Service Manual User Manual

TESTING HYDRAULIC RELIEF
VALVE PRESSURES
The reason for testing the main relief valves is to
assure that the relief valves open and to limit the
pressure in the lines at that time.
Circuit relief valves are used in some circuits to
protect the Gradall Materials Handler from external
forces.
Other relief valves are installed the circuit to limit
the pressures for that circuit or to control flow
during specific actions.
GRADALL LOED MATERIAL HANDLER 534B TESTING AND ADJUSTING
The engine should be turning at full governed
rpm.
The hydraulic oil should be warmed up to
operating temperature.
The test gage or gages should be installed in the
circuit being tested.
The circuit function should be stalled by either
running the cylinder to the end of its stroke or by
stalling the motor action.
With the control levers actuated, a gage reading
is taken. The gage indicates the setting of the
respective relief valve.
A.
B.
C.
D.
E.
ADJUSTING RELIEF VALVES
All of the relief valves can he adjusted using an allen
wrench or a screwdriver. Loosen the lock nut, and
turn the adjusting screw clockwise to increase the
pressures. Turning it counter-clockwise will
decrease the pressures. The valve adjustment is
sensitive, so adjust in small moves, like 1/8 to 14
turn at a time. Tighten lock nut after adjustment.
HOW TO TEST AND ADJUST
MAIN CONTROL VALVE RELIEF
Set pressures with oil at operating temperature and
engine at 2800 rpm.
Install gage in test port tandem pump
outboard tube.
Retract boom fully and hold control lever full
to left.
Gage should read 3000 psi.
Adjust, reseal or replace relief valve, as
necessary.
Remove gage and recap test port.
1.
2.
3.
4.
5.
3
Park Materials Handler on
level ground with forks on,
ground. Shut off engine, set
parking brake and remove
ignition key. Chock the
wheels before performing
any servicing.