GROUP 3 PILOT CIRCUIT

Remote control valve Remote control valve

Travel pedal RCV dozer
(LH lever) (RH lever)

Boom swing pedal

Safety lock
solenoid valve Swing parking brake
Control valve

Travel speed solenoid valve

Line filter

Relief valve
30 kgf/cm2

Pilot pump
Suction filter

R35Z73HC00

The pilot circuit consists of suction circuit, delivery circuit and return circuit.
The pilot pump is provided with relief valve, receives the oil from the hydraulic tank through the suction
filter.
The discharged oil from the pilot pump flows to the remote control valve through line filter, solenoid
valve assemblies, swing parking brake, main control valve and safety lock solenoid valve.

3-5
 1. SUCTION, DELIVERY AND RETURN CIRCUIT

TRAVEL MOTOR-RH TRAVEL MOTOR-LH

R/G R/H L/H R/G SWING MOTOR

Ps Ps

DB PB
a1 a2 a2 a1

BM SWING
DOZER ARM CYLINDER
CYLINDER CYLINDER
STOP VALVES
P2(FW) P1(BW) T1 T2 T2 T1 P2(BW) P1(FW)

GA B(CCW) A(CW) GB
Mu
BUCKET BOOM
CYLINDER CYLINDER TURNING
JOINT

Pa8
Pa10 Pb8' Dr2 Pa7 P1 P2 Pa6 Pa5 Pa4 Dr1 P3 Pa3 Pa2 Pa1

B5
B8
B10

A6

B6
B7

A7
A10

A5

A4

B4
A9

B3

B2

A2

B1
A3

A1
BK BM TR-RH TR-LH SW BM DOZ
AM PTO SW

Pb10 T2 Pb7 Dr1 Pb6 Pb5 Pb4 T1 Pb3 Pb2 Pb1

Pb8
BU Pp1

TRAVEL DOZER
L/H R/H DW UP
2 1 4 3 1 2

SAFETY Pb6 Pa6 Pa7 Pb1 Pa1

Pb7
SOLENOID
VALVE PILOT PUMP
ACC BM SWING 2WAY OPTION SWING ARM BUCKET BOOM MAIN PUMP
A1 A2 LH RH LH RH OUT IN IN OUT UP DW R1 A1 A2 A4 A3
1 2 1 2 1 3 2 4 3 1 2 4

P
Pa2 Pb2 Pa4 Pb4 Pb3 Pa3 Pb5 Pb10 Pa10 Pb8
T Pa5 Pa8

S1

HYD TANK LINE FILTER

R35Z93HC03

The pilot pump receive oil from the hydraulic tank. The discharged oil from the pilot pump flows to
the safety solenoid valve through the line filter. The oil is filtered by the line filter. The pilot relief valve
is provided in the pilot pump for limiting the pilot circuit pressure.
The oil filtered by line filter flows remote control valve, MCV and swing port through safety solenoid
valve.
The return oil flow from remote control valve is returned to the hydraulic tank.

3-6
 2. SAFETY VALVE (SAFETY LEVER)

TRAVEL MOTOR-RH TRAVEL MOTOR-LH

R/G R/H L/H R/G SWING MOTOR

Ps Ps

DB PB
a1 a2 a2 a1

BM SWING
DOZER ARM CYLINDER
CYLINDER CYLINDER
STOP VALVES
P2(FW) P1(BW) T1 T2 T2 T1 P2(BW) P1(FW)

GA B(CCW) A(CW) GB
Mu
BUCKET BOOM
CYLINDER CYLINDER TURNING
JOINT

Pa8
Pa10 Pb8' Dr2 Pa7 P1 P2 Pa6 Pa5 Pa4 Dr1 P3 Pa3 Pa2 Pa1

B5
B8
B10

A6

B6
B7

A7
A10

A5

A4

B4
A9

B3

B2

A2

B1
A3

A1
BK BM TR-RH TR-LH SW BM DOZ
AM PTO SW

Pb10 T2 Pb7 Dr1 Pb6 Pb5 Pb4 T1 Pb3 Pb2 Pb1

Pb8
BU Pp1

TRAVEL DOZER
L/H R/H DW UP
2 1 4 3 1 2

SAFETY
SOLENOID
VALVE Pb6 Pa6 Pa7 Pb1 Pa1
Pb7
LEVER DOWN PILOT PUMP
ACC BM SWING 2WAY OPTION SWING ARM BUCKET BOOM MAIN PUMP
A1 A2 LH RH LH RH OUT IN IN OUT UP DW R1 A1 A2 A4 A3
1 2 1 2 1 3 2 4 3 1 2 4

P
Pa2 Pb2 Pa4 Pb4 Pb3 Pa3 Pb5 Pb10 Pa10 Pb8
T Pa5 Pa8

S1

LEVER UP HYD TANK LINE FILTER

R35Z93HC04

When the lever of the safety solenoid valve is moved downward, oil flows into the remote control
valve through solenoid valve and line filter.
When the lever of the safety solenoid valve is moved upward, oil does not flow into the remote
control valve, because of the blocked port.

