A major refinery in Thailand was having problems operating their Shin Nippon stripper pumps. These are low specific speed single stage OH2 pumps. For this particular process, the customer operates 2 pumps in parallel operation.
While operating the pumps, the refinery operators had a problem that while their B pump was operating as per the performance curve, the A pump was constantly tripping due to high power consumption. Customer provided some data and indeed the A pump was consuming 20% more power than the performance curve and near the motor limit.
The refinery operators were struggling with this problem for a while and had all the data available for us to study. Our Engineering team gleaned through the data and found out that pump A had a head loss of 3-4% as compared to pump B. Seeing the systematic approach by our engineers, the customer decided to let us perform a root cause analysis of the problem.
Our first step was to inspect pump A and look at the wear ring clearances, Impeller and volute damage, etc. We were surprised to learn that there were no abnormal conditions found.
Next, we requested customer access to scan the pump. This was difficult as the customer was operating the pumps continuously at site. But finally the customer found a 24 hour window where both the A and B pumps were brought back to the PSS workshop. PSS engineers performed the scan within 1 day using our state of the art Faro Quantum scanner.
The results were out within a few days and we were surprised to learn that the two impellers in pumps A and pump B were not the same. The outer diameters, outlet width, inlet projected angles, and wrap angles were quite different and it was quite clear that there had been a mixup when the impellers were supplied. Some calculations were performed on head with the new geometry and our engineers confirmed the reason for the head loss on Pump A.
We offered customers two solutions to tackle their problem. In the short term, we proposed to replace the pump wear rings with Vespel to improve pump efficiency. Secondly, we also offered new re-engineered impellers. Customers have accepted our findings and our solutions. We are happy to report that this problem has now been resolved and the customer is now operating both pumps successfully.