What faults could be expected with onboard pumps and how to deal with them?

03 Nov '18, 06:28

Nov. 3, 2018, 6:28 a.m.
KnowledgeBase's gravatar image


Here is a brief check list of pump faults and causes. Identify the root cause and eliminate it to bring the pump's operation to normal.

Pump cannot discharge:

  • Pump not completely or insufficiently filled with liquid.
  • Much air leakage in suction line.
  • Air pocket in suction line.
  • Suction lift too high.
  • Wrong direction of rotation.
  • Suction strainer and suction line clogged.
  • Speed too low.
  • Impeller clogged.

Pump has insufficient discharge

  • Air leakage.
  • Speed too low.
  • Discharge head too high.
  • Suction lift too high.
  • Suction pipe end not sufficiently submerged.
  • Suction strainer and suction line clogged.
  • Impeller clogged.
  • Wrong direction of rotation.
  • Clearance between impeller and mouth ring due to latter's wear down
  • Cavitation due to high liquid temperature.

Prime mover (electric motor) overload

  • Speed too high (power frequency too high)
  • Impeller touches mouth ring.
  • Rotating elements touch due to bent shaft.
  • Casing deformed.
  • Liquid specific gravity is greater than designed one.
  • Voltage too low (constant input, but increase in current)

Bearing overheating

  • Grease is too little.
  • Grease is too much.
  • Grease or oil has improper consistency or it is deteriorated.
  • Misalignment.
  • Shaft is bent.
  • Damaged or worn ball bearing.
  • Too much thrust force.

Abnormal noise in bail bearing

  • Damaged balls or rolling face.
  • Too much clearance due to abnormal wear.
  • Abnormal wear in retainer.


  • Misalignment
  • Shaft bent.
  • Impeller partially clogged with foreign matter.
  • Incorrect installation.
  • Weak foundation.
  • Suction and discharge pipings not sufficiently secured.
  • Rotating elements touch stationary elements.

Leakage in Mechanical Seal

  • Injury or excessive wear down in rubbing faces.
  • Foreign matter in rubbing faces.
  • Insufficient tightening of mechanical seal cover.
  • Break down of "O" ring.
  • Insufficient tightening of screws for stopper ring (54-7).
  • Injury or wear down of part of shaft or sleeve where rotary ring s "O" ring (54- 5) contacts.
  • Scale sticks in groove for "O" ring, causing rotary ring to stick and rubbing faces to open.

Suction pressure

Check every day if there is no abnormal pressure drop and take record.
If low, stop pump immediately and check suction line.

Bearing temp.

Check and record every three days.
In the case it reached of ambient temp plus 40 deg C stop the pump and eliminate the cause.


Renew grease as per manual, supply monthly If deterioration occurs earlier confirm if specified grease is used.

Lubricating oil

Check oil level by oil level gauge once a week. Renew oil as per manual. Supply oil if the level is low. When renewing oil stop pump.

Ball bearing

Check for abnormal noise once a month.
If abnormal noise occurs and besides there is heating stop the pump, eliminate the cause, renew the ball bearing if necessary.

Stuffing box seal

Check for leakage, heating abnormal noise every three days.
Stop the pump immediately and remove cause

Line bearing

Check for heating in the pertinent part, great vibration in the whole pump and heating in the bail bearing every three days.
Stop the pump and check if the lubricating water is passing and if the line bearing clearance has become too great.

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03 Nov '18, 06:35

Nov. 3, 2018, 6:35 a.m.
cheng's gravatar image

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