Tips For Centrifugal Pumps

Pump Selection

  • Do not oversize pumps. This leads to uneconomical operation and generally narrows the safe operation range of capacities.
  • Do not try to select pumps with excessively low required NPSH (Net Positive Suction Head).
  • Do not falsify real available NPSH, trying to keep a margin up your sleeve. This leads to selection of pumps with excessively high Suction Specific Speeds and high minimum flows.
  • Do evaluate economical advantages of variable speed operation. It is more efficient and results in longer pump life.
  • Don't overestimate value of pump efficiency if it's obtained at cost of reliability.
  • Do not use a mechanical seal when packing is more than adequate for the intended service.



  • Do provide sufficient submergence over intake piping to prevent vortex formation.
  • Do not use suction elbows in a plane parallel to the shaft; place them in the plane perpendicular to the shaft.
  • Do not use the pump casing as an anchor for the piping. If you use expansion joints, supports and anchor them independently of the pump.
  • Do provide adequate flow, pressure and temperature instrumentation for each pump.
  • Pump and driver alignment must be rechecked under normal operating conditions.



  • Do not operate pumps below the recommended minimum flow.
  • Do not operate pumps with suction valve closed.
  • Do not run two pumps in parallel when a single pump can carry the reduced system load.
  • Do not stop a pump while it is activating. Reestablish normal operation first and then stop the pump if you have to.
  • A pump handle liquids. Keep air out.
  • Do not run a pump if excessive noise or vibration occurs.
  • Do run spare pumps occasionally to check their availability.



  • Run a performance test at reasonable intervals of time, to follow effect of increased internal clearances.
  • Do not open pumps for inspection unless factual or circumstantial evidence warrants it.
  • Do not over lubricate grease lubricated bearings.
  • Do not overcool outer races of ball bearings. Inner races continue to expand and balls are squeezed out of shape.
  • Packing stuffing boxes is an art. Do not assign this to inexperienced personnel.
  • Do not tighten stuffing box glands excessively. Let enough leakage flow to cool and lubricate packing.
  • Do monitor the pressure drop across suction strainers. An excessive pressure drop indicates clogging and may reduce available NPSH to a dangerous degree.
  • Do keep an adequate stock of spare parts.
  • Except in an emergency, use original equipment manufacturer's replacement spares.
  • Consider upgrading material for parts that wear or corrode too rapidly. This lengthens interval between overhauls.
  • Do examine and recondition, if necessary, all metal-to-metal fits.
  • Do examine parts parts for corrosion, erosion or other damage.
  • Do check concentricity of all parts of the rotor before reassembly.
  • Do use new gaskets for complete overhaul.