Low Pump Output Flow; Pressure Or Flow Instability - Danfoss 45 E Frame Series Service Manual

Service Manual
Series 45 E Frame Open Circuit Pumps
Troubleshooting
Item
Check external system relief valve setting.
Check pump inlet pressure/vacuum.

Low pump output flow

Item
Check fluid level in reservoir.
Hydraulic fluid viscosity above acceptable limits.
Check external system relief valve setting.
Check PC and LS control setting.
Check pump inlet pressure/vacuum.
Check input speed.
Check pump rotation.

Pressure or flow instability

Item
Check for air in system.
Check control spools.
Check LS setting.
Check LS signal line.
Check external relief valve and PC setting.
Check external relief valve.
22 | © Danfoss | September 2016
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Description
Fluid passing through relief valve adds heat to
system.
High inlet vacuum adds heat to system.
Description
Insufficient hydraulic fluid will limit output flow
and cause internal damage to pump.
Fluid viscosity above acceptable limits or low
fluid temperature will not allow the pump to fill
or control to operate properly.
Eternal relief valve set below PC setting causes
low output flow.
Low PC setting prevents the pump from
achieving full stroke.
High inlet vacuum causes low output flow.
Low input speeds decrease flow.
Incorrect rotational configuration causes low
flow.
Description
Air in system causes erratic operation.
Sticking control spools cause erratic operation.
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.
Action
Adjust external system relief valve setting
following manufacturer's recommendations.
External relief valve setting must be above PC
setting for proper operation.
Correct inlet pressure/vacuum conditions.
Action
Fill the reservoir to proper level.
Allow system to warm up before operating, or
use fluid with the appropriate viscosity grade for
expected operating temperatures. See Hydraulic
Fluids and Lubricants Technical Information
Manual, 520L0463.
Adjust external relief valve following
manufacturer's recommendation. External relief
valve setting must be above PC setting to
operate properly.
Adjust PC and LS setting. Refer to the
Adjustments chapter.
Correct inlet pressure conditions.
Adjust input speed.
Use pump with appropriate rotational
configuration.
Action
Activate PC allowing system to bleed air. Check
inlet line for leaks and eliminate source of air
ingression.
Inspect spools for free movement in bore. Clean
or replace.
Adjust LS setting to proper level. See the
Adjustments chapter.
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.
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