressure connection
27 Shuttle valve AX Pressure connection, sealed
29 Restrictor FE Pressure connection of control oil pump
30 Gear pump / pilot control S Suction connection
40 Pump casing T Leak oil connection
44 Measuring point / pSK (control chamber X2 Measuring point / LS pressure
pressure)
46 Mounting plate X3 Connection of control oil unit LR
47 Connecting flange X4 Connection U-p reduction
48 Qmin stop screw
LHB/en/Edition: 03/2010

7.06.2
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 Service Manual DPVO 165 variable-displacement pump
Description

Fig. 2 Hydraulic schematic of DPVO

1 to hydraulic tank 24 Lever (rocker)

3 from stop valve / tank 25 Performance regulator
4 Pressure spring / Up 26 Flow regulator
10 Pressure spring / begin of regulation 27 Shuttle valve
15 Connecting pin (swivel yoke) 29 Restrictor
16 Return piston 30 Gear pump / pilot control
20 DPVO pump unit 31 Gear pump / fan control
21 Powertrain 44 Measuring point / actuating pressure
22 Control piston 50 from/to control oil unit
23 Measuring piston 100 to control valve block
LHB/en/Edition: 03/2010

7.06.3
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DPVO 165 variable-displacement pump Service Manual
Technical data

2 Technical data

Machine A/R 900 C Litronic

from serial number 39762
Pump type DPVO 165
Input speed 1800 rpm
Drive power of diesel engine 95 kW
(nominal power) = Pmax
Volumetric delivery
max. 300 l/min
min. 40 l/min
Hydraulic performance (basic performance) 27 kW
Begin of regulation (with basic settings) 50 ± 2 bar
Control oil pump / pilot control 40 l/min
Checking measurement X (Q min. stop) 15.6 mm

Current from solenoid valve Y50, see adjustment protocols in group 3

For parameters and reference values, see adjustment protocols in group 3.

Tab. 1 Technical data

3 Functional description

3.1 Powertrain 21, see Fig. 9

The drive shaft 5 is borne in the mounting plate 46 and the mounting flange 47 with a cylindrical roller
bearing 8 and a sliding bearing 10. The shaft drives the cylinder 16 and the nine pistons with slippers
19 via the gearing. The gearing on the drive shaft also drives the integrated flange-mounted gear
pump 30/31.
The pistons 19 with slippers are held by means of the return plate 34 and the return ball 33 on the
swivel yoke 7 with the sliding disc 31.
The hydrostatic bearing by means of bores in the pistons 19 reduces the high surface pressure bet-
ween the rotating slippers and the sliding disc 31.
If there is no pressure, the pressure springs 35 / 36 press the cylinder 16 and the return ball 33
against the pilot plate 17. As soon as the pressure rises, the hydraulic forces add to the spring force
LHB/en/Edition: 03/2010

so that an oil film is maintained, while the amount of leak oil is small.
The leak oil lubricates all moving parts of the powertrain, and is subsequently returned to the tank
through external lines.
For every rotary motion of the cylinder 16, the pistons 19 execute a double stroke. The length of the
stroke is determined by the inclination of swivel yoke 7. The swivel yoke is borne on the roller bea-
rings 14 and can be tilted. The rotary motion of the swivel yoke 7 is effected by establishing a con-
nection between the control piston 22 and the connecting link 37 at every axial motion of the piston.

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 Service Manual DPVO 165 variable-displacement pump
Functional description

The volumetric delivery of the pump per time interval is determined by the piston capacity (piston di-
ameter x stroke) and the speed of the drive shaft 5.
The pilot plate 17 separates the pressure side from the suction side of the powertrain. The pilot plate
17 features a kidney-shaped opening on the suction side, and three smaller kidney-shaped openings
on the pressure side.

Fig. 3 Detail of powertrain

16 Cylinder 33 Return ball

17 Pilot plate 34 Return plate
18 Pin 35 Pressure spring
19 Piston 36 Pressure spring

3.1.1 Adjusting the pivoting angle of the pump, see Fig. 9

The connecting link 37 provides a mechanical connection between the swivel yoke 7 and the control
piston 22. The connecting link engages in the opening on the control piston 22. It is secured by means
of the pin 12 and the roll pin 11. The axial motion of the control piston 22 (and thus the swivelling
motion, i.e. the change of the angle of the swivel yoke 7) is determined by way of the performance
regulator and/or flow regulator.
The LS signal generated by the consumer sets the flow regulator to its actuating position so that the
pump pressure reaches the control chamber. As a result, the pump is pivoted out. The pump pivots
back as soon as the control chamber is connected through the flow regulator (no LS signal) or through
the performance regulator (output too high) to the tank.
In stand-by mode (i.e. all pilot control units in neutral position), the pump supplies only minimum flow
volumes, (see Tab. 1 on page4).

3.1.2 Maximum and minimum pivoting angle of the pump

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The maximum pivoting angle of the pump powertrain is determined by the dead stop (collar 39) of the
control piston 22 in the control cylinder. The stop cannot be adjusted.
The minimum pivoting angle of the powertrain is determined by the stop screw 48 (with the lock nut
38). It is factory-set. It is recommended not to tamper with these minimum pivoting angle settings.

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DPVO 165 variable-displacement pump Service Manual
Pump regulation

Fig. 4 Adjusting the swivel yoke

7 Swivel yoke 39 Sleeve

11 Roll pin 42 Steel bushing*
12 Bolt 43 Backing ring*
22 Control piston 44 O-ring*
37 Connecting link 48 Q-min stop screw
38 Lock nut

* introduced during serial production, (see Fig. 9 on page11)

4 Pump regulation

4.1 Performance regulator 25 (LR) / hyperbolic regulator

The purpose of the performance regulator is to adapt the flow rates from the pump with respect to the
pump pressure (performance reduction) to the power characteristic of the diesel engine. As a result,
the pump performance is regulated along a hyperbolic line. The pump delivers larger volumes at low
pressures and smaller volumes at high pressures. The basic setting of the regulating spring 90 /91
corresponds to the mechanical begin of basic regulation. It can be adjusted to load limit control via
the control pressure pMLR at the connection X3.
The pressure springs 90 / 91 push the spool 97 to the right against the lever 99. This opens the control
edge S1 so that the control chamber (SK) of the control cylinder 22 is pressurised with pump pressure
pP. The pump pivots to Qmax. The return piston 96 has a mechanical connection with the swivel
yoke through the connecting pin 95.
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4.1.1 Begin of pump regulation

When the working pressure pP in the system rises to the value of the begin of regulation, the force
applied by the measuring piston 98 to the lever 99 is increased. The spool 97 is shifted against the
pressure spring 90 and opens, through the control edge S2, the connection from the control chamber
(SK) to the tank (T). The pump pivots back. The pump pivoting back results in an axial movement of
the return piston 96 against the pressure spring 83 by means of the connecting pin 95 in the bearing
pin of the swivel yoke. As a consequence, the force characteristic of the measuring piston 98 against

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 Service Manual DPVO 165 variable-displacement pump
Pump regulation

the lever 99 is shifted in the direction of the fulcrum. The force exercised by the lever 94 on the spool
97 is reduced so that the pressure spring 90 moves the spool 97 back to its neutral position. The con-
nection between the control chamber (SK) and the tank (T) is closed. The pump delivers a constant
flow rate, which results in a constant drop in performance (at the prevailing pP).

4.1.2 Pivoting of the pump (at pressures below the begin of regulation)
As soon as the working pressure pP in the system drops, the force exercised by the piston 98 on the
lever 99 is reduced. The spring 90 shifts the spoon 97 against the lever 99. The connection through
the control edge S1 pump pressure (P) in the control chamber (SK) is opened. The pump is set to a
larger pivoting angle. The pivoting motion shifts the return piston 96 in the direction of the screw plug
81. The measuring piston 98 is pushed away from the fulcrum of the lever 99. The resulting force
applied by the lever 99 to the spool 97 is increased, i.e. an equilibrium is re-established, and the pis-
ton 97 is shifted to its closing position (S1 and S2 closed).

Fig. 5 Control edges S1 and S2

90 Pressure spring Pp Pump pressure

91 Pressure spring SK Control chamber pressure
97 Spool T Tank pressure
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Fig. 6 Sectional drawing of performance regulator 25

26 Flow regulator, complete 92 Bushing (*)

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DPVO 165 variable-displacement pump Service Manual
Pump regulation

49 Regulator housing 93 Spring plate

81 Screw plug 94 Ball
82 Threaded stud 95 Connecting pin (swivel yoke)
83 Pressure spring 96 Return piston
84 O-ring 97 Spool
85 O-ring 98 Piston with slipper (measuring piston)
87 Sealing nut 99 Lever
88 Adjusting screw pP Working pressure
89 Screw plug SK Control chamber pressure
90 Pressure spring (begin of regulation) T Tank pressure
91 Pressure spring

(*) this part is obsolete from 04.2009. The screw plug 89 has been extended.

Note!
Tightening torques: screw plug 81 / 89 = 35 Nm; sealing nut 87 = 18 Nm.

4.2 Flow regulator 26 (LS regulator)

The flow regulator 26 is used to adapt the flow rate of the pump to the requirements of the consumer.
The flow regulator 26 is screw-mounted on the mounting plate 49. It consists of the following main
components: 3-piece piston 63/64/65 and pressure spring 59 with adjusting screw 52.
The spool 62 is held in its controlling position by the equilibrium of the pressures (pP, pLS) and the
spring force of the pressure spring 59. When the pressure forces change, the control chamber is con-
nected to the tank, or the pump pressure is applied to the control cylinder. The spring force of the
pressure spring 59 and thus the setting of rp can be adjusted / set by turning the adjusting screw 52.

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Fig. 7 Flow regulator, inserted in regulator housing

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 Service Manual DPVO 165 variable-displacement pump
Pump regulation

26 Flow regulator, complete 63 Piston

49 Regulator housing 64 Control sleeve
51 Screw plug 65 Piston
52 Adjusting screw 73 O-ring with backing ring
56 Sealing nut Pp Pump pressure
58 Lock nut pLS LS pressure
59 Pressure spring (adjustment Up) T Return line
60 Pressure spring X2 Connection control valve block-LS
61 Seal X4 Connection T to tank
62 Spool

Note!
Screw the flow regulator 26 all the way to stop. Tighten it with max. 5 Nm.
Sealing nut 56 = 8 Nm; nut 58 = 120 Nm.

4.3 Regulation of pressure difference UP LS

4.3.1 Stand-by
When all consumers are closed, the flow from the pump builds up a backpressure in channel pP. The
backpressure acts on the piston 63. If the pressure exceeds the forces of the pressure springs 59/60,
the control edge S2 is opened, i.e. the connection between SK and T is opened. The powertrain is
swivelled back until the spring forces and the pressure forces on the spool 62 are balanced, or until
the powertrain is set to Qmin.

4.3.2 Pivoting out

The spool 62 is shifted to the right by the pressure spring 59. The control edge S1 is opened and the
pump pressure pP is applied through the channel SK to the control chamber of the pump. The pump
swivels to a large pivoting angle and the pumped volume is increased.
The pressure building up at the connection pLS (by means of operating a consumer) increases the
sum of the forces acting on the spring side of the spool 62, so that the spool 62 is shifted to the right.
The control edge S1 is opened.
– The pump pressure pP is applied through the channel SK to the control camber / control piston.
– The pump swivels to a large pivoting angle.
– The pumped volume increases.
Backpressure pP caused by the increasing pump volume is built up and acts on the piston 63. As
soon as the backpressure reaches the value set at the pressure spring 59, the spool 62 is shifted to
the left again until the control edge S1 closes. The pump pressure pP ceases to act on the control
chamber of the control piston, but is not released to the channel T, as the control edge S2 is still
closed. As a result, the powertrain is fixed and the flow rate of the pump is levelled out at a constant
value.
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4.3.3 Pivoting back

If the pump pressure pP at the spool 62 exceeds the total value in pLS (consumer pressure at X2)
and the spring force of the pressure spring 59,
– the spool 62 is shifted to the left,
– the control edge S1 is closed,
– the control edge S2 is opened, and
– the spool pressure is relieved through SK to the tank.

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DPVO 165 variable-displacement pump Service Manual
Adjustment of DPVO variable-displacement pump settings

– The pump pivots back.

Fig. 8 Control edges S1 and S2 at the flow regulator

51 Screw plug 68 Backing ring

52 Adjusting screw 72 Backing ring
56 Sealing nut 73 O-ring
58 Nut
59 Pressure spring (adjustment Up) pP Working pressure
60 Pressure spring pLS LS pressure
62 Spool S1 Pump pressure control edge
63 Piston S2 Tank pressure control edge
64 Bushing SK Control chamber pressure
65 Piston T Tank pressure
66 Bushing X2 Connection at regulator housing
67 O-ring X4 Connection at regulator housing

5 Adjustment of DPVO variable-displacement pump settings

5.1 Adjustment of the differential pressure Up LS and begin of the hydraulic regu-
lation

Note!
The procedure to adjust the differential pressure and begin of regulation of the pump is described
in group 6 "Adjustment protocol" and "Adjustment guidelines".
LHB/en/Edition: 03/2010

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 Service Manual DPVO 165 variable-displacement pump
Adjustment of DPVO variable-displacement pump settings
LHB/en/Edition: 03/2010

Fig. 9 Sectional drawing of DPVO

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DPVO 165 variable-displacement pump Service Manual
Adjustment of DPVO variable-displacement pump settings

4 Locking ring 32 Set of discs

5 Drive shaft 33 Return ball
6 Regulator housing 34 Return plate
7 Swivel yoke 35 Pressure spring
8 Cylindrical roller bearing 36 Pressure spring
9 O-ring 37 Connecting link
10 Sliding bearing 38 Hex nut
11 Roll pin 39 Stop sleeve
12 Bolt 40 Pump casing
13 O-ring 42 Steel bushing*
14 Cylindrical roller bearing 43 Backing ring*
15 Pin 44 O-ring*
16 Cylinder with bushing 46 Mounting plate
17 Pilot plate 47 Connecting flange
18 Locking pin (tampering protection) 48 Stop screw
19 Piston with slipper 100 Flange with O-ring
22 Control piston
30 Gear pump C previous installation version
31 Sliding disc D new installation version

* introduced during serial production

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 Service Manual DPVO 165 variable-displacement pump
Regulating characteristic

6 Regulating characteristic

Fig. 10 Performance characteristic of DPVO 165

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DPVO 165 variable-displacement pump Service Manual
Regulating characteristic

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 Service Manual DPVP 108 double variable-displacement pump
Function

DPVP 108 double variable-displacement pump

1 Function

The DPVP double variable-displacement pump is of the axial piston swash-plate type. The powertrain
and integrated pilot-control gear pump are powered by the diesel engine via the flexible coupling (tor-
sion damper).
The variable-displacement pump regulates its flow rate according to current requirements (load sen-
sing principle) and supplies the required quantities of oil to the various consumers (lifting / bucket /
stick / travel / support / slewing gear / pivot grapple).
The variable-displacement pump consists of the following main components:
– Powertrain 21/23
– Regulating unit 22/24
– Mounting plate 25
– Connecting flange 26
– Pump distribution gear 27, see group 5.20.
The DPVP variable-displacement pump is flanged to the diesel engine with connection flange 26.
The powertrains 21/23 consist of a drive shaft, a cylinder and a piston. They can be adjusted / regu-
lated by means of the swivel yoke.
The regulating units 22 and 24 are mounted to the powertrains 21 and 23. The performance regula-
tors 22.1/24.1 for the regulation and adjustment of the pump performance) are mounted in the regu-
lator unit 22/24. They obtain feedback concerning the pivoting angle by means of a pin.
The flow regulator 24.5 used to adjust the flow and the differential pressure Up is also screw-moun-
ted to the regulator unit 24.
The gear pump 30 (pilot control) is mounted to the mounting plate 25. It is driven by means of an in-
ternal drive shaft. There is an opening in the mounting plate for the installation of an additional gear
pump, if required.
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DPVP 108 double variable-displacement pump Service Manual
Function

Fig. 1 Components of the DPVP

20 Pump unit DPVP 108, complete 25 Mounting plate

21 Powertrain P1 26 Connecting flange
22 Regulating unit P1 27 Pump distribution gear PVG 352 C 359
22.1 Performance regulator P1 28 Q min. - stop P1
22.6 Shuttle valve (Fa1) 29 Q min. - stop P2
23 Powertrain P2 30 Gear pump / pilot control
24 Regulating unit P2 41 Allen head screw
24.1 Performance regulator P2 43 Measuring point M2 / control chamber
pressure P2
24.5 Flow regulator P1 / P2 44 Measuring point M1 / control chamber
pressure P1
24.6 Shuttle valve (Fa2)

A1/P1Pressure line S Suction line

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A2/P2Pressure line T to tank

Fa1 from the control oil unit connection P1 X2 to the control block connection LS
Fa2 from the control oil unit connection P1 X3 to the control oil unit connection LR
FE to control oil unit P X4 to the control oil unit connection LS

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 Service Manual DPVP 108 double variable-displacement pump
Function

Note!
In order to prevent damage to the pump, observe the torque (87 Nm) for the Allen head screws 41
when installing the gear pump 30.

Fig. 2 Hydraulic schematic of DPVP

20 Pump unit DPVP 108, complete 24 Regulating unit P2

21 Powertrain P1 24.1 Performance regulator P2
21.1 Control piston 24.3 Restrictor (Ø 1.5)
22 Regulating unit P1 24.5 Flow regulator P1 / P2
22.1 Performance regulator P1 24.6 Shuttle valve (Fa2)
22.3 Restrictor (Ø 1.5) 30 Gear pump - control oil unit
22.6 Shuttle valve (Fa1) 43 Measuring point M2 / control chamber
LHB/en/Edition: 03/2010

pressure P2
23 Powertrain P2 44 Measuring point M1 / control chamber
pressure P1
23.1 Control piston

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DPVP 108 double variable-displacement pump Service Manual
Technical data

2 Technical data

Machine A 904 C - Litronic A 914 C - Litronic A 924 C - Litronic

Type 1003/1004/1005/1071 1044/1045 1047/1048/1050/1051
from serial number 30580 35112 34519
Pump type DPVP 108 DPVP 108 DPVP 108
Input speed 1800 rpm 1800 rpm 1800 rpm
Drive power of diesel engine 105 kW 120 kW 135 kW
(nominal power) = Pmax
Volumetric delivery
max. 2 x 189 l/min 2 x 215 l/min 2 x 215 l/min
min. 2 x 40 l/min 2 x 40 l/min 2 x 40 l/min
Hydraulic performance (basic per- 105 kW 120 kW 135 kW
formance)
Begin of regulation (with basic set- 50 ± 2 bar 70 + 2 bar 70 + 2 bar
tings)
Control oil pump / pilot control 40 l/min 40 l/min 40 l/min
Checking measurement X (Q min. approx. 27.0 mm approx. 27.0 mm approx. 27.0 mm
stop)

Settings and reference values Current of

solenoid valve
Y50/Y51
For parameters and reference values, see adjustment proto-
cols in group 6.

Tab. 1 Technical data

3 Functional description of variable-displacement pump

see Fig. 9 and Fig. 10

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3.1 Powertrains 21/23

The drive shaft 5 is borne in the mounting plate 25 and the mounting flange 26 with a cylindrical roller
bearing 8 and a sliding bearing 10. The shaft drives the cylinder 16 and the nine pistons with slip-
pers 19 via the gearing. The toothing on the drive shaft drives the flange-mounted gear pump 30 (pilot
control).
The pistons 19 with slippers are held by means of the return plate 34 and the return ball 33 on the
swivel yoke 7 with the sliding disc 31.

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 Service Manual DPVP 108 double variable-displacement pump
Functional description of variable-displacement pump

The hydrostatic bearing by means of bores in the pistons 19 reduces the high surface pressure bet-
ween the rotating slippers and the sliding disc 31.
If there is no pressure, the pressure springs 35 / 36 press the cylinder 16 and the return ball 33
against the pilot plate 17. As soon as the pressure rises, the hydraulic forces add to the spring force
so that an oil film is maintained, while the amount of leak oil is small.
The leak oil lubricates all moving parts of the powertrain, and is subsequently returned to the tank
through external lines.
For every rotary motion of the cylinder 16, the pistons 19 execute a double stroke. The length of the
stroke is determined by the inclination of swivel yoke 7. The swivel yoke is borne on the rotary roller
bearing 14. The rotary motion of the swivel yoke 7 is effected by establishing a connection between
the control piston 32 and the connecting link 37 at every axial motion of the piston.
The volumetric delivery of the pump per time interval is determined by the piston capacity (piston di-
ameter x stroke) and the speed of the drive shaft 5.
The pilot plate 17 separates the pressure side from the suction side of the powertrain. The pilot plate
17 has kidney-shaped openings on the suction side, and three smaller kidney-shaped openings on
the pressure side.

Fig. 3 Detail of powertrain

3.1.1 Adjusting the pivoting angle of the pump

The connecting link 37 provides a mechanical connection between the swivel yoke 7 and the control
piston 32. The connecting link engages in the opening on the control piston 32. It is secured by means
of the pin 12 and the roll pin 11. The axial motion of the control piston 32 (and thus the rotary motion,
i.e. the change of the angle of swivel yoke 7) is determined by way of the performance regulator and/
or flow regulator.
The LS signal generated by the consumer sets the flow regulator to its actuating position so that the
pump pressure reaches the control chamber. As a result, the pump is pivoted out. The pump pivots
LHB/en/Edition: 03/2010

back as soon as the control chamber is connected through the flow regulator (no LS signal) or through
the performance regulator (output too high) to the tank.
In stand-by mode (i.e. all pilot control units in neutral position), the pump delivers only min. flows
(about 40 l/min - pre-set in the factory by means of stop screw 28/29).

3.1.2 Maximum and minimum pivoting angle of the pump

The maximum pivoting angle of the pump powertrain is determined by the dead stop (collar 39) of the
control piston 32 in the control cylinder. The stop cannot be adjusted.

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DPVP 108 double variable-displacement pump Service Manual
Pump regulation

The min. pivoting angle of the powertrain is determined by stop screw 28/29 (with lock nut 38). It is
factory-set. It is recommended not to tamper with these minimum pivoting angle settings.

Fig. 4 Adjusting the swivel yoke

7 Swivel yoke 38 Lock nut

11 Roll pin 39 Sleeve
12 Pin 42 Steel bushing*
22 Control piston 43 Backing ring*
25 Mounting plate 44 O-ring*
28 Q min. - stop P1
29 Q min. - stop P2 C previous installation version
32 Regulating cylinder D new installation version
37 Connecting link

* introduced during serial production, (see Fig. 10 on page13)

4 Pump regulation

4.1 Performance regulator 22.1 / 24.1 (LR) hyperbolic regulator

LHB/en/Edition: 03/2010

The purpose of the performance regulator is to adapt the flow rates from the pump with respect to the
pump pressure (performance reduction) to the power characteristic of the diesel engine. As a result,
the pump performance is regulated along a hyperbolic line. The pump delivers larger volumes at low
pressures and smaller volumes at high pressures. The basic setting of the regulating spring 90 /91
corresponds to the mechanical begin of basic regulation. It can be adjusted to load limit control via
the control pressure pMLR at the connection X3.
The pressure springs 90 / 91 push the spool 97 to the right against the lever 99. This opens the control
edge S1 so that the control chamber (SK) of the control cylinder 22 is pressurised with pump pressure

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 Service Manual DPVP 108 double variable-displacement pump
Pump regulation

pP. The pump pivots to Qmax. The return piston 96 has a mechanical connection with the swivel
yoke through the connecting pin 95.

4.1.1 Begin of pump regulation

When the working pressure pP in the system rises to the value of the begin of regulation, the force
applied by the measuring piston 98 to the lever 99 is increased. The spool 97 is shifted against the
pressure spring 90 and opens, through the control edge S2, the connection from the control chamber
(SK) to the tank (T). The pump pivots back. The pump pivoting back results in an axial movement of
the return piston 96 against the pressure spring 83 by means of the connecting pin 95 in the bearing
pin of the swivel yoke. As a consequence, the force characteristic of the measuring piston 98 against
the lever 99 is shifted in the direction of the fulcrum. The force exercised by the lever 94 on the spool
97 is reduced so that the pressure spring 90 moves the spool 97 back to its neutral position. The con-
nection between the control chamber (SK) and the tank (T) is closed. The pump delivers a constant
flow rate, which results in a constant drop in performance (at the prevailing pP).

4.1.2 Pivoting of the pump (at pressures below the begin of regulation)
As soon as the working pressure pP in the system drops, the force exercised by the piston 98 on the
lever 99 is reduced. The spring 90 shifts the spoon 97 against the lever 99. The connection through
the control edge S1 pump pressure (P) in the control chamber (SK) is opened. The pump is set to a
larger pivoting angle. The pivoting motion shifts the return piston 96 in the direction of the screw plug
81. The measuring piston 98 is pushed away from the fulcrum of the lever 99. The resulting force
applied by the lever 99 to the spool 97 is increased, i.e. an equilibrium is re-established, and the pis-
ton 97 is shifted to its closing position (S1 and S2 closed).

Fig. 5 Control edges S1 and S2

90 Pressure spring Pp Pump pressure

91 Pressure spring SK Control chamber pressure
97 Spool T Tank pressure
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DPVP 108 double variable-displacement pump Service Manual
Pump regulation

Fig. 6 Sectional drawing of performance regulator 22.1 / 24.1

24.5 Flow regulator, complete 92 Bushing (*)

49 Regulator housing 93 Spring plate
81 Screw plug 94 Ball
82 Threaded stud 95 Connecting pin (swivel yoke)
83 Pressure spring 96 Return piston
84 O-ring 97 Spool
85 O-ring 98 Piston with slipper (measuring piston)
87 Sealing nut 99 Lever
88 Adjusting screw pP Working pressure
89 Screw plug SK Control chamber pressure
90 Pressure spring (begin of regulation) T Tank pressure
91 Pressure spring

(*) this part is obsolete from 04.2009. The screw plug 89 has been extended.

Note!
Tightening torques: screw plug 81 / 89 = 35 Nm; sealing nut 87 = 18 Nm.

4.2 Flow regulator 24.5 (LS regulator)

The flow regulators 24.5 are used to adapt the flow rates of the pump to the requirements of the con-
LHB/en/Edition: 03/2010

sumers.
The flow regulators 24.5 are screw-mounted to the regulator housing 49. It consists of the following
main components: 3-piece piston 63/64/65 and pressure spring 59 with adjusting screw 52.
The spool 62 is held in its controlling position by the equilibrium of the pressures (pP, pLS) and the
spring force of the pressure spring 59. When the pressure forces change, the control chamber is con-
nected to the tank, or the pump pressure is applied to the control cylinder. The spring force of the
pressure spring 59 and thus the setting of rp can be adjusted / set by turning the adjusting screw 52.

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 Service Manual DPVP 108 double variable-displacement pump
Pump regulation

Fig. 7 Flow regulator, inserted in regulator housing

24.5 Flow regulator, complete 63 Piston

49 Regulator housing 64 Control sleeve
51 Screw plug 65 Piston
52 Adjusting screw 73 O-ring with backing ring
56 Sealing nut Pp Pump pressure
58 Lock nut pLS LS pressure
59 Pressure spring (adjustment Up) T Return line
60 Pressure spring X2 Connection control valve block-LS
61 Seal X4 Connection T to tank
62 Spool
s

Note!
Screw the flow regulator 24.5 all the way to stop. Tighten it with max. 5 Nm.
Sealing nut 56 = 8 Nm; nut 3 = 120 Nm.

4.3 Regulation of pressure difference UP LS

4.3.1 Stand-by
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When all consumers are closed, the flow from the pump builds up a backpressure in channel pP. The
backpressure acts on the piston 63. If the pressure exceeds the forces of the pressure springs 59/60,
the control edge S2 is opened, i.e. the connection between SK and T is opened. The powertrain is
swivelled back until the spring forces and the pressure forces on the spool 62 are balanced, or until
the powertrain is set to Qmin.

4.3.2 Pivoting out

The spool 62 is shifted to the right by the pressure spring 59. The control edge S1 is opened and the
pump pressure pP is applied through the channel SK to the control chamber of the pump. The pump

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DPVP 108 double variable-displacement pump Service Manual
Pump regulation

swivels to a large pivoting angle and the pumped volume is increased.

The pressure building up at the connection pLS (by means of operating a consumer) increases the
sum of the forces acting on the spring side of the spool 62, so that the spool 62 is shifted to the right.
The control edge S1 is opened.
– The pump pressure pP is applied through the channel SK to the control camber / control piston.
– The pump swivels to a large pivoting angle.
– The pumped volume increases.
Backpressure pP caused by the increasing pump volume is built up and acts on the piston 63. As
soon as the backpressure reaches the value set at the pressure spring 59, the spool 62 is shifted to
the left again until the control edge S1 closes. The pressure pP ceases to act on the control chamber
of the control piston, but is not released to the tank or the channel T (as the control edge S2 is still
closed). As a result, the powertrain is fixed and the flow rate from the pump is levelled out at a con-
stant value.

4.3.3 Pivoting back

If the pump pressure pP at the spool 62 exceeds the total value in pLS (consumer pressure at X2)
and the spring force of the pressure spring 59,
– the spool 62 is shifted to the left,
– the control edge S1 is closed,
– the control edge S2 is opened, and
– the spool pressure is relieved through SK to the tank.
– The pump pivots back.

Fig. 8 Control edges S1 and S2 at the flow regulator

51 Screw plug 68 Backing ring

52 Adjusting screw 72 Backing ring
56 Sealing nut 73 O-ring
58 Nut
59 Pressure spring (adjustment Up) pP Working pressure
60 Pressure spring pLS LS pressure
LHB/en/Edition: 03/2010

62 Spool S1 Pump pressure control edge

63 Piston S2 Tank pressure control edge
64 Bushing SK Control chamber pressure
65 Piston T Tank pressure
66 Bushing X2 Connection at regulator housing
67 O-ring X4 Connection at regulator housing

7.07.10
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 Service Manual DPVP 108 double variable-displacement pump
Adjustment of DPVP variable-displacement pump

5 Adjustment of DPVP variable-displacement pump

5.1 Adjustment of the differential pressure Up LS and begin of the hydraulic regu-
lation

Note!
The procedure to adjust the differential pressure and begin of regulation of the pump is described
in group 3 "Adjustment protocol" and "Adjustment guidelines".

5 Drive shaft 27 Pump distributor gear

7 Swivel yoke 28 Q min. - stop P1
8 Roller bearing 29 Q min. - stop P2
10 Sliding bearing 30 Gear pump
11 Roll pin 31 Sliding disc
12 Pin 32 Regulating cylinder
14 Roller bearing 33 Return ball
15 Connecting pin 34 Return plate
16 Cylinder 35 Pressure spring
17 Pilot plate 36 Pressure spring
18 Cylinder pin 37 Connecting link
19 Piston with slipper 38 Lock nut
20 Pump unit 39 Sleeve
21 Powertrain (P1) 41 Allen head screw
22 Regulating unit (P1) 42 Steel bushing*
LHB/en/Edition: 03/2010

22.1 Performance regulator (P1) 43 Backing ring*

23 Powertrain (P2) 44 O-ring*
24 Regulating unit (P2)
24.1 Performance regulator (P2) C previous installation version
25 Mounting plate D new installation version
26 Connecting flange

* introduced during serial production

7.07.11
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DPVP 108 double variable-displacement pump Service Manual
Adjustment of DPVP variable-displacement pump

LHB/en/Edition: 03/2010

Fig. 9 Sectional drawing 1

7.07.12
copyright by

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 Service Manual DPVP 108 double variable-displacement pump
Adjustment of DPVP variable-displacement pump
LHB/en/Edition: 03/2010

Fig. 10 Sectional drawing 2

7.07.13
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DPVP 108 double variable-displacement pump Service Manual
Performance characteristic - DPVP

6 Performance characteristic - DPVP

LHB/en/Edition: 03/2010

Fig. 11 Performance characteristic - DPVP 90

7.07.14
copyright by

MJFCIFSS
 Service Manual FMF hydraulic fixed displacement motor
Purpose

FMF hydraulic fixed displacement motor

1 Purpose

The FMF hydraulic fixed displacement motor is of the built-in type. Its purpose is to drive the slewing
gear mechanism of the machine.
The axial piston motor is of the swash plate design and sits on the slewing gear of the machine.

Fig. 1 FMF hydraulic fixed displacement motor

LHB/en/Edition: 09/2004

7.20.1
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FMF hydraulic fixed displacement motor Service Manual
General information and tightening torques

2 General information and tightening torques

Type of oil motor FMF 45 FMF 45

3
Oil flow consumption 45 cm per round 45 cm3 per round
Leak oil max. at (350 bar) 6 l/min 6 l/min

Tab. 1 Technical data

Allen head screws 14 118 Nm

Screw plug / leak-oil connection S 68 Nm
Pressure relief valve 134 / 135 100 -120 Nm
Screw plug / suction valve 133.1 250 Nm
Measuring connection 137 / 138 27 Nm

Note!
Adjustment of valves 134 / 135: see adjustment protocol and adjustment guideline in group 6.

3 Description

Axial-piston oil motors are energy transformers best characterised by the axial orientation of their pis-
tons in a cylinder.
Oil motor 130 consists mainly of two components:
– Motor housing 12 with powertrain 132
– Mounting plate 13 with suction valves 133 and pressure relief valves 134 / 135
Furthermore, there are the measuring connections 137 / 138 on top of mounting plate 13.
Powertrain pistons 132 (with slippers) rotate on the swash plate. The inclined arrangement of the
slide faces is responsible for the stroke of the pistons in the cylinder and, thus, the constant oil flow
consumption of the oil motor.
The force resulting from hydraulic pressure and piston areas generates the required torque on the
output shaft.
LHB/en/Edition: 09/2004

7.20.2
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 Service Manual FMF hydraulic fixed displacement motor
Functional description

Fig. 2 FMF fixed displacement motor

12 Housing 134 Relief valve with additional pressure level

13 Mounting plate 135 Relief valve with additional pressure level
130 Oil motor 137 Measuring connection MA
132 Powertrain 138 Measuring connection MB
133 Suction valve

4 Functional description

4.1 Functioning of the oil motor, see Fig. 3 and see Fig. 4
Nine pistons 5 are arranged in housing 12, in a circle, parallel to output shaft 3. They run in
cylinder 4, which is in gear with output shaft 3.
The bottom ends of the pistons are designed as ball joints and sit in slippers 5.1. They are held on
fixed eccentric disc 6 by return ball 8 and return plate 7.
The hydrostatic bearing arrangement of slippers 5.1 on thrust washer 6 (by means of bores in piston
5 and slippers 5.1) reduces the otherwise high friction between slippers and eccentric disc to a mini-
mum.
LHB/en/Edition: 09/2004

When there is no pressure, cylinder 4 is pressed against disc cam 8 by pressure springs 8.1 which
are installed in return ball 8. As soon as the pressure goes up, cylinder 4 and disc cam 9 are balanced
by hydraulic forces in such a way that the oil film at the control surface is maintained at all times, even
under high loads, and the amount of leak oil is reduced to a minimum. Some of the leak oil is used to
lubricate the moving parts of the powertrain and guided externally back to the tank.
If pressure oil is supplied to operating connections A or B, it will act on four pistons 5 in each case,
via kidney-shaped slots in pilot plate 9. Another four pistons 5 displace the oil not carrying energy via
kidney-shaped openings in pilot plate 9 and connection B and/or A back to the tank. A ninth piston

7.20.3
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FMF hydraulic fixed displacement motor Service Manual
Functional description

is situated in the area of the dead centre, i.e. at the point of return of motion.
The oil acting on the four pistons on the pressure side will generate a certain force resulting from pres-
sure and piston area. That force acts on eccentric disc 6 via piston 5 and slipper 5.1.
The radial component of that force (together with the limb of the cylinder acting as a lever arm) ge-
nerate a torque which is transmitted on to cylinder 4 and output shaft 3 .
That torque can be influenced only by the oil pressure applied, i.e. high pressure = high torque. The
two-way action acting on the oil motor (connection A or B) effects a change of direction of the torque
at drive shaft 3 (left or right-hand rotation).
For every rotary motion of cylinder 4, pistons 5 execute a double stroke. That stroke of the piston cor-
responds to the inclination of eccentric disc 6 and determines the amount of oil consumed.
As the oil flow consumption remains constant at all times, it is the travel / output speed of the oil motor
that is changed accordingly via the spool when the oil supply changes.

Fig. 3 Sectional drawing: fixed displacement motor

2 Roller bearing 15 Locking ring

3 Output shaft 16 Radial shaft seal ring
LHB/en/Edition: 09/2004

4 Cylinder 17 O-ring
5 Piston 18 O-ring
5.1 Slipper 19 O-ring
6 Eccentric disc 22 Snap ring
7 Return plate 23 Snap ring
8 Return ball 26 Needle bearing
8.1 Pressure spring 27 Shim

7.20.4
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 Service Manual FMF hydraulic fixed displacement motor
Functional description

9 Pilot plate 28 Shim

10 Locking pin 29 Shim
12 Housing 30 Shim (supplied only with repair set /lok-
king ring
13 Mounting plate 134 Pressure relief valve B with additional
pressure level
13.21 Screw plug 135 Pressure relief valve B with additional
pressure level
14 Allen head screw 137 Measuring point MA / pivot right

4.2 Functioning of valves on the mounting plate, see Fig. 4

4.2.1 Suction valves 133

The suction valves (acting as check valves) make sure the oil motor is always properly filled (no ca-
vitation e.g. when relief valves blow off or in the event of leaks). If there is a lack of pressure at con-
nection A or B, the pressure difference lifts cone 133.10 (against the force of spring 133.14) from its
seat, and the oil can flow from connection S to suction side A or B. This prevents cavitation in the oil
motor.

4.2.2 Pressure relief valves with additional pressure level 134 and 135
These valves limit the high pressure that may arise at main connections A and B with respect to the
control pressure at connections XA / XB.

Pressure control
If the pressure increases in the slewing gear circuit in undesirable ways, destruction would hit the
weakest point, e.g. screwed connections or hydraulic hoses.
In order to prevent that, we provide a sort of pre-determined breaking point. So, in our case, the in-
creasing operating pressure in the slewing gear circuit acts on a pressure relief valve. It limits the
max. pressure in the slewing gear and its connection to the pre-set value.
For the ease of functioning and manufacture, we use indirect (pilot-controlled) pressure relief valves.
With these valves, we use a relief valve that works directly as a pilot control valve to actuate a second,
larger valve.
The resulting pressure (in A or B) acts on the front face of piston (main cone) .19, as well as on its
backside (via a small bore) and closes it. At the same time, the pressure acts on pilot control
cone .20. Pressure spring .23 pushes pilot control cone .20 into its closing position (static condition).
Pressure springs .24 and .31 serve as return devices.
As soon as the pressure in the consumer circuit attains a value exceeding the set value of pressure
and adjusting spring .23, pilot control cone .20 is lifted from its seat, and some oil can penetrate into
the return channel.
The differing cross-sections of the bores in piston .19 and valve insert .18 generate a pressure diffe-
rence between the front and back sides of piston .19. The effect of the pressure difference is that pis-
LHB/en/Edition: 09/2004

ton .19 is shifted against pressure spring .23, and a high amount of oil can flow off to return side 5
and/or the other side.

Additional pressure level

If the pilot control valve for the actuation of the slewing gear is not actuated, connection XA / XB is
relieved.

Level 1 (low pressure = braking pressure - see adjustment protocol of hydraulic system)
Connection XA and/or XB is connected to the tank: Pressure spring .23 has a lower pre-loading force.

7.20.5
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FMF hydraulic fixed displacement motor Service Manual
Functional description

The pressure limitation of relief valve 134 / 135 is set to the low value (level 1).
If the pilot control valve is switched to slewing gear control, the pilot pressure acts on piston .12 via
connection XA or XB and internal bores in mounting plate 13 plus more bores and annular passages
in valve 134 / 135.
Level 2 (higher pressure = pivoting pressure - see adjustment protocol of hydraulic system)
Pressure spring .23 is pre-loaded a bit more by shifting piston .12, ball .21 and spring plate .11, so
that there is a higher blow-off pressure.
The pressure limitation of relief valve 134 / 135 is set to the high value (level 2).
Adjustment of relief valves 134 / 135 with additional pressure level: see adjustment protocol and ad-
justment guideline in group 6.

Fig. 4 Sectional drawing: mounting plate

13 Mounting plate 134.19 Piston

14 Allen head screw 134.20 Cone
133 Check valve / suction valve 134.21 Ball
LHB/en/Edition: 09/2004

133.10 Cone 134.22 O-ring

133.11 Plug 134.23 Pressure spring
133.14 Pressure spring 134.24 Pressure spring
133.17 O-ring 134.25 O-ring
134 Pressure relief valve / turn right A with 134.26 Backing ring
additional pressure level
134.10 Adjusting screw 134.27 O-ring

7.20.6
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 Service Manual FMF hydraulic fixed displacement motor
Maintenance and repairs

134.11 Spring plate 134.28 O-ring

134.12 Piston 134.29 O-ring
134.13 Nut 134.30 O-ring
134.14 Bushing* 134.31 Pressure spring
134.15 Bushing 134.98 Seal kit
134.16 Nut 135 Pressure relief valve / turn left B with
additional pressure level items 10 - 98,
see 134
134.17 Bushing* 137 Measuring point MA / turn right
134.18 Valve seat 138 Measuring point MB / turn left

* one piece (roller bearing)

5 Maintenance and repairs

Note!
Liebherr oil motors do not require any maintenance whatsoever. For sealing and repair jobs, please
refer to separate repair instructions "Liebherr fixed displacement oil motors FMF".

