Troubleshooting charts for eight categories of hydraulic problems
Apr 26, 2016
The following troubleshooting guides cover five categories of hydraulic problems. Possible causes and remedies are listed for each type of trouble. Causes are listed in order of probability; remedies are listed adjacent to the associated cause.
Abnormal / exessive noise
Source/Symptom: Pump
| Possible Problem | Recommended Action |
| Cavitation |
Replace dirty strainers. Clean clogged inlet line. Clean reservior breather vent. Change to proper pump drive motor speed. |
| Air in fluid |
Tighten leaky inlet connection. Fill reservoir to proper level. Bleed air from system. Replace pump shaft seal. |
| Coupling |
Tighten coupling. Check condition of seals and bearings. |
| Pump worn or damaged | Repair or replace. |
Source/Symptom: Motor
| Possible Problem | Recommended Action |
| Coupling misaligned or loose |
Realign coupling. Check condition. |
| Motor worn or damaged | Repair or replace. |
Source/Symptom: Mechanical vibrations
| Possible Problem | Recommended Action |
| Misaligned, loose coupling |
Realign coupling and remove any unneccessary clearances. |
| Vibration of pipes |
Tighten pipe clamps and add more clamps where necessary. |
Source/Symptom: Relief valve
| Possible Problem | Recommended Action |
| Improper setting |
Install pressure gauge and adjust to correct valve setting pressure. Make sure setting is not too close to operating pressure or to another valve setting. |
| Valve worn or damaged |
Repair or replace. |
Excessive Heat
Source/Symptom: Pulp
| Possible Problem | Recommended Action |
| Pump worn or damaged | Repair or replace. |
Source/Symptom: Relief
| Possible Problem | Recommended Action |
| Incorrect setting |
Install pressure gauge and adjust to correct setting pressure. |
Source/Symptom: Flow losses between pressure and return sides
| Possible Problem | Recommended Action |
| Pressure set improperly |
Set pressure to the diagram raiting. |
| Defective valve function or damaged seals |
Repair or replace it. |
Source/Symptom: Insufficient cooling
| Possible Problem | Recommended Action |
| Cooling water system unavailable |
Make cooling water available. |
| Deposits in cooling water system |
Clean cooling water strainer and equipment. |
Source/Symptom: Tank heater
| Possible Problem | Recommended Action |
| Heater on too much |
Check program for proper command. Check disconnect for proper operation. |
Source/Symptom: Viscosity too low
| Possible Problem | Recommended Action |
| Oil damaged |
Drain and refill with fresh oil. |
| Water contamination |
Find and repair water source, then drain and refill with fresh oil. |
| Improper oil |
Drain and refill with fresh correct oil. |
Incorrect Flow
Source/Symptom: No flow
| Possible Problem | Recommended Action |
| Pump not receiving fluid |
Replace dirty strainers. Clean clogged inlet line. Clean reservoir breather vent. |
| Pump motor not operating | Repair or replace. |
| Pump-to-drive |
Check for damaged pump or drive. Replace and align sheared coupling. |
| Pump motor rotation incorrect |
Reverse rotation. |
| Directional valve in wrong position |
Check position of manually-operated valves. Check electrical circuit for solenoid-operated valves. |
| Entire flow passing |
Adjust relief valve over relief valve setting. |
| Damaged pump |
Check for damaged pump or drive. Replace and align coupling. |
Source/Symptom: Low flow
| Possible Problem | Recommended Action |
| Flow control set too low |
Adjust |
| Variable displacement mechanism malfunctioning |
Repair or replace. |
Source/Symptom: Excess flow
| Possible Problem | Recommended Action |
| Flow control set too high |
Adjust |
Source/Symptom: Flow losses between pressure and return sides
| Possible Problem | Recommended Action |
| Maximum pressure set too high |
Re-adjust pressure setting per diagram. |
| Pressure valve cannot close due to dirt or foreign particles |
Clean system. Repair or replace parts. |
| Cylinder tube, piston or seal damaged |
Repair or replace damaged part. |
| Seal damaged due to incompatible materials |
Replace with seals that fit the system or change the hydraulic fluids to fit the seals. |
Incorrect Pressure
Source/Symptom: No pressure
| Possible Problem | Recommended Action |
| Dirty pump strainers |
Replace. Clean clogged inlet line. |
| Pump motor not operating |
Repair or replace. |
| Pump-to-drive coupling sheared |
Repair and align coupling. |
| Pump motor rotation incorrect |
Reverse rotation. |
| Directional valve in wrong position |
Check position of manually-operated valves. Check electrical circuit for solenoid-operated valves. |
| Entire flow passing over relief valves |
