18. OUTLINES OF SERVICE
18.3 OUTLINE OF HYDRAULIC SYSTEM
During operation and immediately after operation is ended, the temperature of the hydraulic system
still remains high.
In addition, high hydraulic pressure is applied to the system. Take care when inspecting and
maintaining the hydraulic system.
o Stop the machine on level ground, lower the bucket to the ground, then set so that there is no
pressure applied to the cylinder circuit.
o Always stop the engine.
o Immediately after operations, the hydraulic oil and lubricating oil are at high temperature and
high pressure, so wait for the oil temperature to go down before starting maintenance.
Even when the temperature goes down, the circuit may still be under internal pressure, so when
loosening the plug or screw, or the hose joint, do not stand in front of the part. Loosen it slowly
to release the internal pressure before removing it.
o When carrying out inspection or maintenance of the hydraulic circuit, always bleed the air form
the hydraulic tank to remove the internal pressure.
Periodic maintenance includes the inspection of the hydraulic oil level, replacement of the filter and
refilling of hydraulic oil.
When the high pressure hose, etc. is removed, check the O-ring for damage. If necessary, replace
it.
After the hydraulic filter element and strainer are cleaned or replaced, or after the hydraulic system
is repaired or replaced or the hydraulic piping is removed, bleed air from the hydraulic circuit.
The accumulator is charged with high-pressure nitrogen gas. Incorrect handling may be dangerous.
For the handling procedure, see “11.16 HANDLING ACCUMULATOR”.
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