Komatsu PC-01 – Testing and adjusting hydraulic pressure

Lower the work equipment completely to the ground and stop the engine. Operate the control levers several times to release the remaining pressure in the hydraulic piping. Then loosen the oil filler plate slowly to release the pressure inside the hydraulic tank.

1. Measuring
1) Remove the pressure pick-up plugs (1) or (2) from the side to be measured, and install hydraulic pressure gauge {19.6 MPa (200 kg/cm2)}.
– Plug (1): For bucket, boom, R.H. travel, blade
– Plug (2): For L.H. travel, arm, swing, boom swing

2) Run the engine, operate the circuit to be measured, and measure the relief pressure.
– For the swing circuit, measure the relief pressure of the safety valve.
(The set pressure of the safety valve is lower than the set pressure of the main relief valve, so the main relief valve is not actuated.)
– When relieving the swing circuit, put the bucket in contact with a pillar or block to lock the swing.
– When relieving the travel circuit, fit wooden block [1] between the track shoe and sprocket to lock the track. Measure the pressure for one side at a time.

– If the result of the measurement shows that there is an abnormality in the set pressure, adjust the set pressure of the main relief valve as follows.
1) Loosen locknut (5) of the main relief valve (3) or (4) on the side to be adjusted, turn adjustment screw (6), and adjust the set procedure.
– (3): For bucket, boom, R.H. travel, blade
– (4): For L.H. travel, arm, swing, boom swing
– Turn the adjustment screw to adjust as follows.
To INCREASE pressure, turn CLOCK-WISE
– One turn of the adjustment screw
adjusts by: 12.2 MPa {124 kg/cm2}. 3 Locknut:
19.6 ± 0.98 Nm {2 ± 0.1 kgm}
– After adjusting, repeat Step 1 to check again.


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