Komatsu ecot3 PC300-8, Shop Manual

Page: 394 / 1035

30 Testing and adjusting
54
PC300, 350-8
SEN02625-06
Inspecting locations of hydraulic
drift of work equipment
a
If hydraulic drift occurred on the work equipment
(cylinder), check to see if the cause is on the cyl-
inder packing side or control valve side accord-
ing to the following procedure.
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) When inspecting the boom cylinder, shift the
boom control lever to RAISE side and when
inspecting the bucket cylinder, shift the
bucket control lever to CURL side.
If, as the result, drifting speed increases,
failure on the cylinder packing should be
suspected.
If the speed remains unchanged, failure on
the control valve should be suspected.
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.
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) Shift the arm control lever to IN side.
If, as the result, drifting speed increases,
failure on the cylinder packing should be
suspected.
If the speed remains unchanged, failure on
the control valve should be suspected.
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] When the cause of the hydraulic
drift is in the defective packing, following
explains why such occurred.
1] If the work equipment is set to the above
posture (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 smaller 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.