5.1 Sealing jobs on valves on mounting valve

Replacement of O-ring 133.17 or spring 133.14 on suction valves 133:

Remove screw plug 133.11 complete with measuring connections 137 / 138. Remove cone 133.10,
spring 133.14 and O-ring 133.17.
Check cones 133.10 for free movement. Place new spring or O-ring in valve, and put together again.
When re-mounting the valve, be sure to properly re-tighten screw plug 133.11 complete with measu-
ring connections 137 / 138 (250 Nm).

Sealing jobs on pressure relief valves 134 and 135

Use seal kit .93.
Remove and/or dismount valve 134 / 135 completely, as needed.
Check parts for good functioning, and whether fit for re-use.

Note!
When you are finished replacing the defective sealing element, be sure to correctly assemble. Install
complete valve (torques between 100 and 120 Nm).
After the replacement of O-rings .22, .27, .29, it is imperative to re-adjust the response pressures of
the valve. See adjustment guideline and protocol in group 6.
LHB/en/Edition: 09/2004

7.20.7
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FMF hydraulic fixed displacement motor Service Manual
Maintenance and repairs

LHB/en/Edition: 09/2004

7.20.8
copyright by

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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Function and design

HMF 75-02P hydraulic fixed-displacement motor

1 Function and design

The hydraulic fixed-displacement motor is a axial piston motor of the swash plate type designed for
an open circuit. The high-pressure hydraulic motor has a constant pivot angle. It is used to drive the
slewing gear mechanism of the machine and features all functions that are required for optimised sle-
wing gear operation.
– Way valve function for rotation
– Priority valve for slewing gear
– Torque control
– Secondary and suction valve 131/132 with controllable characteristic
– Feeder valve
– Anti-reaction function
– Outlet function
The hydraulic fixed-displacement motor 130 consists of three main components:
– The motor housing 1 encases the drive shaft and the complete powertrain.
– The valves are combined in a compact unit in the control base receptacle 2.
– Anti-reaction plate 139 with internal A-B connection.
LHB/en/Edition: 10/2009

Fig. 1 Hydraulic fixed-displacement motor 130

7.22.1
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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Function and design

Fig. 2 Basic design of powertrain

1 Motor housing 7 Cylinder block

2 Control base receptacle 131 Secondary pressure-relief valve / swivel-
ling right
3 Radial shaft seal ring 132 Secondary pressure-relief valve / swivel-
ling left
4 Shaft 141 Check valve / LS pressure
5 Working piston 142 Check valve / tank return line
6 Control base
LHB/en/Edition: 10/2009

7.22.2
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Function and design

Fig. 3 Exploded view of control base receptacle 2

131 Secondary pressure-relief valve / turning 143 Feeder valves

right
132 Secondary pressure-relief valve / turning 145 Measuring point / turning right
left
133 Spool / turning 146 Measuring point / turning left
134 TC pressure-relief valve 147 Measuring point / control pressure
135 Restrictor check valve / control pressure 148 Shuttle valve
136 Stroke limiter / spool d1 Nozzle in restrictor check valves
137 Torque control valve d2 Nozzle in actuating circuit of pressure-
LHB/en/Edition: 10/2009

relief valves
131/132
138 Input pressure balance d3 Pilot control pressure nozzle (for torque
Priority switching / swivelling control)
139 Anti-reaction valve d4 Nozzle / LS pressure at input pressure
balance
140 Check valve d5 Nozzle for torque control valve 137
141 Check valve / LS pressure d6 Housing flushing nozzle

7.22.3
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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Technical data

142 Preload valve d7 Nozzle for A-B connection

Return check valve

2 Technical data

Machine series A 914 C Litronic A 924 C Litronic

from serial number 35112 34519
Type of oil motor HMF 75-O2P
Flow consumption cm3 75.9
Leak oil max. at (200 bar) l/min 9.0
Start of movement bar 8.5 ±0.5
Spool 133

Nozzle dimensions
Nozzle d1 Ø mm 0.4
Nozzle d2 Ø mm 0.6
Nozzle d3 Ø mm 0.6
Nozzle d4 Ø mm 0.6
Nozzle d5 Ø mm 1.3
Nozzle d6 Ø mm 1.6
Nozzle d7 Ø mm 1.0 construction / 1.2 industry

Tightening torques
Sealing flange nut 16 Nm 60
Lock nut 125 Nm 50
Lock nut 127 Nm 5
Secondary pressure-relief val- Nm 80 +10
ves 131/132
Lock nut 117 at secondary pres- Nm 70
sure-relief valves 131/132
Restrictor check valve 135 Nm 9
Sealing flange nut at Nm 60
TC pressure-relief valve 134
Torque control valve 137 Nm 100

Tab. 1 Technical data

LHB/en/Edition: 10/2009

3 Functional description

3.1 Way valve 133, Fig. 4 and Fig. 5

The spool 133 of the way valve is used to actuate the motor. It is centred in its neutral position by the
two springs 15. The pump pressure acts on the motor through the connection P.

7.22.4
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Functional description

Using the pilot control unit, the operator can build up the control pressure in the spring chamber X/Y
necessary to perform the desired swivelling motion.
The spool 133 is shifted according to the preselected control pressure and the oil flows from P to A
(B) and to B (A) and T.
The open channel acts as a gauge orifice after which the LS pressure is measured and transmitted
to the pump controller. The oil flow (slewing gear speed) is adjusted according to the control pressure.
The piston stroke can be restricted with a stop screw 17 so that the maximum flow rate is limited. The
restrictor check valves 135 attenuate the spool movement in both directions.

Fig. 4 Hydraulic schematic

LHB/en/Edition: 10/2009

7.22.5
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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Functional description

LHB/en/Edition: 10/2009

Fig. 5 Sectional drawing of the control base receptacle 2

15 Pressure spring 139 Anti-reaction valve

16 Sealing flange nut 140 High pressure check valve
17 Stop screw 141 Check valve / LS pressure
18 Shims 142 Preload valve
Return check valve
19 Control cap 143 Feeder valves

7.22.6
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Functional description

22 Pressure spring 145 Measuring point / turning right

23 Pressure spring 146 Measuring point / turning left
130 Slewing gear motor with way valve 147 Measuring point / control pressure
131 Secondary pressure-relief valve / turning 148 Shuttle valve
right
132 Secondary pressure-relief valve / turning d1 Nozzle in restrictor check valves 135/136
left
133 Spool / turning d2 Nozzle in actuating circuit of pressure-
relief valves
131/132
134 TC pressure-relief valve d3 Pilot control pressure nozzle (for torque
control)
135 Restrictor check valve / control pressure d4 Nozzle / LS pressure at input pressure
balance
136 Stroke limiter / spool d5 Nozzle for torque control valve 137
137 Torque control valve d6 Housing flushing nozzle
138 Priority switching swivelling / d7 Nozzle for A-B connection
input pressure balance

3.2 Priority valve 138 (input pressure balance), see Fig. 7

The priority valve 138 is installed in the channel P in front of the spool 133, see Fig. 5.
The system LS pressure that is applied onto the hydraulic motor through the connection LS does not
affect the control system of the input pressure balance 138, and the check valve 141 in the control
base receptacle 2 prioritizes the slewing gear.

Fig. 6 Control base receptacle 2, see Fig. 2

LHB/en/Edition: 10/2009

3.3 Torque control, see Fig. 6

The TC valve 137 determines the acceleration pressure. The machine operator selects the desired
oil flow rate as well as the variable acceleration pressure at the pilot control unit. This prevents the
pressure-relief valves 131/132 (secondary valves) from being opened. The maximum acceleration
pressure is set at the TC pressure-relief valve 134.

7.22.7
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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Functional description

Fig. 7 Sectional drawing, see Fig. 5

18 Piston 134 TC pressure-relief valve

20 Regulating piston 137 Torque control valve
22 Spring 138 Priority switching swivelling /
input pressure balance
23 Adjusting spring

3.4 Secondary pressure relief valves with suction function

The secondary pressure-relief valves 131/132 are adjustable. They are factory-set to a basic value.
When a control pressure of > 5 bar is applied at the connections X/Y, (see “Hydraulic schematic” on
page 5) the set valve pressure is changed from the basic value to the maximum value. The control
pressure of the way valve is used as the actuating pressure.
During the acceleration phase, the associated secondary pressure-relief valve is adjusted to the ma-
ximum set value, depending on the control pressure and along a characteristic. If the machine ope-
rator wishes to make smooth movements, the pilot control unit must be held in 0 position, and the
uppercarriage is moved against the basic settings of the secondary pressure-relief valves 131/132
(minimum setting 80 bar).
If the operator desires hard braking of the uppercarriage, he must change the setting of the respective
secondary pressure-relief valve 131/132 to the maximum value. The uppercarriage is now slowed
down against maximum pressure. Depending on the control pressure set by the machine operator,
the controllable secondary pressure-relief valves 131/132 can be used to adjust the brake pressure
along a defined characteristic with minimum and maximum value.
The minimum and maximum value are mechanically adjustable from the outside. The control pres-
LHB/en/Edition: 10/2009

sure can be adjusted along the TC characteristic from the outside.

The outlet side of the pressure-relief valves 131/132 is exposed to the preload tank return pressure,
facilitating reloading through the suction valves.

7.22.8
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Functional description

Fig. 8 Secondary pressure relief valves 131 / 132

70 Piston 119 Adjusting screw

71 Needle piston 120 Stop screw
72 Spring 121 Spring
73 Spring 124 Adjusting screw
76 Valve cone 125 Lock nut
77 Spring 126 Adjusting screw
115 Spring 127 Lock nut
116 Piston T/T1 to hydraulic tank
117 Lock nut x/y Control pressure connections

3.5 Feeder valves 143

To prevent cavitation, it is possible to supply the slewing gear system directly through the feeder val-
ves 143 that are connected to the preloaded tank return line in the control block.
LHB/en/Edition: 10/2009

Fig. 9 Feeder valve 143

7.22.9
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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Functional description

3.6 Anti reaction valve 139

During the stop phase, the anti-reaction valve 139 connects the two main connections A and B so
that all pressure is effectively released. The uppercarriage comes to a smooth halt.

Fig. 10 Anti-reaction valve

96 Valve plunger 103 O-ring

97 Nozzle 139 Anti-reaction valve
98 Nozzle 145 Measuring point / turning right
99 Nozzle 146 Measuring point / turning left
100 Screw plug d7 Nozzle for A-B connection
LHB/en/Edition: 10/2009

3.7 Outlet function, (see “Hydraulic schematic” on page 5)

The tank return line (channel T) is always preloaded. A metered amount of oil is fed through the nozz-
le D3, acting as flushing oil to cool the housing of the hydraulic motor. It then leaves the housing to-
gether with any leak oil to the connection L/U.

7.22.10
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Checking and adjusting the slewing gear functions

4 Checking and adjusting the slewing gear functions

Location of Measuring
Check / adjustment Unit Setting
adjustment point
Turning
Secondary pressure / turning right bar 260 +10 131 1/2
+10
Secondary pressure / turning left bar 260 132 1/2
Braking
Secondary pressure / turning right bar 85 +10 131 3/4
+10
Secondary pressure / turning left bar 85 132 3/4
± 0,1
Secondary pressure (control pressure bar 14 147
14 bar)
Turning right bar 160 +10 131 145
Turning left bar 160 +10 132 146
± 0.1
TC characteristic (control pressure 16 bar 16 147
bar)
Turning right bar 160 +5 145
Turning left bar 160 +5 146
Adjustment from serial no. 47186 (A 914 C), 42466 (A 924 C)
TC characteristic (control pressure 16 bar 16 ± 0.1 147
bar)
Turning right bar 130 +5 145
+5
Turning left bar 130 146
Primary pressure (high pressure)
Turning right bar 240 +10 131 145
+10
Turning left bar 240 132 146
+ 0.1
Stroke limitation (checking measure- mm 41.3 X
ment)

Tab. 2 Setting data

Danger!
The uppercarriage may execute uncontrolled rotary movements, pose a hazard to mechanics and
equipment.
X Apply the slewing gear brake (switch S17).
The uppercarriage is locked in its position.
X Park the machine on level ground.
X Lower the attachment to the ground.
LHB/en/Edition: 10/2009

7.22.11
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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Checking and adjusting the slewing gear functions

4.1 Checking and adjustment of the high pressure-relief valves 131/132

4.1.1 Adjusting the upper pressure level (counter-pressure)

Fig. 11 Adjustment of accelerating/braking movement

In order to facilitate the adjustment of the basic settings of the TC pressure-relief valve 134 and the
Torque Control valve 137, proceed as follows:
X Turn in both valves 134 and 137 by three revolutions.
The secondary pressure can be adjusted.

Note!
– Turn clockwise = increase pressure
– Turn counter-clockwise = reduce pressure
– One full revolution corresponds to a pressure change of approx. 235 bar.

X Connect a pressure sensor to the measuring point 145/146.

X Block the uppercarriage and actuate the switch S17.
X Start the machine, move the safety lever to its bottom position and preselect mode P.
X Press the pilot control unit for turning right to the stop.
X Compare the pressure with the settings (measuring point 145).
If necessary, loosen the lock nut 2 and adjust the settings of the pressure-relief valve 131 with
the adjusting screw 1.
X Press the pilot control unit for turning left to the stop.
X Compare the pressure with the settings (measuring point 146).
If necessary, loosen the lock nut 2 and adjust the settings of the pressure-relief valve 132 with
the adjusting screw 1.
LHB/en/Edition: 10/2009

7.22.12
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Checking and adjusting the slewing gear functions

Fig. 12 Adjustment of accelerating/braking movement

4.1.2 Adjustment of the lower pressure level (braking)

Danger!
Rotating movements of the uppercarriage during dynamic measurement pose a hazard to mecha-
nics and equipment.
X Ensure that no persons or other objects are located in the swivelling range.

X Connect a pressure sensor to the measuring point 145/146.

X Start the machine, move the safety lever to its bottom position and preselect mode P.
X Release the slewing gear brake (switch S17).
X Press the pilot control unit for turning right to the stop.
After the maximum swivelling speed is reached, release the pilot control unit and read the pres-
sure indicated at the measuring point 145.
X Compare the pressure with the settings (measuring point 145).
If necessary, loosen the lock nut 3 and adjust the pressure-relief valve 131, using adjusting
screw 4 and the special tool no. 18.
X Press the pilot control unit for turning left to the stop.
After the maximum swivelling speed is reached, release the pilot control unit and read the pres-
sure indicated at the measuring point 146.
X Compare the pressure with the settings (measuring point 146).
If necessary, loosen the lock nut 3 and adjust the pressure-relief valve 132, using adjusting
screw 4 and the special tool no. 18.
X Remove the pressure sensor and seal the measuring point.

4.1.3 Checking and adjustment of characteristic (high pressure-relief valves)

Note!
LHB/en/Edition: 10/2009

These valves are factory-set, (see “Diagram of slewing gear settings” on page 16) and it is normally
not necessary to check and readjust them.
If the characteristic has been changed, the brake pressure must be checked and adjusted accordin-
gly, (see “Adjustment of the lower pressure level (braking)” on page 13).

X Connect a pressure sensor to the measuring point 147.

X Block the uppercarriage.
X Start the machine, move the safety lever to its bottom position and preselect mode P.

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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Checking and adjusting the slewing gear functions

X Adjust the pilot pressure for turning left/right with the pilot control unit (select a high initial pressure
and then lower it; for prescribed pressure value, see settings).
X Read the pilot pressure indicated at the measuring point 147.
X Compare the pressure values with the settings (measuring point 145/146).
If necessary, loosen the lock nut 5 and adjust the characteristic with the adjusting screw 6.
– One full revolution corresponds to a pressure change of approx. 28 bar.
X Remove the pressure sensor and seal the measuring point.

4.2 Checking and adjustment of the maximum acceleration pressure

Fig. 13 Adjustment of pressure-relief valve 134

Note!
– Turn clockwise = increase pressure
– Turn counter-clockwise = reduce pressure

The TC pressure-relief valve 134 limits the acceleration pressure for turning right/left.
X Connect a pressure sensor to the measuring point 145/146.
X Turn out the TC pressure-relief valve 134 by three revolutions.
X Block the uppercarriage.
X Start the machine, move the safety lever to its bottom position and preselect mode P.
X Press the pilot control unit for turning left/right to the stop.
X Compare the pressure value with the setting data (measuring point 145/146).
If necessary, loosen the lock nut 2 and adjust the settings of the pressure-relief valve 134 with
the adjusting screw 1.
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 Service Manual HMF 75-02P hydraulic fixed-displacement motor
Checking and adjusting the slewing gear functions

4.3 Checking and adjustment of the Torque Control valve 137 (characteristic)

Fig. 14 Adjustment of Torque Control valve 137

X Connect a pressure sensor to the measuring point 145/146/147.

X Turn out the Torque Control valve 137 by three revolutions.
X Block the uppercarriage.
X Start the machine, move the safety lever to its bottom position and preselect mode P.
X Adjust the pilot pressure for turning left/right with the pilot control unit to 16 bar (select a high initial
pressure and then lower it to 16 bar).
X Read the pilot pressure indicated at the measuring point 145/146.
X Compare the pressure value with the setting data (measuring point 145/146).
If necessary, loosen the lock nut 2 and set the Torque Control valve 137 using the adjusting
screw 1.
If the pressure settings of the Torque Control valve 137 cannot be adjusted, first adjust the characte-
ristic of the high pressure limitation, (see “Checking and adjustment of characteristic (high pressure-
relief valves)” on page 13).

Note!
The values shown in the diagram below are sample values only. For the actual applicable values,
see the adjustment protocol.

– I Relationship between the secondary protection and the control pressure for swivelling
– II Relationship between high pressure and the control pressure for swivelling
– 1 Minimum secondary set value.
– 2 Secondary set value, Pst-dependent
– 3 Minimum secondary set value
– 4 Limitation by control pressure
– 5 Torque control
Secondary pressure relief
LHB/en/Edition: 10/2009

Working pressure for lowering

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HMF 75-02P hydraulic fixed-displacement motor Service Manual
Checking and adjusting the slewing gear functions

LHB/en/Edition: 10/2009

Fig. 15 Diagram of slewing gear settings

* to serial no. 35237

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 Service Manual DMVA regulating motor (travel drive)
Design of hydraulic travel motor

DMVA regulating motor (travel drive)

1 Design of hydraulic travel motor

The axial-piston oil motor is of the swash-plate type. It is flange-mounted to the transmission of the
machine. It consists of a motor housing with built-in powertrain, swivel yoke and a mounting plate with
regulating and adjusting unit.
The mounting plate features a brake valve working in both directions of travel. The mounting plate is
also equipped with the secondary pressure-relief valves and the suction valves.
The flow volume of the variable-displacement pump is fed through connections A or B to the travel
motor and acts on the piston of the powertrain. The pistons (moving in axial direction inside the cy-
linder of the powertrain) act on the cylinder and drive shaft and generate a certain torque.
The regulating and adjusting unit built into the mounting plate adjusts the pivoting angle to the flow
consumption of the oil motor (= flow consumption of the travel motor).
The variable oil flow consumption of the travel motor determines the torque and speed of the drive
shaft. Both values are in inverse ratio, i.e.:
High oil flow consumption Qmax = high torque = low speed of travel motor
Low oil flow consumption Qmax = low torque = high speed of travel motor
The brake valve integrated into the mounting plate restricts the return flow to the control valve block
or the tank respectively, thus slowing down the drive. This approach prevents overspeeding of the
travel motor when travelling down a slope and consequent cavitation.
LHB/en/Edition: 03/2010

Fig. 1 DMVA travel motor

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DMVA regulating motor (travel drive) Service Manual
Technical data

2 Technical data

Machine A 900 C A 900 C ZW A 904 C A 914 C

A 924 C
from serial number 24677 31354 30580 34519
Oil motor DMVA 165 DMVA 165 DMVA 165 DMVA 165
3 3 3
Max. oil flow consumption 165 cm /rev 165 cm /rev 165 cm /rev 165 cm3/rev
Min. oil flow consumption 94 cm3/rev 94 cm3/rev 94 cm3/rev 94 cm3/rev
Begin of regulation (high pressure) 240 bar 240 bar 240 bar 240 bar
End of regulation (high pressure) 320 bar 320 bar 320 bar 320 bar
Max. pivoting angle 22° 22° 22° 22°
Min. pivoting angle 10,8° 10,8° 10,8° 10,8°
Max. permissible leak oil volume 7 l/min 7 l/min 7 l/min 7 l/min
at 350 bar and an oil temperature of 50°C
Settings of oil motor
A Begin of regulation of the oil motor 240 bar 240 bar 240 bar 240 bar
at the adjusting screw 64
B Min. pivoting angle
Dimension X of the stop screw 35
(guide value)
Standard machine 21.0 mm 21.0 mm 21.0 mm 21.0 mm
Speeder 25.0 mm 25.0 mm 25.0 mm 25.0 mm
Standard machine A 924 C 22.5 mm
Type 1050/1051 HD 25.0 mm
C Drive shaft speed When adjusting the drive shaft speed,
Standard machine take into account the tyre size.
Speeder For adjustment values, refer to the adjustment protocols of the re-
spective machine in group 3.
D Secondary pressure-relief valves 380 +20 bar 380 +20 bar 380 +20 bar 380 +20 bar

Tab. 1 Technical data

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 Service Manual DMVA regulating motor (travel drive)
Description

3 Description

The travel motor consists of the following main components:

– Powertrain 172
– Mounting plate 30
– Regulator 60
The housing 80 encloses the entire powertrain 172 with swivel yoke, piston, pilot plate and sliding
disc.
The housing 80 is screwed to the mounting plate 30. The mounting plate contains the secondary
pressure-relief valves 176/177, the control and regulating unit and the brake valve acting in both di-
rections of travel.

Fig. 2 Design of the travel motor

30 Mounting plate 172 Complete powertrain

60 Regulator, complete 176 Secondary pressure-relief valve
80 Housing 177 Secondary pressure-relief valve
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DMVA regulating motor (travel drive) Service Manual
Functional description of the travel motor

4 Functional description of the travel motor

4.1 Function of powertrain

The housing 80 encloses the powertrain 172 with the drive shaft 4, cylinder 3, piston 2 with slipper,
etc. Parallel to the drive shaft 4, there are nine pistons 2 arranged in a circle. They run in axial arran-
gement in the cylinder 3, which is in gear with drive shaft 4. The bottom ends of the pistons are desi-
gned as ball joints and sit in slippers. They are held on the swivel yoke 9 by the return ball 6 and the
return plate 7 (swash plate).
The hydrostatic bearing of the slipper on the sliding disc 8 of the swivel yoke 9 (through bores in the
piston 2 and the slippers) reduces the high friction to a minimum, despite the high surface pressure
between the slipper and the swivel yoke 9.
When there is no pressure, the cylinder 3 is pressed by the pressure springs 13 in the return ball 6
against the pilot plate 5. When the pressure increases, the cylinder 3 and the pilot plate 5 are balan-
ced by hydraulic forces in such a way that the oil film at the control surface is maintained at all times,
even under high loads, and the amount of leak oil is reduced to a minimum. Some of the leak oil is
used to lubricate the moving parts of the powertrain and is fed externally back to the tank.
If pressure oil is supplied to the operating connections A or B, the respective four pistons are pres-
surised through the kidney-shaped slots in the pilot plate 5. Another four pistons press the non-ener-
gised oil through the kidney-shaped openings in the piston plate 5 through the connection A or B to
the tank. A ninth piston is situated in the area of the dead centre, i.e. at the point of return from the
pressure to the suction phase.
The oil acting on the four pistons on the pressure side generates a certain force determined by the
pressure and the piston area. This force acts via the pistons 2 with slippers onto the swivel yoke 9.
The radial component of the above force (together with the section of the cylinder acting as a lever
arm) generates a torque which is transferred onto the cylinder 3 and the drive shaft 4. Changing the
pressure side of the travel motor (connection A or B) results in a change of direction of the torque at
the drive shaft 4 (clockwise or anticlockwise rotation respectively).
With every rotary motion of the cylinder 3, the pistons execute a double stroke. That stroke corres-
ponds to the inclination of swivel yoke 9 and determines the amount of oil consumed.

4.2 Function of the regulating unit

The sectional drawing shows the following regulating positions of the travel motor:
The powertrain 172 (swivel yoke 9) is already set to a maximum pivoting angle. The working pressure
acts on the piston face of the control piston 173 (minimum pressure valve at the end of regulation),
see Tab. 1.
The regulating piston 174 is in regulating position, i.e. the flow from the high pressure side through
the check valve 175 to the large piston surface of the spool 173 and the flow from the large piston
surface of the spool 173 to the tank side are blocked. The maximum pivoting angle is determined by
the stop of the spool 173 at the guide bushing 33. The motor remains in this position, until the high
LHB/en/Edition: 03/2010

pressure drops below the pressure value at the end of regulation.

Within the regulated range, the travel motor can reach any position that corresponds to a working
pressure of between Qmax and Qmin. If the working pressure drops below the value at the begin of
regulation, the spool 173 touches the stop screw 35, i.e. the travel motor's flow consumption capacity
is lowest at high drive shaft speed, high speed and low drawing pull.

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 Service Manual DMVA regulating motor (travel drive)
Functional description of the travel motor

Fig. 3 Sectional drawing of the regulating unit (spool)

32 Mounting plate 38 Lock nut

33 Guide bushing 42 Pin
34 Connecting link 50 Measuring connection of the actuating pres-
sure M
35 Stop screw

4.3 Function prior to the begin of regulation

see Fig. 3 and Fig. 4
The pressure oil from the respective high pressure side A or B respectively, acts on the piston ring
surface of the spool 173 through the check valves 175 and the internal bores in the mounting plate
32. The swivel yoke 9 is kept at a small pivoting angle by the connecting link 34. The minimum pivo-
ting angle is limited by the stop screw 35.
The working pressure acts on the spool 174 through the check valves 175. The spool 174 is held by
the preloaded adjusting spring 68 in its basic position so that the flow from the high pressure side
through the check valve 175 to the large piston surface of the spool 173 is blocked. The flow from the
large piston surface of the spool 173 to the tank side is opened. The travel motor remains in this po-
sition until the working pressure exceeds the pressure value of the begin of regulation, see Tab. 1.

4.4 Function from begin of regulation

see Fig. 3 and Fig. 4
The spool 174 is held in the regulating position by the adjusting spring 68 and the return spring 69 (+
the working pressure acting on the shuttle check valve 195). Regulating position of the spool 174
spring force of the return spring 69 + force resulting from the working pressure on the surface diffe-
rence = spring force of the adjusting spring 68.
If the existing working pressure rises above the value at the begin of regulation, it acts on the surface
LHB/en/Edition: 03/2010

difference Ø D - Ø d, (see Fig. 5 on page6) of the spool 174, pushing it against the adjusting spring
68. The control edge of the spool 174 opens the oil flow to the large piston surface of the spool 173.
The surface difference of the spool 173 generates the necessary actuating force to swivel the po-
wertrain in direction Qmax. As a result, the powertrain is swivelled to a large pivoting angle. The push
rod 67 acts as a sensing device and relieves the return spring 69, so that the force ratio between the
adjusting spring 68 + return spring 69 differs from the working pressure. As a result, the spool 174
returns to its regulating position (= closed position) and the actuating procedure is completed.
At the respective working pressure (end of regulation) the powertrain is set again to the maximum
pivoting angle.

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DMVA regulating motor (travel drive) Service Manual
Functional description of the travel motor

Fig. 4 Sectional drawing of the regulator

61 Bushing 69 Pressure spring (regulating spring)

62 Bushing 72 Ball
63 Spring plate 77 Lead seal
64 Adjusting screw 174 Spool
65 Spring plate A High pressure through valve 52
66 Spring plate SK Pressure to control piston 173
67 Pressure rod C High pressure through valve 195
68 Pressure spring (adjusting spring) T to tank

Fig. 5 Magnified view of the surface difference (detail Z)

4.5 Protection
LHB/en/Edition: 03/2010

The two pilot-controlled pressure-relief valves 176 / 177 protect the travel motor against overpressure
(secondary protection).
The suction valves (check valves) 196 prevent cavitation when the secondary pressure-relief valves
176 / 177 respond.

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 Service Manual DMVA regulating motor (travel drive)
Functional description of the travel motor

Fig. 6 Arrangement of the valves for pressure protection

173 Control piston 194 Check valve

176/177 Secondary pressure-relief valves 196 Check valve

4.6 Creeper gear mode

The travel motor is kept at a maximum pivoting angle (creeper gear mode) when the switch S21 (stan-
dard equipment) is actuated on the control console and the solenoid valve Y24 located on the control
oil unit is powered as a result.
When the switch S21 is actuated, the pilot control pressure from the solenoid valve Y24 acts through
the control connection "X" on the spool 174, which is then pushed against the pressure spring 68. As
a result, the high pressure immediately acts on the large surface of the control piston 173 (indepen-
dent of regulation settings) so that the travel motor is switched to a maximum pivoting angle. The ma-
chine is thus easier to steer, while the drawing pull is not increased.
LHB/en/Edition: 03/2010

4.7 Function of brake valve

When a travel motion of the machine is initiated, the working pressure that is being built up acts th-
rough the restrictor bolt 193 (restrictor check valve) on the brake piston 192 and pushes it against the
pressure spring 48. As a result, the flow is opened on the return side A or B so that the oil is displaced
to the tank.
If the pressure in the feed line A or B drops, be it as a result of a steering movement or a change in
load, for example during travel down a slope, the pressure in the spring chamber is reduced through

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DMVA regulating motor (travel drive) Service Manual
Functional description of the travel motor

the restrictor bolt 193. The brake piston 192 is put into braking position by the pressure spring 48,
whereby the equilibrium of forces between the pilot control pressure at the brake piston 192 and the
pressure spring 48 determines the automatic brake function. The brake effect results from the rest-
riction of the oil flow from the motor. Irregular braking of the travel motor is prevented by the check
valves 196 with bypass bores, see Fig. 6.

Fig. 7 Arrangement of the valves for the brake function

45 Valve seat 192 Piston

46 Spring plate 193 Restrictor bolt
47 Lid 194 Check valve
48 Pressure spring
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 Service Manual DMVA regulating motor (travel drive)
Maintenance and repair

5 Maintenance and repair

Note!
Liebherr oil motors do not require any maintenance whatsoever.
This travel motor has been factory-set and its settings should not be changed.
For sealing and repair work, please refer to the separate
repair instructions for DMVA regulating motors.

6 Checking and adjusting the travel motor

Danger!
For inspection, adjustment and repair work, it is necessary to access the undercarriage.
This can be very dangerous for the mechanic. There is a risk of serious injury or event death, if the
machine begins to move.
X Extend the supports.
X Place the attachment on the ground. Lift the undercarriage from the ground, if required.
X Apply the parking brake.
X Establish visual or acoustic contact with the operating personnel.

6.1 Checking and adjusting the begin of regulation of the travel motor
The checking and adjustment of the begin of regulation of the travel motor is described in detail in
group 3 "Adjustment protocol" and "Testing and adjusting tasks".

6.2 Checking and adjusting of the maximum output speed / maximum travel speed
(setting C)

Note!
The maximum output speed of the travel motor is determined by the minimum flow consumption of
the oil motor and the maximum flow volume of the spool for travelling (stroke limitation 160.1/160.2).
The maximum speed is factory-set by the manufacturer and may not be changed.
The minimum flow consumption of the oil motor is limited by the Qmin stop screw 35.

If the maximum travel speed of the vehicle is unsatisfactory, the setting can be adjusted. To determi-
ne the actual value, check the dimension Y of the stroke limitation adjusting screw 160.1 / 160.2.
To determine the maximum travel speed accurately, measure the speed of the universal joint shaft
(connection of gear system and axle) using a HT 460 speed meter (for tools, see group 2.01). For
settings see Tab. 1.
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DMVA regulating motor (travel drive) Service Manual
Checking and adjusting the travel motor

Fig. 8 Control axle / travel at control valve block

100 Compact control block 160.1 Stroke limitation / reverse travel

160.2 Stroke limitation / forward travel

6.3 Checking and adjusting the minimum pivoting angle (setting B)

The minimum pivoting angle, i.e. the minimum oil flow consumption is determined by the stop screw
35. The angle is factory-set by the manufacturer and may not be changed.
To check the position of the stop screw 35 in the mounting plate 32, use dimension X (between the
stop screw 35 and the lock nut 38) as a guide value, see Tab. 1.

Fig. 9 Setting value of Qmin stop screw

32 Mounting plate 38 Lock nut

35 Stop screw 51 Protective cap

Note!
The location of installation of the oil motor depends on the machine model.
LHB/en/Edition: 03/2010

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 Service Manual DMVA regulating motor (travel drive)
Hydraulic schematic of the travel motor

6.4 Checking travel motor for leakage

Oil temperature in machine: 50°C
X Disconnect the leak oil hose to connection T1 and seal the hose.
X Screw a matching hose section to connection T1 on the travel motor and place the other end of
the hose in a suitable oil collection container.
X 2. Put the machine in gear, press the brake pedal to the stop and apply the maximum pressure to
the travel motor (maximum high pressure).
X Measure the volume of leaked oil and compare it with the permissible volume, see Tab. 1.
If there is excessive leakage, replace the oil motor.
X Remove the hose section and reconnect the leak oil hose to connection T1.

Fig. 10 Connection T1 for the leakage check of the travel motor

7 Hydraulic schematic of the travel motor

34 Connecting link 190 Travel brake valve, complete

35 Stop screw 192 Brake piston
67 Pressure rod 193 Restrictor bolt
68 Pressure spring (adjusting spring) 194 Check valve
69 Pressure spring (regulating spring) 195 Shuttle valve
170 Travel motor, complete 196 Check valve
172 Complete powertrain
173 Control piston X Connection for control pressure from sole-
noid valve Y24
174 Spool T1 Leak oil connection
175 Check valve R Pressure/return line connection, reverse
176 Secondary pressure-relief valve V Pressure/return line connection, forward
forward
177 Secondary pressure-relief valve M Measuring connection / control chamber
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reverse pressure

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DMVA regulating motor (travel drive) Service Manual
Hydraulic schematic of the travel motor

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Fig. 11 Hydraulic schematic of the travel motor

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 Service Manual DMVA regulating motor (travel drive)
Hydraulic schematic of the travel motor

Item Item
2 Piston with slipper 34 Connecting link
3 Cylinder with bushing 35 Stop screw
4 Drive shaft 36 Backing ring
5 Pilot plate 37 O-ring
6 Return ball 38 Lock nut
7 Return plate 39 Allen head screw
8 Sliding disc 41 Jacket ring
9 Swivel yoke 42 Pin
10 Locking ring 43 Roll pin
11 Pin 45 Valve seat
12 Pin 46 Spring plate
13 Pressure spring 47 Lid
14 Cylindrical roller bearing 48 Pressure spring
15 Cylindrical roller bearing 50 Screw cap (measuring point M)
16 Cylindrical roller bearing 51 Safety cap
17 Shaft seal 80 Housing
18 O-ring 82 O-ring
19 Snap ring 83 Cylinder pin
20 Snap ring 172 Complete powertrain
21 Allen head screw 173 Control piston
22 Roll pin 192 Piston
31 Screw plug 193 Restrictor bolt
32 Mounting plate 194 Check valve
33 Guide bushing

Note!
Observe setting value B, see Tab. 1.
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DMVA regulating motor (travel drive) Service Manual
Sectional drawings

8 Sectional drawings

LHB/en/Edition: 03/2010

Fig. 12 Sectional drawing of transmission and brake valve

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 Service Manual DMVA regulating motor (travel drive)
Sectional drawings

Item Item
9 Swivel yoke 71 Circlip
30 Mounting plate, complete 72 Ball
31 Screw plug 73 O-ring
32 Mounting plate 74 O-ring
39 Allen head screw 75 Allen head screw
40 Allen head screw 76 Protective cap
44 Pin 77 Lead seal
45 Valve seat 78 Washer
48 Pressure spring 79 Allen head screw
49 O-ring 80 Housing
60 Regulator, complete 81 Cylinder pin
61 Bushing 173 Control piston
62 Bushing 174 Spool
63 Spring plate 175 Check valve
64 Adjusting screw 176 Secondary pressure-relief valve
65 Spring plate 177 Secondary pressure-relief valve
66 Spring plate 192 Piston
67 Pressure rod 193 Restrictor bolt
68 Pressure spring (adjusting spring) 194 Check valve
69 Pressure spring (regulating spring) 195 Shuttle valve
70 Lock nut

Note!
Observe set values A and D, see Tab. 1.
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DMVA regulating motor (travel drive) Service Manual
Sectional drawings

LHB/en/Edition: 03/2010

Fig. 13 Sectional drawing of pilot plate and brake valve

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 Service Manual DMVA regulating motor (travel drive)
Design of hydraulic travel motor

DMVA regulating motor (travel drive)

1 Design of hydraulic travel motor

The axial-piston oil motor is of the swash-plate type. It is flange-mounted to the transmission of the
machine. It consists of a motor housing with built-in powertrain, swivel yoke and a mounting plate with
regulating and adjusting unit.
The mounting plate features a brake valve working in both directions of travel. The mounting plate is
also equipped with the secondary pressure-relief valves and the suction valves.
The flow volume of the variable-displacement pump is fed through connections A or B to the travel
motor and acts on the piston of the powertrain. The pistons (moving in axial direction inside the cy-
linder of the powertrain) act on the cylinder and drive shaft and generate a certain torque.
The regulating and adjusting unit built into the mounting plate adjusts the pivoting angle to the flow
consumption of the oil motor (= flow consumption of the travel motor).
The variable oil flow consumption of the travel motor determines the torque and speed of the drive
shaft. Both values are in inverse ratio, i.e.:
High oil flow consumption Qmax = high torque = low speed of travel motor
Low oil flow consumption Qmax = low torque = high speed of travel motor
The brake valve integrated into the mounting plate restricts the return flow to the control valve block
or the tank respectively, thus slowing down the drive. This approach prevents overspeeding of the
travel motor when travelling down a slope and consequent cavitation.
LHB/en/Edition: 03/2010

Fig. 1 DMVA travel motor

7.28.1
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DMVA regulating motor (travel drive) Service Manual
Technical data

2 Technical data

Machine A 900 C A 900 C ZW A 904 C A 914 C

A 924 C
from serial number 48070 50658 51328 51833
Oil motor DMVA 165 DMVA 165 DMVA 165 DMVA 165
3 3 3
Max. oil flow consumption 165 cm /rev 165 cm /rev 165 cm /rev 165 cm3/rev
Min. oil flow consumption 94 cm3/rev 94 cm3/rev 94 cm3/rev 94 cm3/rev
Begin of regulation (high pressure) 240 bar 240 bar 240 bar 240 bar
End of regulation (high pressure) 320 bar 320 bar 320 bar 320 bar
Max. pivoting angle 22° 22° 22° 22°
Min. pivoting angle 10.8° 10.8° 10.8° 10.8°
Max. permissible leak oil volume 7 l/min 7 l/min 7 l/min 7 l/min
at 350 bar and an oil temperature of 50°C
Settings of oil motor
A Begin of regulation of the oil motor 240 bar 240 bar 240 bar 240 bar
at the adjusting screw 64
B Min. pivoting angle
Dimension X of the stop screw 35
(guide value)
Standard machine 21.0 mm 21.0 mm 21.0 mm 21.0 mm
Speeder 25.0 mm 25.0 mm 25.0 mm 25.0 mm
Standard machine A 924 C 22.5 mm
Type 1050/1051 HD 25.0 mm
C Drive shaft speed When adjusting the drive shaft speed,
Standard machine take into account the tyre size.
Speeder For adjustment values, refer to the adjustment protocols of the re-
spective machine in group 3.
D Secondary pressure-relief valves 380 +20 bar 380 +20 bar 380 +20 bar 380 +20 bar

Tab. 1 Technical data

LHB/en/Edition: 03/2010

7.28.2
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 Service Manual DMVA regulating motor (travel drive)
Description

3 Description

The travel motor consists of the following main components:

– Powertrain 172
– Mounting plate 30
– Regulator 60
The housing 80 encloses the entire powertrain 172 with swivel yoke, piston, pilot plate and sliding
disc.
The housing 80 is screwed to the mounting plate 30. The mounting plate contains the secondary
pressure-relief valves 176/177, the control and regulating unit and the brake valve acting in both di-
rections of travel.

Fig. 2 Design of the travel motor

30 Mounting plate 172 Powertrain, complete

60 Regulator, complete 176 Secondary pressure-relief valve
80 Housing 177 Secondary pressure-relief valve
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DMVA regulating motor (travel drive) Service Manual
Functional description of the travel motor

4 Functional description of the travel motor

4.1 Function of powertrain

The housing 80 encloses the powertrain 172 with the drive shaft 4, cylinder 3, piston 2 with slipper,
etc. Parallel to the drive shaft 4, there are nine pistons 2 arranged in a circle. They run in axial arran-
gement in the cylinder 3, which is in gear with drive shaft 4. The bottom ends of the pistons are desi-
gned as ball joints and sit in slippers. They are held on the swivel yoke 9 by the return ball 6 and the
return plate 7 (swash plate).
The hydrostatic bearing of the slipper on the sliding disc 8 of the swivel yoke 9 (through bores in the
piston 2 and the slippers) reduces the high friction to a minimum, despite the high surface pressure
between the slipper and the swivel yoke 9.
When there is no pressure, the cylinder 3 is pressed by the pressure springs 13 in the return ball 6
against the pilot plate 5. When the pressure increases, the cylinder 3 and the pilot plate 5 are balan-
ced by hydraulic forces in such a way that the oil film at the control surface is maintained at all times,
even under high loads, and the amount of leak oil is reduced to a minimum. Some of the leak oil is
used to lubricate the moving parts of the powertrain and is fed externally back to the tank.
If pressure oil is supplied to the operating connections A or B, the respective four pistons are pres-
surised through the kidney-shaped slots in the pilot plate 5. Another four pistons press the non-ener-
gised oil through the kidney-shaped openings in the piston plate 5 through the connection A or B to
the tank. A ninth piston is situated in the area of the dead centre, i.e. at the point of return from the
pressure to the suction phase.
The oil acting on the four pistons on the pressure side generates a certain force determined by the
pressure and the piston area. This force acts via the pistons 2 with slippers onto the swivel yoke 9.
The radial component of the above force (together with the section of the cylinder acting as a lever
arm) generates a torque which is transferred onto the cylinder 3 and the drive shaft 4. Changing the
pressure side of the travel motor (connection A or B) results in a change of direction of the torque at
the drive shaft 4 (clockwise or anticlockwise rotation respectively).
With every rotary motion of the cylinder 3, the pistons execute a double stroke. That stroke corres-
ponds to the inclination of swivel yoke 9 and determines the amount of oil consumed.

