Testing Parts Which Cause Hydraulic Drift Of Work Equipment - Komatsu PC200-8M0 Shop Manual

SEN06127-00
Testing parts which cause
hydraulic drift of work equipment
a If the work equipment (cylinder) drifts hydrauli-
cally, check to see if the causal part is the cyl-
inder packing or control valve side according to
the following procedure.
1. Measurement of boom and bucket cylin-
ders
1) Set the machine in the posture for mea-
suring hydraulic drift and stop the engine.
a Fill the bucket with a rated load or
with dirt and sand.
2) When checking the boom cylinder, set the
boom control lever to the RAISE position.
When checking the bucket cylinder, set
the bucket control lever to the CURL posi-
tion.
q If the lowering speed is increased at
this time, the cylinder packing is
defective.
If the lowering speed does not
q
change at this time, the control valve
is defective.
a Operate the control lever while the
starting switch is in the ON position.
a If the pressure in the accumulator is
lost, run the engine for approximately
5 seconds to increase the pressure in
the accumulator.
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Testing parts which cause hydraulic drift of work equipment

2. Inspection of arm cylinder
1) Stop the arm cylinder approximately 100
mm before the IN stroke end and stop the
engine.
2) Operate the arm control lever in the IN
position.
q If the lowering speed is increased at
this time, the cylinder packing is
defective.
q If the lowering speed does not
change at this time, the control valve
is defective.
a Operate the control lever while the
starting switch is in the ON position.
a If the pressure in the accumulator is
lost, run the engine for approximately
5 seconds to increase the pressure in
the accumulator.
[Reference]
Reason why the lowering speed is increased
by the above operation when the cylinder
packing is the cause of the hydraulic drift:
1) If the machine is set in the above posture
(where the holding pressure is applied to
the bottom side), the oil leaks from the
bottom side to the head side. Since the
volume on the head side is less than that
on the bottom side by the volume of the
rod, the pressure in the head side is
increased by the oil flowing in from the
bottom side.
2) As the pressure in the head side is
increased, it is balanced at a certain level
(which depends on the leakage), and then
the lowering speed is lowered.
3) If the circuit on the head side is opened to
the drain circuit by the above operation of
the lever (the bottom side is closed by the
check valve at this time), the oil on the
head side flows in the drain circuit. As a
result, the pressure is unbalanced and the
lowering speed is increased.
101 Testing and adjusting, Part 1
PC200, 200LC, 220, 220LC-8M0