A drop in performance can be the first indication that something is going wrong with your pumps. This was certainly the case for one water industry customer. Its four Uniglide pumps had been in operation for approximately seven years but had not been subject to any serious maintenance in that time. ClydeUnion Pumps (a Celeros Flow Technology brand) was the original pump manufacturer and so was invited to conduct a comprehensive health check of the pumps to determine the reason for their reduced performance. A qualified team of engineers attended the site to investigate the customer’s concerns.
Health check
Mike Golds, Global Upgrade and Rerate programme manager at Celeros Flow Technology (Celeros FT), explained: “There are numerous reasons why pumps may run less efficiently than they should. These might include a change in process parameters or operational conditions; alterations in the operational environment, such as a change in temperature or humidity; general wear and tear caused by variants in the duty cycle, contaminant levels and so on; or a change in the properties of the fluid being pumped.
“Our pump aftermarket service combines the vast engineering expertise inherent in our team with access to sophisticated analysis tools. This means we can not only pinpoint the root cause of any performance issues, but also model a number of potential solutions to identify which will deliver the best outcome for our customer, prior to any investment being made.”
Detective work
Initial testing confirmed that the performance of the Uniglide pumps was significantly down on original design parameters. When the top half casing was removed, the Celeros FT team discovered that the impellers on all four pumps were badly damaged, and the wear rings were severely worn.
“Upon investigating the root cause of the damage, we determined that the water supply tank often dropped to a low level, which resulted in cavitation occurring,” explains Mike Golds. Over time, this cavitation had caused holes to develop in the impeller inlet vanes on all four Uniglide pumps. Further discussion with the customer made it clear that the low tank levels could not be prevented, which meant that the impellers as originally specified would have to be replaced every six years.
Maintenance of this order would be costly, so Celeros FT proposed a materials’ upgrade as a more cost-effective and long-term solution. Its proposal was to replace the existing cast iron impellers with ones of aluminium bronze (material BS 1400 AB2), which is more resistant to cavitation damage. The customer accepted this recommendation. Celeros FT manufactured the new impellers at the ClydeUnion Pumps site, complete with new wear rings for the four pumps. The upgraded units were then reassembled and tested again to ensure they met performance requirements.
Outcomes
Replacing the impellers and fitting new wear rings on the Uniglide pumps achieved an immediate 6% increase in performance. Despite their exposure to cavitation, the new aluminium bronze impellers have a design life of more than 15 years – more than doubling the Mean Time Between Failures (MTBF). Return on investment for this project was calculated to be within two years. The aftermarket team at Celeros FT have not only solved the pump performance issues but also increased their operational life by 50%.
