Daewoo Solar 420LC-V, Manual

Page: 8 / 151

Page 7
Hydraulic System Troubleshooting, Testing and
Adjustment
Return to Master Table of Contents
ARM OPERATING CIRCUIT
The arm operating circuit includes both the right and left hydraulic main pumps, the both sides of the
control valve, arm regen. valve, and the arm cylinder. The circuit can be operated in the two-stage speed
control mode which works through both halves of the control valve and doubles the volume of oil flowing to
the cylinder.
Overload relief valves set at 360 kg/cm
2
(5,112 psi) have been installed at the crowd and dump cylinder
ports on ARM1 side of the control valve to protect the circuit and system components from possible
damage caused by shocks or overload pressure. additional protection - to prevent cavitation of the cylinder
- is provided by a make-up valve and reservoir return circuit, which ensures that the volume of oil going to
the cylinder will not exceed the volume of oil coming out.
ARM CROWD CIRCUIT
When the arm control lever is put in the crowd
mode, the left side pilot valve generates
secondary pressure that is transmitted to the
ARM1 and ARM2 of the control valve
simultaneously.
When secondary pilot pressure reaches 7 - 10
kg/cm
2
(100 - 142 psi), the arm control valve
spool on the ARM1 and ARM2 spools open.
Output flow from both pumps are directed to the
arm cylinder.
When working in the arm crowd mode, under
certain conditions, arm cylinder could be forced
out by the weight of the arm and bucket itself. At
this time insufficient oil flow to the cylinder could
lead to cavitation in the cylinder head and/or
surging or irregular movement. This is prevented
by a regeneration valve attached to the control
valve which maintains the balance between oil
flowing into the cylinder and oil flowing out.
ARM DUMP CIRCUIT
When the arm control lever is put in "dump"
mode, the left side pilot valve generates
secondary pilot pressure that goes to both
ARM1 and ARM2 the control valve
simultaneously.
When pilot pressure reaches 7 - 10 kg/cm
2
(100
- 142 psi), the control spools open allowing oil
from PUMP(L) and PUMP(R) to flow to the arm
cylinder.
ARM
CYLINDER
ARM2 ARM1
PUMP(L)
PUMP(R)
ATS0770L
ARM CROWD
PILOT
REGEN V/V
Figure 4
ARM
CYLINDER
ARM2
ARM1
PUMP(L)
PUMP(R)
ATS0780L
ARM DUMP
PILOT
Figure 5