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BOOM AND OUTRIGGER CIRCUIT:
The relief valve pressure setting at the inlet for boom control sections is 3000 PSI (207bar).
This pressure is required for all but the swing control section. Two work port relief valves are
installed in the swing section. These relief valves are set at 1500 PSI (103bar).
The relief pressure at the inlet end of the valve can be adjusted with a wrench and an allen
wrench. Loosen the nut and tighten the threaded stem with an allen wrench to increase pres-
sure, and loosen the stem to decrease pressure. Lock in place with the nut. Actuate the BOOM
LOWER or TELESCOPE RETRACT function with the cylinder fully retracted when making this
adjustment.
While the pressure gauge is attached, the swing function may be checked by capping the two
work ports of the swing section and actuating the swing control lever in each direction. If these
pressures are improper, the work port relief valve can be removed and shims added or removed
as needed. Part numbers for the work port relief valves and shims are listed below:
9-340-00070 Work Port Relief Valve-Gresen #7460-002 PS 1500 C
9-340-00032 Shim -- .010" -- Gresen #0462-001
9-340-00031 Shim -- .020" -- Gresen #0459-001
9-340-00030 Shim -- .040" -- Gresen #0458-001
(Pressure is changed approximately 100 to 125 PSI (7 to 9bar) for each .010" shim).
BOOM LIFT CYLINDER HOLDING VALVES
A holding valve is mounted to the base of each boom lift cylinder barrel. These valves are de-
signed to hold the boom in position should loss of power or pressure line failure occur.
To check the boom lift cylinder holding valve, set the outriggers, place the boom in the horizon-
tal position over the front of the crane and raise rated load about six inches (15cm) above the
ground using the boom lift cylinder (not the hoist). The best load for this test is the rated load at
the 20-foot (6.0m) load radius, with outriggers extended, and the boom over the front. Turn the
engine off and move the BOOM lever to the LOWER position. If the boom moves down, a hold-
ing valve may be malfunctioning or a boom lift cylinder may have leakage past the piston seal.
W A R N I N G
Before working on the holding valves or plumbing to the boom lift cylinders, always re-
lieve trapped pressure by lowering the boom fully, turning off the engine, and cycling the
BOOM lever.
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