System Will Not Operate In Either Direction; System Noise Or Vibration; Sluggish System Response - Danfoss H1P 045 Service Manual

Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Troubleshooting

System Will Not Operate in Either Direction

Item Description
Oil level in reservoir. Insufficient hydraulic fluid to supply system loop.
Pump control orifices Control orifices are blocked.
Pump control screens Control screens are blocked.
Bypass function open If bypass function is open, the system loop will be
depressurized.
Low charge pressure with Low charge pressure insufficient to recharge system loop.
pump in neutral
Low charge pressure with Low charge pressure resulting from elevated loop leakage.
pump in stroke Insufficient control pressure to hold pump in stroke.
Pump charge relief valve A pump charge relief valve that is leaky, contaminated, or
set too low will depressurize the system.
Charge pump inlet filter A clogged filter will under supply system loop.
Charge pump A malfunctioning charge pump will provide insufficient
charge flow.
System pressure Low system pressure does not provide enough power to
move load.
High pressure relief or Defective high pressure relief or pressure limiter valves
pressure limiter valves cause system pressure to be low.
Input to control Input operating improperly

System Noise or Vibration

Item Description
Reservoir oil level Low oil level leads to cavitation.
Aeration of the oil/pump Air in system decreases efficiency of units and controls.
inlet vacuum Excessive noise, foaming oil, and hot oil all indicate air in
system.
Cold oil If oil is cold, it may be too viscous for proper function and
pump cavitates.
Pump inlet vacuum High inlet vacuum causes noise/cavitation.
Shaft couplings A loose shaft coupling will cause excessive noise.
Shaft alignment Misaligned shafts create noise.
Charge/system relief valves Unusual noise may indicate sticking valves and possible
contamination.

Sluggish System Response

Item Description
Oil level in reservoir Low oil level causes sluggish response.
High pressure relief valves/ Incorrect pressure settings affects system reaction time.
pressure limiter settings
© Danfoss | June 2020
Action
Fill reservoir to proper level.
Clean control orifices.
Replace control screens. Only a Danfoss Authorized Service
Center may remove the unit's endcap without voiding the
warranty.
Close bypass valves. Replace high pressure relief valve if
defective.
Measure charge pressure with the pump in neutral. If
pressure is low, go to Pump charge relief valve.
Deadhead the pump to isolate it from the motor.With
pump in partial stroke and engaged for only a few seconds,
check pump charge pressure. Low charge pressure
indicates a malfunctioning pump. Continue to next step.
Good charge pressure indicates a malfunctioning motor or
other system component. Check motor charge relief
operation (if present).
Adjust or replace pump charge relief valve as necessary.
Inspect filter and replace if necessary.
Repair or replace the charge pump.
Measure system pressure. Continue to next step.
Repair or replace high pressure relief or pressure limiter
valves.
Repair/replace control.
Action
Fill reservoir.
Find location where air is entering into the system and
repair. Check that inlet line is not restricted and is proper
size.
Allow the oil to warm up to its normal operating
temperature with engine at idle speed.
Check that inlet line is not restricted and is of proper size.
Check filter and bypass switch.
Replace loose shaft coupling..
Align shafts.
Clean/replace valves and test pump.
Action
Fill reservoir.
Adjust or replace high pressure relief valves.
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