Doyle Online Pump Training 11

• Centrifugal Pump Theory

• Pump Terminology

• Reading Centrifugal
  Pump Curves

• Centrifugal pump
  Operating Range

• Pump Enquiry Information

• System Curves

• Pump Parallel / Series
  Operation

• Cavitation

• NPSH - Nett Positive
  Suction Head

• Affinity Laws

• Troubleshooting

• Disclaimer

TROUBLESHOOTING

Only one thing is a better troubleshooting tool than pressure & vacuum gauges...that is:
readings from pressure & vacuum gauges taken prior to the problem.
ie: monitoring.

Gauge readings will help diagnose pump and system problems quickly, by reducing the possible causes.
Flow measurement would allow full diagnosis of pump performance but is sometimes expensive and usually not possible (Cheap versions include: V notch weir, measuring discharge from horizontal pipe, & timing of filling / emptying). System curves can be used in evaluating results.

Following is troubleshooting table for a typical pump showing symptom and possible cause.

1. Pump does not prime..	Suction lift too great. Insufficient water at suction inlet. Suction inlet or strainer blocked. Suction line not air tight. Suction hose collapsed. Mechanical seal / packing drawing air into pump.
2. Not enough liquid..	Incorrect engine speed. Discharge head too high. Suction lift too great. Suction inlet or strainer blocked. Suction line not air tight. Suction hose collapsed. Mechanical seal drawing air into pump. Obstruction in pump casing/impeller. Impeller excessively worn. Delivery hose punctured or blocked.
3. Pump ceases to deliver liquid after a time..	Suction lift too great. Insufficient water at suction inlet. Suction inlet or strainer blocked. Suction hose collapsed. Excessive air leak in suction line. Mechanical seal / packing drawing air into pump. Obstruction in pump casing/impeller. Delivery hose punctured or blocked.
4. Pump takes excessive power..	Engine speed too high. Obstruction between impeller and casing. Viscosity and / or SG of liquid being pumped too high.
5. Pump vibrating or overheating ..	Engine speed too high. Obstruction in pump casing/impeller. Impeller damaged. Cavitation due to excessive suction lift / friction loss.
6. Pump leaking at seal housing..	Mechanical seal damaged or worn. Due to: Dry Running during priming or loss of liquid. Cracking of ceramic seat can occur (thermal shock) after pump has run dry or against shut head (heating the water) and then cool water enters the pump casing.