Investigation into pump reliability problems at sewage treatment works

A UK water company experienced significant reductions in dry well sewage pump reliability at one of its main sewage treatment works. Reliability had decreased following a number of changes implemented at the pumping station including changing the inlet screens allowing coarser solids to enter the well, altering the pump sealing technology from packed glands to mechanical seals and changing the maintenance contractor.

ESR Technology was commissioned to determine the cause of the reduced pump reliability, perform on-site and laboratory investigations and work with the water company to deliver a long-term solution.

Following detailed investigations by ESR Technology, the main causes of pump failure were identified as shaft fatigue and blockage of the pump by gross solids. The shaft fatigue was caused by a combination of poor maintenance practices and increased shaft loading due to the change in sealing technology, while the increased frequency of blockages were caused by the change in screening methodology.

ESR Technology recommended a series of improved maintenance procedures to reduce the susceptibility of the pump shaft to fatigue and a change to the wear ring design to make the pump less susceptible to blockages.

These steps resulted in a significant improvement in reliability of the pumps at the sewage treatment works leading to improved performance and much reduced maintenance costs.

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