4 - 3
Main Relief Valve (MRV)
1 Prepare the Machine
a Put the operator levers into neutral and lower the
gate lock lever. Start the engine and park the
machine on level ground. Operate the dipper out
and lower the boom to set the bucket on the
ground. Stop the engine. Release the hydraulic oil
tank pressure. (See Releasing Tank Pressure).
b Install a 0 - 400 bar (0 - 6000 lb/in
2
) pressure
gauges at test points G1 and G2 (see view A on
page 4 - 1).
c Start the engine, and confirm that the engine is at its
maximum no-load speed and it is in the S mode.
d Raise the boom and then operate the dipper out
control. Read the pressure gauges with the dipper
ram stalled at the end of its stroke.
2 Pressure Setting
Note: For accurate setting, the pressure should be
adjusted up to the required level. Release lock nut
X. Adjust setting screw Y to indicate a pressure
below the required level and then bring the pressure
back up for final setting. Tighten lock nut X.
a The pressure gauges reading should be compared
to the technical data at the start of the section. If it
is outside the limits, adjust MRV as above.
3 Stop the engine
4 Confirmation of the rated pressure
a Start the engine, raise the r.p.m to maximum in the
S mode. Check for leakage at the adjusted points.
b Operate the dipper in control to bring the ram to the
end of its stroke. Continue to hold the lever with the
ram stalled in this position.
d The pressure gauge reading should be compared to
the technical data at the start of the section. If it is
outside the limits, repeat the procedure from
step 2.
5 Stop the engine and relieve the pressure in the
hydraulic oil tank (see Releasing Tank Pressure) .
Remove the pressure gauges and adaptors.
Section E Hydraulics
9803/6410
Section E
4 - 3
Issue 1
Pressure Testing
AA
A306490
312450
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