Oshkosh Corporation Classification: Unrestricted
44 IMT Electric Cranes Operation & Safety Manual # 99904381
Purging Air from Hydraulic System
Air trapped in the hydraulic cylinder will cause an erratic “bumpy” motion. To expel the air:
1 Hold the control open for a few seconds after the function has “bottomed out”.
2 Move the function in the opposite direction. Again, hold the control open a few seconds after
the function has “bottomed out”.
3 Attempt to operate the crane in the normal manner to determine if the air has been purged.
Hydraulic Pressure Relief
The hydraulic system relief valve is provided to prevent the user from placing too much strain on
the hydraulic components. The system relief pressure is preset and sealed at the factory, and it
must not be tampered with. If you suspect the system relief pressure of malfunctioning, see your
IMT dealer for testing and replacement.
WARNING
Setting the pressure relief higher than the
specification for your model crane is unsafe.
DO NOT ATTEMPT. Excessive relief pressure
w ill damage the equipment and can result in
injury or death. Only an authorized IMT
representative may adjust the relief pressure
and reseal the relief valve. A broken seal on
the relief valve w ill void the warranty.
Hydraulic Cylinder Holding Capability
The hydraulic cylinders have holding valves that prevent sudden movement of the cylinder rods
in the event of a hydraulic hose or other hydraulic component failure. The valves are non-
adjustable and failure is unlikely.
Check the hydraulic cylinder using the following steps:
1 With a full rated load, extend the cylinder in question and kill the engine.
2 Operate the control valve to retract the cylinder. To check the main (lower) cylinder, set the
boom horizontally with the maximum load. To check the extension boom cylinder, set the
crane at maximum articulation (angle). If the cylinder “creeps”, replace the holding valve. If
the cylinder does not “creep”, the valve is serviceable.
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