700 / 800 SER IES B ACK H O E
LO ADER.
H USCO H YDRAUL IC SYST EM .
FRO M SERIAL No.
(1) 3905.
And in addition – 3904,3903,3900,3896,
3895,3894,38933892,3890,3888,3885,
3883,3874,3836,3829,3761,3739,3733.
700/800 SERIES.
P100 RANGE HUSCO HYDRAULIC SYSTEM.
A new hydraulic system has been introduced to the Fermec P 100 -700/800 Range of
Backhoe Loaders from Serial No (1) 3905.
Incorporated in the system are new Loader & Backhoe control valves that are
Manufactured by Husco. This new system is fitted to the 700/800 Series only, the 900 Series
Models currently remain unchanged.
The new Husco valve replaces the current mechanically operated Danfoss PVG 83 Valves.
The commercial Tandem Gear Pumps continues with 142 Litres / Min flow on 700 Series
Machines & 160 Litres / Min on the 800 Series. The unloader valve has moved from its
front Pump Mounting & is mounted on the chassis & is combined with the Steering Priority
Valve.
The Extending Dipper Valve is now incorporated in the Husco 7 Spool Valve Assy & with
the use of a Solenoid operated Changeover Valve also acts as the Control Valve for the
Auxiliary Circuit. Resulting in the use of one Foot Pedal to operate both services.
Main Changes P 100
700 & 800 Series.
1. New Husco 3 Spool Loader Control Valve.
2. New Husco 7 Spool Backhoe Control Valve.
3. The new Unloader Valve which is no longer mounted on the tandem pump, now
it is combined with the Steering Priority Valve, that is Chassis mounted.
4. New Changeover Valve, Electrically operated to divert the Hydraulic flow to the
Extending Dipper or the Auxillary Hydraulics. Now one Pedal to operate either
Service. The earlier single Spool Valve for the Extending Dipper no longer exists.
5. New Hydraulic Cooler Pack ( Gives improved cooling).
6. Hydraulic Return Line Filter now Chassis Mounted ( Still 13 Microns ).
7. New Stabiliser Tubes on Sideshift Machines.
8. New Stabiliser Leg Hoses on Center Mount Machines.
9. Modified Transmission Cooling Installation.
10.Hammer Return Line now goes directly to Tank.
HYDRAULIC CIRCUIT 750,760,860
SIDE SHIFT & CENTRE MOUNT BACKHOE
GENERAL DESCRIPTION. (NEUTERAL FLOW)
Oil is drawn from the Hydraulic Reservoir through a 125 Micron Suction Strainer into
the Tandem Gear Type Pumps.
Oil from the inner (80 LPM) Pump flows to the Steering Flow Priority Valve Mounted on
the Chassis. If the closed centre Steering Orbitrol Unit is in neuteral the oil is automatically
directed to the Loader Control Valve.
As oil enters the control valve the flow is restrictedby a bypass compensating Spool which
is in the closed position, at this point the pressurebegins to rise & opens the Spool against
a 20 Bar rated spring allowing the oil to enter the Block.
The open centre Loader Control Valve is a three spool monobloc which supplies oil to the
Loader Beam / Bucket & 7 in 1 Clam ( If fitted). On machines fitted with the standard
Loader Buckets the ports of the centre S pool are blanked off.
NEUTRAL FLOW CONTINUED.
If all the Spools are in the neutral position the oil flows through the open centre
of the Loader Valve to the Backhoe Control Valve.
Oil from the outer pump( 860 - 80 LPM or 750/760 - 62 LPM) flows through to
the new Unloader Valve mounted on the Chassis where it joins the flow from the
outer 80 LPM pump to the Loader Control Valve.
The 7 Spool Backhoe Monoblock Control Valve is of the closed centre type.
If all the Spools are in the neuteral position oil passes through a parallel Gallery
Via a return line 6 Bar rated check valve through the Return Line Filter & Cooler
back to the Tank.
Machine Circuit Diagram: Spools In neutral
HYDRAULIC CIRCUIT
( LOADER BEAM SPOOL SELECTED).
Operation of the Loader Spool closes the Open Centre Gallery & directs the flow of
oil along the Pressure Gallery into Loader Lift Port. A Check Valve in the Pressure
Gallery prevents movement of the services until residual pressure in the Loader Service
has been overcome by pump pressure.
Oil coming back from the return side of the Loader Lift Cylinder passes through the
Spool Valve into the return gallery. This oil then returns to the Tank Via the Backhoe
Control Valve, it opens the 6 Bar Check Valve & allows the oil to pass through the
Return Line Filter & Cooler back to Tank.
When pressure is created by using any of the Services and it reaches the Unloader Relief
Valve setting of 207 Bar ( 3000 PSI ) the Unloader Valve opens & allows oil from the
outer pump to discharge directly back to the reservoir.
The inner Pump will continue to supply the service until the pressure reaches 225 Bar
( 3250 PSI ) at which point the Main Relief Valve in the Loader Control Valve opens.
Machine Circuit Diagram: Loader Lift Spool Selected to Raise
HYDRAULIC CIRCUIT
( BACKHOE BOOM SPOOL SELECTED).
