Doosan DX480LC - Left Swing Operating Circuit; Right Swing Operating Circuit; Swing Relief Valve and Makeup Valve; Travel Operating Circuit

SP001751Hydraulic System Troubleshooting, Testing and Adjustment
Page 12
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 right side pump regulator and right half of the control valve.
Output flow from the right 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 right side of the control valve
moves in the opposite direction and output flow from the right
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 285 kg/cm
2
(4,052 psi) relief valve is installed in
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.
PUMP(R)
PR
CONTROL
VALVE(L)
CONTROL
VALVE(R)
SWSWD
TL
ARS1620L
PILOT VALVE
Figure 8
PUMP(R)
PR
CONTROL
VALVE(L)
CONTROL
VALVE(R)
SWSWD
TL
ARS1610L
PILOT VALVE
Figure 9