99903514:TELESCOPIC CRANE:
2-8 SECTION 2: MAINTENANCE
2-5-7: 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 THAT SPECIFIED FOR
YOUR MODEL CRANE IS UNSAFE. DO
NOT ATTEMPT. EXCESSIVE RELIEF
PRESSURE WILL DAMAGE THE EQUIP-
MENT AND CAN RESULT IN SERIOUS
INJURY OR DEATH. ONLY AN AUTHO-
RIZED IMT REPRESENTATIVE MAY AD-
JUST THE RELIEF PRESSURE AND
RESEAL THE RELIEF VALVE. A BROKEN
SEAL ON THE RELIEF VALVE WILL VOID
THE WARRANTY.
2-5-8: HYDRAULIC CYLINDER HOLDING
CAPABILITIES
The hydraulic cylinders have holding valves that
prevent sudden movement of the cylinder rods
in the event of a hydraulic hose or other hydrau-
lic component failure. The valve is non-adjust-
able 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 cylinder, set the
boom horizontally with the maximum load. To
check the extension boom cylinder, set the
crane at maximum articluation (angle).
If the cylinder “creeps”, replace the holding
valve. If the cylinder does not “creep”, the valve
is serviceable.
2-5-9: HYDRAULIC FILTER REPLACE-
MENT
The hydraulic oil filters remove contaminating
particles. To avoid residue accumulation in the
reservoir and to protect hydraulic system
components, the filter must be changed after 50
hours of new-unit operation and every 200 hours
thereafter.
Check the vacuum gauge reading on the suc-
tion line filter for a reading greater than 8” of
mercury.
If the gauge reads higher than 8”, it could dam-
age the pump due to cavitation. In addition, the
filter elements should be replaced 50 hours after
the repair of a major hydraulic component.
To change filter cartridges:
1. Kill the engine.
NOTE
WHEN CHANGING THE SUCTION LINE
FILTER, ALWAYS CLOSE THE GATE
VALVE AT THE RESERVOIR FIRST.
2. Replace the cartridge with a new one
ensuring proper rubber seal seating and tighten-
ing as much as possible with both hands. Hand
tighten only.
3. Open the gate valve, engage the PTO,
and test for leaks.
2-5-10: HYDRAULIC SYSTEM TROUBLE-
SHOOTING
Problems with hydraulic oil viscosity can lead to
systems that do not function properly.
Hydraulic oil that is too light causes:
1. Excessive leakage.
2. Lower volumetric efficiency of the pump.
3. Increased component wear.
4. Loss of system pressure.
5. Lack of positive hydraulic control.
6. Lowered overall efficiency.
Hydraulic oil that is too heavy causes:
1. System pressure increase.
2. Increased system temperature.
3. Sluggish system operation.
4. Low mechanical efficiency.
5. Higher power consumption.
20030115
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