4.2 Function of the regulating unit

The sectional drawing shows the following regulating positions of the travel motor:
The powertrain 172 (swivel yoke 9) is already set to a maximum pivoting angle. The working pressure
acts on the piston face of the control piston 173 (minimum pressure valve at the end of regulation),
see Tab. 1.
The regulating piston 174 is in regulating position, i.e. the flow from the high pressure side through
the check valve 175 to the large piston surface of the spool 173 and the flow from the large piston
surface of the spool 173 to the tank side are blocked. The maximum pivoting angle is determined by
the stop of the spool 173 at the guide bushing 33. The motor remains in this position, until the high
LHB/en/Edition: 03/2010

pressure drops below the pressure value at the end of regulation.

Within the regulated range, the travel motor can reach any position that corresponds to a working
pressure of between Qmax and Qmin. If the working pressure drops below the value at the begin of
regulation, the spool 173 touches the stop screw 35, i.e. the travel motor's flow consumption capacity
is lowest at high drive shaft speed, high speed and low drawing pull.

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 Service Manual DMVA regulating motor (travel drive)
Functional description of the travel motor

Fig. 3 Sectional drawing of the regulating unit (spool)

32 Mounting plate 38 Lock nut

33 Guide bushing 42 Pin
34 Connecting link 50 Measuring connection of the actuating pres-
sure M
35 Stop screw

4.3 Function prior to the begin of regulation

see Fig. 3 and Fig. 4
The pressure oil from the respective high pressure side A or B respectively, acts on the piston ring
surface of the spool 173 through the check valves 175 and the internal bores in the mounting plate
32. The swivel yoke 9 is kept at a small pivoting angle by the connecting link 34. The minimum pivo-
ting angle is limited by the stop screw 35.
The working pressure acts on the spool 174 through the check valves 175. The spool 174 is held by
the preloaded adjusting spring 68 in its basic position so that the flow from the high pressure side
through the check valve 175 to the large piston surface of the spool 173 is blocked. The flow from the
large piston surface of the spool 173 to the tank side is opened. The travel motor remains in this po-
sition until the working pressure exceeds the pressure value of the begin of regulation, see Tab. 1.

4.4 Function from begin of regulation

see Fig. 3 and Fig. 4
The spool 174 is held in the regulating position by the adjusting spring 68 and the return spring 69 (+
the working pressure acting on the shuttle check valve 195). Regulating position of the spool 174
spring force of the return spring 69 + force resulting from the working pressure on the surface diffe-
rence = spring force of the adjusting spring 68.
If the existing working pressure rises above the value at the begin of regulation, it acts on the surface
LHB/en/Edition: 03/2010

difference Ø D - Ø d, (see Fig. 5 on page6) of the spool 174, pushing it against the adjusting spring
68. The control edge of the spool 174 opens the oil flow to the large piston surface of the spool 173.
The surface difference of the spool 173 generates the necessary actuating force to swivel the po-
wertrain in direction Qmax. As a result, the powertrain is swivelled to a large pivoting angle. The push
rod 67 acts as a sensing device and relieves the return spring 69, so that the force ratio between the
adjusting spring 68 + return spring 69 differs from the working pressure. As a result, the spool 174
returns to its regulating position (= closed position) and the actuating procedure is completed.
At the respective working pressure (end of regulation) the powertrain is again set to the maximum
pivoting angle.

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DMVA regulating motor (travel drive) Service Manual
Functional description of the travel motor

Fig. 4 Sectional drawing of the regulator

61 Bushing 69 Pressure spring (regulating spring)

62 Bushing 72 Ball
63 Spring plate 77 Lead seal
64 Adjusting screw 174 Spool
65 Spring plate A High pressure through valve 52
66 Spring plate SK Pressure to control piston 173
67 Pressure rod C High pressure through valve 195
68 Pressure spring (adjusting spring) T to tank

Fig. 5 Magnified view of the surface difference (detail Z)

4.5 Protection
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The two pilot-controlled pressure-relief valves 176 / 177 protect the travel motor against overpressure
(secondary protection).
The suction valves (check valves) 196 prevent cavitation when the secondary pressure-relief valves
176 / 177 respond.

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 Service Manual DMVA regulating motor (travel drive)
Functional description of the travel motor

Fig. 6 Arrangement of the valves at the various sectional levels

192 Brake piston 196 Check valve

195 Shuttle valve l
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Fig. 7 Arrangement of the valves at the various sectional levels

175 Check valve 192 Brake piston

176 Secondary pressure-relief valve 194 Check valve
177 Secondary pressure-relief valve

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DMVA regulating motor (travel drive) Service Manual
Functional description of the travel motor

4.6 Creeper gear mode

The travel motor is kept at a maximum pivoting angle (creeper gear mode) when the switch S21 (stan-
dard equipment) is actuated on the control console and the solenoid valve Y24 located on the control
oil unit is powered as a result.
When the switch S21 is actuated, the pilot control pressure from the solenoid valve Y24 acts through
the control connection "X" on the spool 174, which is then pushed against the pressure spring 68. As
a result, the high pressure immediately acts on the large surface of the control piston 173 (indepen-
dent of regulation settings) so that the travel motor is switched to a maximum pivoting angle. The ma-
chine is thus easier to steer, while the drawing pull is not increased.

4.7 Function of brake valve

When a travel motion of the machine is actuated, the working pressure that is being built up acts th-
rough the restrictor bolt 193 (restrictor check valve) on the brake piston 192 and pushes it against the
pressure spring 48. As a result, the flow is opened on the return side A or B so that the oil is displaced
to the tank.
If the pressure in the feed line A or B drops, be it as a result of a steering movement or a change in
load, for example during travel down a slope, the pressure in the spring chamber is reduced through
the restrictor bolt 193. The brake piston 192 is put into braking position by the pressure spring 48,
whereby the equilibrium of forces between the pilot control pressure at the brake piston 192 and the
pressure spring 48 determines the automatic brake function. The brake effect results from the rest-
riction of the oil flow from the motor. Irregular braking of the travel motor is prevented by the check
valves 196 with bypass bores, see Fig. 6.

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 Service Manual DMVA regulating motor (travel drive)
Maintenance and repair

Fig. 8 Arrangement of the valves for the brake function

45 Valve seat 192 Piston

46 Spring plate 193 Restrictor bolt
47 Lid 194 Check valve
48 Pressure spring

5 Maintenance and repair

LHB/en/Edition: 03/2010

Note!
Liebherr oil motors do not require any maintenance whatsoever.
This travel motor has been factory-set and its settings should not be changed.
For sealing and repair work, please refer to the separate
repair instructions for DMVA regulating motors.

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DMVA regulating motor (travel drive) Service Manual
Checking and adjusting the travel motor

6 Checking and adjusting the travel motor

Danger!
For inspection, adjustment and repair work, it is necessary to access the undercarriage.
This can be very dangerous for the mechanic. There is a risk of serious injury or event death, if the
machine begins to move.
X Extend the supports.
X Place the attachment on the ground. Lift the undercarriage from the ground, if required.
X Apply the parking brake.
X Establish visual or acoustic contact with the operating personnel.

6.1 Checking and adjusting the begin of regulation of the travel motor
The checking and adjustment of the begin of regulation of the travel motor is described in detail in
group 3 "Adjustment protocol" and "Testing and adjusting tasks".

6.2 Checking and adjusting of the maximum output speed / maximum travel speed
(setting C)

Note!
The maximum output speed of the travel motor is determined by the minimum flow consumption of
the oil motor and the maximum flow volume of the spool for travelling (stroke limitation 160.1/160.2).
The maximum speed is factory-set by the manufacturer and may not be changed.
The minimum flow consumption of the oil motor is limited by the Qmin stop screw 35.

If the maximum travel speed of the machine is not correct, check the speed of the universal joint shaft
(connecting gearbox and axle) using a HT 460 speedometer (tool, see group 2.01). For settings, see
adjustment protocol of the respective machine.

LHB/en/Edition: 03/2010

Fig. 9 Control axle / travel at control valve block

100 Compact control block 160.2 Stroke limitation / forward travel

160.1 Stroke limitation / reverse travel

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 Service Manual DMVA regulating motor (travel drive)
Checking and adjusting the travel motor

6.3 Checking and adjusting the minimum pivoting angle (setting B)

The minimum pivoting angle, i.e. the minimum oil flow consumption is determined by the stop screw
35. The angle is factory-set by the manufacturer and may not be changed.
To check the position of the stop screw 35 in the mounting plate 32, use dimension X (between the
stop screw 35 and the lock nut 38) as a guide value, see Tab. 1.

Fig. 10 Setting value of Qmin stop screw

32 Mounting plate 38 Lock nut

35 Stop screw 51 Protective cap

Note!
The location of installation of the oil motor depends on the machine model.

6.4 Checking travel motor for leakage

Oil temperature in machine: 50°C
X Disconnect the leak oil hose to connection T1 and seal the hose.
X Screw a matching hose section to connection T1 on the travel motor and place the other end of
the hose in a suitable oil collection container.
X 2. Put the machine in gear, press the brake pedal to the stop and apply the maximum pressure to
the travel motor (maximum high pressure).
X Measure the volume of leaked oil and compare it with the permissible volume, see Tab. 1.
If there is excessive leakage, replace the oil motor.
X Remove the hose section and reconnect the leak oil hose to connection T1.
LHB/en/Edition: 03/2010

7.28.11
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DMVA regulating motor (travel drive) Service Manual
Hydraulic schematic of the travel motor

Fig. 11 Connection T1 for the leakage check of the travel motor

7 Hydraulic schematic of the travel motor

34 Connecting link 190 Travel brake valve, complete

35 Stop screw 192 Brake piston
67 Pressure rod 193 Restrictor bolt
68 Pressure spring (adjusting spring) 194 Check valve
69 Pressure spring (regulating spring) 195 Shuttle valve
170 Travel motor, complete 196 Check valve
172 Complete powertrain
173 Control piston X Connection for control pressure from sole-
noid valve Y24
174 Spool T1 Leak oil connection
175 Check valve R Pressure/return line connection, reverse
176 Secondary pressure-relief valve V Pressure/return line connection, forward
forward
177 Secondary pressure-relief valve M Measuring connection / control chamber
reverse pressure

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 Service Manual DMVA regulating motor (travel drive)
Hydraulic schematic of the travel motor

Fig. 12 Hydraulic schematic of the travel motor

LHB/en/Edition: 03/2010

Item Item
2 Piston with slipper 34 Connecting link
3 Cylinder with bushing 35 Stop screw
4 Drive shaft 36 Backing ring
5 Pilot plate 37 O-ring

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DMVA regulating motor (travel drive) Service Manual
Hydraulic schematic of the travel motor

Item Item
6 Return ball 38 Lock nut
7 Return plate 39 Allen head screw
8 Sliding disc 41 Jacket ring
9 Swivel yoke 42 Pin
10 Locking ring 43 Roll pin
11 Pin 45 Valve seat
12 Pin 46 Spring plate
13 Pressure spring 47 Lid
14 Cylindrical roller bearing 48 Pressure spring
15 Cylindrical roller bearing 50 Screw cap (measuring point M)
16 Cylindrical roller bearing 51 Protective cap
17 Shaft seal 80 Housing
18 O-ring 82 O-ring
19 Snap ring 83 Cylinder pin
20 Snap ring 172 Complete powertrain
21 Allen head screw 173 Control piston
22 Roll pin 192 Brake piston
31 Screw plug 193 Restrictor bolt
32 Mounting plate 194 Check valve
33 Guide bushing 195 Shuttle valve

Note!
Observe setting value B, see Tab. 1.

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 Service Manual DMVA regulating motor (travel drive)
Sectional drawings

8 Sectional drawings
LHB/en/Edition: 03/2010

Fig. 13 Sectional drawing of transmission and brake valve

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DMVA regulating motor (travel drive) Service Manual
Sectional drawings

Item Item

Item Item
9 Swivel yoke 70 Lock nut
30 Mounting plate, complete 71 Circlip
31 Screw plug 72 Ball
32 Mounting plate 73 O-ring
39 Allen head screw 74 O-ring
40 Allen head screw 75 Allen head screw
44 Pin 76 Protective cap
45 Valve seat 77 Lead seal
48 Pressure spring 78 Washer
49 O-ring 79 Allen head screw
60 Regulator, complete 80 Housing
61 Bushing 81 Cylinder pin
62 Bushing 173 Control piston
63 Spring plate 174 Spool
64 Adjusting screw 175 Check valve
65 Spring plate 176 Secondary pressure-relief valve
66 Spring plate 177 Secondary pressure-relief valve
67 Pressure rod 192 Brake piston
68 Pressure spring (adjusting spring) 193 Restrictor bolt
69 Pressure spring (regulating spring) 194 Check valve

Note!
Observe set values A and D, see Tab. 1.

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7.28.16
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 Service Manual DMVA regulating motor (travel drive)
Sectional drawings
LHB/en/Edition: 03/2010

Fig. 14 Sectional drawing of pilot plate and brake valve

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DMVA regulating motor (travel drive) Service Manual
Sectional drawings

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 Service Manual Hydraulic cylinder
Function

Hydraulic cylinder

1 Function

The LIEBHERR hydraulic cylinders are primarily used as working cylinders for the movement of at-
tachments. Due to their design, they are classified as differential cylinders.
When hydraulic oil is fed to the piston side, the cylinder is extended; when oil is fed to the piston rod
side, the cylinder retracts.
The maximum forces of the cylinder depend on the size and shape of the effective surfaces

Extending Piston surface

Retracting Piston ring surface

and the max. admissible operating pressure, which is greater during extending than retracting. The
speed of the cylinder extending or retracting depends on the amount of oil fed per interval of time,
and on the surface. It is reciprocally proportional to the force, so that it is higher at retracting than at
extending.
LIEBHERR offers hydraulic cylinders for various fields of application that differ in stroke (length of ex-
tension), diameter (power) and cushioning system (end-of-travel cushioning).
Our machines are equipped with hydraulic cylinders with and without end-of-travel cushioning.

Note!
As the machines feature a great range of seals, guides, pistons and cushioning equipment, it was
not possible to cover all components in detail in the service manual. For details, please refer to the
ET spare parts catalogue and the delivery documents.
LHB/en/Edition: 11/2007

Fig. 1 Hydraulic cylinder

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Hydraulic cylinder Service Manual
Description

2 Description

Hydraulic cylinders consist basically of a cylinder tube 10 with welded cylinder base and bearing bore,
a screwed-in piston rod bearing 13 (acting as cylinder head) and a piston rod 8 with bearing bore and
screwed-in piston 12.
To seal off the pressure chambers to the inside and outside, the cylinder is equipped with O-rings and
backing rings, as well as Glyd-Rimseal rings and Stepseal seal rings in the piston 12 and the piston
rod bearing 13. The scraper ring in the piston rod bearing 13 protects the piston rod 8 against dirt.
The guide rings on the piston 12 and in the piston rod bearing 13 guide the piston rod.
For a detailed description of the sealing elements of the piston 12 and the piston rod bearing 13, see
Fig. 3.
For further details concerning the piston see Fig. 16, the end-of-travel cushioning see Fig. 17 and the
stroke reductionsee Fig. 18.

Fig. 2 Exploded view of a hydraulic cylinder with various piston, cushioning and stroke shorte-
ning options.

1 Bushing 20 Hex head screw

2 Sleeve (stroke reduction as optional 25 Circlip
extra)
LHB/en/Edition: 11/2007

3 Piston (stroke reduction as optional extra) 31 Screw

4 Piston nut 32 Cushioning sleeve
8 Piston rod 33 Disc
9 Cushioning sleeve 34 Cushioning pin
10 Cylinder 35 Threaded bushing
12 Piston 60 Retaining washer
13 Piston rod bearing 65 Allen head screw

7.30.2
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 Service Manual Hydraulic cylinder
Description

15 Radial seal ring

Fig. 3 Sealing elements at the piston 12 and the piston rod bearing 13

9 Cushioning sleeve 125 Backing ring

12 Piston 126 Piston guide ring
13 Piston rod bearing 131 Guide ring
25 Ring 132 Backing ring
91 O-ring 133 O-ring
92 Seal ring 134 Scraper ring
121 Piston guide ring 135 O-ring
122 Turcon-Glyd ring 136 Rimseal ring (secondary protection)
123 O-ring 137 O-ring
124 O-ring 138 Turcon Stepseal (primary protection)
LHB/en/Edition: 11/2007

2.1 Cylinder variants, see Fig. 17 / Fig. 18

The uncushioned hydraulic cylinder (type I) is used mainly with supports and with certain (less fre-
quently used) cylinders for working attachments such as grapple and regulating cylinders, etc. and
for on-road travel.
Cushioned hydraulic cylinders can be equipped with one-side and two-side end-of-travel cushioning.
See type II (one-side) and/or type III and type IV (two-side).
Depending on the application, cylinders might be used in conjunction with stroke reduction. The stro-

7.30.3
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Hydraulic cylinder Service Manual
Functional description

ke can be reduced either by inserting a sleeve 2 (type G) on the piston side, or by inserting a piston
3 on the piston rod side (type H). Both methods result in the desired shortening of the piston stroke.

3 Functional description

3.1 One-side end-of-travel cushioning

3.1.1 Extending piston rod 8

The hydraulic oil coming from the control valve block flows through the piston-side connection of the
cylinder 10 and acts on the piston 12. The piston rod is driven out and displaces the oil on the rod
side back through the control valve block to the tank.
Shortly before the end of the stroke is reached, the cushioning sleeve 9 is inserted into the cushioning
bore of the piston rod bearing 13.
When the cushioning sleeve 9 is introduced into the bore, the flow cross-section of the displaced oil
is reduced. The oil is fed from the hydraulic cylinder back to the control valve block. This happens
with the help of three splines sitting around the circumference of the sleeve 9.
The extending motion of the piston rod is slowed down, i.e. cushioned, thanks to the strong restriction
of the return oil flow.

3.1.2 Retracting piston rod 8

The hydraulic oil coming from the control valve block flows through the connection into piston rod be-
aring 13 and pushes against the front face of the cushioning sleeve 9 through the ring gap between
the cushioning sleeve 9 and the piston rod 8 and/or the piston rod bearing 13. Through the radial bo-
res and the splines in the cushioning sleeve 9, the oil acts on the piston 12.
The piston rod retracts and displaces the oil on the piston side through the connection bore and the
control valve block back to the tank.

LHB/en/Edition: 11/2007

Fig. 4 Sectional drawing of the hydraulic cylinder

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 Service Manual Hydraulic cylinder
Functional description

3.2 Two-side end-of-travel cushioning, see Fig. 5

3.2.1 Extending piston rod 8

The hydraulic oil coming from the control valve block flows through the connection into the piston side
of the cylinder and acts on the cushioning pin 31 and the piston 12 via the longitudinal slots.
The piston rod 8 is extended (see 3.1, page 4).

3.2.2 Retracting piston rod 8

The hydraulic oil coming from the control valve block flows through the connection into the piston rod
bearing 13 and acts on the front face of the cushioning sleeve 9 through the ring gap between the
cushioning sleeve 9 and the piston rod 8. The oil acts on the piston 12 through the radial bores and
splines in the cushioning sleeve 9.
The piston rod retracts and displaces the oil on the piston side back to the tank. Shortly before the
end of the stroke, the cushioning pin 31 is inserted into the base of the cylinder 10. When the cushio-
ning sleeve 32 enters the cushioning bore, the flow cross-section of the displaced oil is reduced. The
oil flows through two longitudinal slots arranged along the circumference of the sleeve 32 and/or the
pin 34 from the hydraulic cylinder back to the control block.
The retracting motion of the piston rod is slowed down i.e. cushioned, thanks to the strong restriction
of the return oil flow.

Fig. 5 Partial section of end-of-travel cushioning device

LHB/en/Edition: 11/2007

7.30.5
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Hydraulic cylinder Service Manual
Removal and installation of hydraulic cylinders

4 Removal and installation of hydraulic cylinders

Caution!
The dismantling and installation of a cylinder requires lifting gear such as a crane and additional per-
sonnel.
When the cylinder is placed in its bearings, there is a risk of serious injury to hands and other limbs
that might become caught and crushed between the cylinder and other equipment parts. To prevent
accidents, the following precautionary measures must be taken:
X Drive the vehicle onto level and firm ground. Place the attachments and the support on the
ground. Ensure that the cylinder is stopped in a suitable position for removal and installation.
X Switch off the diesel engine. Relieve the hydraulic pressure from pressure lines. To do this,
switch on the ignition and the pilot control system and actuate the pilot control units several times
to the stop.
X Relieve the preload of hydraulic tank by loosening the breather filter at the tank.
X Secure the hydraulic cylinder by attaching it to lifting tackle. Secure other loose equipment, if ne-
cessary.

4.1 Dismantling
X Disconnect the flange connections of the hydraulic hoses. Collect the escaping oil in a suitable
container.
X If necessary, unscrew and remove the connection block with the pressure line from the piston rod
bearing and the cylinder base.
X Seal the lines and hoses with cover plates, screw caps, plugs etc.

Sealing work on the machine

X Release and drive out the bearing pin connecting the piston rod eye to the equipment. Pull out
stuck bolts using a special removal tool.

Complete dismantling
X Release and drive out both bearing pins from the piston rod and the cylinder tube. Pull out stuck
bolts using a special removal tool.

4.2 Installation
X Using lifting tackle, place the hydraulic cylinder into the bearing block so that the bearing bores in
the cylinder base and in the attachment component are aligned to each other.
X Slightly grease the bearing pin and drive/pull it in.
X Secure both bearing pins.
LHB/en/Edition: 11/2007

X Bleed hydraulic cylinder, see 4.3.

X Move the attachments / support to check their functions and tightness of the cylinder and the hy-
draulic connections.

7.30.6
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 Service Manual Hydraulic cylinder
Removal and installation of hydraulic cylinders

4.3 Bleeding cylinder after repair

4.3.1 Bleeding cylinder without bleeder bores

Caution!
After a repair of the cylinder, there is air trapped in the closed chamber. In connection with oil and
high pressure, this could result in explosive ignition ("diesel effect").
This poses a serious risk to persons and property. Therefore complete the following steps:
X When bleeding the cylinder, never extend/retract it to the stop (to prevent maximum pressure
build-up).

X When connecting the pressure lines and tightening the screw connections, ensure that they are
air-tight.
X To accomplish this, connect the hose on the piston side. Completely extend cylinder slowly and
carefully, at low idle rpm, so that the air on the rod side can escape completely from the cylinder.
Collect escaping oil in a suitable container.
X When the cylinder is fully retracted, connect the line to the piston rod.
X Extend and retract the cylinder several times slowly and carefully, at low idle rpm, so that the re-
maining air in the cylinder can escape towards the tank.
X Re-tighten all the lines. Check the screw connections of the flanges for correct torque.

4.3.2 Bleeding of cylinders with integrated bleeder plug, see Fig. 6

Caution!
The cylinder is under pressure.
When you loosen and unscrew the plug 11, it is possible that residual pressure in the line pushes
out the plug with great force, which can result in serious injury.
X Therefore carefully loosen the plug and release the oil pressure (collect oil in suitable container).

X Unscrew the plug 11. (New versions of this design have separate bleeder valves to which an oil
discharge hose can be connected.)
X Insert a mini measuring connection with an oil discharge hose into the bleeder bore and keep a
suitable collecting container ready.
X Completely extend the cylinder slowly and carefully at low idle rpm.
A mixture of air and oil escapes through the hose into the container.
X Remove the mini measuring connection.
X Be sure to properly replace plug after bleeding (torque: 40 Nm).
LHB/en/Edition: 11/2007

Fig. 6 Bleeder screw at the hydraulic cylinder

7.30.7
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Hydraulic cylinder Service Manual
Replacing seals

5 Replacing seals

Fig. 7 Partial section of the hydraulic cylinder

4 Piston nut 33 Disc

8 Piston rod 121 Piston guide ring
9 Cushioning sleeve 122 Turcon-Glyd ring
12 Piston 123 O-ring
13 Piston rod bearing 124 O-ring
20 Hex head screw 125 Backing ring
25 Snap ring 126 Piston guide ring

5.1 Dismantling

Note!
To disassemble and assemble the piston nut 4 and the piston 12, you need great force. Inadvertent
rotation of the piston rod 8 can lead to damage to the chromium surface finish. To prevent this, com-
plete the following steps:
X Lock the piston rod 8 using a suitable clamping or anti-torsion device.
X Avoid damaging the surface of the piston rod.

X Unscrew the hex head screw 20 with washer 33. Pull the piston rod bearing 13 together with the
piston rod 8 and the piston 12 from the cylinder.
X Place the piston rod on a suitable and clean surface to prevent damage.
X Remove the piston guide rings 121.
X Remove the snap ring 25. Unscrew the piston nut 4 (if any).
X Attach a piston spanner and other special tools (see group 2.05) to the piston 12 . Remove the
piston from the piston rod 8.
LHB/en/Edition: 11/2007

X Hydraulic cylinders with end-of-travel cushioning: Remove the cushioning sleeve 9.

X Remove the piston rod bearing 13 from the piston rod 8.

X Remove all sealing elements from the piston, the piston rod bearing and the cushioning system.

7.30.8
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 Service Manual Hydraulic cylinder
Replacing seals

5.2 Assembly of sealing and guide elements on the piston

5.2.1 Installation in piston rod bearing

X Carefully remove all dirt, dust, chips and other foreign matter from the parts.
X Check all parts for suitability for reuse.
X Parts that show damage to the piston rod such as dents and grooves must be replaced.
X Treat the seal housings with Castrol-Tarp corrosion inhibitor (40g tube - ID no. 830005).
X Apply a little oil to the O-ring 135 / 137 and insert it in the piston rod bearing 13. Apply a little oil
to the seal rings 136 and 138 and insert them into the piston rod bearing 13, see Fig. 10 and Fig.
11.
.

Note!
Ensure that the seal rings 136 and 138 are installed in the correct position and direction (see flow
direction of pressurised oil). Pay attention to the different features of the various seals:
• Turcon - Rimseal 136 (dark grey or turquoise) secondary- flexible - like rubber
• Turcon - Stepseal 138 (light grey) primary, see Fig. 10

Fig. 8 Pressing seal and scraper ring into kidney shape ring for assembly

13 Piston rod bearing 137 O-ring

135 O-ring 138 Turcon Stepseal (primary protection)
136 Rimseal Ring (secondary protection)

X Press Stepseal / Rimseal into kidney shape, avoiding kinking.

X Place the pressed Stepseal / Rimseal over the O-ring 135 / 137 and press it into the groove, in the
direction of the arrow, see Fig. 10.
X Compress and place the scraper ring 134 in the same fashion and insert it in its correct position,
see Fig. 10.

5.2.2 Installing the piston rod bearing

LHB/en/Edition: 11/2007

Caution!
For certain piston guide designs, (see Fig. 9, page 10) use a mounting sleeve c (in the ET catalogue,
included with no. 960) for the installation of the piston guide bearing 13.
If this installation aid is not used, the sealing elements in the piston rod bearing 13 get damaged.
X Screw the mounting sleeve c to the piston rod 8.

X Slide the piston rod bearing 13 over the mounting sleeve c onto the piston rod 8.
X Remove the mounting sleeve c.

7.30.9
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Hydraulic cylinder Service Manual
Replacing seals

Fig. 9 Mount the piston rod bearing using the mounting sleeve for special piston rod shapes

c Mounting sleeve, see tools in group 2.01 / 8 Piston rod

2.12
13 Piston rod bearing

X Slide the cushioning sleeve 9 (not required for hydraulic cylinders without end-of-travel cushio-
ning) onto the piston rod 8.

LHB/en/Edition: 11/2007

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 Service Manual Hydraulic cylinder
Replacing seals

Note!
)

Distinguishing features of the seal rings 136 / 138. The various shapes of the Rimseal 136 are
shown here in comparison to the Stepseal 138 ring (see Fig. 10).

Fig. 10 Distinguishing features of seal rings

136 Rimseal ring s Flange - inclined

138 Stepseal ring g Flange - straight

• Colour Rimseal 136 => dark grey - polished or turquoise (new)

Stepseal 138 => light grey - matt
• Elasticity Rimseal 136 => flexible
Stepseal 138 => rigid
• Shape Rimseal 136 => flange inclined
Stepseal 138 => flange straight

5.2.3 Mounting to piston

Note!
The Turcon-Glyd ring 122 must be expanded before mounting and then returned to its normal sha-
pe, as it can otherwise not be slid over the outer edge and into the groove.
X To facilitate installation, we recommend to heat the Turcon-Glyd ring 122 in a water or oil bath
(approx. 60°C).
LHB/en/Edition: 11/2007

X Apply a little oil to the O-ring 125 and the Turcon-Glyd ring 122 and place them onto the piston 12,
using the mounting sleeve b and the expanding sleeve b (for special tools, see group 2.05).
X After installation, return the Turcon-Glyd ring 122 to its original shape, using the piston tightening
strap.
X Insert the first backing ring 125, the O-ring 124 and the second backing ring into the piston 12.
X Apply Castrol Tarp to the internal piston chamber.

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Hydraulic cylinder Service Manual
Mounting of the cylinder after replacement of the seals

Fig. 11 Mounting of sealing and guide elements to the piston, using the mounting sleeve a and
expanding sleeve b

a Mounting sleeve 121 Piston guide ring

b Expanding sleeve 122 Turcon-Glyd ring
9 Cushioning sleeve 123 O-ring
12 Piston 124 O-ring
13 Piston rod bearing 125 Backing ring

6 Mounting of the cylinder after replacement of the seals

6.1 Mounting of the piston and the piston nut onto the piston rod
X Carefully clean all contact and thread faces between the piston rod, the piston and the piston nut.
Apply a thin layer of Gleitmo 800 lubricant (ID no. 8300004) to both sides (see fuels and lubricants
group 1.50).

Note!
If components are mounted without having been treated with lubricant, the turning distance prescri-
bed according to factory standard 4121 cannot be achieved.
As the parts tend to become jammed (seizing), it is also not possible to remove the component at a
later stage.
LHB/en/Edition: 11/2007

X Apply Gleitmo 800 lubricant (ID no. 8300004) to all components.

X Screw the piston 12 onto the piston rod 8.

X Attach a piston wrench or special tool (see group 2.05) to the piston 12.

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 Service Manual Hydraulic cylinder
Mounting of the cylinder after replacement of the seals

Note!
Mount the piston and the piston nut following the instruction in the factory standard 4121 B in group
1.22.
The drawing number and the date of assembly are engraved on the cylinder. The factory standard
4121-095 is specified in the hydraulic cylinder list, see group 7.31 – 7.37. This information is engra-
ved on all newly manufactured pistons.
X Tighten the piston 12 to the piston rod 8 according to the installation instructions, see group 1.22.

X Remove the piston wrench.

X Screw the piston nut 4 onto the piston rod 8.
X Tighten the piston nut 4 to the piston rod, using a suitable piston nut wrench and following the in-
stallation instructions, see group 1.22.
X Remove the piston nut wrench.
X Secure the piston nut 4 with a snap ring 25 (drill new hole, if necessary).

6.2 Mounting the cushioning sleeve 32

Cylinder with two-side end-of-travel cushioning, see Fig. 12

X Clean the thread of the screw 31 (remove all grease).
X Apply Loctite no. 270 to the thread of the screw 31. Apply Gleitmo 800 to the shank.
X Secure the sleeve 32 with the screw 31 to the piston rod 8 (torque: 130 Nm).

Fig. 12 Mounting the piston-side cushioning sleeve

8 Piston rod 121 Piston guide ring

31 Screw 126 Piston guide ring
LHB/en/Edition: 11/2007

32 Cushioning sleeve

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Hydraulic cylinder Service Manual
Mounting of the cylinder after replacement of the seals

6.3 Mounting the piston rod in the cylinder tube

X Place the inside piston guide straps 121 (hard) and the outside straps 126 (soft) on the piston 12.

Note:
For perfect piston assembly, we offer special calibrating sleeves (mounting sleeves, see group
2.05, 2.12 for a number of piston sizes.
X Place the piston tightening strap and/or the mounting sleeve on the piston 12. Gently tighten the
guide rings 121 and 126 to the piston.

X Push the piston rod 8 (complete with piston 12) carefully into the cylinder 10.
X Remove the piston tightening strap and/or mounting sleeve.

6.4 Mounting the piston rod bearing 8 (plug-in type)

Fig. 13 Installation of piston rod bearing

10 Cylinder tube 33 Disc

13 Piston rod bearing 132 Backing ring
20 Screw 133 O-ring

Mount the slightly oiled O-ring 133 and the backing ring 132. Observe the installation position of the
backing 132 and the O-ring 133 (concave).
X Push the piston rod bearing 13 into the cylinder 10. Observe the positions of the hydraulic con-
nections.
X Screw in the hex head screw or socket screw 20 (with washer 33, if any).

6.5 Mounting the piston rod bearing 8 (screw-in type)

X Attach the assembly wrench (special tool group 2.12) to the piston rod bearing 13.

Note!
LHB/en/Edition: 11/2007

Mount the piston and the piston nut following the instruction in the factory standard 4122 B in group
1.22.
The factory standard 4122-017 is specified in the hydraulic cylinder list, see group 7.34 – 7.36. This
information is engraved on all newly manufactured pistons.
X Tighten the piston rod bearing13 in the cylinder tube 10, following the instructions, see group
1.24.

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 Service Manual Hydraulic cylinder
Piston rod bearing types

Fig. 14 Assembly wrenches for screw-type piston rod bearings

8 Piston rod 13 Piston rod bearing

10 Cylinder tube

7 Piston rod bearing types

Fig. 15 Piston rod bearing types

LHB/en/Edition: 11/2007

D Piston rod bearing 13, plug-in type

E Piston rod bearing 13, screw-in type

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Hydraulic cylinder Service Manual
Piston types on hydraulic cylinders

8 Piston types on hydraulic cylinders

Fig. 16 Piston types 12

A Piston 12 secured with piston nut

B Piston 12 with integrated piston nut

LHB/en/Edition: 11/2007

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 Service Manual Hydraulic cylinder
End-of-travel cushioning

9 End-of-travel cushioning

Fig. 17 Options for end-of-travel cushioning and stroke reduction

Option I without end-of-travel cushioning

LHB/en/Edition: 11/2007

Option II one-side end-of-travel cushioning

Option III two-side end-of-travel cushioning
(old)
Option IV two-side end-of-travel cushioning
(new)

9 Cushioning sleeve 34 Cushioning pin

31 Screw 35 Threaded bushing

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Hydraulic cylinder Service Manual
Stroke reduction

32 Cushioning sleeve

10 Stroke reduction

Fig. 18 Cylinder with stroke reduction

Option G Stroke reduction with sleeve 2

Option H Stroke reduction with piston 3

LHB/en/Edition: 11/2007

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 Service Manual Extension and retraction times of hydraulic cylinders
Function and design

Extension and retraction times of hydraulic

cylinders

1 Function and design

The actual extension and retraction times of a cylinder can deviate from the theoretical (calculated)
times, due to malfunction of components.
In order to identify a cause of a malfunction or fault, the theoretical time must be calculated and com-
pared with the actually measured time.

1.1 Calculation of the theoretical extension and retraction time

The times calculated here are based on the maximum volumetric flow of the spool and the maximum
intake capacity of the cylinder.
Differential cylinders feature different volumes for extension and retraction.

Fig. 1 Data required for the calculation of the extension and retraction times

Ad Piston rod area lH Cylinder stoke length

AD Effective area for extension Va Extension rate = < retraction
Adifference Effective area for retraction Ve Retraction rate = > extension

The following data must be determined for calculation purposes:

X Dimensions of the cylinder; measure the dimensions on site, e.g. for model A 914: stick cylinder
piston rod 95 mm. Alternatively, refer to the specifications in the spare parts catalogue (piston di-
ameter: 140 mm).
X Measure the actual stroke length:
fully retract the cylinder, mark the position of the scraper ring on the piston rod, using a felt-tip pen;
fully extend the cylinder and measure the distance between the scraper ring and the above mark.
LHB/en/Edition: 02/2008

X The actual volumetric flow rate of the spool in the way valve (e.g. for stick cylinder) is specified in
the technical data of the control block, group 7.53: 360 l/min for extension and 220 l/min for retrac-
tion.

1.1.1 Formula
tExtension in seconds = piston area x stroke: Flow rate

7.31.1
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Extension and retraction times of hydraulic cylinders Service Manual
Function and design

tRetraction in seconds = piston ring area x stroke: Flow rate

1.1.2 Sample calculations

To be determined: extension time for stick cylinder of model A 914 B

t = 3.46 3,5 seconds

To be determined: retraction time for stick cylinder of model A 914 B

t = 3.05 3 seconds

Note!
The above example refers to a situation where one spool supplies one working cylinder with oil.
Where one spool supplies two working cylinders with oil, the intake volume must be doubled (e.g.
for stick cylinder with industrial stick).
X In the above formula, multiply the respective figure by 2.

To be determined: extension time for stick cylinder of model A 914 B industrial

t = 3.96 4 seconds

1.2 Measuring the extension and retraction times of a cylinder

X Position the machine in such a way that the cylinder to be measured can be fully extended and
LHB/en/Edition: 02/2008

retracted without posing any danger to persons, machines and adjacent buildings or objects.
X Warm up the machine to its normal operating temperature.
X Actuate the respective pilot control unit to the stop.
X Measure the time of the maximum piston stroke (distance travelled by piston rod) from fully retrac-
ted to fully extended and vice versa (use a stop watch to obtain accurate times).
X Compare the average time with the theoretical time, see 1.1.

7.31.2
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 Service Manual Hydraulic double plunger cylinder
Design

Hydraulic double plunger cylinder

1 Design

The LIEBHERR double plunger cylinder is used as a working cylinder to move the ditch cleaning /
swivel bucket.
The hydraulic cylinder consists of the following main components:
– The cylinders 20 inserted in the ditch cleaning / swivel bucket 10.
– The piston rod 8 connected through the swivel bearing 70 to the bearing block 60.

Fig. 1 Hydraulic double plunger cylinder in a ditch cleaning bucket

8 Piston rod 70 Swivel bearing

10 Ditch cleaning / swivel bucket 72 Double check valve
20 Cylinder 74 Hydr. connections from AS1 control block
60 Bearing block 76 Hydr. connections to bearing block
LHB/en/Edition: 02/2008

The pressure chambers are sealed with Zurcon seal rings in the cylinders 20. The scraper ring in the
cylinder 20 protects the piston rod 8 against dirt. The guide rings 50 guide the piston rod 8 during
movement. For more details regarding the sealing elements, see Fig. 4.
Hydraulic oil is fed to the right side of the piston rod 8, pushing the cylinder to the right and swivelling
the bucket to the right. Hydraulic oil is fed to the left side of the piston rod 8, pushing the cylinder to
the left and swivelling the bucket to the left.
The velocity and the force of the extending cylinder (at constant oil flow and pressure) are the same

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Hydraulic double plunger cylinder Service Manual
Functional description

for both movements.

To ensure that there is no leak oil escaping from the extended cylinder, the return oil is fed through
the hydraulically operated double check valve 72. The oil fed through the bearing block 60 opens the
double check valve 72, so that the return oil from the cylinder 20 can flow back to the control block.
The pressure-relief valves in the double check valve 72 act as secondary safety devices.

2 Functional description

When the button S5L or S5R for swivelling the bucket is actuated, the oil flows from the additional
control block AS1 connection A02 / B02 through lines to the bucket.
The oil in the hydraulic circuit AS1 pressurises the double check valve 72 connection V1-C1 or V2-
C2, through the boreholes A1/A2 in the screw-mounted bearing block 60 and the boreholes in the
piston rod of the cylinder 20.
The pressure in the cylinder 20 pushes the bucket connected to the cylinder 20 outwards and swivels
the bucket around its fulcrum.
The return oil from the other cylinder side (retracting cylinder) is fed through the bearing block 60, the
open double check valve 72 and the lines to the additional control block AS1.

