Centrifugal Pump Problem Checklist and Causes.

Vortex Centrifugal Pump

A centrifugal pump is one of the simplest installations of any plant / Engine room. Its purpose is to first convert the energy of the primary motor / prime mover (electric motor or turbine) to velocity or kinetic energy, then into the pressure energy of the pumped liquid. Here the energy changes occur under two main parts of the centrifugal pump, the impeller and the volute or diffuser. The impeller is the rotating component that converts the driver / guide energy into kinetic energy. The stationary parts of the pump, which are diffuser or volute convert kinetic energy to pressure energy.

Centrifugal pumps are one of the most commonly used equipment in the world, their application is continuously expanding, and with this expanding new problem associated with centrifugal pumps are manifesting. However, it is not possible to predict any problem that may occur in the future but having the in-depth knowledge about the different factors which may affect the centrifugal pump’s performance is a smart thing to do.

Listed below are the 10 common problem associated with the centrifugal pumps:

  1. Pump not developing head nor does it deliver liquid.
  2. Bearing Overheating.
  3. Bearing operation with noise.
  4. Bearing having short life.
  5. Gasket leakage.
  6. Mechanical seal leakage.
  7. Pump is consuming too much power.
  8. Pump operating with noise, vibration.
  9. Pump is overheating
  10. Cavitation.

Possible Causes

  1. Pump not developing head nor does it deliver liquid.
  • Pump is not primed
  • Disengaged or broken connection between prime mover and pump
  • Impeller key is missing or broken. No impeller in pump.
  • Shaft is broken.
2. Bearing Overheating
  • Misalignment of pump parts.
  • Improper foundation.
  • Damaged impeller.
  • Bent shaft.
  • Inadequate cooling of bearing.
  • Inadequate cooling of lubricant.
  • Bearing improperly lubricated.
  • Water enter into bearing housing.
  • Faulty Lubrication system.
  • Excessive grease in bearing.
  • Damaged bearing housing.
3. Bearing operation with noise.
  • If you hear Continuous or intermittent low-pitch tone : Bearing brinelled or resonance with other structural pump part.
  • Steady high-pitch tone. : Misalignment or too much clearance between bearing and shaft or housing.
  • Intermittent rattle. : Dirt in bearing or loose machine part.
4.Bearing having short life
  • Misalignment of pump parts.
  • Improper foundation.
  • Damaged impeller.
  • Bent shaft.
  • Inadequate cooling of bearing.
  • Inadequate cooling of lubricant.
  • Bearing improperly lubricated.
  • Water enter into bearing housing.
  • Faulty Lubrication system.
  • Excessive grease in bearing.
  • Damaged bearing housing.
5. Gasket leakage.
  • Unevenly tightening of bolts
  • Uneven thermal expansion.
  • Loose bolts
  • Too much tightening of bolt that gasket rub hard against shaft.
  • Not properly cutting of gasket.
6. Mechanical seal leakage.
  • Incorrect type of mechanical seal.
  • Bent shaft.
  • Dirt in sealing face.
  • Sealing face not perpendicular to pump axis.
  • Mechanical seal improperly installed.
  • Worn out bearing.
  • Mechanical seal has run dry.
  • Abrasive particle coming in contact with seal.
7. Pump is consuming too much power.
  • Power measuring instrument is faulty.
  • Worn out or damaged bearing.
  • Rotating parts rubbing against stationary parts.
  • Over-sized impeller.
  • Misalignment between pump and drive.
  • Mechanical seal is exerting excessive pressure on seat.
  • Bent shaft.
  • Impeller or casing partially clogged with solid matter.
  • Wrong direction of rotation.
  • liquid is not per-heated to keep viscosity below specified limits.
  • Improper lubrication of bearing.
  • Gland too tight.
8.  Pump operating with noise and vibration.
  • Damaged impeller.
  • Wrong direction of rotation.
  • Worn-out bearing.
  • Impeller improperly mounted
  • Air enter pump during operation.
  • Shaft is bent.
  • Resonance.
  • Improper lubrication of bearing.
  • Cavitaion in pipeline.
  • Too small distance between impeller outer diameter and volute casing.
  • Loose bolts.
  • Damaged bearing.
  • Improper foundation.
9. Pump is overheating.
  • Pump allowed to run dry.
  • Poor lubrication.
  • Internal rubbing of rotating parts against stationary parts.
  • Damaged bearing.
  • Air or vapor pockets inside pumps.
10) Cavitation

Cavitation can occur in two ways for centrifugal pump; Suction and discharge cavitation. A suction cavitation can be result of running the pump under low pressure for prolonged period. While discharge cavitation can be the result of running the pump with very high discharge pressure or running it at less than 10% of its BEP (Best efficiency point).

  • Choked strainers and filters.
  • Poor NPSH (Net positive suction head)
  • Wrong pumping design (Pipes and arrangement of pumps).
  • Partial blockage in the suction pipe.
  • Running too left or right of the normal pump curve.
  • Partial blockage on the discharge side.

Read the details about “centrifugal pumps” along with different types of pumps on ship.

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