Adjust relief valve setting. |
| Damaged pump |
Check for damaged pump or drive. Replace and align coupling. |
Source/Symptom: Low pressure
| Possible Problem | Recommended Action |
| Reducing valve set too low | Adjust. |
| Reducing valve worn or damaged | Repair or replace. |
| Relief valve or unloading valve set too low | Adjust. |
| Variable displacement mechanism malfunctioning |
Check pump compensator. Repair or replace. |
| Pump, valve, motor, cylinder or other component worn or damaged | Repair or replace. |
| Water contamination | Drain, fluss and refill |
Source/Symptom: Erratic
| Possible Problem | Recommended Action |
| Air in fluid |
Tighten leaky connections. Fill reservoir to proper level. Bleed air from system. |
Source/Symptom: Excess pressure
| Possible Problem | Recommended Action |
| Reducing valve or unloading valve set too high |
Adjust |
| Variable displacement mechanism |
Check pump compensator. Repair or replace malfunctioning. |
Faulty Operation
Source/Symptom: No movement
| Possible Problem | Recommended Action |
| No pressure or flow | See troubleshooting guides for incorrect flow and incorrect pressure. |
| Limit device / sequence device inoperative or improperly set |
Check mechanical, electrical and/or hydraulic limits and sequence devices. Adjust, repair or replace. |
| Mechanical bind not operating | Locate and repair bind. |
| Cylinder or motor damaged | Repair or replace. |
| Low flow |
See troubleshooting guide for incorrect flow. |
Source/Symptom: Slow movement
| Possible Problem | Recommended Action |
| Fluid viscosity too high |
Fluid may be too cold or dirty. Check heating/cooling system. Change to clean fluid of correct viscosity. |
| Insufficient pressure | See troubleshooting guide for incorrect pressure. |
| Lack of lubricant | Lubricate machine ways or linkage. |
| Cylinder or motor damaged | Repair or replace. |
Source/Symptom: Erratic movements
| Possible Problem | Recommended Action |
| Erratic flow | See troubleshooting guide for incorrect flow. |
| Air in oil | See troubleshooting guide for air in oil. |
| Improper pressure | See troubleshooting guide for incorrect pressure. |
Foaming Oil
Source/Symptom: Tank
| Possible Problem | Recommended Action |
| Oil level in tank too low | Add oil as required. |
Source/Symptom: Suction line
| Possible Problem | Recommended Action |
| Crack of leaking suction line | Repair or replace. |
Source/Symptom: Improper or degraded oil
| Possible Problem | Recommended Action |
| Inadequate anti-foaming agent | Replace with proper oil. |
Directional Control Valve Position not Changing
Source/Symptom: Coil not picking up
| Possible Problem | Recommended Action |
| Electric failure | Fix electric failure and check mechanial spool motion. |
Source/Symptom: Valve spool stuck
| Possible Problem | Recommended Action |
| Impurities between spool and bore | Replace valve if necessary. |
| Throttle set too tight between the main and pilot valve of the two coil solenoid valve | Set the throttle at the correct rating. |
Source/Symptom: Proportional valve not responding
| Possible Problem | Recommended Action |
| Valve not receiving set value from program | Locate and fix electric failure. |
| Set value received but valve not responding | Replace the proportional valve. |
Computer Alarm Messages
Computerized control systems usually have alarm screens which record alarm messages. The following table lists recommended actions to take to resolve common hydraulic alarm.
| Alarm Message | Recommended Action |
| Pressure filter blocked (identified by pump) | Replace old filter with new filter insert. |
| Pressure filter blocked for circulation pump | Replace old filter with new filter insert. |
| Circulation/Filter pump fault MCC | Motor output gives alarm to control desk if that pump is not running. |
| Circulation/Filter pump stopped with main pumps running | Check circulation/filter pump for problems. |
| Hydraulic unit temperature high |
Check cooling pump operation. Check the cooler water strainer. Check water thermostat operation. Check that none of the pressure relief valves were set too low. If required, correct the setting. |
| Return filter blocked | Replace old filter with new filter insert. |
|
Hydraulic oil level low Hydraulic oil level low - pumps stopping |
Determine what is causing the drop in oil level. Add clean oil. The pumps will stop automatically if the level drops to the shutdown level. |
| Pump fault MCC or standby pump fault MCC (identified by pump) | Motor output gives alarm to control desk if that pump is not running. |
For more information on fluids safety and troubleshooting, contact your Valmet representative for training options.