Fig. 2 Hydraulic diagram

LHB/en/Edition: 02/2008

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 Service Manual Hydraulic double plunger cylinder
Exploded view of hydraulic double plunger cylinder

3 Exploded view of hydraulic double plunger cylinder

Fig. 3 Exploded view of double plunger cylinder

1 Hydraulic cylinder, complete 50 Guide ring

8 Piston rod 60 Bearing block
20 Cylinder 70 Swivel bearing
30 Scraper ring 801 Corrosion inhibitor
40 Zurcon-L ring 999 Seal kit
LHB/en/Edition: 02/2008

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Hydraulic double plunger cylinder Service Manual
Sectional drawing of hydraulic double plunger cylinder

4 Sectional drawing of hydraulic double plunger cylinder

8 Piston rod A1 Oil supply to cylinder / right

10 Bearing pipe / bucket A2 Oil supply to cylinder / left
20 Cylinder C Section through oil supply line
30 Scraper ring D Section through oil supply line
40 Zurcon-L ring E Section through bearing block fixture
50 Guide ring F Section through bearing block fixture
60 Bearing block V1 Retracted cylinder
V2 Extended cylinder

LHB/en/Edition: 02/2008

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 Service Manual Hydraulic double plunger cylinder
Sectional drawing of hydraulic double plunger cylinder
LHB/en/Edition: 02/2008

Fig. 4 Sectional drawing of hydraulic double plunger cylinder

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Hydraulic double plunger cylinder Service Manual
Removing / installing double plunger cylinder

5 Removing / installing double plunger cylinder

Caution!
When the cylinder is removed from or installed in its bearings, there is a risk of serious injury to
hands and other limbs that might become caught and crushed between the cylinder and other
equipment parts. To prevent accidents, the following precautionary measures must be taken:
X Drive the vehicle onto level and firm ground. Place the bucket on the ground. Ensure that the
cylinder is stopped in a suitable position for removal and installation.
X Switch off the diesel engine. Release the hydraulic pressure from the pressure lines. To do this,
switch on the ignition and the pilot control system and actuate the pilot control units several times
to the stop.
X Release the preload pressure of the hydraulic tank by loosening the breather filter at the tank.
X Secure the swivel bearing by attaching it to lifting tackle. If necessary, secure the bucket.

5.1 Dismantling, see Fig. 5

X Remove the hydraulic hoses from the double check valve 62 and collect the escaping oil in a sui-
table container with the necessary capacity (as piston rod 8 will be moved).
X Move the piston rod 8 to the stop.
X Remove the snap rings 93 and the shims 92.
X Remove the plug 67 of the inlet bore 10a at the bearing pipe / bucket.
X By moving the swivel bearing 70 , move the bearing block 60 with the piston rod 8 in the cylinders
20 in axial direction until the 1st Allen head screw 62 is aligned with the access bore 10a.
X 1. Remove the Allen head screw 62, and move the piston rod 8 further in axial direction to the next
Allen head screw 62 to be removed, etc.
X Pull out the pin 90 between the two tabs 90 and the bearing block 60. If necessary, use a special
removal tool to pull out the pin 90.
X Remove the flanges with hoses from the bearing block 60.
X Remove the bearing block 60 and the seal 66 (roll pins 61 remain in the piston rod 8).

Note!
The locking mechanism of the cylinders 20 in the bearing pipe / bucket comes in two versions:
– With small buckets, one cylinder 20 is locked with a spacer 110 at the pipe end, and the other
cylinder 20 is locked with a locking bolt 82.
– With large (wide) buckets, the two cylinders 20 are locked with a locking bolt 82.

X Release the locking bolt 82 and remove it from the bearing pipe/bucket.
X Remove the seal cover 80.
LHB/en/Edition: 02/2008

X Through the access borehole 10b on the bearing pipe /bucket, push the following parts from the
bearing pipe / bucket: cylinder 20, piston rod 8, cylinder 20 and spacer 110 (if installed).
X Carefully place the piston rod 8 on a clean surface and reseal the cylinder 20, if necessary, see 6.

7.32.6
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 Service Manual Hydraulic double plunger cylinder
Removing / installing double plunger cylinder

5.2 Installation, see Fig. 5

X Clean the inside of the bearing pipe / bucket.
X Insert the spacer 110 (for small buckets) or a bearing bolt 82 (for wide buckets) in the bearing pipe
/ bucket.
X Mount the complete hydraulic cylinder and push it into the bearing pipe / bucket to the stop at the
spacer of bolt.
X Place the seal kit 66 on the bearing pipe / bucket.
X Insert the seal rings 64 in the piston rod 8.
X Ensure that the roll pins 67 are correctly inserted in the bearing block 60.
X Place the bearing block 60 in the correct position on the piston rod 8 (observe correct position of
the seal rings 64).
X Move the piston rod in axial and radial direction until the 1st through-hole for the Allen head screws
62 is in line with the access borehole 10a.
X 1. Insert and tighten the 1st Allen head screw 62, and move the piston rod 8 further in axial direc-
tion to the next Allen head screw 62 to be tightened, etc.
Tighten all screws according to the factory standard, see group 1.20.
X Seal the access borehole 10a with the plug 65.
X When the piston rod 8 is in one of its maximum positions, apply a little grease to the pin 91 and
drive it in between the two tabs 90 and the bearing block 60.
X Insert the shims 91 and the snap rings 93.
X Reconnect the flanges with hoses to the bearing block 60.
X Connect the hydraulic hoses from the double check valve 72 to the bearing block 60 according to
the relevant instructions, see 5.3.
X Bleed the hydraulic cylinders, see 5.3.
X Apply maximum pressure to both cylinders 20 (max. working pressure) to test them for leakage.
X Preload the seal 66 with the pressure spring 67:
If the spring preload settings are adjusted correctly with the clamping bolt 68 , the seal is pu-
shed in all positions against the bearing pipe / bucket.

Note!
When working in water or mud, there is a risk that dirt collects in the bearing pipe / bucket, even if
the seal 66 is in its correct position. During winter time, the sliding face between the seal and the
bearing pipe might freeze tight.
X If this occurs, clean / flush the bearing pipe ,see 5.4.
X To prevent seizing, apply Gleitmo 900 onto the sliding face of the seal and the bearing pipe, see
group 1.50.
LHB/en/Edition: 02/2008

7.32.7
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Hydraulic double plunger cylinder Service Manual
Removing / installing double plunger cylinder

1 Hydraulic cylinder, complete 67 Plug

10 Ditch cleaning bucket 70 Swivel bearing
10a Access borehole / screws 72 Double check valve
10b Access borehole / spacer / cylinder 80 Lid
60 Bearing block 82 Locking bolt
61 Roll pin 90 Tabs
62 Allen head screw 91 Pin
63 Seal ring 92 Shim
64 Pressure spring 93 Snap ring
65 Clamping screw 110 Spacer
66 Seal

LHB/en/Edition: 02/2008

7.32.8
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 Service Manual Hydraulic double plunger cylinder
Removing / installing double plunger cylinder

Fig. 5 Assembly and dismantling of the double plunger cylinder

5.3 Bleeding cylinder after repair

LHB/en/Edition: 02/2008

Caution!
After a repair of the cylinder, there is air trapped in the closed chamber. In connection with oil and
high pressure, this could result in explosive ignition ("diesel effect").
This poses a serious risk to persons and property. To prevent this, complete the following steps:
X When bleeding the cylinder, never extend/retract it to the stop (to prevent maximum pressure
build-up).

X When connecting the pressure lines and tightening the screw connections, ensure that they are

7.32.9
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Hydraulic double plunger cylinder Service Manual
Removing / installing double plunger cylinder

air-tight.
X Connect the hose and completely extend one cylinder slowly and carefully, at low idle rpm, so that
the air at the other cylinder can escape completely. Collect escaping oil in a suitable container.
X When the cylinder is fully extended, connect the other line.
X Extend and retract the cylinder several times slowly and carefully, at low idle rpm, so that the re-
maining air in the cylinder can escape towards the tank.
X Re-tighten all the lines. Check the screw connections of the flanges for correct torque.
X Now fully pressurise the two cylinder (maximum pressure).

5.4 Maintenance
The bucket maintenance is limited to regular lubrication of the bearing of the bucket and the swivel
bucket. The cylinder does not require any maintenance.
In connection with certain applications, dirt might enter the bearing pipe / bucket near the cylinder,
despite proper preloading and position of the seal 66. In this case, we recommend flushing / cleaning
the system as follows:
X Remove the plug 67.
X Screw off the plug 68 (G1/2“) from the seal 68 and connect the adapter for the water hose and
then connect the water hose.
X Flush the inside of the pipe with water.
X Swivel the bucket several times to remove the dirt from the inside of the pipe.
X After cleaning is completed, disconnect the water line and replace the plug 67 / 68.

Fig. 6 Sealing of bearing pipe

66 Seal 68 Plug
67 Plug
LHB/en/Edition: 02/2008

7.32.10
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 Service Manual Hydraulic double plunger cylinder
Replacing seals

6 Replacing seals

Note!
When dismantling and installing the piston rod 8 , handle the part with special caution as the chro-
mium surface could easily be damaged. Such damage could lead to leakage.
X Avoid damaging the surface of the piston rod.

6.1 Dismantling
X Remove the cylinder 20 with the piston rod 8 from the swivel bucket, see 5.
X Pull the cylinders 20 on both sides from the piston rod 8.
X Remove the scraper ring 30 from the cylinder 20.

Caution!
As it is somewhat difficult to remove the Zurcon seal ring 40 , there is a risk of damage to the groove
faces in the cylinder, which in turn can lead to leakage after installation of the new seal ring 60.
X Do not attempt to remove the seal ring 60 from the groove with a sharp-edged tool.
X Carefully insert a pin-type tool (e.g. tack) into the seal ring 60 and lift it from the cylinder 20.

X If necessary, remove the guide rings 50 from the cylinder 20.

6.2 Assembly
X Carefully remove all dirt, dust, chips and other extraneous material from the parts.
X Check all parts for suitability for reuse.
X Parts that show damage to the piston rod such as dents and grooves near the seal must be re-
placed.
X Treat the seal housings with LIEBHERR corrosion inhibitor (Tarp 40g tube - ID no. 830005).
X Apply a little grease to the guide rings 50 and insert them into the cylinder 20.

Note!
Incorrectly installed seal rings can cause leakage at the cylinder seal.
X Observe correct position for installation (direction of pressure!) of the seal ring 40!

X Apply a little oil to the seal ring 40 and squeeze it together, see Fig. 8, avoiding kinking.
X Insert the seal ring 40 into the cylinder 20.
X Squeeze and place the scraper ring 30 in the same way, see Fig. 8, and insert it in its correct po-
sition, see Fig. 7.
LHB/en/Edition: 02/2008

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Hydraulic double plunger cylinder Service Manual
Replacing seals

Fig. 7 Detailed drawing

8 Piston rod 40 Zurcon-L ring

10 Bearing pipe / ditch cleaning bucket 50 Guide ring
20 Cylinder A1 Oil supply to cylinder / right
30 Scraper ring A2 Oil supply to cylinder / left

LHB/en/Edition: 02/2008

Fig. 8 Installation of sealing rings

20 Cylinder 40 Zurcon Z ring (secondary protection)

30 Scraper ring

7.32.12
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MJFCIFSS
 Service Manual Control oil and regulating unit
Function

Control oil and regulating unit

1 Function

The control oil and regulating unit limits the pressure generated by the servo pump and the regulating
pressures for the working pumps.
The servo pressure is distributed through the control oil and regulating unit to the various solenoid
valves for oscillating axle support, creeper gear shifting or application of the multi-disc brake of the
slewing gear.
The pressure necessary for emergency operation is maintained in the accumulator.

Fig. 1 Control oil and regulating unit

2 Description

The control oil unit 50 consists primarily of an aluminium block. At its front, it is equipped with a pres-
sure-relief valve 51 of the cartridge type that is screwed into the block.
At the top of the unit, the solenoid valves Y3, Y7 and Y66 are integrated into the block. The control
oil unit 50 also features the solenoid valve Y24 for creeper gear shifting, which is located at the side
LHB/en/Edition: 03/2010

of the unit. The measuring point 49 and the accumulator are screw-mounted to the top of the unit.
The measuring points 57 (Up - reduction Y51) and 59 (power control Y50) are located on the respec-
tive variable-displacement pump, see Fig. 2.
The pressure filter 52 is screwed into the base of the unit beside the proportional solenoid valves Y50
and Y51. The control oil block also features an integrated check valve 53.

7.41.1
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Control oil and regulating unit Service Manual
Description

2.1 Arrangement of measuring points

Stationary measuring points 49, 57 and 59 are provided for the measurement of the pressures in the
control oil unit.

Measuring point 49
At this point, the current pilot pressure of the entire pilot control system is measured. For instructions
on how to check pressures, see main group 6.

Measuring point 57 at variable-displacement pump 20

At this point, the control pressure for Up-reduction is measured, which is generated by the solenoid
valve Y51. For details, see flow reduction in group 16.20.

Measuring point 59 at variable-displacement pump 20

At this point, the control pressure for the power control is measured, which is generated by the sole-
noid valve Y50. For details, see power change in groups 7.02 and 7.05.

Fig. 2 Measuring points at the variable-displacement pumps

a A 900 C Litronic b A 904 C Litronic

LHB/en/Edition: 03/2010

7.41.2
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 Service Manual Control oil and regulating unit
Functional description

Fig. 3 Control oil and regulating unit 50

49 Measuring point / control pressure 56 Dummy plate

50 Control oil and regulating unit Y3 Solenoid valve / servo release
51 Pressure-relief valve Y7 Solenoid valve / slewing gear brake
52 Pressure filter Y24 Solenoid valve / creeper gear
53 Check valve Y50 Proportional solenoid valve / power con-
trol
54 Accumulator Y51 Proportional solenoid valve / LS control
55 Dummy plate Y66 Solenoid valve / oscillating axle support

3 Functional description

(see Fig. 3 on page3)

LHB/en/Edition: 03/2010

3.1 Generation of servo pressure

The control oil unit is supplied from the gear pump with oil through connection P. The unit contains
the pressure-relief valve 51 of the cartridge type that is screwed into the unit. It limits the control pres-
sure to a preset value (see adjustment protocol).
The oil flows through the filter 52 and the check valve 53 to the accumulator 54. The accumulator 54
allows for a small number of control operations after the diesel engine has been shut down or in the
event of a gear pump failure.

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Control oil and regulating unit Service Manual
Functional description

The connection P1 is located behind the filter 52. It provides control pressure to the foot pedal.

3.2 Function of the switching solenoid valves

Through the pressure channels in the control oil unit, the pressure oil acts on the switching solenoid
valves Y3, Y7, Y24 and Y66 and on the regulating solenoid valves Y50 and Y51.
When switched, the solenoid valves Y3, Y66 and Y7 provide control pressure to the outlets A1, A2
or A3 and Y24, output A. In neutral position, these outlets are connected to the tank.
Through the connection A1, the solenoid valve Y3 releases control pressure for the pilot control units.
Through the connection A3, the solenoid valve Y7 controls the multi-disc brake in the slewing gear
mechanism.
Through the connection A, the solenoid valve Y24 switches between creeper and on-road gear.
Through the connection A2, the solenoid valve Y66 applies pressure to the circuit for the control of
the oscillating axle support.

3.3 Proportional solenoid valves Y50 / Y51

The proportional solenoid valves for the power control Y50 or flow limitation Y51 of the working
pumps of the control oil unit are used to build up a pressure at the unit's output. This pressure is de-
termined by the actual solenoid current.
The outlet "LR" of the solenoid valve Y50 is connected to connection "X3", which is the pressure
connection for the power control of the working pumps.
The proportional solenoid valve Y51 regulates the control pressure p(LS), which determines the limi-
tation of the pivoting angle of the working pump. This pressure also acts on connection X4 of the
pump regulator. Via the LS regulator, it reduces the preset (UP reduction) and thus limits the maxi-
mum pump flow. This pressure is thus referred to as p (Upred) in other groups in this manual.

LHB/en/Edition: 03/2010

7.41.4
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MJFCIFSS
 Service Manual Control oil and regulating unit
Characteristics of the proportional solenoid valves Y50 and Y51

4 Characteristics of the proportional solenoid valves Y50 and Y51

Fig. 4 Regulation diagrams

a = Y51
b = Y50

The regulation characteristic illustrates the relationship between the input current (I) of the regulating
solenoids and the regulating pressure (p) at the outlets LR or LS.
The effect of the pressures p (GLR) at the outlet LR or p (UPred) at the outlet LS on the power set-
tings and/or the limitation of the pivoting angle of the respective working pumps is described in group
7.
The regulation characteristic of a proportional solenoid valve can be checked by measuring a few
pressure values at the outlet LR (or LS respectively) and comparing them with the solenoid current
ILR of Y50 (or Iev of Y51).
The measurement and subsequent adjustment of the currents IY50 and IY51/EV1 to fixed values can
LHB/en/Edition: 03/2010

be executed with sufficient accuracy by means of the screen menus (see group 8.71).

5 Emergency position of the proportional solenoid valves Y50 / Y51

By removing the cotter pin 2 and tilting the lever 3 into a horizontal position, the solenoid valves Y50
and Y51 can be brought into a pre-defined emergency position.
During operation in emergency position, the connecting plug 1 at the proportional solenoid valve must

7.41.5
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MJFCIFSS
Control oil and regulating unit Service Manual
Emergency position of the proportional solenoid valves Y50 / Y51

be unplugged in order to prevent interference from the control current.

5.1 Adjustment of the emergency position

Set the regulating pressure to the desired fixed value by proceeding as follows:
X Connect a pressure sensor to the measuring point 57 or 59 respectively,(see “Measuring points
at the variable-displacement pumps” on page 2).
X While the engine is running and the lever 3 is in a horizontal position, remove the lock nut 4 and
turn the adjusting screw 5 until the desired pressure is reached.
X Re-tighten the lock nut 4, holding the adjusting screw 5 in its position and re-check the pressure.

Fig. 5 Emergency position of the proportional solenoid valves Y50 and Y51

1 Plug connection 5 Adjusting screw

2 Cotter pin Y50 Proportional solenoid valve / power con-
trol
3 Lever Y51 Proportional solenoid valve / LS control
LHB/en/Edition: 03/2010

4 Lock nut

7.41.6
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MJFCIFSS
 Service Manual Control oil and regulating unit
Maintenance

6 Maintenance

7 Changing the filter cartridge in the control oil unit

The pressure filter 2 is located at the bottom of the control oil unit 50.

Note!
Cleaning and re-using the filter cartridge is prohibited!
X Replace the cartridge 4 each time you open the filter pot 6.

X Unscrew the filter pot 6 of the pressure filter 2 and collect the escaping oil in an oil collecting pan.
X Pull out the filter cartridge 4, allow the oil to drain off and dispose of the cartridge according to the
applicable safety regulations.
X Clean the filter pot 6.
X Apply a little hydraulic oil to the threads and sealing faces at the filter pot 6 and to the control oil
unit 50 as well as to the sealing rings 5 and 7.
X Carefully place the new filter cartridge 4 onto the mounting stud 3.
X Screw in the filter pot 6 to the stop and turn it out by 1/4 revolution (90°).
X Start the engine and check the pressure filter for leakage.

Fig. 6 Control oil unit with pressure filter (example)

2 Pressure filter 6 Filter pot

3 Mounting stud 7 Filter pot sealing ring
4 Filter cartridge 8 Accumulator
5 Filter cartridge sealing ring 50 Control oil unit
LHB/en/Edition: 03/2010

7.41.7
copyright by

MJFCIFSS
Control oil and regulating unit Service Manual
Changing the filter cartridge in the control oil unit

LHB/en/Edition: 03/2010

7.41.8
copyright by

MJFCIFSS
 Service Manual Pilot control unit 1x (travelling foot pedal)
Design

Pilot control unit 1x (travelling foot pedal)

1 Design

The operator controls the operations of the travel gear by means of a foot pedal, to the right, in front
of his seat, in the running plate of the base of the operator's platform. It actuates the pilot control unit.
A regulating piston 12 (pressure control valve) complete with pressure, return and control connec-
tions is inserted in an axial position into the housing 6. The pedal 2 attached to the top of the regula-
ting piston 12 is used to operate it. The foot pedal 2 can be pressed down and acts on a spring-loaded
pushrod. This actuates the regulating piston 12 below the pedal together with the regulating spring
25 and the return spring, opening the pressure channel P (outlet A).
The pushrod, guide bushing etc. are protected against dirt by a cap.

Fig. 1 Pilot control unit 1x, with hydraulic schematic

LHB/en/Edition: 12/2009

7.42.1
copyright by

MJFCIFSS
Pilot control unit 1x (travelling foot pedal) Service Manual
Functional description

2 Functional description

Fig. 3 / Fig. 4
The pilot control unit is of the pressure regulating type. That means, regulating piston 12 of the pilot
control unit builds up pressure on the discharge side, between pilot control unit and control valve
block, and is, thus, shifted, against the pressure from pressure spring 25.
When the pedal 2 is moved, the pushrod 98.1 is pushed down, and the regulating spring 25 shifts the
regulating piston 12. Control oil flows from the pressure channel P through the radial and axial bores
in the regulating piston 12 to the connection 1 and the control line to the solenoid valve for forward /
reverse travel and to the control connections at the control valve block 6.
As the spool 12 in the housing 6 is pressurised, a set pressure that is proportional to the pre-defined
lever travel (Fig. 2) is built up. The pressure acts on the piston surface of the regulating piston 12 and
shifts the regulating piston 12 against regulating spring 25 until the connection with the channel P is
blocked.
Depending on the position of the pedal 2 and the stroke travel of the pushrod 98.1, a preset pilot pres-
sure is established, shifting the spool 12 proportionally to the pressure increase. At a set pressure
(corresponding to the end of the fine-control phase of the spool), the pushrod 98.1 moves the regu-
lating piston 12 downwards. At this point, maximum control pressure is applied to the spool.

3 Repair

3.1 Dismantling of the regulating unit

X Remove hex head screws 86.
X Remove the protective cap 98.5. Remove the plate 1 together with the pedal 2.
X Pull the pushrod 98.1 together with the bushing 98.2 from the housing 6, push the pushrod 98.1
from the bushing 98.2 and remove the O-ring 98.4 and the PDF seal 98.3 from the bushing 98.2.
X Press the regulating piston 12 together with the pressure springs 25 and 26 and the spring plate
15 with disc 23 from the housing 6, pushing it upwards.
X Remove the split disc 23 from the spring plate 15.
X Pull out the regulating piston 12. Remove the pressure spring 25 together with the washers 37 /
38.

3.2 Installation of regulating unit

Before installation, clean all parts and check whether they are fit for re-use.
X Place the washers 37 / 38, the pressure spring 25 and the spring plate 15 on the regulating piston
12. Mount the split disc 23.
X Insert the spring plate 15 together with the preassembled regulating piston 12 and the pressure
springs 26 and 28 into the housing 6 and slide into the bushing 17.
LHB/en/Edition: 12/2009

X Insert a new O-ring 98.4 and PDF seal 98.3 in the bushing 98.2.
X Insert the pushrod 98.1 and install the bushing 98.2 with the pushrod 98.1 in the housing 6.
X Mount the plate 1 and insert the screws 86 together with the washers 85.
X Screw in bolt 7 with the retaining washer 9. Secure it with the cotter pin 11 (see Fig. 3).
X Replace the protective cap 98.5 . Check the pilot control unit for correct operation.

7.42.2
copyright by

MJFCIFSS
 Service Manual Pilot control unit 1x (travelling foot pedal)
Repair

Fig. 2 Diagram: c = control pressure in bar, d = lever displacement in angular degrees

Installed in equipment from serial number Point a Point b

A 900 C Litronic from 14675 6.5 bar 25 bar
A 900 C ZW Litronic, from 21034 6.5 bar 25 bar
A 904 C Litronic from 16000 6.5 bar 25 bar
A 914 C Litronic from 35112 6.5 bar 25 bar
A 924 C Litronic from 34519 6.5 bar 25 bar

A 900 C Litronic from 47851 6.0 bar 27 bar

A 904 C Litronic from 48333 6.0 bar 27 bar
A 914 C Litronic from 48333 6.0 bar 27 bar
A 924 C Litronic from 48333 6.0 bar 27 bar
LHB/en/Edition: 12/2009

7.42.3
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MJFCIFSS
Pilot control unit 1x (travelling foot pedal) Service Manual
Repair

3.3 Exploded view

Fig. 3 Exploded drawing of pilot control unit

1 Plate 26 Pressure spring (return spring)

2 Pedal 37 Washer
6 Housing 38 Washer
7 Bolt 85 Retaining washer
9 Washer 86 Hex head screw
11 Cotter pin 98 Repair kit
12 Regulating piston 98.1 Pushrod
15 Spring plate 98.2 Bushing
17 Bushing (pressed in) 98.3 PDF seal
23 Washer 98.4 O-ring
25 Pressure spring (regulating spring) 98.5 Protective cap
LHB/en/Edition: 12/2009

7.42.4
copyright by

MJFCIFSS
 Service Manual Pilot control unit 1x (travelling foot pedal)
Repair

3.4 Sectional drawing

Fig. 4 Sectional drawing: pilot control unit

LHB/en/Edition: 12/2009

7.42.5
copyright by

MJFCIFSS
Pilot control unit 1x (travelling foot pedal) Service Manual
Repair

LHB/en/Edition: 12/2009

7.42.6
copyright by

MJFCIFSS
 Service Manual Pilot control valve 2 x
Description

Pilot control valve 2 x

1 Description

The two pilot control valves with foot pedals, in front of the operator's seat to the left, in the rnning
plate of the base of the operator's platform, control the operations of the accessory kit.
There are two regulating pistons 12 (pressure control valves), sitting in an axial position in
housing 1, complete with pressure, return and control connections. There are two pedals 2 and 3 on
top, to actuate regulating piston 12.
The two pedals 2 / 3 can be pressed down, and then actuate a spring-loaded pushrod via a threaded
stud. This actuates regulating piston 12 underneath (with regulation spring and return spring) and,
thus, opens it towards pressure channel P, outlet 1/2.
There is a cover to protect pushrod, guide bushing etc. against dirt.

Fig. 1 Pilot control valve 2 x with hydraulic diagram

LHB/en/Edition: 09/2004

7.44.1
copyright by

MJFCIFSS
Pilot control valve 2 x Service Manual
Functional description

2 Functional description

see Fig. 3 / Fig. 4

The pilot control valve is of the pressure regulating type. That means, regulating piston 12 of the pilot
control valve builds up pressure on the discharge side, between pilot control valve and control valve
block, and is, thus, shifted, against the pressure from pressure spring 25.
When pedals 2 and/or 3 are actuated, threaded stud 47 presses pushrod 98.1 down and shifts regu-
lating piston 12 via regulating spring 25. The radial and axial bores in regulating psiton 12 let control
oil from pressure channel P enter into connection 1 or 2 (see Fig. 4) and the control line to flow to one
of the control connections on the additional axle of the control valve block.
Pressurising the spools in the control block will build up a certain pressure which is proportional to
the pre-defined displacement of the lever (see Fig. 2). The presssure acts on the face of regulating
piston 12 and shifts it against regulating spring 25 until the connection with channel P is interrupted.
Depending on how pedal 2/3 is positioned, and what the stroke of pushrod 98.1 is, there will be a
certain pilot pressure, which will shift the spool proportionally. At a certain pressure (which corres-
ponds to the end of the fine control phase of the spool), pushrod 98.1 will move regulating piston 12
down directly. At this point, the spool will receive the max. control pressure.
There is a valve insert 20 in housing 1 of the pilot control valves, a check valve between the control con-
nections. As soon as the actuation of the pilot control valve allows control pressure to flow to the control
valve block via a control connection, the control oil will, at the same time, act on shuttle valve 20. Ball 45
in valve 20 shuts off the connection with the other control connection so that the pressure attained is
available for further control operations via connection 7 (which is closed at this point).

3 Repair

3.1 Dismantling the regulating unit

X Lift pedal 2 / 3
X Remove protective covers 98.5. Remove screws 46. Remove plate 10 complete with pedals
2 / 3.
X Pull pushrod 98.1 with bushing 98.2 from housing 1.
X Press pushrod 98.1 out of bushing 98.2.
X Remove O-ring 98.4 and PDF seal 98.3 from bushing 98.2.
X Press regulating piston 12 complete out of plate 10 (from below), complete with pressure springs
25 and 26 and spring plate 15 with disc 23.
X Remove disc 23 from spring plate 15.
X Pull out regulating piston 12.
X Remove pressure spring 25 with washers 49 / 50.
LHB/en/Edition: 09/2004

3.2 Installing the regulating unit

Before installation, be sure to clean all parts and check whether they are fit for re-use.

7.44.2
copyright by

MJFCIFSS
 Service Manual Pilot control valve 2 x
Repair

X Place washers 49 / 50, pressure spring 25 and spring plate 15 on regulating piston 12. Place
disc 23.
X Push spring plate 15 into housing 10 and bushing 16, complete with pre-installed regulating piston
12 and pressure spring 25 / 26.
X Install new O-ring 98.4 and PDF seal 98.3 in bushing 98.2.
X Insert pushrod 98.1. Install bushing 98.2 complete with pushrod 98.1 in housing 1.
X Place plate 10 complete with pedals 2 / 3. Screw in screws 46.
X Install protective covers 98.5.
X Adjusting pilot control valve

3.3 Pilot control valve adjustment in zero position

The pilot control valve should be adjusted in such a way that the max. control pressure can be rea-
ched in the extreme position (stop), and pedals 2 / 3 can be operated in a comfortable and ergonomic
position.
To adjust: Loosen locknut 48. Turn stud 47 (see Fig. 1) until the pedals reach their new neutral / end
positions and fulfil the conditions as mentioned above.
Install a measuring point to measure the control pressure between connection 1 / 2 and the connec-
tion at the spool / control valve block in question.

3.4 Checking shuttle valve 20

X Valve insert 20 has been installed using Loctite. Heat, and remove completely from housing, using
an Allen key. Be careful with ball 45.
X Check valve for dirt and damage.
X Install ball 45. Install seal 40. Apply Loctite 572 to valve insert 20 and screw in completely
(torque: 10 Nm).
.
LHB/en/Edition: 09/2004

Fig. 2 Diagram: c = control pressure in bar, d = lever displacement in angular degree

Contained in equipment starting with serial number Point a Point b

A 900 C Litronic from 14675 5.8 -0.3 bar 24.3 bar
A 904 C Litronic from 16000 5.8 -0.3 bar 24.3 bar

7.44.3
copyright by

MJFCIFSS
Pilot control valve 2 x Service Manual
Exploded view

4 Exploded view

Fig. 3 Exploded drawing: pilot control valve

1 Housing 40 Seal ring

2 Pedal to the left 41 Washer
2.1 Bushing 42 Washer
3 Pedal to the right 45 Ball
3.1 Bushing 46 Hex head Screw
10 Plate 47 Threaded stud
11 Pin 48 Hex nut
12 Regulating piston 50 Screw plug
13 Bushing (pressed in) 51 Seal ring
15 Spring plate 52 Snap ring
16 Bushing 98 Repair kit
20 Valve insert 98.1 Pushrod
23 Washer 98.2 Bushing
25 Pressure spring (regulating spring) 98.3 PDF seal
26 Pressure spring (return spring) 98.4 O-ring
LHB/en/Edition: 09/2004

33 Screw plug 98.5 Protective cover

35 Plug

7.44.4
copyright by

MJFCIFSS
 Service Manual Pilot control valve 2 x
Sectional drawing

5 Sectional drawing
LHB/en/Edition: 09/2004

Fig. 4 Sectional drawing

7.44.5
copyright by

MJFCIFSS
Pilot control valve 2 x Service Manual
Sectional drawing

LHB/en/Edition: 09/2004

7.44.6
copyright by

MJFCIFSS
 Service Manual Pilot control valve 2 x
Description

Pilot control valve 2 x

1 Description

The operator controls outrigger and/or blade support operations by means of the pilot control valve
and lever (on the control console, to the right).
There are two regulating pistons 12 (pressure control valves), sitting in an axial position in housing
70, complete with pressure, return and control connections. There is a sort of tipping switch on top,
(with lever 64) to actuate regulating piston 12.
The tipping switch 3, which can move to and fro, presses with each movement against a screwed-in
threaded thud which, again, presses against a spring-loaded pushrod. This actuates regulating
piston 12 underneath (with regulating spring and return spring) and, thus, opens it towards pressure
channel P, outlet 1 / 2.
There is a cover to protect pushrod, guide bushing etc. against dirt.

Fig. 1 Pilot control valve 2 x with hydraulic diagram

LHB/en/Edition: 09/2004

A 900 C-LI EDC 24677- 7.46.1

A 904 C-LI EDC 30580- copyright by
A 914 C-LI 35112- MJFCIFSS
A 924 C-LI 34519-
Pilot control valve 2 x Service Manual
Functional description

2 Functional description

The pilot control valve is of the pressure regulating type. That means, regulating piston 12 of the pilot
control valve builds up pressure on the discharge side, between pilot control valve and control valve
block, and is, thus, shifted, against the pressure from pressure spring 25.
Upon actuation, lever 64 and tipping switch 3 act on threaded stud 18, which presses pushrod 98.1
down and, at the same time, shifts regulating 12 via regulating spring 25. The radial and axial bore in
regulating piston 12 lets control oil flow from pressure channel P via connection 1 or 2 and the control
line to one of the control connections of the control valve block.
Pressurising the spools in the control block will build up a certain pressure which is proportional to
the pre-defined displacement of the lever (see Fig. 2). The pressure acts on the face of regulating
piston 12 and shifts it against regulating spring 25 until the connection with channel P is interrupted.

3 Repair

3.1 Dismantling the regulating unit

X Loosen hex nut 68. Unscrew lever 64 complete from tipping switch 3.
X Remove bellows 66. Remove screws from connecting link 90. Remove connection link.
X Remove threaded stud or Allen head screw 20.
This will release axle 24.
X Press out axle 24. Lift and take out complete tipping switch 3.
X Remove protective covers 98.5.
X Remove Allen head screw 21.
X Lift and take out cover plate 29.
X Pull pushrod 98.1 with bushing 98.2 from housing 70.
X Press pushrod 98.1 out of bushing 98.2.
X Remove O-ring 98.4 and PDF seal 98.3 from bushing 98.2.
X Press complete regulating piston 12 out of the housing (from below), complete with pressure
springs 25 and 28 and spring plate 15 with disc 23.
X Remove split disc 23 from spring plate 15 .
X Pull out regulating piston 12. Remove pressure spring 25 with washers 49 / 50.

3.2 Installing the regulating unit

Before installation, be sure to clean all parts and check whether they are fit for re-use.
X Place washers 49 / 50, pressure spring 25 and spring plate 15 on regulating piston 12. Place split
disc 23.
LHB/en/Edition: 09/2004

X Push spring plate 15 into housing 70 (bushing), complete with pre-installed regulating piston 12
and pressure spring 25 and pressure spring 28.
X Install new O-ring 98.4 and PDF seal 98.3 in bushing 98.2.
X Insert pushrod 98.1. Install bushing 98.2 complete with pushrod 98.1 in housing 70.
X Place plate 29. Screw in screws 21.
X Place protective covers 98.5.

7.46.2 A 900 C-LI EDC 24677-

copyright by A 904 C-LI EDC 30580-
MJFCIFSS A 914 C-LI 35112-
A 924 C-LI 34519-
 Service Manual Pilot control valve 2 x
Repair

X Place tipping switch 3. Press in axle 24.

X Re-tighten threaded stud / Allen head screw 20.
X Screw lever 64 complete. to tipping switch 3. Re-tighten hex nut 68.
X Adjusting pilot control valve

3.3 Pilot control valve adjustment in zero position

Stud 18 and pushrod 98.1 must be set and installed in such a way that there is no play between them
when the pilot control valve is not actuated.
Loosen locknut 17. Turn stud 18 until both pushrods 98.1 are in zero position and there is no more
play between screw 18 and pushrod 98.1.
.

Fig. 2 Diagram: c = control pressure in bar, d = lever displacement in angular degree

Contained in equipment starting with serial number Point a Point b

A 900 C Litronic from 14675 5.8 -0.3 bar 24.3 bar
A 904 C Litronic from 16000 5.8 -0.3 bar 24.3 bar
LHB/en/Edition: 09/2004

A 900 C-LI EDC 24677- 7.46.3

A 904 C-LI EDC 30580- copyright by
A 914 C-LI 35112- MJFCIFSS
A 924 C-LI 34519-
Pilot control valve 2 x Service Manual
Exploded view

4 Exploded view

Fig. 3 Exploded drawing: pilot control valve

3 Tipping switch 54 Shim

12 Regulating piston 64 Lever
15 Spring plate 65 Handle
17 Hex nut 66 Bellows
18 Threaded stud 68 Hex nut
20 Allen head screw 70 Housing
21 Allen head screw 71 Bushing (pressed in)
23 Split disc 90 Connecting link
24 Axle 98 Repair kit
25 Pressure spring (regulating spring) 98.1 Pushrod
28 Pressure spring (return spring) 98.2 Bushing
29 Cover plate 98.3 PDF seal
49 Washer 98.4 O-ring
50 Washer 98.5 Protective cover
LHB/en/Edition: 09/2004

52 Shim

7.46.4 A 900 C-LI EDC 24677-

copyright by A 904 C-LI EDC 30580-
MJFCIFSS A 914 C-LI 35112-
A 924 C-LI 34519-
 Service Manual Pilot control valve 2 x
Sectional drawing

5 Sectional drawing

Fig. 4 Sectional drawing: pilot control valve

LHB/en/Edition: 09/2004

A 900 C-LI EDC 24677- 7.46.5

A 904 C-LI EDC 30580- copyright by
A 914 C-LI 35112- MJFCIFSS
A 924 C-LI 34519-
Pilot control valve 2 x Service Manual
Sectional drawing

LHB/en/Edition: 09/2004

7.46.6 A 900 C-LI EDC 24677-

copyright by A 904 C-LI EDC 30580-
MJFCIFSS A 914 C-LI 35112-
A 924 C-LI 34519-
 Service Manual Pilot control unit 4x
Design

Pilot control unit 4x

1 Design

The two pilot control units 200 and 210 with joysticks (to the left and right of the operator's seat) con-
trol the working functions of lifting, stick movements, bucket cylinder movements and turning of the
uppercarriage.
There are four regulating pistons 19 (pressure control valves) , complete with pressure, return and
control connections, inserted in an axial position in the housing 10. The regulating piston 19 is ope-
rated by means of the handle 154/155 (joystick) with the universal joint 16 (see Fig. 2) and the swit-
ching disc 18.
The handle 154/155 can be moved freely in any direction. With each movement, it presses through
the screw-mounted switching disc 18 against one or several spring-loaded pushrods. The regulating
piston 19 located under the pushrods is operated by means of the regulating spring and the reset
spring (see Fig. 2) so that a connection is established from the pressure channel P to the outlet 1 / 2
/ 3 / 4.
For improved fine control of the slewing gear function, the left pilot control unit is equipped with a shut-
tle valve 9.
The bellows 150 protects universal joint, pushrods, guide bushing, etc. against dirt.
LHB/en/Edition: 02/2009

Fig. 1 Diagram of the pilot control unit with joystick and other components

9 Shuttle valve 154 Handle

10 Housing 155 Handle
18 Switch disc 200 Right pilot control unit
19 Regulating piston 210 Left pilot control unit

7.49.1
copyright by

MJFCIFSS
Pilot control unit 4x Service Manual
Design

150 Bellows B335 Pressure switch / slewing gear fine con-

trol

Fig. 2 Exploded view of the pilot control unit

1 Pushrod 100 Sleeve

2 Bushing 105 Nut
9 Shuttle valve (complete) 138 Right control desk
10 Housing 139 Left control desk
15 Spring plate 140 Plate
16 Universal joint 142 Retaining washer
17 Hex nut 146 Allen head screw
18 Switch disc 150 Bellows
19 Regulating piston 154 Handle section
21* Valve seat (shuttle valve) 155 Handle section
26 Pressure spring (regulating spring) 158 Allen head screw
28 Pressure spring (return spring) 160 Screw
32 Cover 162 Cap
LHB/en/Edition: 02/2009

35 Protective cap 163 Screw

45* Seal plug 200 Right pilot control unit
46 PDF seal 210 Left pilot control unit
47 O-ring B19L/R Sensor surface / sensor control
48* Seal plug S5L/R/M Button / grapple rotator
49 Washer S5L/R/M Button / option
50 Back-up washer S30 Switch / travel direction

7.49.2
copyright by

MJFCIFSS
 Service Manual Pilot control unit 4x
Design

55* Ball (shuttle valve) X1046 Plug connection

80 Wire grommet X1047 Plug connection
81 Wire grommet X1048 Plug connection
85 Wire harness X1049 Plug connection
86 Wire harness * only installed in the left pilot control unit
98 Repair kit

Fig. 3 Right pilot control unit with electrical components

LHB/en/Edition: 02/2009

Fig. 4 Left pilot control unit with electrical components

7.49.3
copyright by

MJFCIFSS
Pilot control unit 4x Service Manual
Functional description

2 Functional description

see Fig. 5
The pilot control unit is of the pressure regulating type. This means that the regulating piston 19 of
the pilot control unit builds up a pressure on the discharge side, between the pilot control unit and
control block, and is, thus, shifted against the force of the pressure spring 26.
When the handle 154/155 is moved, the switching disc 18 pushes the pushrod 1 down, and the re-
gulating spring 26 shifts the regulating piston 19. The control oil flows through the radial and axial
bores in the regulating piston 19 from the pressure channel P (through connection 1 or 2 , 3 or 4) and
the control line to one of the control connections at the control block.
As the spools in the control block are pressurised, a pressure that is proportional to the pre-defined
lever travel (see Fig. 6) is built up. The pressure acts on the face of the regulating piston 19 and shifts
it against the regulating spring 26 until the connection to the channel P is blocked.
Depending on the position of the handle 154/155 and the stroke travel of the pushrod 1, a pilot pres-
sure is established, which shifts the spool 19 proportionally to the pressure increase. At a set pres-
sure (corresponding to the end of the fine-control phase of the spool), the pushrod 1 moves the
regulating piston 19 downwards. At this point, maximum control pressure is applied to the spool.

