Right Swing Operating Circuit; Left Swing Operating Circuit; Swing Relief Valve And Makeup Valve; Travel Operating Circuit - Doosan DX140R Shop Manual

Right Swing Operating Circuit

When the swing control lever is pushed to the right swing
position, pilot pressure from the left side pilot valve is directed to
the front side pump regulator and left half of the control valve.
Output flow from the front pump is then directed through the PR
and SWR ports of the control valve to the swing motor.

Left Swing Operating Circuit

When the swing control lever is pushed to the left swing position,
the control valve spool at the left side of the control valve moves
in the opposite direction and output flow from the front pump is
directed through the PR and SWL ports of the control valve to
the swing motor.

Swing Relief Valve and Makeup Valve

Whenever the spool is shifted to the neutral mode during swing
operation, the possibility exists that surge pressure in the circuit
- caused by inertial momentum of the upper works and
correspondingly reduced pressure at the opposite motor port -
could produce cavitation in the circuit. To keep that from
happening, a 270 kg/cm
the swing motor and a large capacity makeup valve is connected
to the entrance port of the hydraulic reservoir, helping maintain
acceptable pressures on both sides of the circuit.

Travel Operating Circuit

Output flow from both halves of the pump assembly is directed
to the right and left travel motors through the right and left sides
of the control valve, and the upper works center joint.
Hydraulic System Troubleshooting, Testing and Adjustment
Page 12
2
(3,840 psi) relief valve is installed in
CONTROL
VALVE(L)
SWD
TL
Figure 8
CONTROL
VALVE(L)
SWD
TL
Figure 9
PILOT VALVE
SW
PR
CONTROL
VALVE(R)
FG015082
PUMP(F)
PILOT VALVE
SW
PR
CONTROL
VALVE(L)
FG015083
PUMP(F)
SP001942