Daewoo Solar 420LC-V, Manual

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Page 6
Hydraulic System Troubleshooting, Testing and
Adjustment
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OPERATION OF WORKING COMPONENTS
BOOM OPERATING CIRCUIT
The boom operating circuit includes the right and left main hydraulic pumps (both halves of the main pump
assembly), both sides of the control valve and the boom cylinder. The circuit operates in boom down mode
through the first shift position and through the second shift position in boom up mode. Overload relief
valves set at 360 kg/cm
2
. (5,112 psi) protect the hydraulic system from damage as a result of overloads or
shocks to the boom. 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.
BOOM UP CIRCUIT
When you pull the boom control lever backward,
the right side pilot valve generates secondary
boom up pilot pressure that is transmitted to the
BOOM1 and BOOM2 spools of the control valve
simultaneously. When secondary pilot pressure
reaches 7 - 10 kg/cm
2
(100 - 142 psi), boom
spools open and oil from both pumps goes to
the boom cylinder.
BOOM DOWN CIRCUIT
When the boom control lever is pushed forward,
the right side pilot valve generates secondary
boom down pilot pressure that is transmitted
only to BOOM1 spool of the valve. When
secondary pilot pressure reaches 7 - 10 kg/cm
2
(100 - 142 psi), the BOOM1 spool opens so that
oil from only one pump (PUMP(L)) assembly
goes to the boom cylinder for boom lowering.
BOOM
CYLINDER
BOOM UP
PILOT
BOOM1 BOOM2
PUMP(L)
PUMP(R)
ATS0750L
Figure 2
BOOM
CYLINDER
BOOM1 BOOM2
PUMP(L)
PUMP(R)
ATS0760L
BOOM DOWN
PILOT
Figure 3