1 Pushrod 105 Nut

2 Bushing 150 Bellows
9 Shuttle valve (complete) 154 Handle section
10 Housing 155 Handle section
15 Spring plate B19R Sensor transducer / right
16 Universal joint B19L Sensor transducer / left
17 Hex nut B335 Pressure switch / slewing gear control
18 Switch disc S5 Left push button
19 Regulating piston S5R Push button (turn grapple right)
26 Pressure spring (regulating spring) S5L Push button (turn grapple left)
28 Pressure spring (return spring) S5M Button (reserve)
32 Cover S6 Right push button
49 Washer S6R Push button (optional)
50 Back-up washer S6L Push button (optional)
85 Wire harness S6M Push button (horn)
LHB/en/Edition: 02/2009

86 Wire harness S30 Switch / travel direction

100 Sleeve

7.49.4
copyright by

MJFCIFSS
 Service Manual Pilot control unit 4x
Functional description

Fig. 5 Sectional drawing of the pilot control unit

LHB/en/Edition: 02/2009

7.49.5
copyright by

MJFCIFSS
Pilot control unit 4x Service Manual
Repair, see Fig. 2 and Fig. 5

3 Repair, see Fig. 2 and Fig. 5

3.1 Dismantling

3.1.1 Dismantling the pilot control unit

X Pull up the bellows 150.
X Loosen the lock nut 105. Remove the sleeve 100 with the handle 154 / 155.
X Unscrew the nut 17 and the switch disc 18. Remove the universal joint 16 from the housing 10.
X Remove the protective caps 35 and the cover 32. Pull the pushrod 1 together with the bushing 2
from the housing 10.
X Press the pushrod 1 out of the bushing 2.
X Remove the O-ring 47 and the PDF seal 46 from the bushing 2.
X Press the regulating piston 19 with the pressure springs 26 and 28 as well as the spring plate 15
from the housing 10, pushing it upwards.
X Pull out the regulating piston 19. Remove the pressure spring 26 with the washers 49 / 50.

3.1.2 Dismantling the handle

X Loosen the screw 163 and remove the cap 162.
X Loosen the screws 158 and remove the handle sections 154 / 155 from the sleeve 100.
X If necessary, disconnect the push button S5/S6 and remove it from the cable harness 85/86.

3.2 Installation

3.2.1 Installing the handle

X Connect the push button S5/S6 to the cable harness 85/86 and insert it in the handle sections 154
/ 155.
X Secure the handle sections 154 / 155 with the screws 158 to the sleeve.
X Place the cap 162 over the push button S5 / S6 and tighten the screw 163.

3.2.2 Installing the pilot control unit

X Prior to installing the unit, clean all parts and check whether they are fit for re-use.
X Place the washers 49 / 50, the pressure spring 26 and the spring plate 15 on the regulating piston
19.
X Insert the spring plate 15 together with the preassembled regulating piston 19 and the pressure
springs 26 and 28 into the housing 10 and the bushing 13.
X Insert a new O-ring 47 and PDF seal 46 into the bushing 2.
LHB/en/Edition: 02/2009

X Insert the pushrod 1 and install the bushing 2 with the pushrod 1 in the housing 10.
X Replace the cover 32 and the protective cap 35. Screw in the universal joint 16 (torque: 20 Nm).
X Screw in the switch disc 18 complete with the nut 17. Adjust the pilot control unit to zero position.
X Screw the sleeve 100 together with the handle sections 154/155 into the nut 17 and then tighten
the nut 105, ensuring that the handle is in the correct position.

7.49.6
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 Service Manual Pilot control unit 4x
Repair, see Fig. 2 and Fig. 5

3.3 Pilot control unit adjustment in zero position, see Fig. 5

The switch disc 18 and the pushrod 1 must be installed in such a way that there is no play between
them when the pilot control unit is not actuated.
X To adjust the play, loosen the nut 17 and turn the switch disc 18 until all four pushrods are in zero
position and there is no more play between switch disc 18 and the four pushrods 1.
X After completed adjustment, re-tighten the nut 17.
X Pull the bellows 150 down over the disc 140.

Fig. 6 Diagram: c = lever travel in degrees

Built into machine Point a Point b

A/R 900 C EDC- A 924 C EDC 6 -0.5 bar 28 +1.5 bar
LHB/en/Edition: 02/2009

7.49.7
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Pilot control unit 4x Service Manual
Repair, see Fig. 2 and Fig. 5

LHB/en/Edition: 02/2009

7.49.8
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MJFCIFSS
 Service Manual LSC control valve block
Function/design

LSC control valve block

1 Function/design

All machines of the Litronic series are equipped with the LSC control system.
The control unit of the hydraulic LSC control was designed as a compact control block with LUDV
system. The control valve block contains five spools (working and travel functions) with the corres-
ponding valves.
There is an additional control valve block segment for the slewing gear drive and the 'turn grapple'
function (AS1).

1.1 Sections of control valve block, see Fig. 1

Input section:
– Connection P for oil pump flow
– Connection K for return flow to hydraulic cooler
– Connection MP for pump pressure
– Connections MLS and LS1 for external load signal from 'travel direction right', control valve block
side
– Connection LS with shuttle 107 for load signal line to pump's flow regulator
– Check valve 7 (3.5 bar) in block for return backpressure
– Pressure balance / remaining flow 103 for a fast and direct response in the system
– Pressure cut-off valve 104 as a limiting valve for the working pressure
– Pump safety valve 105 protecting the system
Control and distribution section:
– Operating connections A1 - A5 and B1 - B5 for supply and return flows of consumers
– Connection H for pilot control oil from control oil unit
– Connection S for direct suction of slewing gear motor
– Connection T for return oil to hydraulic tank
– Pressure sequence valve 8 (7 bar) in block for return, as cooler bypass valve
– Minimum-flow pressure balance 102 stabilising load pressure
– Control caps of the various axles with stroke limitation of the spools 160 / 220 / 240 / 260 and 280;
control pressure connections a1 - a5 and b1 - b5, and regulating and return spring
– Spools 160 / 220 / 240 / 260 and 280 for the working movements of the travel gear, boom, stick,
bucket and support
– Suction valves 161 and 162 to prevent cavitation in the travel drive system
– Pressure balances 164 / 224 / 224 / 264 and 284 for LS signal re. compensation of the individual
axles
– Restrictor check valves 127 / 167 / 227 and 247 for the fine control of the spools 120 / 160 / 220
and 240
LHB/en/Edition: 07/2010

– Secondary pressure-relief valves 221 / 222 / 241 / 242 / 261 and 262 to protect the consumer cir-
cuit in closed state

Note!
For the slewing gear and auxiliary attachments, you can flange-mount kits and other individual com-
ponents with a spool to the compact block.

7.51.1
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LSC control valve block Service Manual
Function/design

LHB/en/Edition: 07/2010

Fig. 1 Design of control valve block

7.51.2
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MJFCIFSS
 Service Manual LSC control valve block
Function/design

7 Check valve (3.5 bar) 220 Spool / hoist cylinder

8 Pressure sequence valve (7.0 bar) 221 Secondary pressure-relief valve / exten-
ding
100 Compact control block 5x 222 Secondary pressure-relief valve / retrac-
ting
102 Pressure balance / minimum flow 224 Pressure balance (pilot-controlled)
103 Pressure balance / remaining flow 227 Restrictor check valve
104 Pressure cut-off valve 240 Spool / stick cylinder
105 Pump safety valve 241 Secondary pressure-relief valve / retrac-
ting
107 Shuttle valve (omitted from serial no. 242 Secondary pressure-relief valve / exten-
48069 (A900 C); 51328 (A904 C) ding
108 LS main orifice 244 Pressure balance (pilot-controlled)
109 Shuttle valve (from serial no. 39333) 247 Restrictor check valve
110 Mounting plate 260 Spool / bucket cylinder
111 Allen head screw 261 Secondary pressure-relief valve / retrac-
ting
120 Spool / slewing gear 262 Secondary pressure-relief valve / exten-
ding
122 Input pressure balance 264* Pressure balance (directly controlled)
123 Check valve 264 Pressure balance (pilot-controlled)
127 Restrictor check valve 280 Spool / support
134 Control lid 281 Screw plug
135 Allen head screw 284 Pressure balance (directly controlled)
140 Screw plug (bucket only) 334 Control lid
160 Spool / travel gear 540 Auxiliary control axle AS1
161 Suction valve, forward 810 Mounting plate
162 Suction valve, reverse 811 Allen head screw
164 Pressure balance
167 Restrictor check valve *only in model A 904 C Industrial
LHB/en/Edition: 07/2010

7.51.3
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LSC control valve block Service Manual
Function/design

LHB/en/Edition: 07/2010

Fig. 2 Hydraulic schematic of construction model

7.51.4
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 Service Manual LSC control valve block
Function/design
LHB/en/Edition: 07/2010

Fig. 3 Hydraulic schematic of industrial model

7.51.5
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MJFCIFSS
LSC control valve block Service Manual
Technical data

2 Technical data

A 904 C Litronic
Built into A 900 C Litronic A 904 C Litronic A 904 C Litronic
1003/1005
Type 1002 (construction) 1004 (HD) 1071 (industrial)
(construction)

Construction mo- M7-1676-30/7 M7-22 M7-1643-30/7 M7-22

del

Industrial M7-1544-31/7 M7-22 M7-1544-31/7 M7-22

Spool Unit 220 240 260 280 160 120

Boom Stick Bucket Support Travel Slewing
cylinder cylinder cylinder cylinder motor gear
Ex- Re- Ex- Re- Ex- Re- Ex- Re- Ex- Re- Ex- Re-
tend tract tend tract tend tract tend tract tend tract tend tract
Nominal width of mm 22 22 22 22 22 20
block
Consumer connec- (“) 1“ 1“ 1“ 1“ 1“ 3/4“
tion
Ø piston rod mm 25 25 25 25 25 25
Piston stroke mm 11.0 11.0 11.0 11.0 11.0 11.0 11.0 11.0 11.0 11.0 9.0 9.0
Setting value Y mm
A 900 C 17.0 15.5 15.8 15.8 16.0 15.7 16.0 16.0 15.5 15.5 16.0 16.0
A 904 C 17.0 15.7 15.8 15.8 17.0 16.5 16.3 16.0 15.5 15.5 15.8 15.8

p1 ± 0.5 bar 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0 7.0
p2 ± 0.5 bar 20.6 20.6 20.6 20.6 20.6 20.6 20.6 20.6 20.6 20.6 20.6 20.6
Qn (A)/Qn (B) l/min
A 900 C (1002) 270 120 260 210 250 150 220 140 200 200 130 130
A 904 C (1003) 300 120 260 210 250 150 130 70 200 200 130 130
A 904 C (1005) 300 120 260 210 250 150 130 70 200 200 130 130
A 904 C HD (1004) 270 90 350 250 250 150 220 140 200 200 135 135
A 904 C (1071) 270 90 350 250 250 150 220 140 200 200 135 135
Restrictor check mm
valve
at connection a 0.8 0.8 0.8 0.8
LHB/en/Edition: 07/2010

(mm) 0.8 0.8 0.8 0.8

at connection b
(mm)
Leak oil max cm3/min 60 60 60 60 60 60
at load pressure bar 150 150 150 150 150 150
at oil temperature °C 50 50 50 50 50 50

Tab. 1 Technical data

7.51.6
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 Service Manual LSC control valve block
Input section / input element

3 Input section / input element

3.1 Design
The input element contains the central system functions such as the pump safety valve 105, the LS
pressure-relief (cut-off valve 104), the remaining flow pressure balance 103, the minimum-flow pres-
sure balance 102 and the LS central nozzle 108, as well as the check valve 7 (cooler valve) and the
check valve 8 (tank valve).
LHB/en/Edition: 07/2010

Fig. 4 Exploded drawing of input element

7.51.7
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LSC control valve block Service Manual
Input section / input element

100 Compact block 210 Valve seat

102 Pressure balance / minimum flow 211 Restrictor bolt
103 Pressure balance / remaining flow 219 Valve seat
104 Pressure cut-off valve 221 Spring plate
105 Pump safety valve 222 Pressure spring
107 Shuttle valve 225 Screw plug
108 LS main orifice Ø 1.6 mm 275 Screw plug

3.2 Minimum-flow pressure balance / input pressure balance 102

The valve 102 (which is screwed into the block 100 from the top) allows a small amount of oil (approx.
0.7 l/min.) to flow continuously from the LS line to the tank. This eliminates pressure increases in the
LS line due to impacts. The valve 102 also ensures that the LS line is relieved to the tank if the con-
sumers are not actuated (neutral position of spools).
The 2-way flow limitation valve consists of an orifice and a pressure balance with regulating piston
11. The pressure balance keeps the pressure drop Up constant. As a result the amount of outflowing
oil is also constant and independent of the LS pressure. Value Up is derived from the selected cross-
section of the orifice (spool).
The valve cannot be adjusted and needs no maintenance. In the event of malfunctions, it is possible
to check the valve for dirt and/or broken spring by removing and dismantling it. If necessary, replace
it completely. In the event of leaks on the outside, use a new seal kit (items 15 - 18).

LHB/en/Edition: 07/2010

Fig. 5 Sectional drawing of input pressure balance

1 Cone 17 Back-up ring

2 Pressure spring (7.0 bar) 18 Back-up ring
3 Shim 100 Compact block
4 O-ring 102 Pressure balance / minimum flow

7.51.8
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 Service Manual LSC control valve block
Input section / input element

8 Check valve 160 Spool / travel

10 Valve insert 164 Pressure balance
11 Piston 169 Screw plug
12 Bushing (pressed in) 272 Nozzle Ø 0.6 mm
13 Stop sleeve 273 Nozzle Ø 1.2 mm
14 Pressure spring 274 Line to check valve 274
15 O-ring 278 Screw plug
16 O-ring

3.3 Remaining flow pressure balance 103, see Fig. 6

In standby mode, there is a continuous flow volume Qmin amounting to about 30 - 40 l/min. When
consumers are not in operation, this generates a standby pressure at pump connection MP (due to
Up of the valve, and the additional tank preload). Therefore, the system pressure levels out at max.
35 bar in this operating mode.
The standby pressure shifts the piston 103 through the integrated channels against the force of the
spring 222. Simultaneously, the LS channel is relieved through the valve 102 to the tank. This esta-
blishes a connection between the pressure side P and the tank side T, and the presetpreset quantity
of oil flows off. The valve ensures that, in the event of idle run, there is still a minimum volume flow
Qmin to the tank at standby pressure. The resulting loss of power in this mode is thus rather low.
When a consumer is operated, the load pressure of the consumer acts on the piston. The pressure
and spring force shift the piston 103 in proportion to the required volume and reduces the outlet cross-
section of the orifice to the tank.
If the minimum volume of the consumer is smaller, the quantity allotted through the gauge orifice of
the spool is fed with priority to the consumer, due to the lower Up spool. The differential quantity con-
tinues to flow to the tank side via the adjusted control edge.
As soon as the volumes requested by one or more spool(s) exceed Qmin, the valve 103 closes com-
pletely and shuts off the connection to the tank side.
The valve cannot be adjusted and needs no maintenance. In the event of malfunctions, it is possible
to check the valve for dirt and/or damage. To do this, unscrew the screw plug 225. Take the compo-
nents 221 and 222 from the housing. Check for re-usability and good function. Replace them, if ne-
cessary.

3.4 Pressure cut-off valve 104, see Fig. 6

The LS pressure cut-off valve 104 works as a pressure controller. As soon as the preset nominal
pressure value is reached, it reduces the volumetric flow of the pump to Qmin. This function has pri-
ority over the pump's power and flow regulation systems. This means that, as soon as the pressure
cut-off has been actuated, load sensing and/or power regulation are no longer possible.
Once a consumer reaches its max. permissible operating pressure, the cut-off valve is actuated and
relieves the LS signal behind the LS main nozzle in the control valve block to the tank. The LS signal
LHB/en/Edition: 07/2010

sent to the pump cannot increase any further, and the pump regulates the flow in such a way that a
max. pump pressure of LS + Up is built up in the pump channel.
The pressure cut-off valve is simply a pressure-relief valve in the LS line.
Ensure that the valve is periodically checked and adjusted according to the maintenance schedule.

7.51.9
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LSC control valve block Service Manual
Input section / input element

Fig. 6 Sectional drawing of input element

1 Valve insert 100 Compact block

4 Adjusting screw 103 Pressure balance / remaining flow
5 Spring plate 104 Pressure cut-off valve
6 Pressure spring 107 Shuttle valve
7 Washer 108 Restrictor (LS central nozzle)
8 Lock nut 210 Valve seat
LHB/en/Edition: 07/2010

10 Circlip 211 Restrictor bolt

11 Back-up ring 219 Valve seat
12 Back-up ring 221 Spring plate
13 Back-up ring 222 Pressure spring
14 O-ring 225 Screw plug
15 O-ring 275 Screw plug
16 O-ring

7.51.10
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 Service Manual LSC control valve block
Input section / input element

3.5 Pump safety valve 105

The pump safety valve protects the pump against excessive pressure in the event of failure of the
secondary pressure-relief valve and the cut-off valve. It is supposed to respond only in emergencies.
Therefore, its pressure setting is significantly higher than that of the cut-off valve and the installed
secondary pressure-relief valves.
This valve is identical as regards function and design to the secondary pressure-relief valves of the
control axles for boom, stick and bucket (see “Pressure and feeder valves” on page 29).

3.6 LS shuttle valve 107

The orifices of the LS shuttle 107 limit the volume flow to the LS regulator of the pump. The propa-
gation of abrupt pressure peaks to the regulator and resulting peaks at the pump are prevented in the
LS line, thanks to the interrelation between the various orifices and capacities. Peaks are smoothe-
ned thanks to the pulsating of the hose and/or the compressibility of the oil volume. This prevents
aggressive or unwanted responses of the pump to sudden peaks, ensuring stable operating beha-
viour.
In the event of malfunction, it is possible to check the valve 107 for dirt. To do this, unscrew the valve
insert and pull out the double-sided cone. Check for correct function and re-usability. Replace, if ne-
cessary.

3.7 Radiator and tank pressure sequence valves 7 / 8

The compact control block is equipped with a central cooler and tank connections. The return lines
are preloaded by the pressure springs 2 / 6 of the check valves. The resulting backpressure at the
outlet ensures sufficient inflow in the event of negative external loads (boom down, uphill travel etc.)
and, thus prevents cavitation / empty running.
The volume required for refill the system is usually available from the volume displaced by the con-
sumer.
The priority of the return flow of the oil through the cooler is implemented by means of different pre-
loads of the valves with different pressure springs 2 (7.0 bar for tank preload) and 6 (3.5 bar for ra-
diator protection). With increasing volume flow, the resistance in the cooler line increases and the
additional volume is fed directly to the tank.
The valves do not require maintenance. In the event of a malfunction, the valve can be removed to-
gether with the screw plug, the pressure springs 2 / 6 and the cone 1 / 5 from the housing 100 for
inspection (contamination, defect), testing and replacement. If there are leaks on the outside, replace
the O-ring 4 / 10.
LHB/en/Edition: 07/2010

7.51.11
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LSC control valve block Service Manual
Functional description (summary description)

Fig. 7 Radiator and tank pressure sequence valves 7 / 8

1 Cone 7 Check valve (radiator)

2 Pressure spring 8 Check valve (tank)
3 Shim 9 Shim
4 O-ring 10 O-ring
5 Cone 100 Control valve block
6 Pressure spring

4 Functional description (summary description)

4.1 Neutral position

All spools 160 / 180 / 220 / 240 / 260 and 280 are held in their neutral position by means of the regu-
lating and return spring 132. The connection between the pump and consumer is closed. The con-
nection between the consumer and tank is closed.
The pressure balances 164 / 224 / 244 / 264 and 284 are in their neutral position (connections
closed).
The pressure balance / remaining flow 103 is open, i.e. the preset flushing volume is pumped by the
variable-displacement pump through 103 to the tank.

4.2 Working position of a spool, Fig. 9

The connection between sections P and P’ opens and oil flows.
LHB/en/Edition: 07/2010

The pressure balances 224 to 284 are pressurised and open completely.
When the spool is in its working position, oil flows through the pressure balances to the flow regulator.
The pump pressure is increased and exceeds that of the load holding function. The consumer is sup-
plied with oil.
The pressure balance 103 closes. As a result, the volume flow from the pump is now available to the
consumer.

7.51.12
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 Service Manual LSC control valve block
Functional description (summary description)

4.2.1 Working positions of several spools, see Fig. 9

The connection between sections P and P’ opens and oil flows.
The pressure balances 224 to 284 are pressurised and shifted in the direction of the spring side (in
proportion to the LS pressure). This means that the consumer with the highest load pressure deter-
mines the LS pressure. The pressure balances 224 to 284 of each spool thus switch to the same
pressure difference (U-p), even at different load pressures.
Pivoting of the pump is effected according to the oil requirements of the various consumers.
The oil is fed via the control edge of the respective pressure balance and load-holding valves 170 -
172 to section PA or PB, to the consumer connection A 1-5 or B 1-5 and to the consumer.
The remaining flow pressure balance 103 closes. The flow from the pump is now available to the con-
sumer.
Advantage of the LSC control:
– The pump delivers only the oil required by the individual consumers.
– The speeds of the consumers are determined only by the pre-selected pilot pressure on the spool.
It remains constant, irrespective of the load pressure of the respective consumer.
LHB/en/Edition: 07/2010

Fig. 8 Spool 160-280

100 Control valve block 240 Spool / stick

160 Spool / travel 260 Spool / bucket
220 Spool / boom 280 Spool / support

7.51.13
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LSC control valve block Service Manual
Functional description (summary description)

LHB/en/Edition: 07/2010

Fig. 9 Hoist, stick and bucket cylinder sections

7.51.14
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 Service Manual LSC control valve block
Functional description (summary description)

100 Compact control block 241 Secondary pressure-relief valve

134 Control lid 242 Pressure-relief valve / stick
140 Screw plug (only with bucket axle) 244 Pressure balance, pilot-controlled
170 Cone 247 Restrictor check valve
171 Pressure spring 260 Spool / bucket
172 Cone 261 Secondary pressure-relief valve
220 Spool / boom 262 Pressure-relief valve / bucket
221 Secondary pressure-relief valve 264 Pressure balance, pilot-controlled/
direct
222 Secondary pressure-relief valve / boom a3-a5 Control pressure connections, bottom
224 Pressure balance, pilot-controlled b3-b5 Control pressure connections, top
227 Restrictor check valve A3-A5 Control pressure connections, bottom
240 Spool / stick B3-B5 Control pressure connections, top
LHB/en/Edition: 07/2010

7.51.15
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LSC control valve block Service Manual
Functional description (summary description)

LHB/en/Edition: 07/2010

Fig. 10 Sectional drawing of travel/support section

7.51.16
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 Service Manual LSC control valve block
Control and distribution section

100 Compact control block 170 Cone

134 Control lid 171 Pressure spring
140 Screw plug (only with bucket axle) 172 Cone
160 Spool / travel / support 280 Spool / support
161 Suction valve, forward 281 Dummy cartridge (only support)
162 Suction valve, reverse 284 Pressure balance, directly controlled
164 Pressure balance, pilot-controlled a2/b2 Control pressure connections, bottom/
top
167 Restrictor check valve A2/B2 High pressure connection, bottom/top
169 Screw plug

5 Control and distribution section

5.1 Control axles

Each control axle is equipped with the necessary spool complete with actuation (control lid, regulation
springs) required for its respective function, a pressure balance and the corresponding connections
with secondary protection.

5.1.1 Spools 160, 240, 260 and 280

The geometry of the spools and their gauge orifices has been designed and adapted to match the
characteristics of the respective consumer. The control of the consumer in the LUDV system is inde-
pendent of the load pressure. At a constant Up, the volume flow rate is generated by changing the
cross-section of the gauge orifice through the stroke of the spool. The maximum volume flow to the
consumer is thus determined by the available maximum open cross-section.
In the event of a malfunction, check the spools 160 to 280. To do this, remove the upper control lid
134, pull out the respective spool and check it for damage, contamination, etc. Test its function. If
necessary replace it.

5.1.2 Dismantling of spools 160 to 280

Caution!
Before dismantling the control lines, relieve the pressure from the hydraulic circuit.
The lid 134 is spring-loaded.
Risk of injury!
X Pull the spools 160 to 280 from the control valve block 100.

X Dismantle the control line in question.

X Remove the screws 135.
X Remove the lid 134 with the O-ring 130.
X Remove the pressure spring 132 and the spring plate 131.
LHB/en/Edition: 07/2010

5.1.3 Installation of spools

Important information for the installation / replacement of pistons:
– The individual spools are matched to the specific requirements of their respective working func-
tions (boom, stick, etc.) and are not interchangeable.
– If you need to dismantle several spools at a time, make sure they are re-installed in their original
bores.

7.51.17
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LSC control valve block Service Manual
Control and distribution section

– Usually, the bores in the control valve blocks are made for perfect fit. If this applies to all the bores
in the block, the type plate of the block contains the end digits "000". The zeroes indicate that the
bores have ± 0 µm tolerance. This means that the spools supplied for replacement usually have
a tolerance range of 8-10 µm, and that the amount of leak oil is within the normal range.
– Perfect-fit bores are marked with the steel stamping numeral 0. They can be replaced with corre-
sponding spools from the spare parts catalogue.
– If one or several bores of the control valve block do not fall within zero tolerance standard, this is
indicated on the type plate. To determine the bores to which this applies, remove the top lid of the
spool you wish to check.
– The tolerance of the bore is indicated on the front face of the control valve block, e.g. 10 = 10 µm.
This means that replacement of the spool with one from the spare parts catalogue is not possible.
A special spool for that particular tolerance must be produced.
When ordering spare spools, always submit all information indicated on the type plate. See also ser-
vice information no. 1-14-52 / 2000.
When installing the spool, ensure that it is in the correct position.
X Choose a matching spool and grease it lightly.
X Carefully insert it into the control valve block 100.
X Place the spring plate 131 and the pressure spring 132 on the spool.
X Place the lid 134 together with the O-ring 130 on the control valve block 100 and secure it with the
screws 135.

LHB/en/Edition: 07/2010

7.51.18
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 Service Manual LSC control valve block
Control and distribution section

Fig. 11 Control and distribution section

100 Compact control block 167 Restrictor check valve

130 O-ring 220 Spool / boom
131 Spring plate 227 Restrictor check valve
132 Regulation spring 240 Spool / stick
134 Control lid 247 Restrictor check valve
135 Allen head screw 260 Spool / bucket
140 Screw plug 280 Spool / support
160 Spool / travel gear
LHB/en/Edition: 07/2010

7.51.19
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LSC control valve block Service Manual
Control lid 134

6 Control lid 134

Fig. 12 Control lid 134

1 Cap nut 140 Screw plug (bucket)

2 O-ring 167 Restrictor check valve (travel)
3 Lock nut 227 Restrictor check valve (boom)
4 Adjusting screw / stroke limitation 247 Restrictor check valve (stick)
134 Control lid Y Setting value of stroke limitation
135 Allen head screw

The control lid 134 is located on both sides of the spools 120 to 280 and is fixed to the compact block
100. The control oil required for the actuation of the spool is fed through the control connection a / b
of the control lid 134.
Some of the control axles have a shuttle dampening function (restrictor check valve 167 / 227 / 247)
in the inlet area of the control connection. It restricts the flow of the oil displaced by the spool in the
opposite control lid and, thus, reduces the shifting speed of the spool. This ensures a smooth starting
motion of the consumer as well as good handling and fine control.
The dampening of the respective consumer movement (A) is effected by means of the restrictor
check valve 167 / 227 / 247 in the opposite control lid (B). Oil enters the control lid (e.g. at connection
a) through the opening valve seat. The oil displaced by the spool (e.g. via connection b) closes the
valve seat so that the displaced control oil must flow through the orifice of the valve. The cross-section
of the orifice (and thus the shifting speed) is matched to the characteristics of each individual consu-
mer. Thanks to the restriction in the outlet towards T, the dampening effect works with swift actuation
as well as with swift release.
In addition, the control lid is equipped with a stroke limitation 4 for the spool. It allows for the limitation
of the max. speed of the consumer.
LHB/en/Edition: 07/2010

The setting has been preset by the supplier / manufacturer and may not be modified. The adjusting
screws 4 are secured with the lock nuts 3 and protected against damage by the cap nuts 1.
Checking the setting value Y serves as a rough adjustment. Precise adjustment of the absolute max.
volumes fed to the consumer is only possible by using a flow meter attached to the outlet of the con-
trol valve block.
The flushing grooves a of the spools 160 to 280 form a connection between the tank and control lid
134. Together with the tank preload of the control valve block, they facilitate a continuous flow of oil
when the pilot control unit is not actuated. This means that the flushing volume required for prehea-

7.51.20
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 Service Manual LSC control valve block
Control lid 134

ting of the control oil circuit is available.

Fig. 13 Sectional drawing of control lid 134

1 Cap nut 167 Restrictor check valve

2 O-ring 220 Spool / boom
3 Lock nut 227 Restrictor check valve
4 Adjusting screw / stroke limitation 240 Spool / stick
5 Shuttle 247 Restrictor check valve
6 Orifice 260 Spool / bucket
100 Control valve block 280 Spool / support
131 Spring plate a Flushing grooves
132 Regulation spring a1-a5 Control pressure connection, bottom
134 Control lid b1-b5 Control pressure connections, top
160 Spool / travel gear
LHB/en/Edition: 07/2010

7.51.21
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LSC control valve block Service Manual
Pressure balances in the control valve block

7 Pressure balances in the control valve block

Fig. 14 Pressure balances in the control valve block

164 Pressure balance (pilot-controlled) 224 Pressure balance (pilot-controlled)

165 Pressure spring 244 Pressure balance (pilot-controlled)
167 Screw plug 264 Pressure balance (pilot-controlled)
168 Screw plug 264* Pressure balance (directly controlled)
LHB/en/Edition: 07/2010

169 Screw plug 284 Pressure balance (directly controlled)

*A904 C (industrial)

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Pressure balances in the control valve block

7.1 Directly controlled pressure balance 264* / 284

On-demand flows are controlled by means of the cross-section of the opening of the respective spool
shaft and the LS pressure at the pump regulator.
Responsible for that are the pressure balances connected to each spool shaft and sitting in the con-
trol valve block.
The LUDV pressure balance 264 / 284 with the pressure spring 165 of each section is situated
downstream of the gauge orifice of the spool.
This pressure balance signals the pressure of the consumer with the highest load to the pump regu-
lator. For all consumers with lower loads, the pressure balance compensates the LS pressure with
the prevailing load pressure of the consumer in question.
In neutral position of the spool, the connection between the pump and the channel p’ is blocked by
the spool (see Fig. 16). In this position, the pressure in the channel p and behind the load-holding
valves is reduced to a level close to the tank level by the spool play. The consumer connections are
blocked by covering the spool in the housing. The consumer thus sits between two oil columns and
is fixed.

Fig. 15 Directly controlled pressure balances 264 / 284

163 Screw plug 264 Pressure balance

165 Pressure spring 284 Pressure balance, directly controlled
166 O-ring

7.2 High pressure

As soon as the spool is shifted, the supply orifice of the spool opens the connection between the
pump connection p and the channel p’. The resulting pressure in this space shifts the pressure ba-
lance. Through the internal channels in the pressure balance, the pressure also acts on the rear side
of the load holding valves.
The consumer pressure pc of connection A acts through the channels in the spool and is available
LHB/en/Edition: 07/2010

at the front side of the left-hand load holding valve. With the pump pressure p’ rising above the con-
sumer pressure pc, the load holding valve opens. The connection between the pump and the consu-
mer is now established and initiates the movement. The displaced oil flows back to the tank via the
outlet orifice. The secondary pressure-relief valves remain closed as long as the pressure in the con-
sumer connection remains below the preset pressure value.

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Pressure balances in the control valve block

Fig. 16 Pressure balance in high-pressure position

pc high = LS signal to pump regulator

7.3 Consumer with highest load is actuated

For individual movements, or when the load pressure of the consumer pc is the highest in the system,
the LS pressure is generated from the spring chamber of the corresponding pressure balance. Tap-
ping pressure at this point guarantees that only the highest load pressure is signalled. The pressure
balances of the other sections block off any effects caused by other consumers.
This LS signal is sent to the flow regulator (LS regulator) of the variable-displacement pump, and also
to the spring chambers of the other LUDV pressure balances. The pressure balance is fully open.
Channel p’ is connected to consumer the connection pc, without pressure reduction.
Feeding the LS signal of the load-holding valves guarantees that the consumer connection is blocked
until the necessary working pressure is reached, and prevents sudden drops in the event of negative
(pulling) loads.

7.4 Low pressure

7.4.1 Load-sensing function

In the saturated range, the LUDV system operates as a load-sensing regulation system only. The
speed of the consumer is controlled independently of the load pressure, by means of the opening
cross-section of the gauge orifice (spool).
If several movements overlap, the load pressure of the consumer with the highest pressure acts via
the central LS line in the spring chamber on the other LUDV pressure balances. The resulting pres-
sure in channel p’ of this section results from the highest signalled LS pressure (p’ = LS + spring
force). The LUDV pressure balances automatically regulate the pressure p’ of the various axles by
limiting the flow cross-section to the consumer channel to the same value. Value Up at the gauge
LHB/en/Edition: 07/2010

orifice is identical. This means that the speed of the consumer is independent of the difference in the
load pressures. As the pressure balance is under the influence of the load signal with the highest load
on the spring side, it cannot open completely. The pressure balance, which is only partly open, ge-
nerates another pressure difference which depends on the individual load.

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Pressure balances in the control valve block

Fig. 17 Pressure balance in low-pressure position

d = LS = pc high
e = pc low
F = spring chamber
R = regulating orifice

7.4.2 LUDV function

The LUDV system works even if there is a saturation deficit. In such a case, the oil volume requested
on the basis of the sum of the open gauge orifice cross-sections at the existing Up exceeds the ma-
ximum flow rate of the pump within the limits of the power control. The LS regulator of the pump is no
longer in a position to build up the preset Up by means of pivoting the variable-displacement pump
further. Up set at the regulator collapses.
Under these conditions, the LUDV system maintains Up at the same level across all the open gauge
orifices. This means that, in the event of a saturation deficit, the system does not simply shut off the
consumer(s) with the highest load. Instead, the speeds of all the actuated consumers drops propor-
tionally to the open cross-sections.
When all the pressure balances are in balance:
– The LS system pressure in all spring chambers of the pressure balances is the same
– p’ in front of the gauge orifices of the section with the lower load corresponds to the LS pressure
of the consumer with the highest load
Up inlet orifice = ppump - p’
Up at the inlet orifices of all consumers is always equal. In the event of a saturation deficit, Up drops
at all consumers at the same rate.
The pressure differences Up inlet orifices between p’ and each individual consumer pressure pc is re-
gulated and equalised automatically by adapting the opening cross-section, so that the volumetric
LHB/en/Edition: 07/2010

flows are split proportionally.

7.4.3 Negative load

Speed control of the consumers through the opening of the inlet orifice is not possible with negative
(pulling) loads. In such cases, the consumer is controlled in relation to the actual load, through the
outlet orifices.

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Fig. 18 Pressure balance in position "spool closed"

a No LS signal 164 Piston / pressure balance

b LS signal 280 Spool
100 Control valve block 284 Piston / pressure balance
160 Spool / travel

7.5 Pilot-controlled pressure balances 164 / 284 / 224 / 244 and 264
The pilot-controlled pressure balances 164 / 284 / 224 / 244 and 264 serve the same functions in the
LUDV system as the directly controlled pressure balances 164 and 184. The function of the pilot-con-
trolled pressure balances thus corresponds to the basic function of the directly controlled pressure
balances.

Additional features of pressure balances 164 / 284 / 224 / 244 and 264:
Finer and more precise regulation behaviour thanks to the pilot control piston 1 with pressure spring
2 integrated into the pressure balance.
This fast-responding pilot control piston take over the blocking and opening functions with respect to
the pressure signal between the consumers with the highest and with the lower load pressures.

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Pressure balances in the control valve block

Fig. 19 Pressure balances, pilot-controlled

163 Screw plug 193 Spring plate

164 Pressure balance (pilot-controlled) 194 Spring plate
165 Pressure spring 224 Pressure balance (pilot-controlled)
166 O-ring 225 Restrictor 2x Ø 0.8 mm
168 Screw plug 244 Pressure balance (pilot-controlled)
169 Screw plug 245 Restrictor 2x Ø 0.8 mm
191 Pilot control piston 264 Pressure balance (pilot-controlled)
192 Pressure spring 284 Pressure balance (pilot-controlled)

7.6 Low pressure range:

The pilot control piston 1 is in its initial position, so that it connects the existing LS pressure of the
LHB/en/Edition: 07/2010

consumer with the highest load pressure to the spring side of the pressure balance. The pressure
balance thus regulates the pump pressure of the consumers with the lower load pressure and adjusts
it to the LS pressure of the consumer.

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Pressure balances in the control valve block

Fig. 20 Pressure balance in low-pressure position (LS signal from consumer with highest load)

7.7 High pressure range:

The pilot control piston 1 is shifted against the pressure spring 2. As a result, the spring side of the
main piston is relieved. At the same time, the consumer with the highest load pressure is connected
to the LS pressure. This pressure acts on the LS regulator of the working pump.

Fig. 21 Pressure balance in high-pressure position (pc high = LS signal to pump regulator) LHB/en/Edition: 07/2010

Fig. 22 Pressure balance in position "spool closed"

1 Pilot control piston 264 Pressure balance

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Pressure and feeder valves

2 Pressure spring F Spring chamber

100 Control valve block R Regulating orifice
224 Pressure balance pch High pressure (LS)
240 Spool pcl Low pressure
244 Pressure balance

8 Pressure and feeder valves

Fig. 23 Pressure and feeder valves in the control valve block

100 Compact control block 171 Pressure spring / load holding valve
102 Pressure balance / minimum flow 172 Screw plug
105 Primary pressure-relief valve 222 Secondary pressure-relief valve
162 Suction valve 242 Secondary pressure-relief valve
170 Cone / load holding valve 262 Secondary pressure-relief valve

8.1 Functional description

The pilot-controlled pressure-relief valves 105 / 221 - 262 of the various consumer connections are
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all of the cartridge type and screwed directly into the control valve block 100. They limit the pressure
between the pump, the control valve block and the working tools and/or between the working tools
and the control valve block when the spools are closed (secondary function).
If the pressure in the circuit of a working tool increase too fast, the weakest point such as the fittings
or the hydraulic hoses could be destroyed. In order to prevent this, the system features a pre-deter-
mined breaking point (defined weak point). In our scenario, the increasing pressure in the hydraulic
system acts on an integrated hydraulic device. This device is called a pressure-relief valve. It limits
the maximum pressure in the consumer and in the consumer's connection to a preset value.

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Pressure and feeder valves

As the pressure valves in the hydraulic system must be able to cater for large flows of oil, our machi-
nes are equipped with indirectly acting (pilot-controlled) pressure-relief valves for reasons of manuf-
acture and better functioning. With these valves, a direct acting pressure-relief valve is installed as
the direct pilot control valve to actuate a second, larger valve.
At the same time, the pressure-relief valves act as feeder valves. Different flow rates of the oil ente-
ring and leaving the operating cylinders lead to a vacuum. This happens for instance if there are ex-
ternal pulling loads, for example when the stick cylinder of a large stick is extended. In such a case,
the speed of the consumer is not controlled by means of the volume determined by the gauge orifice,
but (independent of the loads) via the outlet edge of the spool.
In order to prevent this, the valves connect the return side with the corresponding low-pressure side
so that additional oil can be taken in.

8.1.1 Pressure limitation, see Fig. 23

The pressure (P) built up in the consumer circuit acts on the front face of the main cone 3 and, through
the bore D1, also on the rear surface of the main cone 3. At the same time, the pressure also acts on
the pilot control cone 4. The springs 8 / 9 and 5 push the main cone 3 and the pilot control cone 4 into
their closing positions (static status).
As soon as the pressure in the consumer circuit reaches a value above the preset value of the pres-
sure and adjusting spring 5, the pilot control cone 4 is lifted from its seat, and some oil can enter the
return channel.
Due to the different cross-sections of the bores D1 in the main cone 3 and D2 in the valve insert 2,
there is a pressure difference between the front side and the spring side of the main cone 3.
As a result of this pressure difference, the main cone 3 is shifted against the pressure springs 8 / 9,
and a substantial volume of oil flows to the non-pressurised return side T.

8.1.2 Infeed
If there is a vacuum in a working circuit, the higher pressure in the hydraulic tank acts through the
bore T of the housing 1 on the ring face of the main cone 3. As a result of the pressure difference
across the effective surface of the main cone 3, the main cone is pressed against the force of the
pressure springs 8 / 9 so that the required volume of oil can flow through the bore T to the respective
side of the consumer.

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Pressure and feeder valves

Fig. 24 Pressure and feeder valve

1 Housing 9 Pressure spring

2 Valve insert 10 Protective cap
3 Main cone 11 Piston seal
4 Pilot control cone 12 O-ring
5 Pressure spring 13 O-ring
6 Adjusting screw 14 Back-up ring
7 Lock nut 15 O-ring
8 Pressure spring 16 O-ring

8.2 Feeder valves 161 / 162

The feeder valves (i.e. suction valves / check valves) are used with rotating consumers.
The danger of insufficient oil supply to the oil motors (cavitation) is greatest when the machine is de-
celerated (downhill travel). During deceleration, the oil motor of the travel gear runs idle. The pressure
peaks caused by the high moment of inertia during downhill travel trigger the brake valves while the
spools are blocked.
At a certain angle of inclination, the speed of the motor (and thus the oil volume to be fed) is no longer
determined by the aperture of the inlet orifice of the spool, but depends on the load and the downhill
LHB/en/Edition: 07/2010

force.
The feeder valve provides the required volume of oil to the operating connection to avoid cavitation.

