GROVE Published 10-21-2010, Control# 198-04 4-27
5540F/YB5515 SERVICE MANUAL HYDRAULIC SYSTEM
Brake Holding Valve
The holding valve has three functions:
1. Inhibit cavitation of the motor.
2. Give full control of the lowering of the load.
3. Hold the load in event of a hydraulic failure.
Pilot pressure from the down stream side of the motor opens
the holding valve. If the motor starts to turn faster than the
pump can supply oil to the motor, there will be a decrease in
the pilot pressure. The holding valve will close and interrupt
the flow of oil from the motor. The holding valve will interrupt
the flow as often as necessary to keep the flow constant to
the motor. Also, if there is a failure of the pump or a hydraulic
line, the holding valve will hold the load in position.
Engine speed is important for smooth operation. At low
engine speed, normally there will not be enough oil from the
pump to keep the motor turning. As a result, the load will
move down in a movement that is not regular.
Hydraulic Swivel
See Hydraulic Swivel information in this section.
WARNING
Do not adjust the holding valve setting. The valve is
adjusted by the manufacturer.
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