Komatsu PC130-8, Руководство по ремонту, Страница: 961 / 1043

50 Disassembly and assembly SEN04130-01
PC130-8
33
Removal and installation of anti-
drop valve for boom assembly
1
k Place the machine on a level ground.
k Remove the anti-drop valve assembly from
the machine body, and then perform disas-
sembling of the anti-drop valve assembly.
k High pressure may remain in the anti-drop
valve assembly even after performing nor-
mal releasing procedure. Be sure to per-
form this procedure, and then perform the
releasing procedure.
k When the arm cylinder moves only in one
direction inside the anti-drop valve for arm,
operate the cylinder to the stroke end in a
movable direction. Lower the bucket to the
ground, and then perform releasing the
remaining pressure.
k If the bucket is not lowered and the anti-
drop valve is removed from the cylinder,
the high pressurized oil may spurt out. It is
very dangerous.
a
Wash around the anti-drop valve assembly in
order to prevent any dust or dirt from entering
it, and then perform the work.
a
Install a plug or flange in the place where a
hydraulic hose is disconnected to prevent oil
from flowing out.
a
Check the connector numbers and installed
positions before disconnecting wirings and
hoses, and record them.
Removal
1. Check for the function of PPC circuit accumu-
lator.
1)
Set the arm cylinder and bucket cylinder
to the most retracted position (maximum
arm OUT/bucket DUMP position), and
hold the work equipment at the height (a)
off from the ground.
a
(a) : 1.5 m
2) Keep the arm cylinder and bucket cylinder
at the most retracted position. Turn the
starting switch to OFF position to 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.
k Perform the step3. to 5 in 15 seconds
after the engine stopped, since the bat-
tery charge in the PPC accumulator
lowers gradually.
k If the work equipment is not lowered or
stops on the way, the battery charge of
the PPC accumulator may be lowered.
In such case, the remaining pressure
cannot be released with this proce-
dure.
a
If the work equipment is lowered by its
own weight to the ground, the battery
charge of the PPC accumulator is normal.
a
PPC accumulator is a periodic inspection
item and an important periodic replace-
ment part.
2. Releasing the remaining pressure in hydraulic
cylinder circuit
1)
Start the engine.
2) Set the arm cylinder and bucket cylinder
to the most extended position (maximum
arm IN/bucket CURL position) or the most
retracted position (maximum arm OUT/
bucket DUMP position), and lower the
work equipment to the ground.
a
Anti-drop valve is installed to the bot-
tom side of the boom cylinder.

When the work equipment is lowered
with this posture, the oil in the bottom
side of the boom cylinder is drained,
and the remaining pressure is low.