Inspection Of Locations Of Hydraulic Drift Of Work Equipment - Komatsu Galeo PC800-8 Shop Manual

30 Testing and adjusting
Inspection of locations of
hydraulic drift of work equipment
a If there is any hydraulic drift in the work equip-
ment (cylinders), check in the following manner
to determine if the cause is in the cylinder pack-
ing or in the control valve.
1. Inspection of boom and bucket cylinders
1) Set the work equipment in the same posture
as when measuring hydraulic drift, and stop
the engine.
a Fill the bucket with earth or apply the rat-
ed load to the bucket.
2) Operate the control lever to the RAISE posi-
tion or the bucket control lever to the CURL
position.
• If the lowering speed increases, the cyl-
inder packing is defective.
• If there is no change, the control valve is
defective.
a Operate the control lever with the engine
starting switch in the ON position.
a If pressure in the accumulator has
dropped, run the engine for approx. 10
seconds to charge the accumulator
again.
PC800, 850-8
2. Inspection of arm cylinder
1) Operate the arm cylinder to move the arm to
the position 100 mm before the digging
stroke end, and stop the engine.
2) Operate the arm control lever to move the
arm to the digging side.
• If the lowering speed increases, the cyl-
inder packing is defective.
• If there is no change, the control valve is
defective.
a Operate the control lever with the engine
starting switch in the ON position.
a If pressure in the accumulator has
dropped, run the engine for approx. 10
seconds to charge the accumulator again.
[Reference]If the cause of the hydraulic drift is in the
defective packing, and the above opera-
tion is carried out, downward movement
is accelerated for the following reasons.
1) If the work equipment is set to the above pos-
ture (holding pressure applied to the bottom
end), the oil at the bottom end leaks to the head
end. However, the volume at the head end is
small than the volume at the bottom end by the
volume of the rod end, so the internal pressure
at the head end increases because of the oil
flowing in from the bottom end.
2) As the internal pressure on the head side is
increased, the pressure on the bottom side is
also increased and they are balanced at a cer-
tain level (which depends on the leakage), then
the lowering speed is lowered.
3) When the pressure is balanced, the downward
movement becomes slower. If the lever is then
operated according to the procedure given
above, the circuit at the head end is opened to
the drain circuit (the bottom end is closed by the
check valve), so the oil at the head end flows to
the drain circuit and the downward movement
becomes faster.
SEN00912-02
13