Operation Of Working Components; Boom Operating Circuit; Boom Up Circuit; Boom Down Circuit - Doosan DX140R Shop Manual

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
system from being damaged as a result of overloads or shocks
to the boom.

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
2
- 9 kg/cm (100 - 130 psi), boom control valve 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 the BOOM1 spool of the control valve.
When secondary pilot pressure reaches 7 - 9 kg/cm
psi), the BOOM1 spool on the right side of the control valve
opens so that oil from only one pump (PUMP (rear)) assembly
goes to the boom cylinder for boom lowering.
Hydraulic System Troubleshooting, Testing and Adjustment
2
(5,112 psi) protect the hydraulic
2
BMD
TL
Figure 2
(100 - 130
PILOT VALVE
Figure 3
BOOM
CYLINDER
BM1 PILOT VALVE BM2
PL PR
CONTROL
VALVE(L)
PUMP(L) PUMP(R)
BM1 BMD
PL TL
CONTROL
VALVE(R)
PUMP(R)
CONTROL
VALVE(R)
ARS1560L
BOOM
CYLINDER
FG015148
SP001942
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