8.3 Closing position:

The high pressure in channel P acts through the bore D and on the spring side of the main cone 3,
pressing the cone against the sealing edge of the valve insert 1 so that the valve 161 / 162 is closed

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Pressure and feeder valves

towards the consumer side.

8.4 Suction
If there is a vacuum in the working circuit, the higher pressure in the hydraulic tank acts through the
bore T of the valve insert 1 on the ring face of main cone 3.
As a result of the pressure difference across the effective surface of the main cone 3, the main cone
is pressed against the force of the pressure spring 8 so that the required volume of oil can flow th-
rough the bore T to the respective side of the consumer A2 / B2.

Fig. 25 Feeder valves

1 Valve insert 33 O-ring

3 Main cone 34 Back-up ring
6 Screw 35 O-ring
8 Pressure spring 37 O-ring
31 Piston seal
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Repair work on the control valve block

9 Repair work on the control valve block

Caution!
Before carrying out any repair work on the control valve block, release the tank pressure and the
servo preload.
X Shut down the diesel engine.
X Unscrew the breather filter on the hydraulic tank by about 1 revolution (slow de-pressurisation).

Releasing backpressures
X Turn the ignition key to contact position.
X Actuate all pilot control units in all possible directions to the stop.

9.1 Leaks on the outside

In the event of leaks on control valve blocks, replace the seals on fittings, SAE flanges, caps and val-
ves.

9.1.1 Spool

Note!
If you want to remove several spools at a time, be sure you put them back into the correct bores
afterwards (observe markings, etc.).
Spare spools are equipped with spool axle markings A1 - A5 engraved on the front side opposite
the spring and on the shaft of the spring plate package.

X Before installing the spool, check the O-rings in the housing (spool lid seals) for damage. Ensure
that the spools are in good working order (no scores on surface).
X To install the spools, complete the above steps in reverse order. Insert spools precisely and with
care. Avoid jamming. Do not use force.

9.1.2 Pressure balances and valves

To repair pressure balances and valves, remove them from housing.
First remove the suction valves 161 / 162 / 181 / 182 and the secondary pressure-relief valves 221 -
262 and then screw the respective load-holding valve 170 - 172 from the housing.
When installing valves, check the external sealing rings for damage.
X Do not use damaged, twisted or warped seals. Fit seals tightly.
Tighten the auxiliary axles, valves and fittings with the prescribed torque.
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Maintenance

9.1.3 Tightening torques for the control valve block 100

Check valve 7/8 10 Nm Valve seat 210/219 15 Nm
Pressure balance 102 25 Nm Pressure-relief valves 221 - 262 120 Nm
Pressure cut-off valve 104 25 Nm Screw plug 229 60 Nm
Pressure-relief valve 105 120 Nm Screw plug 275 10 Nm
Shift valve 106 80 Nm Screw plug 277 10 Nm
Nozzle 108 6.5 Nm Screw plug 278 10 Nm
Nozzle 109 8 Nm Allen head screw 320 70 Nm
Allen head screw 111 110 Nm Allen head screw 335 10.5 Nm
Allen head screw 135 10.4 Nm Screw plug 369 90 Nm
Screw plug 140 20 Nm Screw plug 373 120 Nm
Restrictor check valve 127/167/187/227/247 20 Nm Screw plug 475 30 Nm
Screw plugs 163/168/169 300 Nm Screw plug 491 3.5 Nm
Load-holding valve 172 150 Nm Allen head screw 811 55 Nm
Suction valves 161/162 120 Nm

Instructions for installation:

– The contact surface must be absolutely even.
– Mounting bolts must be tightened evenly, in a cross-wise pattern.
– The contact faces of the SAE connections must be clean.
– Pipes and hose lines must be properly laid, without any twisting, warping, stress, etc.
– Observe the prescribed tightening torques for the screws, fittings, etc. (see group 1.20 "Torques
of screws, bolts, screw-in studs").

10 Maintenance

Regularly check the control valve block for leaks. Regularly check the pressure cut-off valve 104 and
the secondary pressure-relief valves 221 - 262 for correct settings, following the maintenance instruc-
tions. To check the secondary pressure-relief valves 182, increase the set value for the pressure cut-
off valve 104 to value above the expected injection value (see adjustment protocol and guidelines for
hydraulic system in group 6).

11 Auxiliary control axles

11.1 Slewing gear element, Fig. 27

Sections of the element:
– Connections A01 and B01 for slewing gear supply and return flows
– Connection LSDR for load signal to right control valve block side
LHB/en/Edition: 07/2010

– Connection DRDA for pressure line of the proportional pressure-relief valve Y451
– Spool 120 for working movements of the uppercarriage, turning left and right
– Input pressure balance 122 for priority circuit
– Check valve 123 preventing effects on the slewing gear from any consumers actuated at the same
time at higher load pressure
– Control lid 334 of the axle, limiting the stroke of the spool 120, and including the control pressure
connections a01 and b01 as well as the regulating and return spring 335
– Restrictor check valves 127 for the fine control of the spool 120

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Auxiliary control axles

11.2 Repair work on the control valve block

Leaks on the outside

In the event of external leaks, replace the sealing rings of flanges, lids and valves. Replace leaking
screw plugs.

Spool
X Unscrew the respective control line.
X Remove the Allen head screws 335.
X Remove the control lid 334. (Caution: lid 334 is spring-loaded.)
X Remove the pressure spring 332. Pull the spool 120 from the housing.
X Install the components by completing the above steps in reverse order.

Valves
To repair a valve, remove the entire valves from the housing. If necessary, replace it with a spare
valve as listed in the spare parts catalogue.

Fig. 26 Hydraulic schematic of the slewing gear element 120

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Fig. 27 Slewing gear segment

109 Shuttle valve Ø 0.8-2.0, from 39333 369 Screw plug

120 Spool / slewing gear segment 371 Pressure spring
122 Input pressure balance 372 O-ring
127 Restrictor check valve 373 Screw plug
131 Nozzle Ø 1.8 mm 466 Valve seat
132 Cone 468 Valve seat
330 O-ring 475 Screw plug
331 Spring plate 476 Check valve
332 Pressure spring 490 Screw plug
334 Control lid 810 End plate
LHB/en/Edition: 07/2010

335 Allen head screw 811 Allen head screw

365 Pressure spring Y451 Proportional solenoid valve

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Auxiliary control axles

11.3 Functional description of the slewing gear axle

11.3.1 Priority of slewing gear

In the single-circuit LUDV system, all consumers are arranged in parallel and supplied by one and
the same working pump. In the LUDV system, the slewing gear is always given priority and can be
controlled independently of all the other consumers.
The question of priorities arises whenever the system must work at a saturation deficit and the LUDV
system automatically adjusts the speed of movements depending on the degree of the actual satu-
ration deficit.
Prioritising the slewing gear is necessary as most operators do not want the rotational speed being
affected by other movements. They also do not accept automatic acceleration caused by the LUDV
principle.
The slewing gear is therefore given priority whenever several movements must be carried out simul-
taneously. This is achieved as follows:
The module is the only consumer in the system that works with a 2-way pressure balance in the inlet
to the gauge orifice. The pressure balance for the section, in front of the gauge orifice, compares the
load pressure LS slewing gear and the setting of the spring of the pressure balance with pressure p
from the gauge orifice. The Up from the gauge orifice is kept at a constant level (determined by the
type of spring used) and thus allows for speed control independent of the load pressure. The only
way to modify the volume or speed is a change at the gauge orifice.

11.3.2 Attachment section is consumer with highest load pressure

Thanks to the check valve in the LS line between the module and the system, the control of the sle-
wing gear is not influenced by consumers with higher loads that happen to run at the same time.
The difference between the pump pressure psystem and the operating pressure p of the slewing gear
element is always controlled and regulated by the preceding pressure balance, even if the consumer
pressures fluctuate significantly. The regulating cross-section of the pressure balance has been cho-
sen to allow for quick regulation in case of great differences between psystem and p and increases /
opens with decreasing pressure differences.
The volumes supplied by the pump and not required by the slewing gear within the performance re-
gulation range are distributed proportionally to the other active consumers according to the LUDV
principle.

11.3.3 Slewing gear section is consumer with highest load

LSslewing gear is signalled to the LS line of the compact control block (via the check valve) to be the
highest pressure in the system. It acts on the rear sides of the LUDV pressure balances and the Up
regulator of the variable-displacement pump. The volumes supplied by the pump and not required by
the slewing gear within the performance regulation range are distributed to the other active consu-
mers according to the LUDV principle.

11.3.4 Slewing gear torque control

For fine acceleration of the slewing gear, a torque control (pressure control) function is required in
order to control the rate of acceleration.
LHB/en/Edition: 07/2010

During acceleration from zero, the slewing gear requests only a small volume of oil. With LS control,
it nevertheless generates the maximum load pressure in the slewing gear and thus the maximum ro-
tary acceleration. For this reason, the one speed that is independent of the load pressure (via 2-way
supply pressure balance 360) is overridden by a torque control.
The control pressure preset by the operator is converted by the pressure sensor B335 (see hydraulic
unit) into a signal that is then sent to the UEC control unit. The UEC control supplies a current that
corresponds to the preset control pressure to the proportional solenoid valve Y451. Depending on
the current, the proportional solenoid valve Y451 closes or opens the primary pressure connection in
the slewing gear circuit to the tank. This results in the control of the available torque. The correspon-

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ding operating pressure is generated proportionally to the control pressure, and thus to the angle of
the pilot control unit. By changing the set parameters in %, the operator can adjust the rotational
speed to achieve a more sensitive rotary movement.

11.3.5 Loss-free acceleration

The proportional solenoid valve Y451 is a separate unit located near the control valve block in the LS
line of the module of the pressure balance. This design ensures that the slewing gear is supplied only
with the volume of oil required to build up the necessary working pressure. As soon as the preset
pslewing gear is reached, the upstream pressure balance reduces the flow, and only supplies the
amount necessary to maintain the pressure. Thanks to this combination, the acceleration of the sle-
wing gear works without any losses.
The maximum permissible acceleration pressure is approx. 10 - 20 bar below the topmost setting of
the 2-step slewing gear valves in the oil motor. This means that the secondary valves do not respond
and loss is avoided. Thanks to the torque control, the volume supplied to the slewing gear motor in-
creases as pslewing gear drops, until the required pressure according to the preset Up pressure spring
is reached via the gauge orifice.

11.3.6 Deceleration of the slewing gear

The slewing gear is decelerated through the outlet orifices of the spool to the tank, and the pressure-
relief valves in the line leading to the motor. The minimum deceleration is determined by the lower
pressure setting of the 2-step slewing gear pressure valves. They have been tuned to a lower level
in order to provide for smooth deceleration. Again, the rule applies: as pcontrol pressure increases, the
additional pressure level of the secondary cartridge is continuously adjusted upwards to the maxi-
mum permissible value.
Both values can be controlled independently by regulating the permissible acceleration pressure with
the proportional solenoid valve Y451 and adjusting the deceleration via the brake valves on the mo-
tor.
When the spool is in neutral position, the slewing gear is hydraulically fixed by means of the closed
consumer connections A and B.
Should adjustments become necessary, proceed according to the adjustment protocol and the in-
spection and adjustment instructions in group 3.
In the event of malfunctions, it is possible to check the valve for dirt and/or a broken spring: remove
and dismantle the valve; if necessary, replace it completely.

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Fig. 28 Sectional drawing of slewing gear element

120 Spool / slewing gear segment 372 O-ring

122 Input pressure balance 373 Screw plug
127 Restrictor check valve 475 Screw plug
130 Nozzle Ø 0.9 mm D1 Feed gauge orifice p-A01 or p-B01
131 Nozzle Ø 1.5 mm D2 Outlet orifice A01 - T or B01 - T
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132 Cone (load holding function) pV Consumer pressure

334 Control lid pM Pressure in front of gauge orifice
365 Pressure spring a01/b0 Control oil connection
369 Screw plug A01 Consumer connection
371 Pressure spring B01 Consumer connection

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LSC auxiliary control axles

12 LSC auxiliary control axles

M7 - 205
M7 - 205 M7 - 205
Secondary
Secondary valve 2 axles
Designation SX/14-1X valve without
Unit with additional (AHS 1 + AHS
additional
pressure level 11)
pressure level

Built into AS1 AHS 1 AHS11 AHS 12

Spool 540 500 510 520
for Grapple rotator Kit AHS 1 Kit AHS 11 Kit AHS 12
left right Exten- Re- Exten- Retrac- Exten- Retrac-
ding trac- ding ting ding ting
ting
Nominal width of (“) 14 20 20 20
block (G3/4“) (SAE 3/4“) (SAE 3/4“) (SAE 3/4“)
Consumer connec-
tion
Ø piston rod mm 18 25 25 25
Piston stroke mm 8 8 11 11 11 11 11 11
Setting value Y
A 900 C mm 15.6 15.6 14.2 14.2 14.2 14.2 14.2 14.2#
A 904 C mm 15.6 15.6 14.2 14.2 14.2 14.2 14.2 14.2#

p1 ± 0.5 bar 2.0 2.0 7.0 7.0 7.0 7.0 7.0 7.0
p2 ± 0.5 bar 23.4 23.4 20.6 20.6 20.6 20.6 20.6 20.6
Qn (A)/Qn (B)
A 900 C l/min 30 30 220 150 200 200* 200 200*
A 904 C l/min 30 30 220 150 200 200* 200 200*
Restrictor check
valves mm 1.0 1.0 1.0
At connection a mm 1.0 1.0 1.0
At connection b
Max. leak oil cm3/min 60 60 60
at load pressure bar 150 150 150
at oil temperature °C 50 50 50
LHB/en/Edition: 07/2010

Tab. 2 List of LSC auxiliary control axles

* = if connected to horizontal boom adjustment system, reduce flow on both sides. To adjust, turn the stop screw to Y =
15mm (top) and Y = 12 mm (bottom).
# = if connected to regulating cylinder / hydraulic boom adjustment device, reduce flow to piston rod side to 140 l/min. To
adjust, turn the stop screw by 270 degrees = 0.7 mm. Dimension Y is reduced to 13.5 mm.

Solenoid Y22 / Y23 12 Nm Allen head screws 122 110 Nm at AHS 12

Pressure-relief valve 541 / 542 90 Nm Allen head screws 811 55 Nm at AS1
Seal Lock collar nut 1.70 38 Nm Pressure balance 544 160 Nm

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LSC auxiliary control axles

Allen head screw 20 10 Nm Pressure-relief valve 502 120 Nm

Screw plug 29 100 Nm Pressure-relief valve 501 120 Nm
Allen head screws 122 70 Nm Restrictor check 112 20 Nm
valve

– Qn (A) / Qn (B) = nominal flow rate at outlet A / Bat Up = nominal value

– p1 = control pressure at begin of regulation
– p2 = control pressure in final position

12.1 Grapple rotator element (kit AS1/540)

The additional element AS1(540) is flange-mounted as a kit to the control valve block next to the sle-
wing gear element. The working movements "turn grapple" and "tilt bucket" thus receive oil from the
main working pump.

12.2 Kit elements (kits AHS 1, AHS 11 and AHS 12)

For additional functions, e.g. accessory kits AHS1(500), AHS11(510) and AHS12(520), more auxili-
ary axles can be flange-mounted to the left-hand side of the compact control block.

12.3 Additional control valve block for accessory kits AS1, AHS 11 and AHS 12
To control additional working movements, you can mount an additional 1x element to the compact
block 100.
Each control axle (additional control valve block) includes the spool complete with actuation devices
(control lid, regulating springs), required for its respective function, a pressure balance and the cor-
responding connections with secondary protection. It is hydraulically connected to the series block
100 via the pressure, return and LS channels. O-rings seal off the flange faces of the channels.
The geometry of the spools and their gauge orifices has been designed and adapted to match the
characteristics of the respective consumer. The control of the consumer in the LUDV system is inde-
pendent of the load pressure. At constant Up, the volumetric flow is generated by modifying the
cross-section of the gauge orifice through the stroke of the spool. The maximum volume flow to the
consumer is thus determined by the available maximum open cross-section.
To retrofit one or more auxiliary axles, remove the end plate 110 or 810 and mount the new axle bet-
ween the block 100 and the plate 110 / 810.
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LSC auxiliary control axles

Fig. 29 Auxiliary control axles

12.4 Additional control valve block for accessory kit AS 1, see Fig. 30
The individual segment for the working movement "grapple rotator" is equipped with a magnetic-hy-
draulic actuation for the spool. This means that the proportional actuation of the piston has been de-
signed differently from the other two auxiliary axles as an "on-off control".
The control pressure at connection a / b is fed to the spring chamber of the spool 540 only after ac-
tuation of the respective solenoid Y22 / Y23. This way, the spool completely switches through. The
pressure balance 544 fulfils the same function as the other pressure balances in the compact block
100.
For functions and settings, see group 16. LHB/en/Edition: 07/2010

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LSC auxiliary control axles

Fig. 30 Auxiliary axle at AS1

540 Auxiliary control axle AS1 810 Mounting plate

541 Secondary pressure-relief valve 811 Allen head screw
542 Secondary pressure-relief valve Y22 Solenoid valve / grapple rotation left
544 Pressure balance Y23 Solenoid valve / grapple rotation right
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LSC auxiliary control axles

Fig. 31 Auxiliary control axle AS1

27 Cone / load-holding valve 541 Secondary pressure-relief valve

LHB/en/Edition: 07/2010

28 Pressure spring / L 542 Secondary pressure-relief valve

29 Screw plug 544 Pressure balance
30 O-ring 810 Mounting plate
31 Seal-Lock collar nut 811 Allen head screw
32 Adjusting screw / stroke limitation Y22 Solenoid valve / grapple rotation left
33 Pressure spring Y23 Solenoid valve / grapple rotation right
540 Spool / additional control valve block AS1

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LSC auxiliary control axles

12.5 Additional control valve block for accessory kit AHS 1

The design of the individual segment for the working movement "hydraulic boom adjustment" etc. cor-
responds to that of the boom, stick and bucket axles of the compact block.
For functions and settings, see group 16.

Fig. 32 Additional control valve block AHS1

500 Auxiliary control axle AHS1 504 Pressure balance

501 Secondary pressure-relief valve 507 Restrictor check valve
502 Secondary pressure-relief valve

12.6 Additional control valve block for accessory kit AHS11 with Tool Control
The design of the individual segment for the working movement "hydraulic hammer" corresponds to
that of the boom, stick and bucket axles of the compact block. Only function "actuating hydraulic ham-
mer" comes with a 2-step secondary pressure-relief valve.
For functions and settings, see group 16.
LHB/en/Edition: 07/2010

Fig. 33 Additional control valve block AHS11 with Tool Control

510 Auxiliary control axle AHS 11 514 Pressure balance

511 Pressure-relief valve, process pressure- 517 Restrictor check valve
controlled

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LSC auxiliary control axles

512 Pressure-relief valve, process pressure- Y414 Proportional solenoid valve

controlled

12.7 Additional control valve block for accessory kit AHS 12 with Tool Control
The design of the individual segment for the working movement "hydraulic adjustment of boom hy-
draulic hammer / hydraulic adjustment of boom telescopic demolition stick / scrap shear / concrete
crusher / sorting grapple" etc. corresponds to that of the boom, stick and bucket axles of the compact
block.
Only function "actuating hydraulic hammer" comes with a 2-step secondary pressure-relief valve.
For functions and settings, see group 16.

Fig. 34 Additional control valve block AHS12 with Tool Control

500 Auxiliary control axle AHS1 511 Pressure-relief valve, process pressure-
controlled
501 Secondary pressure-relief valve 512 Pressure-relief valve, process pressure-
controlled
502 Secondary pressure-relief valve 514 Pressure balance
504 Pressure balance 517 Restrictor check valve
507 Restrictor check valve 520 Auxiliary control axle AHS 12
510 Auxiliary control axle AHS 11 Y414 Proportional solenoid valve
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LSC auxiliary control axles
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Fig. 35 Auxiliary axles AHS1, AHS11 and AHS 2 with Tool Control

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LSC auxiliary control axles

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Fig. 36 Auxiliary control axles AHS 1

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LSC auxiliary control axles
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Fig. 37 Auxiliary control axles AHS11

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LSC control valve block Service Manual
LSC auxiliary control axles

15 Control lid 110 End plate

20 Allen head screw 122 Allen head screw*
27 Cone 500 Spool / segment AHS 1
28 Pressure spring 501 Secondary pressure-relief valve
29 Screw plug 502 Secondary pressure-relief valve
34 O-ring 504 Pressure balance
70 O-ring 507 Restrictor check valve
71 Screw plug 510 Spool / segment AHS 11
72 Pressure spring 511 Pressure-relief valve, process pressure-
controlled
90 Spring plate 512 Pressure-relief valve, process pressure-
controlled
91 Pressure spring 514 Pressure balance
100 Compact block 517 Restrictor check valve

* various lengths (depending on the number of additional elements)

12.8 Pressure-relief valves 511 / 512

If the pressure in the circuit of a working attachment rises, it begins to act on a built-in hydraulic de-
vice. This device is called a pressure-relief valve. It limits the maximum pressure in the consumer and
the consumer's connections to the preset value.
As high flows result in pressure on the pressure valves of the hydraulic unit, the machine is equipped
with indirectly acting (pilot-controlled) pressure-relief valves. With these valves, a direct acting pres-
sure-relief valve is installed as the direct pilot control valve to actuate a second, larger valve.
The pressure-relief valves 511 / 512 are process pressure-controlled. The oil flowing to the tank when
the valve is opened is fed externally via the proportional solenoid valve Y414, which is opened or
closed. The current to the proportional solenoid valve Y414 thus determines the settings of the se-
condary protection: minimum current = low pressure and maximum current= high pressure.

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LSC auxiliary control axles

Fig. 38 Proportional pressure control

12.9 Functional description of secondary pressure-relief valve 511 / 512

The pressure P built up in the consumer circuit acts on the front face of the main cone 5 and, through
the bore B1, also on the rear face of the main cone 5.
The main cone 5 is kept in its closed position as the area B3 is greater than the area B4 exposed to
the same pressure P.
The spring 3 pushes the pilot control cone 4 into its closed position.
As soon as the pressure in the consumer circuit reaches a value exceeding the preset value of the
pressure and adjusting spring 3, the pilot control cone 4 is lifted from its seat, and some oil can flow
through the valve Y414 via connection (T) to the tank, see 12.10.
Due to the different cross-sections of the bore B1 in the bushing 12 and the ring face B2 in the screw
plug 6 respectively, a pressure difference between the front and rear sides of the main cone 5 is es-
tablished. The main cone 5 is lifted and the connection T to the tank is opened. Any excess pressure
is thus released to the tank (secondary relief).
LHB/en/Edition: 07/2010

12.10 Proportional pressure control

In order to achieve proportional pressure control, the pressure (P) in the consumer circuit is controlled
by the valve Y414 through the connection Y in the pressure-relief valve 511 / 512.
The minimum and maximum pressure settings (as preset in the menu) are controlled relative to the
current (which in turn is controlled by the BST).
The later the valve Y414 is opened via T1, the higher the operating pressure. When the valve Y414
opens the connection to T1, the pressure of the column in the pressure-relief valve drops in propor-
tion to the actual current to the valve. The main cone 5 is thus lifted from its seat and the oil flow chan-

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LSC auxiliary control axles

nel P - T is opened. The pressure preset in the menu is established.

The settings for the proportional valve Y414 can be manually adjusted (in %) and saved for each at-
tachment in the respective menu, see group 16.

Fig. 39 Sectional drawing of pressure-relief valve 511 / 512 (process pressure-controlled)

1 Adjusting screw 511 Secondary pressure-relief valve for pres-

sure reduction
2 Lock nut 512 Secondary pressure-relief valve for pres-
sure reduction
3 Pressure and adjusting spring
4 Pilot control cone B1 Bore for pressure behind cone 5
5 Main cone B2 Ring face between screw plug 6 and cone
LHB/en/Edition: 07/2010

4
6 Screw plug B3 Effective surface behind cone 5
7 Housing B4 Effective surface in front of cone 5
11 Pressure spring P Pressure connection
12 Bushing T Tank connection
14 Solenoid Y Process pressure connection
15 Valve seat

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LSC auxiliary control axles
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LSC auxiliary control axles

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 Service Manual LSC pilot plate
Function

LSC pilot plate

1 Function

All machines of the Litronic series are equipped with the LSC control system.
The control unit of the hydraulic LSC control has been designed as a modular pilot plate.
The way valves for the travel function and the functions of the boom, stick and bucket cylinders, the
supports and the grapple rotation are flange-mounted to the pilot plate.
For additional functions, e.g. AHS 11 and (AHS 12+AHS 11 = AHS 12) attachment kits, additional
way valves can be flange-mounted to the left side of the pilot plate.

Note!
For detailed instructions regarding the settings of the individual components of the LSC pilot plate,
see group 3 in the service manual.
LHB/en/Edition: 04/2008

Fig. 1 LSC pilot plate

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LSC pilot plate Service Manual
Technical data

2 Technical data

Spool Unit 220 240 260 280 160 540

Boom Stick Bucket Support Travel Grapple
cylinder cylinder cylinder cylinder motor Rotate
Ex- Re- Ex- Re- Ex- Re- Ex- Re- Ex- Re- Ex- Re-
tend tract tend tract tend tract tend tract tend tract tend tract
Nominal width of mm 25 25 18 18 18 14
block
Consumer connec- (“) 1“ 1“ 3/4“ 3/4“ 3/4“ 3/4“
tion
Ø piston rod mm 32 32 25 25 25 20
Piston stroke mm 12.1 12.1 12.5 12.5 10.1 10.1 10.0 10.0 10.0 10.0 5.0 5.0
Setting value X mm
A 914 C 48.1 48.1 48.3 48.3 41.5 41.2 38.4 38.6 40.5 40.5 36.0 36.0
(construction)
A 924 C 48.1 48.1 48.3 48.3 41.5 41.2 38.4 38.6 40.5 40.5 36.0 36.0
(construction)
A 924 C (industrial) 48.1 48.1 48.5 48.5 41.5 41.2 41.0 41.0 40.5 40.5 36.0 36.0
D (shims) mm 1.6 1.6 1.3 2.0 2.3 2.3 2.3 2.3 2.0 2.0 3.0 3.0
p1 ± 0.5 bar 8.5 8.5 9.0 8.5 8.5 8.5 8.5 8.5 8.0 8.0 - -
p2 ± 0.5 bar 25.5 25.5 26.8 26.2 24.5 24.5 23.8 23.8 23.2 23.2 - -
Qn (A)/Qn(B) l/min
A 914 C 380 120 425 320 280 170 130 95 200 200 30 30
(construction)
A 924 C 380 120 425 320 280 170 130 95 200 200 30 30
(construction)
A 924 C (industrial) 330 115 410 160 280 170 250 250 200 200 30 30
Restrictor check mm
valve
At connection x 1.15 1.15 0.8
At connection y 0.8 0.8
3
Leak oil max. cm /min 75 75 70 70 70
at load pressure bar 150 150 150 150 150
at oil temperature °C 50 50 50 50 50

Tab. 1 Technical data

Note!
Shim thickness: "D": 0.3mm; 0.5mm; 1.0mm
Qn (A)/ Qn (B) = nominal flow rate at outlet A / B at 30 bar U-p = nominal value
p1 = control pressure at begin of control
p2 = control pressure in final position
LHB/en/Edition: 04/2008

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 Service Manual LSC pilot plate
Technical data

Fig. 2 Setting values

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LSC pilot plate Service Manual
Design

3 Design

Fig. 3 Front view of pilot plate (construction model)

LHB/en/Edition: 04/2008

Note!
The pressure-relief valve 248 is only installed in machines with LSC pilot plate (construction model).

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Design
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Fig. 4 Hydraulic diagram of construction model

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LSC pilot plate Service Manual
Design

41 Measuring point xP (pump pressure) 246 Restrictor check valve / control pressure
45 Measuring point xLS (LS pressure) 247 Stroke limiter / spool
100 Pilot plate 248 Pressure-relief valve / bypass valve
101 Pressure cut-off valve (LS pressure) 260 Way valve / bucket cylinder
102 Pump valve 261 Secondary pressure-relief valve / exten-
ding
103 Restrictor (LS relief) 262 Secondary pressure-relief valve / retrac-
ting
106 Valve / LS shutdown of grapple 263 Spool / boom cylinder
107 Pressurisation valve / return T 264 Pressure-relief bleeder valve
108 Pressurisation valve / return K 265 Pressure-relief bleeder valve
109 Pressure build-up 267 Stroke limiter / spool
110 Regeneration plate 280 Way valve / support
111 Shift valve 281 Suction valve / support
112 Shuttle valve 282 Suction valve / support
113 Piston 283 Spool / support
114 Piston 284 Pressure-relief bleeder valve
115 Lowering restrictor / boom cylinder 285 Pressure-relief bleeder valve
116 Lowering restrictor / stick cylinder 286 Restrictor check valve
Control pressure
117 Lowering restrictor / bucket grapple cylin- 287 Stroke limiter / spool
der
160 Way valve / travel motor 287 Stroke limiter / spool
161 Suction valve 540 Way valve / grapple rotator
162 Suction valve 543 Spool / grapple rotator
163 Spool / travel 544 Secondary pressure-relief valve
164 Pressure-relief bleeder valve 547 Stroke limiter / spool
165 Pressure-relief bleeder valve 549 Input pressure balance
166 Restrictor check valve Y22 Solenoid valve / grapple rotation right
Control pressure
167 Stroke limiter / spool Y23 Solenoid valve / grapple rotation left
220 Way valve / boom cylinder Y53 Radiator shift valve
221 Secondary pressure-relief valve / exten- A-A5 High-pressure connections
ding
222 Secondary pressure-relief valve / retrac- B-B5 High-pressure connections
ting
223 Spool / boom cylinder K Radiator connection
224 Pressure-relief bleeder valve LS/LSS LS pressure signal
225 Pressure-relief bleeder valve P1 Pump 1 connection
226 Restrictor valve / control pressure P2 Pump 2 connection
LHB/en/Edition: 04/2008

227 Stroke limiter / spool P3 Control pressure connection

240 Way valve / stick cylinder T/T1 Tank connection
241 Secondary pressure-relief valve / exten- T2 Leak oil connection
ding
242 Secondary pressure-relief valve / retrac- X1-X5 Control pressure connections, A side
ting
243 Spool / stick cylinder Y1-Y5 Control pressure connections, B side
244 Pressure-relief bleeder valve Z/Z1 Control pressure connection

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 Service Manual LSC pilot plate
Design

245 Pressure-relief bleeder valve DHS Pressure build-up

Note!
For a detailed description of the individual way valves, (see “Design and function of the way valves”
on page 21).
LHB/en/Edition: 04/2008

Fig. 5 Front view of pilot plate (industrial model)

Note!
In contrast to the construction model, the section 240 for the stick cylinders is installed at a 180°
angle.

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Design

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 Service Manual LSC pilot plate
Design

Fig. 6 Hydraulic diagram of industrial model

41 Measuring point xP (pump pressure)

45 Measuring point xLS (LS pressure) 246 Restrictor check valve / control pressure
100 Pilot plate 247 Stroke limiter / spool
101 Pressure cut-off valve (LS pressure) 260 Way valve / bucket cylinder
102 Pump valve 261 Secondary pressure-relief valve / exten-
ding
103 Restrictor (LS central nozzle) 262 Secondary pressure-relief valve / retrac-
ting
106 Valve / LS shutdown of grapple 263 Spool / boom cylinder
107 Pressurisation valve / return T 264 Pressure-relief bleeder valve
108 Pressurisation valve / return K 265 Pressure-relief bleeder valve
109 Pressure build-up 267 Stroke limiter / spool
110 Regeneration plate 280 Way valve / support
111 Shift valve 281 Suction valve / support
112 Shuttle valve 282 Suction valve / support
113 Piston 283 Spool / support
114 Piston 284 Pressure-relief bleeder valve
115 Lowering restrictor / boom cylinder 285 Pressure-relief bleeder valve
116 Lowering restrictor / stick cylinder 286 Restrictor check valve
Control pressure
117 Lowering restrictor / bucket grapple cylin- 287 Stroke limiter / spool
der
160 Way valve / travel motor 287 Stroke limiter / spool
161 Suction valve 540 Way valve / grapple rotator
162 Suction valve 543 Spool / grapple rotator
163 Spool / travel 544 Secondary pressure-relief valve
164 Pressure-relief bleeder valve 547 Stroke limiter / spool
165 Pressure-relief bleeder valve 549 Input pressure balance
166 Restrictor check valve Y22 Solenoid valve / grapple rotation right
Control pressure
167 Stroke limiter / spool Y23 Solenoid valve / grapple rotation left
220 Way valve / boom cylinder Y53 Radiator shift valve
221 Secondary pressure-relief valve / exten- A-A5 High-pressure connections
ding
222 Secondary pressure-relief valve / retrac- B-B5 High-pressure connections
ting
223 Spool / boom cylinder K Radiator connection
224 Pressure-relief bleeder valve LS/LSS LS pressure signal
225 Pressure-relief bleeder valve P1 Pump 1 connection
LHB/en/Edition: 04/2008

226 Restrictor valve / control pressure P2 Pump 2 connection

227 Stroke limiter / spool P3 Control pressure connection
240 Way valve / stick cylinder T/T1 Tank connection
241 Secondary pressure-relief valve / exten- T2 Leak oil connection
ding
242 Secondary pressure-relief valve / retrac- X1-X5 Control pressure connections, A side
ting

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LSC pilot plate Service Manual
Design

243 Spool / stick cylinder Y1-Y5 Control pressure connections, B side

244 Pressure-relief bleeder valve Z/Z1 Control pressure connection
245 Pressure-relief bleeder valve DHS Pressure build-up

Note!
For a detailed description of the individual way valves, (see “Design and function of the way valves”
on page 21).

LHB/en/Edition: 04/2008

Fig. 7 Rear view of pilot plate 100

A-A5 High-pressure connections X1-X5 Control pressure connections

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 Service Manual LSC pilot plate
Design

B-B5 High-pressure connections Y1-Y5 Control pressure connections

K Radiator connection Y53 Radiator shift valve
LS LS pressure signal 102 Pump valve
P1 Pump 1 connection 110 Regeneration plate
P2 Pump 2 connection 115 Lowering restrictor / boom cylinder
P3 Control pressure connection 116 Lowering restrictor / stick cylinder
T Tank connection 117 Lowering restrictor / bucket grapple cylin-
der
T2 Leak oil connection

3.1 Installation of the way valves

The way valves 160-540 are designed as disc valves. They are flange-mounted to the pilot plate 100.
The way valves 220, 240 and 260 are flange-mounted to the front side, while the way valves 160 and
280 are flange-mounted to the side of the plate.
In machines with optional equipment, there might be additional flange-mounted way valves required,
(see “Auxiliary way valves for AHS 1 and AHS 11” on page 34).
The connections T,P and LS, (see Fig. 7 on page10) between the way valves and the pilot plate are
established through internal channels and flange bores in the connecting faces.
All consumer connections A and B are located at the front side (seen in direction of travel). With way
valves that are used for the control of hydraulic cylinders, the connection A is always connected to
the piston face, while the connection B is connected to the rod side.
LHB/en/Edition: 04/2008

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LSC pilot plate Service Manual
Design

Fig. 8 Installation of the way valves

100 Pilot plate 248 Pressure-relief valve / bypass valve

(in construction models only)
123 End plate 260 Way valve / bucket cylinder
160 Way valve / travel 280 Way valve / support cylinder
220 Way valve / boom cylinder 540 Way valve / rotating grapple
240 Way valve / stick cylinder
LHB/en/Edition: 04/2008

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 Service Manual LSC pilot plate
Design

3.2 Pilot plate 100

LHB/en/Edition: 04/2008

Fig. 9 Design of pilot plate

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Design

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Fig. 10 Design of the regeneration plate

100 Pilot plate 112 Shuttle valve (2x in construction model)

101 Pressure cut-off valve (LS pressure) 113 Piston
102 Pump valve 114 Piston
103 Restrictor 115 Lowering restrictor / boom cylinder
106 Valve / LS grapple shutdown 116 Lowering restrictor / stick cylinder

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 Service Manual LSC pilot plate
Functions of the valves in the pilot plate 100

107 Pressurisation valve / return T 117 Lowering restrictor / bucket grapple cylin-
der
108 Pressurisation valve / return K Y53 Radiator shift valve
109 Pressure build-up 112 Shuttle valve
110 Regeneration plate A Construction model
111 Shift valve B Industrial model

3.3 Functional description

All way valves for the control of working and travel movements are flange-mounted to the pilot plate
100.
The pilot plate is supplied with oil through the connections P1 and P2 by the two working pumps. It
combines the two flows in a single pressure channel and then distributes the hydraulic oil to all way
valves.
At the return side, the pilot plate collects the oil flowing from the T channel of the way valves and feeds
it through the pressurisation valves 107 and 108 and then through the connection "T" (directly to
tank) and "K" (first to radiator) and then back to the hydraulic tank. The automatic control of the oil
cooling system is based on the hydraulic fan control and the proportional solenoid valve Y53 attached
to the valve 110.
In addition, the pilot plate 100 generates the highest LS pressure based on the pressures in the va-
rious LS channels of the way valves. This high pressure flow is then communicated through the con-
nection "LS" to the pump controller.

4 Functions of the valves in the pilot plate 100

4.1 Pressure cut-off valve 101

4.1.1 Function of pressure cut-off valve

This valve limits the maximum LS pressure in the pilot plate 100 to the preset value.
This ensures that the maximum pump high pressure is limited by the pump regulator to a pressure
that is maximum U-p (LS) higher.
If the consumer is for example moved to the stop, the working pump of the LS regulator is swivelled
to the Qmin stop and the maximum pressure is maintained. The higher set secondary pressure-relief
valves fail to respond.
LHB/en/Edition: 04/2008

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LSC pilot plate Service Manual
Functions of the valves in the pilot plate 100

Fig. 11 Section drawing of pressure cut-off valve

1 Valve cartridge 6 Valve cone

2 Sealing flange nut 7 Backing ring
3 Threaded stud 8 O-ring
4 Spring plate 9 O-ring
5 Valve insert 10 Spring

4.2 Pump valve 102

The valve 102 limits the pressure difference between the pump high pressure and the LS pressure
to a value above the valueU-p (LS) set at the pump.
The valve prevents pressure peaks that might occur in the dynamic behaviour of the pump and that
cannot be reduced by the U-p regulator, for example during the sudden closing of a spool, when the
drive motor is started, etc.).

LHB/en/Edition: 04/2008

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 Service Manual LSC pilot plate
Functions of the valves in the pilot plate 100

Fig. 12 Sectional drawing of pump valve

11 Valve cartridge 15 Spring plate

12 Adjusting screw 16 Valve insert
13 Sealing flange nut 17 Backing ring
14 Spring 18 O-ring

4.3 Valve / LS grapple shutdown 106 grapple operation, see Fig. 13

If grapple operation is preselected (push button S85 actuated) and if the movements "extending stick"
is started, the connection "Z1" of the pilot plate 100 is pressurised with servo pressure and the shifting
piston of the valve 106 is switched to its closed position.
The pressure in the "close grapple" circuit is thus not built up in the main LS channel.
This prevents that the high pressure in the "close grapple" circuit resulting in a reduction in the stick
extending speed. The option to propel a load using the grapple remains therefore still possible, even
if the operator keeps the grapple tongs closed against the stop.

4.4 Pressurisation valves 107 and 108, see Fig. 13

These valves are used to maintain a slight counterpressure in the return circuit of the way valves (pre-
vention of cavitation).
At normal operating temperatures, the oil flows through the pressurisation valve 108 (3bar) back to
the hydraulic oil cooler. If the hydraulic oil is cold, the counterpressure in the return circuit is increa-
sed. The valve 107 (5bar) set to a slightly higher value is opened and allows the oil to flow back to
LHB/en/Edition: 04/2008

the tank. The hydraulic oil cooler is thus protected against pressure peaks.
The pistons 113 and 114 in the valve 110, (see Fig. 9 on page13), can increase the response pressure
of the valves 107 and 108 for certain work procedures.

4.5 Valve 110 for the oil return from boom and stick, see Fig. 13
The servo pressures at the connection “y1“ of the way valve 220 (retracting boom cylinder) and at

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LSC pilot plate Service Manual
Functions of the valves in the pilot plate 100

the connection “x2“ of the way valve 240 (extending stick cylinder) are connected by internal bores
in the valves and in the pilot plate 100 with the valve 110.
If one of the above movements is started, the shift valve 111 is switched via the shuttle valve 112 (in
industrial models: one valve only). The pilot control pressure at the connection “P3“ of the pilot plate
100 is built up at the external working surfaces of the pistons 113 and 114.
These pistons apply a force to the cones in the valves 107 and 108. This force is in the same direction
as the effect of the preload spring of the valves.
This results in an increase in the counterpressure in the tank channel of the pilot plate and thus faci-
litates the taking up of oil at the piston side of the boom cylinders (or at the piston side of the stick
cylinder). Caviation is thus prevented.

4.6 Temperature-dependent hydraulic oil cooling

4.6.1 No oil cooling (for oil temperatures up to 40 °C), see Fig. 10

The valve Y53 is powered (740 mA). The channel for the control oil from connection P3 to the piston
113 is open through the valves Y53 and 112.
The cone of the pressurisation valve 108 is pressurised at the spring side and thus blocks the return
oil flow to the oil cooler.

4.7 Oil cooling (for oil temperatures above 40°C), see Fig. 10
The valve Y53 blocks the channel of the control oil to the piston 113 proportionally to the current to
Y53 (740 mA-100 mA). The valve 108 is released.
The oil flow (return oil flow) increases proportionally to the opening movement of the valve Y53 (3 bar
opening pressure) through the valve 108, the connection K and the oil cooler.

