June 12, 2008

Pumps - 50 Troubleshooting Tips

All of us as a process engineer face different problems related to pump operation. Be it a problem of low capacity, low head, pump loosing prime,
requires excessive power, stuffing box or seal leakages which are very common, bearings life, overheating etc.

All these problems are critical if the pump is in process fluid service which is either corrosive or hazardous. Therefore a step by step approach is necessary to attend to these problems. Recnetly I came across a compiled list of such 50 tips which I am sharing here for you. Note down these tips & follow them whenever you get any pump problem for troubleshooting.
Pumps are rotary devices which converts velocity or kinetic energy into pressure energy for compresible fluids to pump them from one location to the other. Being a rotary device they are prone to general wear & tear problems therefore, a process engineer should know how to handle these problems & do effective troubleshooting.

Here is the list of 50 such tips for pump troubleshooting categorized into different heads.
  • Suction Troubles

    1. Pump not primed.
    2. Pump or suction pipe not completely filled with liquid.
    3. Suction pipe lift too high.
    4. Limiting pipe size in suction or higher velocities resulting in flashing.
    5. Insufficient margin between suction pressure and vapor pressure.
    6. Excessive amount of air or gas in liquid.
    7. Air pocket in suction line.
    8. Air leaks in suction line.
    9. Air leaks into pump through stuffing box.
    10. Foot valve too small.
    11. Foot valve partially clogged.
    12. Inlet of suction pipe insufficiently submerged.
    13. Water seal pipe plugged.
    14. Seal cage improperly located in stuffing box, preventing sealing fluid entering space to form seal.

  • System Troubles

    1. Speed too low.
    2. Speed too high.
    3. Wrong direction of rotation.
    4. Total head of system higher than design head of pump.
    5. Total head of system lower than design head of pump.
    6. Specific gravity of liquid different from design.
    7. Viscosity of liquid different from design criteria.
    8. Operation at very low capacity.
    9. Parallel operation of pumps unsuitable for such operation
    10. Incorrect piping layout.

  • Mechanical Problems

    1. Foreign matter in impeller.
    2. Misalignment.
    3. Foundations not rigid.
    4. Shaft bent.
    5. Rotating part rubbing on stationary part.
    6. Bearings worn.
    7. Wearing rings worn.
    8. Impeller damaged.
    9. Casing gasket defective permitting internal leakage.
    10. Shaft or shat sleeves worn or scored at the packing.
    11. Packing improperly installed.
    12. Incorrect type of packing for operating conditions.
    13. Shaft running off center because of worn bearings or misalignment.
    14. Rotor out of balance resulting in vibration.
    15. Gland too tight resulting in no flow of ;liquid to lubricate packing.
    16. Failure to provide cooling liquid to water cooled stuffing box.
    17. Excessive clearance at bottom of stuffing box between the shaft and casing, causing packing to be forced into pump interior.
    18. Dirt or grit in sealing liquid, leading to scoring of shaft or shaft sleeves.
    19. Excessive thrust caused by a mechanical failure inside the pump or by the failure of the hydraulic balancing device, if any.
    20. Excessive grease or oil in bearing housing or lack of cooling, causing excessive bearing temperature.
    21. Lack of lubrication.
    22. Improper installation of antifriction bearings (damage during assembly, incorrect assembly of stacked bearings, use of unmatched bearings as a pair, etc.).
    23. Dirt getting into bearings.
    24. Rusting of bearings due to water getting into housing.
    25. Excessive cooling of water cooled bearing resulting in condensation in the bearing housing from moisture in the atmosphere.
    26. Wear Ring clearance.

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