Pressure Or Flow Instability (Continued); System Pressure Not Reaching Pc Setting; High Inlet Vacuum - Sauer Danfoss 45 Series Service Manual

PRessuRe oR fLow
instabiLity (continued)
system PRessuRe not
ReaCHing PC setting

HigH inLet vaCuum

 Caution
High inlet vacuum causes
cavitation which can
damage internal pump
components.
20
Series 45 G Frame Open Circuit Axial Piston Pumps
Service Manual
Troubleshooting
item
Check LS setting.
Check LS signal line.
Check external relief valve and PC
setting.
Check external relief valve.
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.
item
Check fluid temperature.
Inspect inlet screen.
Check inlet piping.
Hydraulic fluid viscosity above
acceptable limits.
520L0605 • Rev AB • December 2010
Description
Low LS setting may cause
instability.
Blocked LS signal line interferes
with proper LS operation.
Insufficient pressure differential
between PC setting and external
relief valve.
Chattering external relief valve
may cause unstable feedback to
pump control.
Description
System pressure will not rise above
PC setting.
External relief valve setting below
PC setting prevents 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.
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 LS setting to proper level.
See Adjustments, page 21.
Remove blockage.
Adjust external relief valve or PC
control settings to appropriate
level. Relief valve setting must
be above PC setting to operate
properly.
Adjust or replace relief valve.
action
Adjust PC to appropriate setting.
Refer to Adjustments, page 21.
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,
Series 45 Technical Information
Manual, 520L0519.