Screw Pump Troubleshooting

What are the reasons for the malfunction of a Screw Pump?

A malfunction in a pump system may be caused by a number of reasons and is not necessarily the pump itself. Issues with the pipework or other fluid accessories within the system can be contributing factors. Another major contributing factor, would be operating the pump in conditions that are extremely different to the ones provided at the time of specification.

Consequently, it is always recommended to check the following first:

  • - Has the pump been installed correctly?
  • - Are the operating conditions still according to the initial specification?
  • - Are the other fluid accessories within the pipework functioning correctly?

In general the following malfunctions can be identified:

  • - Pump provides no flow
  • - Pump provides irregular flow
  • - Capacity is too low
  • - Pump over heats
  • - Motor overheats
  • - Excessive Screw / Rotor wear
  • - Excessive wear of shaft sealing
  • - Pump vibrates excessively or makes too much noise
  • - Pump has seized
  • - Pump stops upon start up

Overleaf is a table of the possible causes and solutions of these malfunctions

XWrong Direction or RotationHave a qualified electrician revers the direction of rotation of the electric motor
XPump is not completely filled with liquidFill the pump casing entirely with fluid and fit a non-return valve to the suction side
XXXXInsufficient Suction Pressure / NPSHaIncrease the suction pressure, lower position of the pump further below the fluid level, enlarge suction pipe ø, shorten / simplify suction pipework, reduce operating speed, reduce product temperature
XXXExcessive vapour is present in the suction line
XXXAir is entering the suction lineCheck Connections
XXXXGas in the suction lineVent suction pipe / pump casing
XXXInsufficient static headIncrease liquid level
XXXXProduct viscosity is too highLower the operating speed / increase product temperature
XProduct viscosity is too lowIncrease the operating speed / lower the product temperature
XXXXXProduct temperature is too highCool the product / pump casing
XXProduct temperature is too lowHeat the product / pump casing
XXXXForeign particles are in the productClean the system / install a suction filter sized according to the max solids passage of the pump
XXXXXXXPressure at delivery side is too highCheck piping for obstructions / simplify the discharge pipework
XXXXXPump casing distorted by pipingCheck alignment / support the piping & install flexible couplings
XXSpeed too highLower the speed
XSpeed too lowIncrease the speed
XXXXXXInsufficient flushingIncrease flushing capacity / pressure
XXXXXXXWorn out bearings / gearsReplace the worn out parts
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