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TEST THE PARTS CAUSING HYDRAULIC DRIFT IN WORK EQUIP-
MENT
TEST THE PARTS CAUSING HYDRAULIC DRIFT IN WORK EQUIPMENT
k
Place the machine on a level ground, lower the work equipment completely to the ground in a stable
posture, set the lock lever to LOCK position, and then stop the engine.
If the cause of hydraulic drift is defective cylinder packing, lowering speed may increase during the test because
of the reasons as follows.
•
Oil leaks from the bottom side to the head side when the machine is set in the measuring posture for hy-
draulic drift (where the holding pressure is applied to the bottom 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.
•
As the pressure in the bottom side (varies depending on the leakage amount) increases, the pressure in the
head side also increases. The pressures are balanced on both side, and then lowering speed decreases. At
this time, operate the lever to the direction that head side oil in tested cylinder is drained to tank circuit, and
head side oil flows to drain circuit (bottom side is blocked by check valve), and. Pressure balance between
head side and bottom side is lost, and then lowering speed increases.
For testing of the isolating of the part causing hydraulic drift in work equipment to perform troubleshooting, refer
to this section.
METHOD FOR TESTING THE PARTS CAUSING HYDRAULIC DRIFT OF BOOM
CYLINDER AND BUCKET CYLINDER
1.
Set the work equipment in the same posture as when
measuring hydraulic drift, and stop the engine
Put a weight equivalent to the rated load in the bucket or
fill the bucket with the earth and sand.
2.
When testing the boom cylinder, set the boom control lever
to RAISE position. When testing the bucket cylinder, set
the bucket control lever to CURL position.
Judging method
•
When the lowering speed is increased at this time:
The cylinder packing is defective.
•
No change: The control valve is defective.
REMARK
• Operate the control lever when the starting switch is turned to ON position.
• If the accumulator pressure is reduced, run the engine for approximately 10 seconds to accumulate the
pressure.
METHOD FOR TESTING THE PARTS CAUSING HYDRAULIC DRIFT OF ARM
CYLINDER
1.
Move the arm cylinder, stop it at approximately 100 mm
before IN stroke end, and stop the engine.
2.
Operate the arm control lever to IN to test.
Judging method
•
When the lowering speed is increased at this time:
The cylinder packing is defective.
•
No change: The control valve is defective.
REMARK
• Operate the control lever when the starting switch is
turned to ON position.
• If the accumulator pressure is reduced, run the engine
for approximately 10 seconds to accumulate the pres-
sure.
30-94
30 TESTING AND ADJUSTING
PC500LC-10R
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