Komatsu ecot3 PC300LC-8 Shop Manual page 188

SEN01994-01
Function
Prevents the pressurized oil from reversing
q
from the work equipment cylinder and the latter
from a sudden drop if the piping bursts
between the control valve and the work equip-
ment cylinder.
Operation
1. When the work equipment lever is in neutral
When the piping is free of burst
Check valve (5) is closed under the holding
q
pressure of the cylinder led from port (CY) to
chamber (b).
q Pilot pressure led to port (PI) from the PPC
valve when in neutral is 0 MPa {0 kg/cm
q Spool (1) is pressed to the left by the force of
springs (2) and (3)
q Chambers (a) and (b) are shut off.
No pressurized oil flows between the control
q
valve and the work equipment cylinder.
q Accordingly, the work equipment is held in
position.
q If the work equipment cylinder has abnormally
high pressure, safety valve (4) is actuated by
the holding pressure of the work equipment
cylinder.
q Chambers (b) of L.H. and R.H. hydraulic drift
prevention valve for the boom are intercon-
nected by port (PCY).
q Chambers (b) will have the same pressure if
the L.H. and R.H. hydraulic drift prevention
valves have a difference in leakage.
62
10 Structure, function and maintenance standard
If the piping is bursted
If piping (A) bursts between the control valve
q
and the work equipment cylinder, chambers (a)
and (b) are shut off same as when the piping
has no burst.
2
}. Pressure for the work equipment cylinder is
q
held to prevent a sudden drop of the work
equipment.
PC300, 350-8