System Pressure Not Reaching Pc Setting; High Inlet Vacuum - Danfoss 45 E Frame Series Service Manual

Service Manual
Series 45 E Frame Open Circuit Pumps
Troubleshooting

System pressure not reaching PC setting

Item
Check PC control setting.
Check external relief valve.
Inspect PC control spring.
Inspect PC spool for wear.
Inspect PC spool for proper orientation.
Check PC control for contamination.

High inlet vacuum

Item
Check fluid temperature.
Inspect inlet screen.
Check inlet piping.
Hydraulic fluid viscosity above acceptable limits.
© Danfoss | September 2016
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Description
System pressure will not rise above PC setting.
External relief valve setting below PC setting
presents pressure compensation.
Broken, damaged, or missing spring will cause
erratic operation.
Wear of PC spool causes internal leakage in the
control.
Improper orientation results in poor operation.
Contamination may interfere with movement of
the PC spool.
C
Caution
High inlet vacuum causes cavitation which can damage internal pump components.
Description
Low temperature increases viscosity. High fluid
viscosity causes high inlet vacuum.
Blocked or restricted inlet screen causes high
inlet vacuum.
Too many fittings, bends, or long piping causes
high inlet vacuum.
High fluid viscosity causes high inlet vacuum.
Action
Adjust PC to appropriate setting. Refer to the
Adjustments chapter.
Adjust external relief valve according to
manufacturer's recommendations. External relief
valve must be set above PC setting to operate
properly.
Replace the spring as required.
Replace the spool as required.
Correct orientation of spool.
Clean PC control components, take appropriate
action to eliminate contamination.
Action
Allow system to warm up before operating.
Clean screen/remove blockage.
Eliminate fittings to make path more direct.
Select fluid with appropriate viscosity for
expected operating temperature. See Hydraulic
Fluids and Lubricants Technical Information
Manual, 520L0463.
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