Manitowoc National Crane 500E2 Service Manual

National Crane Published 08/16/19 Control # 112-05 2-7
500E2 SERVICE MANUAL HYDRAULIC SYSTEM
2
CONTROL VALVE RELIEF ADJUSTMENT
The control valves supplied on this crane are equipped with
adjustable relief valves. After some time of use, it may be
necessary to make some adjustment in pressure because of
spring weakening, etc. The relief valves are adjustable only
through a specific pressure range.
Both the inlet and mid-inlet of the main control valve and inlet
of the winch valve have screw adjustable main relief valves.
Turning the relief in increases pressure relief setting; turning
the relief out decreases pressure relief setting.
The turn circuit pressure can be checked by plugging a port
on the turn motor with a pressure gage. The pressure on the
main control valve stack should be checked by booming the
lift cylinder down against the end of the cylinder stroke. The
winch circuit pressure can be checked by plugging a port on
the winch motor with a pressure gage.
Some valve sections include work port reliefs. The work port
reliefs are shim adjustable. Adjustment is made by adding or
taking out shims. Adding a 0.010 shim will increase pressure
100 psi (0.68 MPa). See “Specifications” section for correct
pressure settings.
Never set pressure above recommendations.
Disconnect drain line from the
outlet end of the unloader valve.
Install cap fitting to the plug outlet
end of the unloader valve.
Operate the function.
Function operates correctly.
Oil is passing through the check
valve in another unloader.
Cap each of the other unloaders in
turn to identify the unloader with
the faulty check valve.
Flush to remove contamination
otherwise replace unloader valve.
The poppet in the unloader is not
seated correctly. remove unloader and
flush to dislodge contamination.
Reinstall, retest and replace unloader
if problem persists.
YES
NO
WARNING
If the machine does not perform properly at these
pressures, the problem is not the relief valve and no
attempt should be made to readjust the setting. It the relief
valves are set to higher pressures than those listed
above, the warranty on the machine is void. Also the
machine could operate in a manner such as to endanger
personnel safety.

Manitowoc National Crane 500E2 Specifications

General

Brand	Manitowoc
Model	National Crane 500E2
Category	Construction Equipment
Language	English