Liquid Engineering Problems With The Pump? How to Reduce Pump Failures

Author / Editor: Dr.-Ing. Friedrich-Wilhelm Hennecke / Dominik Stephan

Pumps that fail prematurely either have not been selected properly, have not been repaired or assembled properly or are not being operated as intended. There are a few important basic rules that need to be observed.

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There are three common causes of pump failure - assembly errors, operational reasons and wear. (Picture: PROCESS)
There are three common causes of pump failure - assembly errors, operational reasons and wear. (Picture: PROCESS)

Note: If a pump fails within hours or days, it is because of an assembly or repair fault. If a pump fails within months, it is for an operational reason due to the system or medium. If a pump fails within a few years, it is because of wear.

Just about every pump will be repaired one or more times before finally being decommissioned – a huge order potential for service providers and a major cost factor for operators. What the operator’s engineers and technicians need to do is identify the causes of failures at an early stage and remedy them. A pump that is properly selected, properly assembled and operated within the intended range will have a long service life until it inevitably succumbs to wear.

Whether a pump is likely to give many years of trouble-free operation depends on whether the right pump was chosen for the particular application. A pump never works in isolation – it is part of a pump system consisting of the intake section including discharge container, the pump assembly (pump, motor, controls), the pressure pipe and consumers (containers, heat exchangers, filters, etc.).

The task of the pump must be specified clearly:

  • What is to be pumped? (All properties of the pumping medium)
  • How much medium is to be pumped, and how often? (Discharge rates, methods of operation)
  • Where is the medium to be pumped from and to? (Pump system, pump lifts)

All possible modes of operation must be considered. Often failures occur because, for instance, cleaning procedures have been forgotten.

This information must be used as the basis for selecting the type of pump: centrifugal pumps, rotating or oscillating positive-displacement pumps in all their diversity. Once this decision has been made, the pump must be configured hydraulically. This is particularly important for centrifugal pumps, because they can only be configured optimally for one operating point.

Of course, estimates will always err on the side of caution. However, excessive caution results in pumps that are much too large and then have to be regulated, usually through throttling. In the best case, this leads only to energy being destroyed. If the permitted minimum discharge rate is not achieved, however, damage could be caused to the pump because the pumping medium becomes too hot, leading to material destruction. At the same time, greater transverse bending of the shaft results in damage to the floating ring seal and bearings.