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4 - 4
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. Lower the blade onto the ground. Stop the
engine. Release the hydraulic oil tank pressure. (See
Releasing Tank Pressure
).
b
Install an adaptor and 0 - 400 bar (0 - 6000 lb/in
2
)
pressure gauge at test point G1 or 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 gauge 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 gauge 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 gauge and adaptor.
Section E
Hydraulics
9803/6020
Section E
4 - 4
Issue 1
Pressure Testing
A
A
292530
293330
Y
X
Summary of Contents for JS70
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