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 Service Manual LSC pilot plate
Functions of the valves in the pilot plate 100

Fig. 13 Sectional drawing of pilot plate

100 Pilot plate 110 Regeneration plate

101 Pressure cut-off valve (LS pressure) 111 Shift valve
LHB/en/Edition: 04/2008

102 Pump valve 112 Shuttle valve (2x in construction model)

106 Valve / LS grapple shutdown 113 Piston
107 Pressurisation valve / return T 114 Piston
108 Pressurisation valve / return K Y53 Radiator shift valve

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LSC pilot plate Service Manual
Functions of the valves in the pilot plate 100

4.8 Lowering restrictors 115-117

Fig. 14 Lowering restrictor at pilot plate

4.8.1 Lowering restrictor for boom cylinder 115

This restrictor is used in the return channel from the piston side of the boom cylinder. It thus limits the
retracting speed of the boom cylinder.

4.8.2 Lowering restrictor for stick cylinder 116

This restrictor is used in the return channel from the piston side of the stick cylinder. It thus limits the
retracting speed of the stick cylinder.

4.8.3 Lowering restrictor for bucket cylinder 117

This restrictor is used in the return channel from the piston side of the bucket cylinder. It thus limits
the retracting speed of the bucket cylinder.

4.9 Pressure-relief valve 248 (bypass valve)

Note!
The pressure-relief valve 248 is only installed in construction models.
The valve is factory-set and its settings may not be changed.

The pressure-relief and suction valve 248 consists of a housing with a main and a pilot control sec-
tion. The main control section consists of the piston 46 with the needle piston 53 and is pressed by
the springs 47 and 48 into the valve seat (sealed seat).
LHB/en/Edition: 04/2008

The pilot control section consists of a valve cone 50 that is pressed by the spring 51 into the valve
seat (sealed seat). The maximum response pressure is adjusted by means of shims 60.
By increasing the control pressure at the piston 58, the maximum pressure value can be lowered. By
turning the adjusting screw 52, the travel of the piston 58 can be limited, so that the lowered response
pressure (caution: factory settings!) of the response pressure can be set to the desired value.
If required, the piston 58 can be blocked with the adjusting screw 52. This disables the control pres-
sure relief and the standard maximum pressure settings are applied.

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 Service Manual LSC pilot plate
Design and function of the way valves

Fig. 15 Pressure-relief valve 248

46 Piston 58 Piston
47 Spring 59 Spring
48 Spring 60 Shims
50 Valve cone 61 Shims
51 Spring 62 Nozzle
52 Adjusting screw 63 O-ring
53 Needle piston A2 Consumer channel
54 Piston face C Chamber C
55 O-ring D Chamber D
56 Transverse slot T1 Tank channel
57 Control pressure channel

5 Design and function of the way valves

This chapter describes the way valve 220 for boom cylinder. The following way valves operate in the
same way:
– 240 for stick cylinder
LHB/en/Edition: 04/2008

– 260 for bucket cylinder

– 280 for support cylinder
– 500 for AHS11 (hydraulic hammer)
– 520 for AHS11 (auxiliary cylinder)
The way valve 220 is designed as a disc valve. It is mounted on the base plate (pilot plate 100) and
consists of a way valve housing 24 with the connections P, LS, T and the consumer flange connec-
tions A and B located above them. The valve contains the spool 223 and the two pressure balances
225 and 226 containing the switches 227 and 228.

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LSC pilot plate Service Manual
Design and function of the way valves

At the secondary side, the unit is equipped with a pressure-relief and suction valves 221 and 222.
The control connections in the lids 19 contain restrictor check valves 25. The bleeder valves 23 for
the lid 19 are mounted in the way valve housing 24.
The stop screws 21 limit the piston stroke and thus determine the flow volume when the nominal va-
lue U-p (LS) is reached in the piston rod.
The shims 18 can be used to adjust the preload of the regulation springs 20 and thus the control pres-
sure at the start of the opening movement.
Depending on the consumer and the fed consumer side, the pilot control connections "x" and "y"
(threaded bores) might be equipped with restrictor check valves 25, see Fig. 17. The bucket cylinder
section 260 does not contain any restrictor check valves 25.
The valves 23 are used to limit the pressure and bleed the control oil in the two lids 19.
The secondary pressure-relief valves 221 and 222 are designed as cartridge valves and are screwed
in below/above the consumer connections in the way valve housing. They limit the secondary pres-
sures between the spool and the consumer to the set maximum values and feature an integrated suc-
tion function. This means that they allow for oil flow from the return to the consumer connection side,
as soon as the pressure in "A" or "B" drops below the pressure in "T".
The suction valves 281 and 282, (see “Way valve for the support section 280” on page 26) are of the
cartridge type and screwed in above/below the consumer connection in the way valve housing 280.
They allow for the flow of oil from "T" to the respective consumer connection "A4" or "B4" and thus
prevent cavitation.

Fig. 16 Hydraulic diagram of the boom cylinder way valve 220

18 Shim 220 Way valve / boom cylinder

19 Lid 221 Secondary pressure-relief valve
20 Regulation spring 222 Secondary pressure-relief valve
21 Stop screw 223 Spool
22 Sealing flange nut 225 Load compensator P-A
23 Pressure-relief valve/bleeder valve 226 Load compensator P-B
LHB/en/Edition: 04/2008

24 Way valve housing 227 Switch

25 Restrictor check valve 228 Switch

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 Service Manual LSC pilot plate
Design and function of the way valves

5.1 Way valve for the boom cylinder section 220

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Fig. 17 Way valve for the boom cylinder section 220

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LSC pilot plate Service Manual
Design and function of the way valves

5.2 Way valve for the stick cylinder section 240

LHB/en/Edition: 04/2008

Fig. 18 Way valve for the stick cylinder section 240

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 Service Manual LSC pilot plate
Design and function of the way valves

5.3 Way valve for the bucket cylinder section 260

LHB/en/Edition: 04/2008

Fig. 19 Way valve for the bucket cylinder section 260

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LSC pilot plate Service Manual
Design and function of the way valves

5.4 Way valve for the support section 280

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Fig. 20 Way valve for the support section 280

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 Service Manual LSC pilot plate
Design and function of the way valves

5.5 Way valve for the travel section 160

The spool 163 contains two pressure balances (load compensators) 165 and 166, which in turn con-
tain the switches 167 and 168.
The spool determines the oil volume fed to the connected consumer, depending on the control pres-
sure applied to the connection "x5" or "y5", the pressure in the LS channels and the total flow volume
of the working pumps.
The stop screws 21 limit the piston stroke and thus determine the flow volume when the nominal va-
lue U-p (LS) is reached at the spool.
The shims 26 can be used to adjust the preload of the regulation springs 20 and thus the control pres-
sure at the start of the opening movement.
Depending on the consumer and the fed consumer side, the pilot control connections "x5" and "y5"
might be equipped with restrictor check valves 23.
The valves 25 are used to limit the pressure and bleed the control oil system in the two lids 19.
The suction valves 161 and 162 are of the cartridge type and screwed in above/below the consumer
connection in the way valve housing. They allow oil to flow from the return side to the consumer con-
nection as soon as the pressure in "A5" or "B5" drops below the pressure in "T".

Fig. 21 Hydraulic diagram of the travel way valve 160

18 Shim 160 Way valve / travel motor

19 Lid 161 Suction valve
20 Regulation spring 162 Suction valve
21 Stop screw 163 Spool
22 Sealing flange nut 165 Load compensator P-A
23 Pressure-relief valve/bleeder valve 166 Load compensator P-B
24 Way valve housing 167 Switch
25 Restrictor check valve 168 Switch
LHB/en/Edition: 04/2008

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LSC pilot plate Service Manual
Design and function of the way valves

LHB/en/Edition: 04/2008

Fig. 22 Way valve for the travel section 160

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 Service Manual LSC pilot plate
Design and function of the way valves

5.6 Way valve for the grapple rotation section 540

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Fig. 23 Way valve for the grapple rotation section 540

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LSC pilot plate Service Manual
Design and function of the way valves

Fig. 24 Hydraulic diagram for the grapple rotation section 540

41 Measuring point xP (pump pressure)

45 Measuring point xLS (LS pressure) 246 Restrictor check valve / control pressure
100 Pilot plate 247 Stroke limiter / spool
101 Pressure cut-off valve (LS pressure) 260 Way valve / bucket cylinder
102 Pump valve 261 Secondary pressure-relief valve / exten-
ding
103 Restrictor (LS central nozzle) 262 Secondary pressure-relief valve / retrac-
ting
106 Valve / LS grapple shutdown 263 Spool / boom cylinder
107 Pressurisation valve / return T 264 Pressure-relief bleeder valve
108 Pressurisation valve / return K 265 Pressure-relief bleeder valve
109 Pressure build-up 267 Stroke limiter / spool
110 Regeneration plate 280 Way valve / support
111 Shift valve 281 Suction valve / support
112 Shuttle valve 282 Suction valve / support
113 Piston 283 Spool / support
114 Piston 284 Pressure-relief bleeder valve
115 Lowering restrictor / boom cylinder 285 Pressure-relief bleeder valve
116 Lowering restrictor / stick cylinder 286 Restrictor check valve
Control pressure
117 Lowering restrictor / bucket grapple cylin- 287 Stroke limiter / spool
der
160 Way valve / travel motor 287 Stroke limiter / spool
161 Suction valve 540 Way valve / grapple rotator
LHB/en/Edition: 04/2008

162 Suction valve 543 Spool / grapple rotator

163 Spool / travel 544 Secondary pressure-relief valve
164 Pressure-relief bleeder valve 547 Stroke limiter / spool
165 Pressure-relief bleeder valve 549 Input pressure balance
166 Restrictor check valve Y22 Solenoid valve / grapple rotation right
Control pressure
167 Stroke limiter / spool Y23 Solenoid valve / grapple rotation left

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 Service Manual LSC pilot plate
Design and function of the valves 161-282

220 Way valve / boom cylinder Y53 Radiator shift valve

221 Secondary pressure-relief valve / exten- A-A5 High-pressure connections
ding
222 Secondary pressure-relief valve / retrac- B-B5 High-pressure connections
ting
223 Spool / boom cylinder K Radiator connection
224 Pressure-relief bleeder valve LS/LSS LS pressure signal
225 Pressure-relief bleeder valve P1 Pump 1 connection
226 Restrictor valve / control pressure P2 Pump 2 connection
227 Stroke limiter / spool P3 Control pressure connection
240 Way valve / stick cylinder T/T1 Tank connection
241 Secondary pressure-relief valve / exten- T2 Leak oil connection
ding
242 Secondary pressure-relief valve / retrac- X1-X5 Control pressure connections, A side
ting
243 Spool / stick cylinder Y1-Y5 Control pressure connections, B side
244 Pressure-relief bleeder valve Z/Z1 Control pressure connection
245 Pressure-relief bleeder valve DHS Pressure build-up

6 Design and function of the valves 161-282

6.1 Secondary pressure-relief valves for the boom, bucket and stick sections 220,
240 and 260 respectively
The pressure-relief and suction valves screwed into the way valves consists of a housing with a main
and a pilot control section. The main control section consists of the piston 26 with the needle piston
33 and is pressed by the springs 27 and 28 into the valve seat (sealed seat).
The pilot control section consists of a valve cone 29 that is pressed by the spring 30 into the valve
seat. The force of the spring 31 acting on the valve cone 29 can be adjusted with the adjusting screw
31, in order to set the response pressure of the pressure-relief valve to the desired value.
LHB/en/Edition: 04/2008

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LSC pilot plate Service Manual
Design and function of the valves 161-282

Fig. 25 Sectional drawing

23 Bleeder valve 34 O-ring

26 Piston 35 Transverse slot
27 Spring 36 Piston face
28 Spring B Chamber B (consumer channel)
29 Valve cone C Chamber C
30 Spring D Chamber D
31 Adjusting screw T Tank channel
32 Lock nut T1 Tank channel
33 Needle piston

Note!
when unscrewing the secondary pressure-relief valves, the O-ring 34 might remain in the valve hou-
sing.
X To prevent this, carefully loosen the secondary pressure-relief valves and unscrew them from
the housing.
X Always remove the O-rings from the housing, inspect them for damage and replace them, if ne-
cessary.
LHB/en/Edition: 04/2008

6.2 Pressure-relief valve function

If the pressure in the chamber B through the channel in the needle piston 33 in chamber C reaches
the setting value of the valve cone 29, the cone is opened. The oil held back behind the valve cone
29 in the chamber D can now flow through the channel T1 to the chamber T.
This results in a pressure drop in the chamber C, and the piston 26 with the needle piston 33 is lifted
by the pressure acting on the effective piston surface 36. The needle piston 33 reaches the valve

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 Service Manual LSC pilot plate
Design and function of the valves 161-282

cone and positions itself at its front face.

The connection from the chamber B to the chamber T is established and the backpressure is relie-
ved. To ensure a more effective control of the pressure-relief valve, the upper front surface of the
needle piston 33 is equipped with a transverse slot 35. If the needle piston 33 is positioned on the
valve cone 29, the transverse slot 35 acts as a restrictor.
The oil flows through the channel in the needle piston 33 and via the transverse slot 35 in the upper
front face to the chamber C. If the pressure is lower than the force of the spring 30, the pressure dif-
ference between the chambers B and C is equalised. As a consequence, the force of the springs 27
and 28 acts on the piston 26, pushing it into its valve seat.

6.3 Suction valve function

The channel T is always pressurised (preload valve in the pilot plate). If pressure is built up in the
chamber B, and this pressure is lower than the pressure in the channel T, a pressure difference oc-
curs and the oil in the chamber T acts on the effective piston surface 36. The piston 26 is pushed
against the force of the springs 27 and 28 so that it is shifted, opening the connection between the
chamber T and the chamber B. The resulting pressure equalisation prevents cavitation.

6.4 Suction valves for travel and support sections 160 and 280 respectively
The suction valves 161, 162, 281, 282 screwed into the way valves 160 and 280 (with bypass) consist
of a housing with the valve seat 43 containing the piston 39 with the spring 40. The valves are factory-
set and cannot be adjusted.
The channel T is always pressurised. If pressure is built up in the chamber B, and this pressure is
lower than the pressure in the channel T, a pressure difference occurs and the oil in the chamber T
acts on the effective piston surface 38. The piston 39 is pushed against the force of the spring 40 so
that it is shifted, opening the connection between the channel T and the chamber B. The resulting
pressure equalisation prevents cavitation.
LHB/en/Edition: 04/2008

Fig. 26 Suction valves for travel and support sections

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LSC pilot plate Service Manual
Auxiliary way valves for AHS 1 and AHS 11

7 Auxiliary way valves for AHS 1 and AHS 11

23 Bleeder valve 160 Way valve / travel

37 Housing 161 Suction valve
38 Effective piston face 162 Suction valve
39 Piston 280 Way valve / support
40 Spring 281 Suction valve with bypass
42 Spring chamber 282 Suction valve with bypass
43 O-ring B Consumer connection
44 Connecting channel T Tank channel

For additional functions, e.g. accessory kits AHS1, AHS11 (AHS1+AHS11=AHS12) more additional
axles can be flange-mounted to the left-hand side of the pilot plate (seen in the direction of travel).
The basic design of the way valves 500 and 520 is identical with that of the valves used for the wor-
king movements 220 etc. (see “Design and function of the way valves” on page 21).
If one or more additional axles are retrofitted, the end plate 123 must be removed and the desired
additional axle must be flange-mounted to the pilot plate 100.

Note!
For a description of the function and settings of the AHS 11/AHS 12 accessory kit, see group 16.50.

LHB/en/Edition: 04/2008

7.55.34
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 Service Manual LSC pilot plate
Technical data

Fig. 27 Way valves for AHS 11 and AHS 12

8 Technical data

Spool Unit 500 520

Hammer/ Additional
cylinder cylinder
LHB/en/Edition: 04/2008

Ex- Re- Ex- Re-

tend tract tend tract
Nominal width of mm 18 14
block
Consumer connec- (“) 3/4“ 3/4“
tion
Ø piston rod mm 25 25

7.55.35
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LSC pilot plate Service Manual
Technical data

Spool Unit 500 520

Hammer/ Additional
cylinder cylinder
Ex- Re- Ex- Re-
tend tract tend tract
Piston stroke mm 9.0 9.0 9.0 9.0
Setting value X mm 40.0 40.0 40.0 40.0
D (shims) mm 2.0 2.0 1.0 1.0
p1bar ± 0.5 mm bar 8.5 8.5 8.5 8.5
p2bar ± 0.5 mm bar 21.5 21.5 21.5 21.5
Qn (A)/Qn(B) l/min
A 914 C 250 250 250 250
A 924 C 250 250 250 250

Restrictor check val- mm

ve
At connection x
At connection y
Leak oil max. cm3/min 90 90
at load pressure bar 150 150
at oil temperature °C 50 50

Tab. 2 Technical data

Note!
Shim thickness: "D": 0.3mm; 0.5mm; 1.0mm
Qn (A)/ Qn (B) = nominal flow rate at outlet A / B at 30 bar U-p = nominal value
p1 = control pressure at begin of control
p2 = control pressure in final position

Fig. 28 Setting values

LHB/en/Edition: 04/2008

8.1 AHS 11 way valve

The design of the individual segment for the working movement "hydraulic hammer" corresponds to
that of the boom, stick and support way valves. For the "hydraulic hammer" function, a secondary
pressure-relief valve that can be adjusted by means of the control pressure is installed.

7.55.36
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 Service Manual LSC pilot plate
Technical data

Fig. 29 Hydraulic diagram of AHS 11

LHB/en/Edition: 04/2008

Fig. 30 AHS 11

501 Secondary pressure-relief valve with addi- 505 Stroke limiter / spool
tional pressure stage

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LSC pilot plate Service Manual
Technical data

502 Secondary pressure-relief valve with addi- 506 Pressure-relief and bleeder valve
tional pressure stage
503 Spool 507 Pressure-relief and bleeder valve
504 Stroke limiter / spool

8.2 Function of the secondary pressure-relief valves 501 / 502

The pilot-controlled pressure-relief and suction valve ensures the pressure and sucks up oil. The pilot
control cone 73 is pre-loaded with the pressure spring 74 and the main cone 71 is hydraulically inser-
ted. The pilot control cone 73 and the main cone 71 are opened as soon as the pressure value is
reached. The preload of the pressure spring 74 and thus the pressure settings are determined based
on the force applied to the piston 76:

8.2.1 without application of control pressure (low pressure)

The force applied to the piston 75 is determined by the adjusting screw 80. The further the piston 75
is pushed inwards through the adjusting screw 80, the greater the preload force of the pressure spring
74 and thus the adjusting pressure of the valve 501 / 502.

8.2.2 with application of control pressure (high pressure)

If the port Z is pressurised through the proportional solenoid valve Y414 with a preset control pres-
sure, the same pressure is applied through the bore Z1 to the piston 76. The piston 76 applies an
additional force to the piston 75. As a result, the total preload force applied to the pressure spring 74
is increased, and thus also the pressure of the valve. The maximum value for the pressure increase
can be adjusted with the limiter screw 80.

LHB/en/Edition: 04/2008

7.55.38
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 Service Manual LSC pilot plate
Technical data

Fig. 31 Pressure-relief valve with external additional control pressure stage

70 Valve cartridge 79 Lock nut

71 Main cone 80 Adjusting screw / low pressure
72 Pressure spring 81 Lock nut
73 Pilot control cone 82 Adjusting screw characteristic
74 Pressure spring 83 Lock nut
75 Piston 501 Secondary pressure-relief valve
76 Piston 502 Secondary pressure-relief valve
77 Pressure spring Z Control pressure connection of Y414
78 Adjusting screw / high pressure Z1 Bore / oil channel

8.3 AHS 12 (AHS 1 + AHS 11) way valve

LHB/en/Edition: 04/2008

The basic design of the individual segment of the working movement "hydraulic hammer", the hydrau-
lic boom adjustment, the telescopic demolition stick, the scrap shears, the concrete crusher, the sor-
ting grapple, etc. correspond to that of the boom, stick and support valve.

7.55.39
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LSC pilot plate Service Manual
Technical data

Fig. 32 Hydraulic diagram of AHS 12

LHB/en/Edition: 04/2008

Fig. 33 AHS 12

521 Secondary pressure-relief valve 525 Stroke limiter / spool

522 Secondary pressure-relief valve 526 Pressure-relief and bleeder valve
523 Spool 527 Pressure-relief and bleeder valve
524 Stroke limiter / spool

7.55.40
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 Service Manual LSC pilot plate
Technical data

8.4 Function of the secondary pressure-relief valves 521 / 522

Note!
For a detailed description of the secondary pressure-relief valves, (see “Secondary pressure-relief
valves for the boom, bucket and stick sections 220, 240 and 260 respectively” on page 31).
LHB/en/Edition: 04/2008

7.55.41
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LSC pilot plate Service Manual
Technical data

LHB/en/Edition: 04/2008

7.55.42
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MJFCIFSS
 Service Manual Cooling unit
Function/design

Cooling unit

1 Function/design

Cooling of the hydraulic oil, the coolant, the fuel and the intercooling air of the diesel engine.
The speed of the hydrostatically driven annular fan RL is controlled according to the cooling require-
ments (i.e. based on the coolant, intercooling air and hydraulic oil temperature as well as on the a/c
system (on/off)).
The flow rate of the hydraulic oil and the intercooling air is not controlled. The flow rate of the engine
coolant is however thermostat-controlled.

Note!
The arrows indicate the inlet and outlet devices of the respective cooling elements of the cooling
unit.

Fig. 1 Cooling unit

4 Expansion tank 14 Pressure-relief valve

LHB/en/Edition: 08/2010

5 Fuel cooler 15 Hub

6 Hydraulic oil cooler FS Finger guard
7 Water cooler (coolant) / engine H Air scoop
8 Intercooling air cooler / engine RL Annular fan / blower rotor
13 Blower motor Y347 Proportional pressure-relief valve

7.60.1
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Cooling unit Service Manual
Function/design

1.1 Cooling elements

The cooling unit consists of 4 cooling elements (heat exchangers):
– Cooler 5 for fuel.
– Oil cooler 6 for hydraulic oil.
– Cooler 7 for engine coolant.
– Cooler 8 for intercooling air.
– They are installed in a shared frame with air ducting plates.
The annular fan (RL) required to produce the air flow is positioned in the opening of the air duct frame.
The annular fan is driven by the blower motor 13. The blower motor speed required to produce the
necessary air flow is automatically controlled by the excavator control system (BST) through the pro-
portional solenoid valve Y347 at the blower motor and the necessary signals from the temperature
sensors at the diesel engine and the hydraulic tank.
The blower motor 13 is protected by the pressure-relief valve 14 that is integrated into the cooling blo-
wer circuit. The pressure-relief valve 14 is factory-set.

1.2 Fan control

The hydrostatic fan drive is controlled by the hydraulic oil temperature B8, the cooling water tempe-
rature B708, the intercooling air temperature B707 and the a/c system Y20 (on/off). The fan speed
is controlled electronically, relative to the temperature, through the proportional solenoid valve Y347.
Between the minimum and maximum values, the current from the excavator control system BST
(U16) to the solenoid valve Y347 is linear, which means that each temperature value between these
two limit points corresponds to a specific current I and pressure p between the minimum and maxi-
mum values, resulting in a specific fan speed.

LHB/en/Edition: 08/2010

Fig. 2 Monitoring of the cooling unit

B8 Temperature sensor / hydraulic oil B708 Temperature sensor / coolant

B707 Temperature sensor / intercooling air Y20 Magnetic clutch / a/c system

7.60.2
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 Service Manual Cooling unit
Function of the fan control

2 Function of the fan control

see Fig. 3
The speed of the blower motor is controlled by the solenoid valve Y347. Depending on the oil and
coolant temperature, the BST (U16) adjusts the current to the proportional solenoid valve Y347, thus
opening / closing the solenoid valve Y347. The more the solenoid valve Y347 is opened, the less hy-
draulic oil flows to the blower motor 13 and the lower the fan speed.
If the temperature of the hydraulic oil in the tank and/or the coolant in the engine and/or the intercoo-
ling air in the turbocharger is lower than or equal to the lower limit value TB8 (min.), TB708 (min.), or
TB707 (min.) respectively, the output current to the proportional solenoid valve Y347 of the BST (U16)
corresponds to IY347 (max.).
In this case, the pressure at the proportional solenoid valve Y347 is reduced to a low value. This has
the effect that the speed of the fan is reduced to the minimum working speed nfan (min.). Surplus oil
from the pump 33 is returned to the tank through the pressure-relief valve 14.
If the temperatures increase from the minimum value to the maximum value TB8 (max.), TÂ708 (max.)
or TB707 (max.) respectively, the current to the proportional solenoid valve Y347 is gradually reduced.
The pressure in the fan drive corresponds now to the upper nominal value. Nearly all oil from the
pump 33 flows to the fan motor 13. The speed of the fan reaches its upper nominal value nfan (max.).
In emergency mode, i.e. in the event of a failure of the control system (I = 0 mA), the oil pressure in
the hydraulic fan drive reaches the emergency value p (emergency) of the pressure-relief valve 14,
and the fan is operated at emergency speed nfan (emergency).
LHB/en/Edition: 08/2010

Fig. 3 Hydraulic schematic of fan control

7.60.3
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MJFCIFSS
Cooling unit Service Manual
Function of the fan control

1 Hydraulic tank B8 Temperature sensor / hydraulic oil

6 Hydraulic oil cooler B707 Temperature sensor / intercooling air
13 Blower motor B708 Temperature sensor / coolant
14 Proportional pressure-relief valve U16 Excavator control BST
33 Gear pump / fan drive Y20 Magnetic clutch / a/c system
100 from control block connection K Y347 Proportional solenoid valve / fan control

Note!
If Y347 is disconnected, the fan switches to emergency speed nemergency

2.1 Fan control diagram

LHB/en/Edition: 08/2010

Fig. 4 Diagram of cooling system (A 900 C EDC)

7.60.4
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 Service Manual Cooling unit
Function of the fan control

Fig. 5 Diagram of cooling system (A 904 C EDC)

(

Β8 (°C) Hydraulic oil temperature

Β707 (°C) Intercooling air temperature
Β708 (°C) Coolant temperature
I Y347 mA Current to solenoid valve Y347
p (bar) Pressure in hydraulic fan drive
n (rpm) Fan speed
LHB/en/Edition: 08/2010

7.60.5
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MJFCIFSS
Cooling unit Service Manual
Maintenance

2.1.1 With software versions from 4.7

Alarm
A 900 C EDC Current from BST Temperature
temperature
Coolant temperature (B708)
min. 650 mA 85 °C >98°C
>101°C from V4.8.1
max. 250 mA 95 °C Warning level
Hydraulic oil temperature
(B8)
min. 650 mA 60 °C >99°C
>90°C from V4.8.1
max. 250 mA 80 °C Warning level
Intercooling temperature
(B707)
min. 650 mA 60 °C -
max. 250 mA 70 °C -
For error codes (combined with symbols / indicator lights), please refer to group 8.80.

2.1.2 With software versions from 4.7

Alarm
A 904 C EDC Current from BST Temperature
temperature
Coolant temperature (B708)
min. 650 mA 85 °C >98°C
>101°C from V4.8.1
max. 200 mA 95 °C Warning level
Hydraulic oil temperature
(B8)
min. 650 mA 60 °C >99°C
>90°C from V4.8.1
max. 200 mA 80 °C Warning level
Intercooling temperature
(B707)
min. 650 mA 60 °C -
max. 200 mA 70 °C -
For error codes (combined with symbols / indicator lights), please refer to group 8.80.

3 Maintenance
LHB/en/Edition: 08/2010

Note!
Maintenance is limited to inspection and cleaning of the cooling unit fins. For all other tasks, see
inspection and maintenance schedule of group 3.

7.60.6
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MJFCIFSS
 Service Manual Cooling unit
Checking the fan control system

4 Checking the fan control system

Location of Measuring
Check / adjustment Unit Setting
adjustment point
Fan speed (fan min) rpm 400 +200 - -
Test current mA approx. 650 - -
+100
Fan speed (fan min) rpm 1500 - -
Test current mA approx. 250 - -
Fan speed (fan emergency) rpm 1600 +200 - -
Test current (emergency operation) mA approx. 0 - -

Tab. 1 Setting data

Danger!
Moving fan blades can cause serious injury to fingers and hands.
X Shut down the motor.
X Do not reach into the fan operating range until the fan blades have come to a standstill.

Fig. 6 Checking and adjusting the fan motor with proportional solenoid valve

Note!
The fan speed cannot be adjusted. The pressure is factory-set by the manufacturer and may not be
changed. If the results of the measurement indicate that there is a substantial difference between
the actual and the prescribed values, check the hydraulic circuit for faults.
The fan speed to be measured is determined by the actual coolant temperature and the hydraulic
oil temperature as well as the switching position of the a/c system (ON/OFF) and the intercooling
air temperature.
LHB/en/Edition: 08/2010

To check the fan speed using a speed meter (tool no. 62 / 63), apply a reflective strip to the fan
blade/jacket.
X Connect the measuring adapter to Y347 and to the multimeter.
X Select set data in the service menu.
X Press the arrow buttons to select submenu set control 2.1.

7.60.7
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Cooling unit Service Manual
Checking the fan control system

4.1 Adjusting the minimum fan speed

X Use the arrow buttons to select menu option fan min.

X Confirm the selection with the menu button.

X Set submenu fan min to (ON).

Fig. 7 fan min

X Start the engine and measure the minimum fan speed.

X Compare the measured fan speed with the prescribed fan speed, see Tab. 1.
X Compare the current values at the multimeter with the prescribed settings.

4.2 Checking the maximum fan speed

X Use the arrow buttons to select menu option fan max.

X Confirm the selection with the menu button.

X Set submenu fan max to (ON).

Fig. 8 fan max

X Start the engine and measure the maximum fan speed.

X Compare the measured fan speed with the prescribed fan speed, see Tab. 1.
X Compare the current values at the multimeter with the prescribed settings.
LHB/en/Edition: 08/2010

4.3 Checking emergency operation

X Use the arrow buttons to select menu option fan emergency.

X Confirm the selection with the menu button.

X Set submenu fan emergency to (ON).

7.60.8
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MJFCIFSS
 Service Manual Cooling unit
Checking the fan control system

Fig. 9 fan emergency

X Start the engine and measure the minimum fan speed.

X Compare the measured fan speed with the prescribed fan speed, see Tab. 1.
X Compare the current values at the multimeter with the prescribed settings.
LHB/en/Edition: 08/2010

7.60.9
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MJFCIFSS
Cooling unit Service Manual
Checking the fan control system

LHB/en/Edition: 08/2010

7.60.10
copyright by

MJFCIFSS
 Service Manual Cooling unit
Function/design

Cooling unit

1 Function/design

Cooling of the hydraulic oil, the coolant, the fuel and the intercooling air of the diesel engine.
The speed of the hydrostatically driven annular fan RL is controlled according to the cooling require-
ments (i.e. based on the coolant, intercooling air and hydraulic oil temperature as well as on the a/c
system (ON/OFF)).
The flow rate of the hydraulic oil and the intercooling air is not controlled. The flow rate of the engine
coolant is however thermostat-controlled.

Note!
The arrows indicate the inlet and outlet devices of the respective cooling elements of the cooling
unit.

Fig. 1 Cooling unit

4 Expansion tank 13 Blower motor

LHB/en/Edition: 08/2010

5 Fuel cooler FS Finger guard

6 Hydraulic oil cooler H Air scoop
7 Water cooler (coolant) / engine RL Annular fan / blower rotor
8 Intercooling air cooler / engine Y347 Proportional pressure-relief valve

7.61.1
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MJFCIFSS
Cooling unit Service Manual
Function/design

1.1 Cooling elements

The cooling unit consists of 4 cooling elements (heat exchangers):
– Cooler 5 for fuel.
– Oil cooler 6 for hydraulic oil.
– Cooler 7 for engine coolant.
– Cooler 8 for intercooling air.
– They are installed in a shared frame with air ducting plates.
The annular fan (RL) required to produce the air flow is positioned in the opening of the air duct frame.
The annular fan is driven by the blower motor 13. The blower motor speed required to produce the
necessary air flow is automatically controlled by the excavator control system (BST) through the pro-
portional solenoid valve Y347 at the blower motor and the respective signals from the temperature
sensors at the diesel engine and the hydraulic tank.

1.2 Fan control

The hydrostatic fan drive is controlled by the hydraulic oil temperature B8, the cooling water tempe-
rature B708, the intercooling air temperature B707 and the a/c system Y20 (on/off). The fan speed
is controlled electronically, relative to the temperature, through the proportional solenoid valve Y347.
Between the minimum and maximum values, the current from the excavator control system BST
(U16) to the solenoid valve Y347 is linear, which means that each temperature value between these
two limit points corresponds to a specific current I and pressure p between the minimum and maxi-
mum values, resulting in a specific fan speed.

LHB/en/Edition: 08/2010

Fig. 2 Monitoring of the cooling unit

B8 Temperature sensor / hydraulic oil B708 Temperature sensor / coolant

B707 Temperature sensor / intercooling air Y20 Magnetic clutch / a/c system

7.61.2
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MJFCIFSS
 Service Manual Cooling unit
Function of the fan control

2 Function of the fan control

see Fig. 3
The speed of the blower motor is controlled by the solenoid valve Y347. Depending on the oil and
coolant temperature, the BST (U16) adjusts the current to the proportional solenoid valve Y347, thus
opening / closing the solenoid valve Y347. The more the solenoid valve Y347 is opened, the less hy-
draulic oil flows to the blower motor 13 and the lower the fan speed.
If the temperature of the hydraulic oil in the tank and/or the coolant in the engine and/or the intercoo-
ling air in the turbocharger is lower than or equal to the lower limit value TB8 (min.), TB708 (min.), or
TB707 (min.) respectively, the output current to the proportional solenoid valve Y347 of the BST (U16)
corresponds to I Y347 (max.).
In this case, the pressure at the proportional solenoid valve Y347 is reduced to a low value. This has
the effect that the speed of the fan is reduced to the minimum working speed nfan (min.). Surplus oil
from the pump 33 is returned to the tank through the proportional pressure-relief valve Y347.
If the temperatures increase from the minimum value to the maximum value TB8 (max.), TB708 (max.)
or TB707 (max.) respectively, the current to the proportional pressure-relief valve Y347 is gradually
reduced.
The pressure in the fan drive corresponds now to the upper nominal value. Nearly all oil from the
pump 33 flows to the fan motor 13. The speed of the fan reaches its upper nominal value nfan (max.).
In emergency mode, i.e. in the event of a failure of the control system (I = 0 mA), the oil pressure in
the hydraulic fan drive reaches the emergency value p (emergency) of the proportional pressure-re-
lief valve Y347, and the fan is operated at emergency speed nfan (emergency).
LHB/en/Edition: 08/2010

Fig. 3 Hydraulic schematic of fan control

7.61.3
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MJFCIFSS
Cooling unit Service Manual
Function of the fan control

1 Hydraulic tank B8 Temperature sensor / hydraulic oil

6 Hydraulic oil cooler B707 Temperature sensor / intercooling air
9 Check valve B708 Temperature sensor / coolant
13 Blower motor U16 Excavator control BST
14 Proportional pressure-relief valve Y20 Magnetic clutch / a/c system
33 Gear pump / fan drive Y347 Proportional solenoid valve / fan control
100 from control block connection K

Note!
If Y347 is disconnected, the fan switches to emergency speed nemergency

2.1 Fan control diagram

LHB/en/Edition: 08/2010

Fig. 4 Diagram of cooling system (A 914 C EDC/A 924 C EDC)

7.61.4
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MJFCIFSS
 Service Manual Cooling unit
Maintenance

Β8 (°C) Hydraulic oil temperature

Β707 (°C) Intercooling air temperature
Β708 (°C) Coolant temperature
I Y347 mA Current to solenoid valve Y347
p (bar) Pressure in hydraulic fan drive
n (rpm) Fan speed

2.1.1 With software versions from 4.6

Alarm
A 914 C EDC/A 924 C EDC Current from BST Temperature
temperature
Coolant temperature (B708)
min. 450 mA 85 °C >98 °C
max. 170 mA 95 °C Warning level
Hydraulic oil temperature
(B8)
min. 450 mA 60 °C >99 °C
max. 170 mA 80 °C Warning level
Intercooling temperature
(B707)
min. 450 mA 60 °C -
max. 170 mA 70 °C -
For error codes (combined with symbols / indicator lights), please refer to group 8.80.

2.1.2 With software versions from 4.7

Alarm
A 924 C EDC Current from BST Temperature
temperature
Coolant temperature
min. 500 mA 85 °C >98°C
>101°C from V4.8.1
max. 150 mA 95 °C Warning level
Hydraulic oil temperature
min. 500 mA 60 °C >99°C
>90°C from V4.8.1
max. 150 mA 80 °C Warning level
Intercooling air temperature
min. 500 mA 60 °C -
max. 150 mA 70 °C -
For error codes (combined with symbols / indicator lights), please refer to group 8.80.
LHB/en/Edition: 08/2010

3 Maintenance

Note!
Maintenance is limited to inspection and cleaning of the cooling unit fins. For all other tasks, see
inspection and maintenance schedule of group 3.

7.61.5
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MJFCIFSS
Cooling unit Service Manual
Checking the fan control system

4 Checking the fan control system

Location of Measuring
Check / adjustment Unit Setting
adjustment point
Fan speed (fan min) rpm 500 +150 -300 - -
Test current mA 500 ±20 - -
+50-100
Fan speed (fan max) rpm 1450 - -
±20
Test current mA 150 - -
Fan speed (fan emergency) rpm 1650 +200-200 - -
Test current (emergency operation) mA approx. 0 - -

Tab. 1 Setting data

Danger!
Moving fan blades can cause serious injury to fingers and hands.
X Shut down the motor.
X Do not reach into the fan operating range until the fan blades have come to a standstill.

Note!
The fan speed cannot be adjusted. The pressure is factory-set by the manufacturer and may not be
changed. If the results of the measurement indicate that there is a substantial difference between
the actual and the prescribed values, check the hydraulic circuit for faults.
The fan speed to be measured is determined by the actual coolant temperature and the hydraulic
oil temperature as well as the switching position of the a/c system (ON/OFF).

Fig. 5 Checking fan speed with speed meter

To check the fan speed with the speed meter (tool no. 62 / 63), apply a reflective strip to one of
the fan blades.
LHB/en/Edition: 08/2010

X Connect a suitable measuring adapter to Y347 and to the multimeter.

X Select set data in the service menu.
X Press the arrow buttons to select submenu set control 2.1.

4.1 Adjusting the minimum fan speed

X Use the arrow buttons to select menu option fan min.

7.61.6
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MJFCIFSS
 Service Manual Cooling unit
Checking the fan control system

X Confirm the selection with the menu button.

X Set submenu fan min to (ON).

Fig. 6 fan min

X Start the engine and measure the minimum fan speed.

X Compare the measured fan speed with the prescribed fan speed, see Tab. 1.
X Compare the current values at the multimeter with the prescribed settings.

4.2 Checking the maximum fan speed

X Use the arrow buttons to select menu option fan max.

X Confirm the selection with the menu button.

X Set submenu fan max to (ON).

Fig. 7 fan max

X Start the engine and measure the maximum fan speed.

X Compare the measured fan speed with the prescribed fan speed, see Tab. 1.
X Compare the current values at the multimeter with the prescribed settings.

4.3 Checking emergency operation

X Use the arrow buttons to select menu option fan emergency.
LHB/en/Edition: 08/2010

X Confirm the selection with the menu button.

X Set submenu fan emergency to (ON).

7.61.7
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MJFCIFSS
Cooling unit Service Manual
Checking the fan control system

Fig. 8 fan emergency

X Start the engine and measure the minimum fan speed.

X Compare the measured fan speed with the prescribed fan speed, see Tab. 1.
X Compare the current values at the multimeter with the prescribed settings.

LHB/en/Edition: 08/2010

7.61.8
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MJFCIFSS
 Service Manual Leak oil check at control valve blocks
Function and design

Leak oil check at control valve blocks

1 Function and design

The leak oil of a spool is measured by means of the extending or retracting speed of the pressurised
hydraulic cylinder, which is connected to the spool in neutral position.
The volume of leak oil in the control valve block should be measured at a load pressure of 150 bar
and a temperature of 50°C (in hydraulic tank).
Before checking the control valve block for leak oil, first check the secondary valves (visual inspec-
tion, with valve exchange, if this is required) and the operating cylinder (dummy), as the respective
values refer only to leakage from the spool in the control valve block.
To check the block for leak oil from the spool, connect a pressure sensor at the respective pressure
line between the operating cylinder and the control valve block (use measuring equipment, if re-
quired).
X Warm up the machine to its normal operating temperature.
X Extend attachment
until the pressure sensor indicates a value of 150 bar (apply load, if necessary).
X Apply a mark (with marker) on the cylinder piston rod in order to measure the distance the piston
rod travels in one minute.
The maximum permissible extending and retracting speed of the piston rod (or the permissible leak
oil volume from the spool respectively) are shown in the diagram, (see “Leak oil diagram” on page 2).
The maximum permissible leak oil volume is specified in the technical data of the respective control
valve block documentation.

