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TELESCOPE CYLINDER HOLDING VALVE
There is a single telescoping cylinder on the RT-400 and it has its own holding valve. This valve
is designed to hold the boom in position, should loss of power or pressure line failure occur.
The holding valve should be checked with the boom elevated to the maximum angle and the
boom extended to a 10-foot (3.0m) load radius. The boom should be about 50.0 feet (15.24m)
long in this configuration. A 36,000-pound (6300kg) load on a 4-part line is required for this test.
Use the hoist to lift this load about 6 inches (15cm) above the ground. The radius of the test
load should be within the rating on the capacity chart. Use great care to prevent the load from
hitting the crane.
Turn the engine OFF, put the key ON, and pull the TELESCOPE RETRACT valve spool, on the
upper control valve. If the boom retracts, the valve should be adjusted.
To adjust the holding valve, loosen the lock nut on the adjusting screw and tighten screw until
unpowered movement stops. Retighten the lock nut to hold the proper adjustment. The boom
will have to be lowered to make adjustments.
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