Hydraulic System; Releasing Remaining Pressure From Hydraulic Circuit - Komatsu PC88MR-10 Shop Manual

Hydraulic system

Releasing remaining pressure from hydraulic circuit

Releasing remaining pressure
C000-22A-K-00-A)
Releasing remaining pressure from hydraulic
tank
Release remaining pressure from the
hydraulic tank according to the following
procedure since hydraulic tank is airtight and
pressurized when removing a hose or a plug
connected to the hydraulic tank.
1. Lower the work equipment to the ground in a
stable posture and stop the engine.
2. Loosen oil filler cap (1) of the hydraulic tank
gradually to release the air in the tank.
Releasing remaining pressure in hydraulic
cylinder circuit
Without anti-drop valve
When disconnecting a pipes between a
hydraulic cylinder and the control valve,
release the remaining pressure from the
piping according to the following
procedure.
1. Release the remaining pressure in the
hydraulic tank. For details, see preceding
"Releasing remaining pressure in hydraulic
tank".
a Leave the oil filler cap of the hydraulic
tank removed.
2. Turn the starting switch to ON position and
set the work equipment lock lever to FREE
position, and then operate the right and left
work equipment control levers forward and
backward, and to the right and left.
a The control valve is operated by the
pressure in the accumulator. The
pressure in the accumulator is used up,
however, after the work equipment
control levers are operated two to three
times.
PC88MR-10
(ALL-C000-001-K-00-A)
(PC88MR-
30 Testing and adjusting
(ALL-C000-001-P-02-A)
3. Start the engine and run it at low idle for 5
seconds to increase the pressure in the
accumulator.
a The engine does not start unless the work
equipment lock lever is set to LOCK
position.
4. Repeat above procedure 2) and 3) 2 to 3
times, and all remaining pressure is released
from the pipes completely.
With anti-drop valve
Check function of PPC circuit accumulator
a Stop the machine on a level ground.
1. Hold the work equipment in the maximum
reach posture (arm OUT, bucket DUMP
stroke end) at height (a) from the ground.
a: 1.5 m
2. Keep the work equipment at the maximum
reach, turn the starting switch to OFF
position, and stop the engine.
3. Turn the starting switch to ON position.
4. Set the work equipment lock lever in FREE
position.
5. Check that the work equipment is lowered to
the ground by slowly operating the work
equipment control lever to the boom LOWER
direction fully to the stroke end.
a If the work equipment is lowered down
under its weight to the ground, the
accumulator is normal.
a Pressure of accumulator drops gradually
after stopping the engine. Be sure to
perform this work (procedure 2 and 3) in
15 seconds after stopping the engine.
a If the work equipment is not lowered or
stops on the way lowering, pressure in
the accumulator may be dropped.
Pressure cannot be released with this
procedure if the function of accumulator
is deteriorated.
Hydraulic system
30-37