Note!
The values in the diagram refer to a system where a single operating cylinder is supplied with oil by
a single spool.
For systems with two operating cylinders supplied by one spool, the maximum permissible speed is
half that for single operating cylinder systems.
LHB/en/Edition: 01/2005

7.68.1
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MJFCIFSS
Leak oil check at control valve blocks Service Manual
Function and design

Fig. 1 Leak oil diagram

– Va: extending speed of piston rod

– Ve: retracting speed of piston rod
LHB/en/Edition: 01/2005

Example:
In a A 904 C machine the single bucket cylinder with a piston diameter D = 120mm and a rod diameter
d = 80mm is fed by a single spool 260 with NW 22.
In this control valve block (NW 22), the maximum leak oil rate per spool is Q= 60 cm3 /min.
According to the diagram, this corresponds to a maximum permissible retracting speed of the cylinder
of 5.2 mm/min. The maximum permissible extending speed of the cylinder is 9.5 mm/min

7.68.2
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MJFCIFSS
 Service Manual Rotary connection 6 x
Description

Rotary connection 6 x

1 Description

The rotary connection is situated at the fulcrum between uppercarriage and undercarriage. It con-
nects the hydraulic system of the uppercarriage with the units situated on the undercarriage.
Stator 2, pipe coupling 4 and flange 5 with connections 1 - 6 are connected to the undercarriage via
the stator of the 7x rotary connection (high pressure) . Rotor 1 with connections 1 - 6 is fixed to the
uppercarriage via the rotor of the 7x rotary connection (high pressure).
There are bores leading from line connections 1 - 6 of the uppercarriage to the annular chambers.
Rotor seal 22 in rotor 1 seals them off against each other.
Every annular chamber is connected to pipe coupling 4 and the connections of flange 5 via a radial
and axial bore in stator 2.
The two V-seals 21 prevent the penetration of dirt.
Lid 3 secures rotor 1 in the axial direction and, at the same time, serves as an additional protection against dirt.
LHB/en/Edition: 07/2008

Fig. 1 Rotary connection

7.70.1
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MJFCIFSS
Rotary connection 6 x Service Manual
Connections and hydraulic connections

2 Connections and hydraulic connections

Connection 1 Brake system / working brake

Supply from the foot brake valve (compact brake block), connection B1, to the
multi-disc brakes / front axle
Connection 2 Transmission
Supply from brake and HBGV switch block (connection A) to shift lo
ck / gearbox connection P1
Connection 3 Transmission
Supply from brake and HBGV switch block (connection B) to shift lo
ck / gearbox connection P2
Connection 4 Oscillating axle support
Supply from solenoid valve Y66 to the support cylinders, connection St
Connection 5 Brake system / working brake
Supply from the foot brake valve (compact brake block), connection B2, to the
multi-disc brakes and/or drum brakes (rear axle)
Connection 6 Regulating travel motor / creeper gear mode
Supply from solenoid valve Y24 to regulator / regulating motor connection X

3 Removal and installation

3.1 Removal of 6 x rotary connection for sealing works, see Fig. 2

X Mark hydraulic lines leading to the rotary connection (bottom). Disconnect.
X Remove hollow screw 6 completely. Pull off flange 5. Be careful with seal washer 7.
X Mark hydraulic lines leading to rotary connection (top). Disconnect.
X Remove Allen head screws 32. Remove driver 30.
X Remove nut 29. Remove washers 28. Pull rotary connection 25 from rotary connection 40.

3.2 Installation of 6 x rotary connection after sealing works, see Fig. 2

X Insert complete rotary connection 25 into rotary connection 40. Install lid 44. Install nuts 29 com-
plete with washers 28 on screws 27.
X Install driver 30 on rotary connection 40. Screw down with Allen head screws 32 and washer.
X Place seal washer 7 in flange 5. Put flange 5 on pipe coupling 4 of the rotary connection. Pay at-
tention to the locking pin in coupling 4, bore in seal washer 7 and flange 5.
X Install hollow screw 6 complete with tooth lock washer 9. Tighten with torque: 50 Nm.
X Connect all the hydraulic lines to the completed rotary connection. Pay attention to markings you
LHB/en/Edition: 07/2008

made before.

7.70.2
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MJFCIFSS
 Service Manual Rotary connection 6 x
Removal and installation

Fig. 2 Installation and removal of rotary connection

LHB/en/Edition: 07/2008

7.70.3
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MJFCIFSS
Rotary connection 6 x Service Manual
Exploded view

4 Exploded view

Fig. 3 Exploded view: rotary connection

1 Rotor 9 Tooth lock washer

2 Stator 11 Allen head screw
3 Lid 12 Allen head screw
4 Pipe coupling 13 Lock washer
5 Flange 21 V seal
LHB/en/Edition: 07/2008

6 Hollow screw 22 Rotor seal

7 Seal washer 25 Rotary connection
8 Thrust washer 999 Seal kit

7.70.4
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MJFCIFSS
 Service Manual Rotary connection 6 x
Sectional drawing

5 Sectional drawing
LHB/en/Edition: 07/2008

Fig. 4 Sectional drawing: rotary connection

7.70.5
copyright by

MJFCIFSS
Rotary connection 6 x Service Manual
Sectional drawing

LHB/en/Edition: 07/2008

7.70.6
copyright by

MJFCIFSS
 Service Manual Rotary connection 7 x
Description

Rotary connection 7 x

1 Description

The rotary connection is situated at the fulcrum between uppercarriage and undercarriage. It con-
nects the hydraulic system of the uppercarriage with the units situated on the undercarriage.
The stator is on the undercarriage. The rotor is held in the axial direction by the lid, which, at the same
time, provides additional protection against dirt. The driving pin locks the rotor with the uppercarriage.
There are cast channels leading from line connections 0 - 6 in the rotor to the annular chambers. Spe-
cial seal rings (seal kit) seal them off against each other. Every annular chamber is connected to its
individual connection 0 - 6 in the stator via a radial and axial bore.
The two outer seal rings (seal kit) seal off the rotor to the outside.
The rotary connection does not need any maintenance.

Fig. 1 Rotary connection

LHB/en/Edition: 07/2008

2 Connections and hydraulic connections

2.1 A 900 C Litronic

Connection 0 Leak oil
Recycling of leak oil from travel motor and auxiliary gearbox

7.75.1
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MJFCIFSS
Rotary connection 7 x Service Manual
Connections and hydraulic connections

Connection 1 Travel motor

Supply from control block connection A2 to travel motor (forward)
Connection 2 Support cylinder
Supply from control block connection B1 to support cylinders (retract)
Connection 3 Travel motor
Supply from control block connection B2 to travel motor (reverse)
Connection 4 Support cylinder
Supply from control block connection A1 to support cylinders (extend)
Connection 5 Steering
Supply from servostat to steering cylinder (travel, right)
Connection 6 Steering
Supply from servostat to steering cylinder (travel, left)

2.2 A 904 C Litronic

Connection 0 Leak oil
Recycling of leak oil from travel motor and auxiliary gearbox
Connection 1 Travel motor
Supply from control block connection A2 to travel motor (forward)
Connection 2 Support cylinder
Supply from control block connection A1 to support cylinders (extend)
Connection 3 Travel motor
Supply from control block connection B2 to travel motor (reverse)
Connection 4 Support cylinder
Supply from control block connection B1 to support cylinders (retract)
Connection 5 Steering
Supply from servostat to steering cylinder (travel, right)
Connection 6 Steering
Supply from servostat to steering cylinder (travel, left)

LHB/en/Edition: 07/2008

7.75.2
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MJFCIFSS
 Service Manual Rotary connection 7 x
Removal and installation

3 Removal and installation

3.1 Removal of 7 x rotary connection for sealing works, see Fig. 2

X Mark hydraulic lines leading to rotary connections 10 and 125. Disconnect.
X Remove Allen head screws 27. Remove driver 25.
X Remove nuts 21. Remove washer 20.
X Pull rotary connection 125 from rotary connection 11.
X Unscrew hex head screw 12. Lift rotary connection 10 out of undercarriage.

3.2 Installation of 7 x rotary connection after sealing works, see Fig. 2

X Replace rotary connection 10 into undercarriage. Let the driving pin snap into driver 19. Replace
screws 12 and 17 complete with retaining washers 18.
X Install rotary connection 125 in rotary connection 10. Place lid 3. Be careful with the seal.
X Install nuts 121 complete with washers 120 on screws 116.
X Install driver 25 on rotary connection 10. Screw down with Allen head screws 27 and washers 26.
X Fasten flange 115 to rotary connection 125, using hollow screw 116 (tooth lock washer 119). Pay
attention to correct position of seal 117.
X Re-connect hydraulic lines to rotary connections 10 and 15 (top and bottom). Pay attention to mar-
kings you made before.
X Re-install all other lines and parts you may have removed before.
LHB/en/Edition: 07/2008

Fig. 2 Installation position of rotary connection

7.75.3
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MJFCIFSS
Rotary connection 7 x Service Manual
Exploded view

4 Exploded view

Fig. 3 Exploded view of rotary connection

3 Lid 19 Driver
4 Screw plug 25 Driver
5 Screw plug 26 Washer
6 Retaining washer 27 Allen head screw
7 Hex head screw 98 Seal kit - consists of 9 seals:
1 felt washer, 2 outer seals top / bottom, 7
inside seals
10 Rotary connection 115 Flange
11 Rotor 116 Hollow screw
12 Hex head screw 117 Seal
LHB/en/Edition: 07/2008

13 Stator 119 Tooth lock washer

15 Felt washer 120 Washer
16 Plug 121 Hex nut
17 Hex head screw 125 Rotary connection
18 Washer 126 Allen head screw

7.75.4
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MJFCIFSS
 Service Manual Rotary connection 7 x
Sectional drawing

5 Sectional drawing
LHB/en/Edition: 07/2008

Fig. 4 Sectional drawing: rotary connection

7.75.5
copyright by

MJFCIFSS
Rotary connection 7 x Service Manual
Sectional drawing

LHB/en/Edition: 07/2008

7.75.6
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MJFCIFSS
 Service Manual Accumulator
Function

Accumulator

1 Function

Liquids are practically incompressible and can therefore not be used to accumulate energy in the
form of pressure.
To pressurise liquids, gases are used as they are highly compressible. In the accumulators of the ex-
cavator, nitrogen is used as a medium.
The accumulators have the following functions:
– Storage of pressure oil for the pilot control system, brake system and oscillating axle support.
– Cushioning of stroke movement for the hydraulic cab elevation and the industrial stick.
The accumulator consists of a hydraulic section and a gas section encased in a metal pressure ves-
sel.
Accumulators are classified according to their design:
– Diaphragm accumulator 10
– Bladder accumulator 20
– Piston accumulator 30
For details, see design and functional descriptions below.
.
LHB/en/Edition: 07/2009

Fig. 1 Accumulator types

10 Diaphragm accumulator 30 Piston accumulator

7.95.1
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MJFCIFSS
Accumulator Service Manual
Design and function

20 Bladder accumulator

2 Design and function

2.1 Diaphragm accumulator 10, see Fig. 2

In diaphragm accumulators, the liquid and gas are separated by a rubber diaphragm 12.

2.1.1 Design
– Welded steel pressure vessel 11 containing the gas and oil.
– Diaphragm 12 in the gas section of the pressure vessel 11.
– Gas valve 15 (screw plug) to fill and empty the gas section.
– Valve plate 13 protecting the diaphragm during emptying.
– Hydraulic connection 16 between the oil section of the accumulator and the hydraulic circuit.

2.1.2 Function
The diaphragm 12 is precharged via the gas valve 15 with nitrogen under pressure, whereby the
pressure is determined by the actual application.
The hydraulic section is filled through the hydraulic connection 17 with pressure oil. As the oil pres-
sure is increased by means of the nitrogen precharge pressure, the nitrogen is compressed by the
diaphragm 12.
When the oil pressure is reduced, the compressed nitrogen expands and displaces the stored oil vo-
lume, which then flows into the circuit.
The accumulator 10 thus ensures that there is sufficient pressure oil available for certain functions,
for example in the control oil circuit and brake circuit, after the oil flow from the pump has been shut
down. It also ensures that there is a pressure oil flow in the event of a pump failure.
The cushioning function is achieved by a precharged oil column between the closed spool in the con-
trol block and the boom cylinder through the nitrogen section of the accumulator G. It dampens post-
oscillation (caused by sudden stop of the cab movement).
If the liquid section is completely emptied, the valve plate 13 seals the hydraulic connection 17 to pre-
vent damage to the diaphragm 12.

LHB/en/Edition: 07/2009

7.95.2
copyright by

MJFCIFSS
 Service Manual Accumulator
Design and function

Fig. 2 Diaphragm accumulator

G Gas section 14 Locking ring

H Hydraulic section 15 Gas valve
11 Pressure vessel 16 Protective cap
12 Diaphragm 17 Hydraulic connection
13 Valve plate
LHB/en/Edition: 07/2009

7.95.3
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MJFCIFSS
Accumulator Service Manual
Design and function

2.2 Bladder accumulator 20, see Fig. 3

In bladder accumulators, the liquid and gas are separated by a rubber bladder 25.

2.2.1 Design
– Seamless steel pressure vessel 21 containing the gas and oil.
– Hydraulic connection 22 between the oil section of the accumulator and the hydraulic circuit.
– Check valve 24 protecting the bladder when the hydraulic section H is emptied.
– Gas valve 23 to fill and empty the gas section.
– Bladder 25 in the gas section G of the pressure vessel 21.

2.2.2 Function
The bladder 25 is precharged via the gas valve 23 with nitrogen under pressure, whereby the pres-
sure is determined by the actual application.
The liquid section H is connected to the piston side of the boom cylinder and is filled with pressure
oil. As the oil pressure is increased by means of the nitrogen precharge pressure, the nitrogen in the
bladder 25 is compressed.
When the oil pressure is reduced, the compressed nitrogen expands and displaces the stored oil vo-
lume, which then flows into the circuit.
Post-oscillation of the attachment (caused by sudden stop of the working movement) is dampened
by the oil column between the closed spool in the control block and the boom cylinder.
The check valve 24 prevents the liquid section from being fully emptied, as this would damage the
bladder 25.

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Design and function

Fig. 3 Bladder accumulator

G Gas section 25 Bladder

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H Hydraulic section 26 Sealing cap

21 Pressure vessel 27 Protective cap
22 Hydraulic connection 28 O-ring
23 Gas valve 29 Bleeder valve
24 Check valve

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Design and function

2.3 Piston accumulator 30, see Fig. 4

In piston accumulators, the liquid and gas are separated by a piston 35.

2.3.1 Design
– Steel pressure cylinder 31 containing the gas and oil.
– Cylinder base 32 with hydraulic connection between the oil section of the accumulator and the hy-
draulic circuit.
– Cylinder cover 33 with gas valve 34 to fill and empty the gas section.
– Movable piston 35 with seals separating the oil and gas sections in the cylinder 31.

2.3.2 Function
The gas section G between the gas valve 34 and the piston 35 is precharged through the gas valve
34 with nitrogen, whereby the precharge pressure is determined by the actual application. The piston
35 is pressed against the cylinder base 32.
The hydraulic section H is connected to the hydraulic circuit and filled with pressure oil. As the oil
pressure is increased by means of the nitrogen precharge pressure, the nitrogen in the gas section
G is compressed.
When the oil pressure is reduced, the compressed nitrogen expands and displaces the stored oil vo-
lume, which then flows into the circuit.
Post-oscillation of the attachment (caused by sudden stop of the working movement) is dampened
by the oil column between the closed spool in the control block and the boom cylinder.

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Design and function

Fig. 4 Piston accumulator

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G Gas section 36 Hydraulic connection

H Hydraulic section 37 Seal ring
31 Pressure vessel 38 Guide ring
32 Cylinder base 39 Turn lock (not included in all designs)
33 Cylinder cover 341 Hexagon socket screw
34 Gas valve 342 Protective cap
35 Piston

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General information

3 General information

Accumulators are pressure vessels and thus subject to the standards laid down in the European
Pressure Vessel Directive (97/23/EC). They are sealed containers designed for the storage of liquids
and gases under pressure.

Danger!
Incorrect installation or handling can lead to serious accidents.
All work on the gas and liquid connections must be carried out by specially trained technicians.
Welding, soldering and any other mechanical work on the accumulator is strictly forbidden. Risk of
explosion!
To prevent explosion, never fill accumulators with oxygen or air.
X Fill accumulators only with nitrogen, using the filler fittings provided, (see Fig. 6 on page10).
X Before carrying out any work on the hydraulic system, depressurise the hydraulic circuit.
X Do not touch the accumulators of hydraulic units at operating temperature with your bare hands.
Always wear protective gloves. Risk of injury from burns!
X Accumulators must be transported with the upmost caution.
X Never install accumulators that have been damaged during transport.

If the accumulator is defective (leaking diaphragm, bladder, piston seal), nitrogen and hydraulic oil
escapes during filling or testing.
X Immediately replace defective accumulators.

4 Commissioning

Accumulators must only be replaced by equivalent accumulators specified in the spare parts list.
X Before installing the new accumulator, check its type designation (sometimes including precharge
pressure specifications, see arrow) and compare it with that of the accumulator to be replaced.
The type designation and ratings are engraved on the accumulator/cylinder or specified on an at-
tached label, see Fig. 5.

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Fig. 5 Marking on the accumulator

10 Diaphragm accumulator 30 Piston accumulator

20 Bladder accumulator

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 Service Manual Accumulator
Maintenance

For correct operation of the machine, the accumulator must be filled with the prescribed precharge
pressure (referred to as P0); for details, see the respective assembly.
Normally, this is given when choosing the correct spare part with matching ID number.
In accumulators used in models A 316 and R 317 Industry with damping accumulator for the hydraulic
cab elevation, the precharge pressure must b reduced; for details, see group 16 "Hydraulic cab ele-
vation system".
In bladder accumulators, the connection on the oil side must be bled through the bleeder screw 26
inserted in the hydraulic connection 22.
X Before commissioning the accumulator, check the screwed connections on the gas and liquid side
for proper tightening.

5 Maintenance

Accumulators are generally maintenance-free. To ensure trouble-free operation and a prolonged ser-
vice life, the following maintenance tasks must however be carried out at regular intervals:
– Check connections for leakage and proper tightening.
– Check fixtures (clamps, etc.) for proper fit and correct tightening torque.
– Check nitrogen precharge pressure.
Adhere to the following maintenance intervals:
– Immediately after installation
– 1 week after installation
– 2 months after installation
If there is no measurable gas loss, the check interval can be prolonged to maximum
– once annually

Note!
Continuous operation at high operating temperatures requires shorter check intervals.
X Operation under extreme conditions (high operating temperature >90°C) requires even shorter
check intervals.

6 Checking of gas precharge pressure

The gas precharge pressure can be checked with or without the filling and checking device, (see Fig.
6 on page10).

6.1 Checking the gas precharge pressure without filling and checking device
The accumulator can be checked easily.
This simple method has the advantage that there is no gas loss, so that there is normally no need to
add gas (provided of course that the precharge pressure has not dropped).
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To check diaphragm brake accumulators, see Fig. 1, proceed as described in group 15.10.
The diaphragm accumulator for the oscillating axle support, see Fig. 1, is filled with a gas precharge
pressure = preservation pressure = 2 bar (accumulator cannot be checked without filling and che-
cking device).
The diaphragm accumulator for the control oil unit, see Fig. 1, is filled with gas at a precharge pres-
sure of 15 bar. To check the gas precharge pressure:
X Switch off the diesel engine.

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Checking of gas precharge pressure

X Fully actuate the right pilot control unit for bucket movement.
Minimum 5 complete movements can be carried out = gas precharge pressure OK.
Less than 5 complete movements can be carried out = gas precharge pressure too low.
The bladder accumulators for the industrial boom cushioning, see Fig. 1, are filled with gas at a
precharge pressure of 150 bar.
To check the gas precharge pressure:
X Actuate the right pilot control unit for boom movement to the stop and the halt the movement ab-
ruptly.
The movement of the attachment is immediately halted = precharge pressure OK.
The attachment continues to oscillate for a considerable period of time = precharge pressure
too low.
The piston accumulators for the industrial boom cushioning, see Fig. 1, are filled with gas at a
precharge pressure of 95 bar.
To check the gas precharge pressure:
X Actuate the right pilot control unit for boom movement to the stop and the halt the movement ab-
ruptly.
The movement of the attachment is immediately halted = precharge pressure OK.
The attachment continues to oscillate for a considerable period of time = precharge pressure
too low.

6.2 Checking the gas precharge pressure and/or reducing the gas precharge
pressure using the filling and checking device FPU-1
To check/reduce the pressure in the accumulator, you must use the specially devised universal filling
and checking device (ID no .814359).

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Fig. 6 Filling and checking device FPU-1, complete

50 Filling and checking device with pres- 53 Filler hose

sure gauge
51 Adapter A3 54 Carrier case

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Checking of gas precharge pressure

Note!
Before carrying out the check, release the liquid from the accumulator (hydraulic outlet).
X Depressurise the hydraulic circuit by repeatedly actuating the connected components (pilot con-
trol units, brake pedal, etc.).

6.2.1 Determining the temperature effect on gas precharge pressures

To ensure that the prescribed gas precharge pressures are met even at relatively high operating tem-
peratures, the gas precharge pressure P0 must be calculated as follows:

Example: the accumulator is cold (20°C), the operating temperature is 70°C and the prescribed gas
precharge pressure is 150 bar: the pressure filter must be precharged with a pressure of 128 bar.

6.2.2 Check procedure

For diaphragm accumulators, see Fig. 2 and Fig. 7

X Remove the protective cap 15.
X Using an Allen key (WS 6), loosen the Allen head screw of the gas valve 14 a little (approx. 1/2
revolution anti-clockwise).
X Mount the filling and checking device 50 on the gas valve 14 (ensure that the dial of the pressure
gauge E is clearly visible).
X Tighten the union nut D by hand.
X Ensure that the relief valve B is closed.
X Turn the spindle A anti-clockwise.
Loosen the Allen head screw to open the gas valve 14.
X When the dial of the pressure gauge E begins to move, turn the spindle A by another full revolu-
tion.
The pressure gauge E indicates the precharge pressure of the accumulator.
The check valve integrated into the filling and checking device prevents nitrogen from esca-
ping.
X When the correct pressure is reached, turn the spindle A clockwise.
The gas valve 13 is closed as the Allen head screw 16 is tightened.
X Unscrew the union nut D and remove the filling and checking device.
X Using an Allen key (WS 6), tighten the Allen head screw of the gas valve 14 (tightening torque 20
Nm).
X Check the gas valve 14 for leakage, using a leak detection spray.
X Mount the protective cap 15 .
If the pressure is not OK (too low/too high), proceed as described in see 6.2.3.
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Checking precharge pressure in bladder accumulators, see Fig. 3 and Fig. 7

X Remove the protective cap 27 and the sealing cap 26.
X Remove the O-ring 28.
X Screw the adapter 51 (A3) onto the gas valve 23.
X Mount the filling and checking device on the adapter 51 (A3) (ensure that the dial of the pressure
gauge E is clearly visible).

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Checking of gas precharge pressure

X Tighten the union nut D by hand.

X Ensure that the relief valve B is closed.
X Turn the spindle A clockwise.
The gas valve 23 is opened.
X When the dial of the pressure gauge E begins to move, turn the spindle A by another full revolu-
tion.
The pressure gauge E indicates the precharge pressure of the accumulator.
The check valve integrated into the filling and checking device prevents nitrogen from esca-
ping.
X When the correct pressure is reached, turn the spindle A anti-clockwise.
The gas valve 23 is closed.
X Unscrew the union nut D and remove the filling and checking device.
X Unscrew the adapter 51 (A3) from the gas valve 23.
X Mount the O-ring 28 on the gas valve 23.
X Check the gas valve 23 for leakage, using a leak detection spray.
X Mount the sealing cap 26 and tighten it (torque 20 Nm).
X Mount the protective cap 27.
If the pressure is not OK (too low/too high), proceed as described in see 6.2.3.

Checking precharge pressure in piston accumulators, see Fig. 4 and Fig. 7

X Remove the protective cap 37.
X Using an Allen key (WS 6), loosen the Allen head screw of the gas valve 34 a little (approx. 1/2
revolution).
X Mount the filling and checking device on the gas valve 34 (ensure that the dial of the pressure gau-
ge E is clearly visible).
X Tighten the union nut D by hand.
X Ensure that the relief valve B is closed.
X Turn the spindle A anti-clockwise.
The gas valve 34 is thereby opened as the Allen head screw is loosened.
X When the dial of the pressure gauge E begins to move, turn the spindle A by another full revolu-
tion.
The pressure gauge E indicates the precharge pressure of the accumulator.
The check valve integrated into the filling and checking device prevents nitrogen from esca-
ping.
X When the correct pressure is reached, turn the spindle A clockwise.
The gas valve 34 is thereby closed as the Allen head screw is loosened.
X Unscrew the union nut D and remove the filling and checking device.
X Using an Allen key (WS 6), tighten the Allen head screw in the gas valve 34 (tightening torque 20
LHB/en/Edition: 07/2009

Nm).
X Check the gas valve 34 for leakage, using a leak detection spray.
X Mount the protective cap 34 of the gas valve
If the pressure is not OK (too low/too high), proceed as described in see 6.2.3.

6.2.3 Filling process

To fill the accumulator, connect it through the filling and checking device 50 and the filler hose 53 to

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Checking of gas precharge pressure

the pressure reducing unit 60 of a conventional nitrogen gas bottle 61.

Fig. 7 Filling accumulator with nitrogen

10 Diaphragm accumulator 50D Union nut

20 Bladder accumulator 50E Pressure gauge
30 Piston accumulator 51 Adapter A3
50 Filling and checking device 53 Filler hose
50A Spindle 60 Pressure reducing unit
50B Relief valve 61 Nitrogen gas bottle
50C Check valve 62 Gas bottle valve

X Place the attachment on the ground.

X Depressurise the hydraulic system.

for diaphragm accumulators 10, see Fig. 2 and Fig. 7

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X Remove the protective cap 15.

X Using an Allen key (WS 6), loosen the Allen head screw of the gas valve 15 a little (approx. 1/2
revolution).
X Mount the filling and checking device 50 on the gas valve 14 (ensure that the dial of the pressure
gauge E is clearly visible).
X Tighten the union nut D by hand.
X Ensure that the relief valve B is closed.

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X Connect the filler hose 53 to the pressure reducing unit 60 of a conventional nitrogen gas bottle 61.
X Turn the spindle A anti-clockwise.
The gas valve 14 is thereby opened as the Allen head screw is loosened.
X Carefully open the nitrogen gas bottle valve 62 a little.
Nitrogen gas slowly flows into the accumulator 10.
The pressure gauge E indicates the achieved precharge pressure of the accumulator 10.
X When the precharge pressure of the accumulator 10 reaches 1 bar, open the nitrogen gas bottle
valve 62 a little more (for faster filling of the accumulator).

Note!
If the filling process takes a long time, it is advisable to interrupt it from time to time and to check the
precharge pressure after the gas has reached ambient temperature. The pressure might need to be
adjusted.

X If the precharge pressure is too high, carefully open the relief valve B (turning it anti-clockwise)
until the pressure at the pressure gauge E drops to the desired precharge pressure.
Nitrogen is thereby released into the air.
X When the correct precharge pressure is reached, turn the spindle A clockwise.
Tighten the Allen head screw to close the gas valve 15.
X Close the nitrogen gas bottle valve 62.
X Release the pressure from the filling and checking device 50 by opening the relief valve B.
X Unscrew the union nut D and remove the filling and checking device 50.
X Disconnect the filler hose 63 from the filling and checking device 50 and the pressure reducing
unit 61.
X Using an Allen key (WS 6), tighten the Allen head screw of the gas valve 15 (tightening torque
20 Nm).
X Check the gas valve 14 for leakage, using a leak detection spray.
X Replace the protective cap 15.

For bladder accumulators, see Fig. 3 and Fig. 7

X Remove the protective cap 27, unscrew the sealing cap 26 and remove the O-ring 28.
X Screw the adapter 51 (A3) onto the gas valve 23.
X Mount the filling and checking device 50 on the adapter 51 (ensure that the dial of the pressure
gauge E is clearly visible).
X Tighten the union nut D by hand.
X Ensure that the relief valve B is closed.
X Connect the filler hose 53 to the pressure reducing unit 60 of a conventional nitrogen gas bottle 61.
X Turn the spindle A clockwise.
The gas valve 23 is opened.
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X Carefully open the nitrogen gas bottle valve 62 a little.

Nitrogen gas slowly flows into the accumulator 20.
The pressure gauge E indicates the achieved precharge pressure of the accumulator 20.
X When the precharge pressure of the accumulator 20 reaches 1 bar, open the nitrogen gas bottle
valve 62 a little more (for faster filling of the accumulator).

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Checking of gas precharge pressure

Note!
If the filling process takes a long time, it is advisable to interrupt it from time to time and to check the
precharge pressure after the gas has reached ambient temperature. The pressure might need to be
adjusted.

X If the precharge pressure is too high, carefully open the relief valve B (turning it anti-clockwise)
until the pressure at the pressure gauge E drops to the desired precharge pressure.
Nitrogen is thereby released into the air.
X When the correct precharge pressure is reached, turn the spindle A anti-clockwise.
The gas valve 23 is closed.
X Close the nitrogen gas bottle valve 62.
X Release the pressure from the filling and checking device 50 by opening the relief valve B.
X Unscrew the union nut D and remove the filling and checking device 50.
X Unscrew the adapter 51 (A3) and mount the O-ring 28.
X Disconnect the filler hose 63 from the filling and checking device 50 and the pressure reducing
unit 61.
X Check the gas valve 23 for leakage, using a leak detection spray.
X Mount the sealing cap 26 and tighten the protective cap 27 (torque 30 Nm).

For piston accumulators, see Fig. 4 and Fig. 7

X Remove the protective cap 37.
X Using an Allen key (WS 6), loosen the Allen head screw of the gas valve 34 a little (approx. 1/2
revolution).
X Mount the filling and checking device 50 on the gas valve 34 (ensure that the dial of the pressure
gauge E is clearly visible).
X Tighten the union nut D by hand.
X Ensure that the relief valve B is closed.
X Connect the filler hose 53 to the pressure reducing unit 60 of a conventional nitrogen gas bottle 61.
X Turn the spindle A anti-clockwise.
Loosen the Allen head screw to open the gas valve 34.
X Carefully open the nitrogen gas bottle valve 62 a little.
Nitrogen gas slowly flows into the accumulator 30.
The pressure gauge E indicates the achieved precharge pressure of the accumulator 30.
X When the precharge pressure of the accumulator 30 reaches 1 bar, open the nitrogen gas bottle
valve 62 a little more (for faster filling of the accumulator).

Note!
If the filling process takes a long time, it is advisable to interrupt it from time to time and to check the
precharge pressure after the gas has reached ambient temperature. The pressure might need to be
adjusted.
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X If the precharge pressure is too high, carefully open the relief valve B (turning it anti-clockwise)
until the pressure at the pressure gauge E drops to the desired precharge pressure.
Nitrogen is thereby released into the air.
X When the correct pressure is reached, turn the spindle A clockwise (20 Nm).
Tighten the Allen head screw to close the gas valve 34.
X Close the nitrogen gas bottle valve 62.

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X Release the pressure from the filling and checking device 50 by opening the relief valve B.
X Unscrew the union nut D and remove the filling and checking device 50.
X Disconnect the filler hose 63 from the filling and checking device 50 and the pressure reducing
unit 61.
X Using an Allen key (WS 6), tighten the Allen head screw 341 (tightening torque 20 Nm).
X Check the gas valve 34 for leakage, using a leak detection spray.
X Mount the protective cap 34 of the gas valve.

7 Repair of accumulator

7.1 Dismantling accumulator

Before carrying out any repair work on the accumulator, it must be disconnected from the hydraulic
circuit.

Danger!
Before dismantling the accumulator, read the safety instructions (see “General information” on
page 8) and strictly adhere to them.
Incorrect handling of the accumulator can lead to serious accidents.
All work on the gas and liquid connections must be carried out by specially trained technicians.

X Before carrying out any repair work, completely depressurise the hydraulic and gas sections,
(see “Checking the gas precharge pressure and/or reducing the gas precharge pressure using
the filling and checking device FPU-1” on page 10).

7.2 Diaphragm accumulator 10

Diaphragm accumulators cannot be dismantled. They can therefore not be repaired.

7.3 Bladder accumulator 20, see Fig. 8

7.3.1 Dismantling
X Remove the protective cap 27, unscrew the sealing cap 26 and remove the O-ring 28.
X Release the nitrogen, using the filling and checking device FPU-1.
X Secure the accumulator properly (vice, assembly workbench).
X Keep a suitable container ready to collect any escaping hydraulic oil.
X Turn the insert at the gas valve 23 clockwise using a gas valve key.
X Unscrew the bleeder valve 29.
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X Unscrew the slotted nut 222 using a hook key.

X Remove the spacer ring 223 (if stiff, loosen it with a plastic mallet).
X Loosen the valve body 221 and slide it into the accumulator 21.
X Reach into the bore and pull out the O-ring 226 and the pressure collar 225 with the backing ring
227 (if installed) from the valve body 221.
X Remove the split ring 224 from the valve body 221, fold it and remove it from the pressure

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Repair of accumulator

vessel 21.
X Remove the valve body 221 from the pressure vessel 21.
X Unscrew the retaining nut 231 from the gas valve 23 and pull the bladder 25 from the pressure
vessel 21.

Fig. 8 Sectional drawing of the bladder accumulator

21 Pressure vessel 223 Spacer ring

22 Hydraulic connection 224 Split ring
23 Gas valve 225 Pressure collar
24 Check valve 226 O-ring
25 Bladder 227 Backing ring
26 Sealing cap 231 Retaining nut
27 Protective cap 232 Gas valve insert
28 O-ring 241 Valve plate
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29 Bleeder valve 242 Valve stem

221 Valve body 243 Lock nut
222 Slotted nut

7.3.2 Checking of individual components

Pressure vessel:
X Carefully clean the inside of the pressure vessel 21 with a detergent that is not aggressive and not

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abrasive.
X Dry the clean surfaces with a lint-free cloth.
X Check the bore at the hydraulic section for damage to ensure properly sealing by the O-ring.
If the bore is OK = proceed to the next check (bladder).
If the bore shows damage at the inside or outside = return the pressure vessel to the manuf-
acturer.

Bladder:
X Carefully fill the bladder 25 with nitrogen or compressed air until it is fully inflated.
X Inspect the bladder 25 for damage and chaffed sections (check in particular depth of chaff marks).
Bladder 25 shows no or only minor scratch marks = bladder 25 is OK.
Bladder 25 shows large (deep) scratch marks = check it again for rough sections; if in doubt,
replace the bladder 25.
X Check the bladder 25 for leakage.
Bladder 25 shows no leakage = bladder 25 is OK.
Bladder 25 shows signs of leakage (even minor) = immediately replace bladder 25.
Gas valve insert 231 is leaking = replace gas valve insert (repair kit).
Gas valve 23 is not tight, despite insertion of new gas valve insert 231 = replace bladder 25.

Valve body (hydraulic section) with fixtures

X Check the valve plate of the check valve 24 in various different positions (radial offset of 90°) for
stiffness.
X Check the valve plate 241 and the valve plate shaft of the check valve 24 for scratch marks. Check
fixture.
Valve plate 241 and valve plate shaft show no signs of damage, and self-locking nut at valve
plate 241 is properly tightened = components can be used again.
Valve plate 241 and valve plate shaft show signs of damage and self-locking nut at the valve
plate is loose = remove nut from valve plate 241 (4 Nm) or replace the entire valve body (oil
valve).
X Check the split ring 224 for damage and wear.
Prominent cracks in the steamer, brittle elastomer sections or signs of ageing (uneven sur-
faces and notches) = replace split ring 224.

Sealing elements and other parts

X Before reassembling the bladder accumulator, replace all seals, O-rings, etc. (sealing kit).
X Check all parts for damage and replace them, if necessary.

7.3.3 Installation
X Carefully wet the inside of the pressure vessel 21 with hydraulic oil.
X Remove the protective cap 27, the sealing cap 26 and the retaining nut 231 from the bladder 25.
X Unscrew the gas valve insert 232.
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X Press the air out of the bladder 25 (roll up large bladders towards the gas valve).

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Note!
To install the bladder 25 without damaging it and to ensure free movement of the bladder 25 in the
pressure vessel 21, treat it with a slip film.
Do not wet the bladder with water, as water does not provide a durable slip film.
X Wet the bladder 25, possibly by spraying it, with hydraulic oil.
X Do not use tools with sharp edges.
X To mount the O-ring 226, use a blunt, rounded screwdriver and cover the thread of the valve
body 221 with adhesive tape.

X Roll up the bladder 25 and slide it with the gas valve 23 ahead into the pressure vessel 21.
X Screw the retaining nut 231 loosely on the gas valve 23.
X Inflate the bladder 25 with compressed air until it touches the inside wall of the pressure vessel 21.
X Fully slide the valve body 221 into the pressure vessel 21.
X Fold the split ring 224 and insert it in the pressure vessel 21.
X Slide the split ring 224 onto the valve body 221 and pull the valve body 221 together with the split
ring 224 into the bore of the pressure vessel 21.
X Insert the following components one after the other (from outside): pressure collar 225, O-ring
226, backing ring 227 and spacer ring 223 .
X Mount the grooved nut 222 and tighten it with a hook key (torque 90 Nm).
X Screw in the bleeder valve 29 (torque 3 Nm).
X Remove the loosely tightened retaining nut 231 and mount it together with the type plate. Tighten
the retaining nut 231 (torque 80 Nm).
X Screw the gas valve insert 231 into the gas valve 23 by turning it anti-clockwise and add precharge
gas into the bladder 25, (see 6.2.3 on page12).
X During filling, wait for minimum 5 minutes to allow the nitrogen to reach ambient temperature
(when filling large volumes of nitrogen and for high pressures, prolong this interval). Continue fil-
ling until the correct precharge pressure is reached in the accumulator.
X Mount the O-ring 28, screw on the sealing cap 26 and tighten it (torque 30 Nm).
X Replace the protective cap 27.

7.4 Piston accumulator 30, see Fig. 9

7.4.1 Dismantling
X Carefully clean the areas around the cylinder base 32 and the cylinder cover 33.
X Release the pressure from the hydraulic section (gas precharge pressure shifts the piston towards
the cylinder base 32).
X Remove the protective cap 231.
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X Release the nitrogen, using the filling and checking device FPU-1, see Fig. 7.
X Secure the accumulator properly (vice, assembly workbench).
X Keep a suitable container ready to collect any escaping hydraulic oil.
X Unscrew the gas valve 34.
X Remove turn lock 39 (if installed).
X Unscrew the cylinder base 32 and the cylinder cover 33 from the pressure vessel 31, using inser-

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ted studs/bolts and suitable flat steels/tool.

X Push the piston 35 from the pressure vessel 31.

Fig. 9 Sectional drawing of the piston accumulator

31 Pressure vessel 37 Seal ring

32 Cylinder base 38 Guide ring
33 Cylinder cover 39 Turn lock (not included in all designs)
34 Gas valve 321 O-ring
35 Piston 341 Hexagon socket screw
36 Hydraulic connection 342 Protective cap

7.4.2 Checking of individual components

Pressure vessel:
X Carefully clean the inside of the pressure vessel 31 with a detergent that is not aggressive and not
abrasive.
X Dry the clean surfaces with a lint-free cloth.
X Check the inside and outside of the pressure vessel 31 for scratches/damage.
If the pressure vessel 31 is OK = proceed to the next check.
If the pressure vessel shows damage on the inside or outside = return the pressure vessel to
the manufacturer.

Cylinder base 32 and cylinder cover 33:

LHB/en/Edition: 07/2009

X Remove the O-rings from the cylinder base 32 and the cylinder cover 33.
X Carefully clean the cylinder base 32 and the cylinder cover 33.
X Check the thread and the O-ring piercings.

Piston:
X Pull the sealing and guide ring 37 / 38 from the piston 35.

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X Carefully clean the piston 35.

X Check the piston 35 for damage.

Sealing elements and other parts

X Before reassembling the piston accumulator, replace all seals, O-rings, etc. (sealing kit).
X Check all parts of the gas valve 34 for damage and replace them, if necessary.

7.4.3 Installation, see Fig. 9

Note!
X Heat the sealing ring 37 to approx. 150 °C.
X Apply a slip film to the sealing and guide ring 37 / 38 and the piston 35.
Do not wet the parts with water, as water does not provide a durable slip film.
Do not use grease, use only hydraulic oil.
X Mount the sealing ring quickly on the piston, using a mounting sleeve (special tool Ø 60 mm)
(stepped side facing the hydraulic section).
X Do not use tools with sharp edges.

X Restore the original shape of the sealing and guide ring 37 / 38, using a calibrating tape.
X Carefully wet the inside of the pressure vessel 21 with hydraulic oil.
X Insert the piston 35 together with the sealing and guide ring 37 / 38 in the correct direction (see
sectional drawing) into the pressure vessel 31.
X Apply grease to the O-rings 321 and mount them on the cylinder base 32 / cylinder cover 33.
X Screw the cylinder base 32 and the cylinder cover 33 into the pressure vessel 31, using inserted
studs/bolts and a suitable flat steel/tool. Ensure that the base and cylinder tightly seal the ends of
the pressure vessel 31.
X For devices with turn lock 39, insert it in the pressure vessel 31.
X Screw the gas valve 34 into the cylinder cover 34 and fill the pressure vessel 21 with gas at the
prescribed precharge pressure, (see 6.2.3 on page12).
X During filling, wait for minimum 5 minutes to allow the nitrogen to reach ambient temperature
(when filling large volumes of nitrogen and for high pressures, prolong this interval). Continue fil-
ling until the correct precharge pressure is reached in the accumulator.
X Mount the protective cap 342 and tighten it (tightening torque 40 Nm).
LHB/en/Edition: 07/2009

7.95.21
copyright by

MJFCIFSS
Accumulator Service Manual
Repair of accumulator

LHB/en/Edition: 07/2009

7.95.22
copyright by

MJFCIFSS