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Troubleshooting For Slurry Pumps

pumps

A guide to common slurry pump and gland problems and how you can overcome them.

Symptoms - Hopper Overflows
 
Possible causes:
 
- Pump not primed
- Excessive amount of air or gas in liquid
- Inlet of suction pipe insufficiently submerged
- Blocked suction line
- Suction valve closed
- Inlet pipe diameter too small or length of inlet pipe too long
- Pump speed too slow or wrong direction of rotation
- Coupling or drive belts not transmitting power
- Total head of system higher than design head
- Specific gravity of liquid different from design
- Entrained air in pump, pump hopper requires baffles
- Badly installed pipeline or gaskets partly blocking pipe
- Foreign matter in impeller
 
 

diesel or electric dewatering pumps

 


Symptoms - Overheating or Seizure of Pump

 

Possible causes:
 
- Pump not primed
- Insufficient margin between suction pressure and vapour pressure
- Operation at very low capacity
- Drive misalignment
- Lack of lubrication
- Improper installation of bearings
- Rotating part rubbing on stationary part
- Impeller out of balance, resulting in vibration
- Excessive thrust caused by a mechanical failure inside the pump
- Excessive amount of lubricant in bearing housing causing high bearing temp 
 
 
Symptoms - Short Bearing Life

 

Possible causes:
 
- Drive misalignment
- Shaft bent
- Rotating part rubbing on stationary part
- Bearings worn
- Impeller out of balance, resulting in vibration
- Shaft running off-centre because of worn bearings or misalignment
- Lack of lubrication
- Excessive amount of lubricant in bearing housing causing high bearing temp
- Improper installation of bearings
- Dirt getting into bearings
- Rusting of bearings due to water getting into housing

 
 

Symptoms - Vibration and noise from Pump

 

Possible causes:
 
- Pump or suction pipe not completely filled with liquid
- Suction lift too high
- Insufficient margin between suction pressure and vapour pressure
- Foot valve too small
- Foot valve partially clogged
- Inlet of suction pipe insufficiently submerged
- Operation at very low capacity
- Badly installed pipe line or gaskets partly blocking pipe
- Drive misalignment
- Rotating part rubbing on stationary part
- Shaft running off-centre because of worn bearings or misalignment
- Foreign matter in impeller 

 

Symptoms - Packing has short life

 

Possible causes:
 
- Misalignment
- Shaft bent
- Shaft or shaft sleeves worn or scored at the packing
- Packing improperly installed
- Shaft running off-centre because of worn bearings or misalignment
- Gland sealing water flow inadequate due to worn shaft seal components
- Gland sealing water pressure inadequate
- Dirt or grit in sealing liquid, leading to scoring shaft sleeve
- Expeller worn or blocked
- Excessive clearance at bottom of stuffing box, forcing packing into pump 
 

Symptoms - Leakage from the stuffing box

 

Possible causes:
 
- Misalignment
- Shaft bent
- Shaft or shaft sleeves worn or scored at the packing
- Packing wrong size
- Packing improperly installed
- Incorrect type of packing for operating conditions
- Shaft running off-centre because of worn bearings or misalignment
- Gland sealing water pressure too high causing packing extrusion
- Dirt or grit in sealing liquid, leading to scoring shaft sleeve
- Expeller worn or blocked
- Excessive clearance at bottom of stuffing box, forcing packing into pump

 

Symptoms - Excessive motor power required

 

Possible causes:
 
- Speed too high
- Wrong direction of rotation
- Total head of system higher than design
- Total head of system lower than design
- Specific gravity of liquid different from design
- Viscosity of liquid differs from that for which designed
- Misalignment
- Shaft bent
- Rotating part rubbing on stationary part
- Packing improperly installed
- Gland too tight, resulting in no flow of liquid to lubricate packing

 

Symptoms - Pump loses prime

 

Possible causes:
 
- Pump or suction pipe not completely filled with liquid
- Suction lift too high
- Excessive amount of air or gas in liquid
- Air pocket in suction line
- Air leaks into suction line
- Air leaks into pump through stuffing box
- Inlet of suction pipe insufficiently submerged
- Blocked suction line
- Foreign matter in impeller
- Inlet pipe diameter too small or length of inlet pipe too long
- Entrained air in pump. Pump hopper requires baffles
- Badly installed pipe line or gaskets partly blocking pipe 

 

Symptoms - Insufficient pressure

 

Possible causes:
 
- Excessive amount of air or gas in liquid
- Speed too slow
- Total head of system higher than design
- Viscosity of liquid differs from that for which designed
- Entrained air in pump. Pump hopper requires baffles
- Badly installed pipe line or gaskets partly blocking pipe
- Impeller damaged or worn
- Casing gasket defective, permitting internal leakage
- Foreign matter in impeller
 

Symptoms - Reduced discharge delivery

 

Possible causes:
 
- Pump or suction pipe not completely filled with liquid
- Suction lift too high
- Insufficient margin between suction pressure and vapour pressure
- Excessive amount of air or gas in liquid
- Air pocket in suction line
- Air leaks into suction line
- Air leaks into pump through stuffing box
- Foot valve too small
- Foot valve partially clogged
- Inlet of suction pipe insufficiently submerged
- Blocked suction line 
- Inlet pipe diameter too small or length of inlet pipe too long
- Speed too slow - slippage of vee belts
- Speed too slow - incorrect size pulleys
- Speed too slow - incorrect "pole" of electric motor
- Wrong direction of rotation
- Total head of system higher than design
- Viscosity of liquid differs from that for which designed
- Entrained air in pump. Pump hopper requires baffles
- Badly installed pipe line or gaskets partly blocking pipe
- Foreign matter in impeller
 

Symptoms - Failure to discharge

 

Possible causes:
 
- Pump not primed
- Pump or suction pipe not completely filled with liquid
- Suction lift too high
- Insufficient margin between suction pressure and vapour pressure
- Air pocket in suction line
- Inlet of suction pipe insufficiently submerged
- Blocked suction line
- Inlet pipe diameter too small or length of inlet pipe too long
- Speed too slow
- Total head of system higher than design
- Impeller damaged or worn
- Foreign matter in impeller

 

Pump Troubleshooting - Glands

Pump Troubleshooting chart

 

Steps for the correct fitting of packing into the stuffing box
 
1. Packing is normally available in pre-cut and formed rings, or alternatively the user can cut rings from a roll.

2. It is critical that each packing ring is cut to the correct length.

3. The packing cut should be at an angle of 45°, ie, a scarf joint.

4. The packing should fill the annulus. A length of key steel or similar should be used to push the packing into the stuffing box. Care should be taken to start fitting the packing on the joint side and then work around the ring to the opposite side. This should prevent stretching the ring, which could lead to overlap at the cut.

5. The packing should push in easily. If not, check the section dimensions. If incorrect the packing should be replaced. Do not roll formed rings.

6. Each packing should be tamped into position before fitting the next packing. Optimum arrangements for multiple rings of packing are shown below.

7. When all packing rings have now been fitted, assemble the gland and nip the bolts to flatten packing rings evenly. Do not tighten fully.

8. Run the pump. If excessive leakage occurs, tighten the bolts slightly and leave for at least an hour. Repeat if excessive leakage continues. Note that a good steady even drip or constant stream is desirable to cool and lubricate the gland

diesel or electric dewatering pumps guide download