The new Husco Isocomp Backhoe Control Valve is a Closed Centre, Load Sensing, Flow
Sharing 7 Spool Valve. The new Monobloc Valve features Pressure Compensation on
each Spool, compared to the Danfoss Valve with Pressure Compensation on the slew
Section only. By locating the Pressure Compensators after the Spool it allows flow to all
Backhoe Services during multi - function operation to keep the cylinders working together.
In this example a Spool has been selected to raise the Backhoe Boom, on selection of the
Spool Load Sense Pressure is relayed via a small-bore hose to the spring side of the Bypass
Compensator in the Loader Control Valve. The Load Sense Pressure plus Spring Pressure
closes off the Bypass Compensator diverting the flow from both pumps directly to the
Backhoe Control Valve. The flow then opens the Pressure Compensator allowing the oil
to flow between the lands of the Boom Spool to the rod side of the Boom Cylinder.
Oil from the head side of the Cylinder flows through the return gallery of the Valve via the
6 Bar Check Valve through the Return Line Filter & Cooler back to Tank.
Machine Circuit Diagram: Backhoe Boom Selected to Raise
TM
Typical IsoComp Circuit
TM
IsoComp Multi-function flow sharing
- Backhoe Grading Function
UNLOADER AND STEERING
PRIORITY VALVE OPERATION.
The P100 Backhoe Loader fitted with the combined Oil Control Steering Priority
/ Unloader Manifold uses two Hydraulic Pumps both delivering 80 LPM at 2200
EngineRPM (860) nor 80/ 62 LPM at 2200 RPM ( 750 / 760 Machine). The power
needed to drive both Pumps up to maximum relief valve pressure 225 Bar is more
than the Engine delivers, so a Unloading Valve is used to divert all the flow from Pump
P2 to Tank when the Load Pressure reaches 207 Bar. The Hydraulic Services can then
continue working at a reduced speed using the flow from the remaining Pump P1.
The output from P1 is delivered first to a LoadSensing steering Priority Spool. This
Spool delivers oil to a Steering Orbitrol Unit according to the demand of the Steering
Wheel.
When sufficient oil is supplied, the Spool shifts to divert exccessive oil to join the flow
from P1 to supply the main hydraulic functions.
UNLOADER VALVE
OPERATION ( SEE FIG 1 )
Oil from P2 enters the Valve, flows through the Check Valve & combines with the flow
from the Steer Priority Spool & exits through Port EF to the Loader or Backhoe Control
Valve. A drilling in the block feeds oil from EF back to the end of the Unloader Spool,
through the orifice in the centre of the spool, through the Spring Chamber to the Relief
Valve & Solenoid Valve. When pressure in EF Exceeds 207 Bar the Relief Valve opens
& oil begins to flow from EF through the orifice in the Spool through the relief valve to
tank. The pressure drop thus created across the orifice & acting on the end of the Spool
exceeds the force of the Spring, allowing the Spool to shift, operating P” to Tank. When
pressure in EF falls below the setting of the Relief Valve it closes, the flow through the
Orifice stops, pressure equalizes at each end of the Spool, the spool is then shifted to its
original position by the spring. Oil from P” passes through the Check Valve again to
combine with the flow from P1 to give full flow to the HydraulicControl Valves.
Similarly, when the Solenoid valve is energized the oil flows along the same path, causes
a pressure drop across the orifice and the spool shifts across & opens P2 to Tank.
STEERING PRIORITY VALVE
OPERATION ( SEE FIG 2 ).
Oil from P1 enters the centre port of the Steer Priority Spool and is diverted to the
controlled flow port CF. Pressure in CF is sensed through 2 small drillings in the
Spool and is directed to the end of the Spool through a 0.8 mm diameter orifice.
When sufficient oil is delivered to the Steering Orbitrol unit to satisfy the Steering
requirement, pressure in CF rises & when it exceeds the setting of the spring, the
spool begins to shift & the excess flow is diverted to EF to combine with the flow
from P2 to the Hydraullic Control Valves.
A load Sense hose directs pressure from the Steering Orbitrol back in to LS.
Thus regardless of the flow demanded by the Steering Orbitrol, the Spool
will always maintains the pressure at CF 9 Bar higher that the load at the
Steering Orbitrol Unit.
HUSCO LOADER VALVE HUSCO BACKHOE VALVE
SERVICE CYLINDER S.L.R.V A.C.V SERVICE CYLINDER S.L.R.V A.C.V
BEAM HEAD 240 BAR YES SLEW HEAD 240 BAR YES
ROD NO NO ROD 240 BAR YES
LDR BKT HEAD 345 BAR YES BOOM HEAD 240 BAR YES
ROD 310 BAR YES ROD 310 BAR YES
AUX HEAD 160 BAR YES DIPPER HEAD 265 BAR YES
ROD NO NO ROD 280 BAR YES
BUCKET HEAD 280 BAR YES
ROD 280 BAR YES
STABS HEAD NO NO
MRV 225 BAR + 7 - 0 ROD NO NO
UNLOADER 207 BAR + 7 - 0. AUX HEAD 155 BAR YES
ROD NO NO
Sez. A-AValve
Diverter
De-energized
C2
P
C1
With coil de-
energized, spring
holds spool in
position 1. Oil enters
at P and flows to C1.
(Note, port not visible
in sectioned view
Sez. A-AValve
Diverter
Energized
C2
P
W ith coil energized,
solenoid pushes
spool to position 2,
diverting flow to C2