3-7
 3. TRAVEL SPEED CONTROL SYSTEM

CONTROL PISTON
PILOT VALVE
TRAVEL MOTOR-RH TRAVEL MOTOR-LH
R/G R/H L/H R/G SWING MOTOR

Ps Ps

DB PB
a1 a2 a2 a1

BM SWING
DOZER ARM CYLINDER
CYLINDER CYLINDER
STOP VALVES
P2(FW) P1(BW) T1 T2 T2 T1 P2(BW) P1(FW)

GA B(CCW) A(CW) GB
Mu
BUCKET BOOM
CYLINDER CYLINDER TURNING
JOINT

Pa8
Pa10 Pb8' Dr2 Pa7 P1 P2 Pa6 Pa5 Pa4 Dr1 P3 Pa3 Pa2 Pa1

B5
B8
B10

A6

B6
B7

A7
A10

A5

A4

B4
A9

B3

B2

A2

B1
A3

A1
BK BM TR-RH TR-LH SW BM DOZ
AM PTO SW

Pb10 T2 Pb7 Dr1 Pb6 Pb5 Pb4 T1 Pb3 Pb2 Pb1

Pb8
BU Pp1

TRAVEL DOZER
L/H R/H DW UP
2 1 4 3 1 2

Pb6 Pa6 Pa7 Pb1 Pa1

Pb7
PILOT PUMP
ACC BM SWING 2WAY OPTION SWING ARM BUCKET BOOM MAIN PUMP
A1 A2 LH RH LH RH OUT IN IN OUT UP DW R1 A1 A2 A4 A3
1 2 1 2 1 3 2 4 3 1 2 4

P
Pa2 Pb2 Pa4 Pb4 Pb3 Pa3 Pb5 Pb10 Pa10 Pb8
T Pa5 Pa8

S1

HYD TANK LINE FILTER

R35Z93HC05

When the travel speed switch is pushed, the travel speed solenoid valve is actuated and the
discharged oil from the pilot pump flows to the Ps port of pilot valve in the travel motors.
As a result, the control piston is pushed by the main oil flow, thus the displacement is minimized.
When the travel speed switch is pushed once more, the travel speed solenoid valve is return to
original position by the force of spring, the hydraulic oil of Ps port returns to the hydraulic tank.
As a result, the control piston is returned by the main oil flow, thus the displacement is maximized.

3-8
 4. SWING PARKING BRAKE RELEASE

TRAVEL MOTOR-RH TRAVEL MOTOR-LH

R/G R/H L/H R/G SWING MOTOR

PARKING BRAKE
Ps Ps

DB PB
a1 a2 a2 a1

BM SWING
DOZER ARM CYLINDER
CYLINDER CYLINDER
STOP VALVES
P2(FW) P1(BW) T1 T2 T2 T1 P2(BW) P1(FW)

GA B(CCW) A(CW) GB
Mu
BUCKET BOOM
CYLINDER CYLINDER TURNING
JOINT

Pa8
Pa10 Pb8' Dr2 Pa7 P1 P2 Pa6 Pa5 Pa4 Dr1 P3 Pa3 Pa2 Pa1

B5
B8
B10

A6

B6
B7

A7
A10

A5

A4

B4
A9

B3

B2

A2

B1
A3

A1
BK BM TR-RH TR-LH SW BM DOZ
AM PTO SW

Pb10 T2 Pb7 Dr1 Pb6 Pb5 Pb4 T1 Pb3 Pb2 Pb1

Pb8
BU Pp1

TRAVEL DOZER
L/H R/H DW UP
2 1 4 3 1 2

Pb6 Pa6 Pa7 Pb1 Pa1

Pb7
PILOT PUMP
ACC BM SWING 2WAY OPTION SWING ARM BUCKET BOOM MAIN PUMP
A1 A2 LH RH LH RH OUT IN IN OUT UP DW R1 A1 A2 A4 A3
1 2 1 2 1 3 2 4 3 1 2 4

P
Pa2 Pb2 Pa4 Pb4 Pb3 Pa3 Pb5 Pb10 Pa10 Pb8
T Pa5 Pa8

S1

HYD TANK LINE FILTER

R35Z93HC06

When the Safety solenoid lever is moved downward, the pilot oil flow into PB port of the swing motor
through solenoid valve. This pressure is applied to swing motor disc, thus the brake is released.
When the safety solenoid lever is moved to upward, oil in the swing motor disc cylinder is drained,
thus the brake is applied.

3-9