Komatsu Galeo PC138US-8 Shop Manual page 230

SEN02550-01
Function
Prevents the pressurized oil from reversing
q
from the work equipment cylinder in order to
prevents sudden drift of the work equipment at
breaking of the piping between the control
valve and the work equipment cylinder.
Operation
1. When the work equipment lever is in neu-
tral
When the piping is free of breakage
Check valve (5) is closed under the holding
q
pressure of the cylinder led from port (CY) to
chamber (b).
At the neutral, pilot pressure led to port (PI)
q
from the PPC valve is 0 MPa {0 kg/cm²}.
Spool (1) is pressed to the left by the force of
q
springs (2) and (3).
Chambers (a) and (b) are shut off.
q
No pressurized oil flows between the control
q
valve and the work equipment cylinder.
Accordingly, the
q
position.
If the work equipment cylinder has abnomally
q
high pressure, safety valve (4) is actuated by
the holding pressure of the work equipment
cylinder.
Chambers (b) of L.H. and R.H. holding valve
q
for the boom are interconnected by port (PCY).
Chambers (b) will have the same pressure if
q
the L.H. and R.H. holding valves have a differ-
ence in leakage.
48
work equipment is held in
10 Structure, function and maintenance standard
If the piping is bursted
If piping (A) is broken between the control
q
valve and the work equipment cylinder, cham-
bers (a) and (b) are shut off in the same way
as the piping is free from damages.
Pressure for the work equipment cylinder is
q
held to prevent a sudden drop of the work
equipment.
PC138US, USLC-8