Industrial centrifugal pumps are designed and built to provide years of trouble free and satisfactory service but only on the condition that they are installed and operated with due care and are properly maintained. But despite care in operation and maintenance, they often do fail. Inability to deliver the desired flow and head is just one of the most common conditions for taking a pump out of service. There are other many conditions in which a pump, despite suffering no loss in flow or head, is considered to have failed and has to be pulled out of service as soon as possible. These include seal related problems (leakages, loss of flushing, cooling, quenching systems, etc.), pump and motor bearing related problems (loss of lubrication, cooling, contamination of oil, abnormal noise, etc.), leakages from pump casing, very high noise and vibration levels, or driver (motor or turbine) related problems.
The list of pump failure conditions mentioned is neither exhaustive nor are the conditions mutually exclusive. Often the root causes of failure are the same but the symptoms are different. A little care when first symptoms of a problem appear can save the pumps from permanent failures. The most important task in such situations is to find out whether the pump has failed mechanically or if there is some process deficiency, or both. Many times when the pumps are sent in for service, the maintenance group does not find anything wrong on disassembling it. Thus the decision to pull a pump out of service for maintenance or repair should be made after a detailed analysis of the symptoms and root causes of suspected pump issues. Also, in case of any mechanical failure or physical damage of pump internals, the operating engineer should be able to relate the failure to the process unit’s operating problems.
Any operating engineer who desires to protect his pumps from frequent failures must develop not only a good understanding of the process but also thorough knowledge of the mechanics of the pump. Effective troubleshooting requires an ability to observe changes in performance over time, and in the event of a failure, the capacity to thoroughly investigate the cause of the failure and take measures to prevent the problem from reoccurring. This is not easy to accomplish though as most diagnostic tools are reactive, providing indicators only after significant damage has occurred. A better strategy is a set of proactive diagnostic tools that show indicators of conditions that would lead to wear and damage before the fact.
Sygnology’s signal processing technique was applied to a large industrial pump used to charge an oil custody transfer meter and pipeline pump. The pump was recently returned to service and had no known issues. However, regular and continual signal patterns were noted in the discharge pressure data for the pump for a couple weeks from the beginning of return to service.
After careful review and analysis, the surveillance engineer was alerted who in turn raised the issue with the field maintenance group suggesting they inspect the pump for a shaft alignment or deflection issue. The pump setup was inspected and which confirmed the pump shaft alignment was out of specification. They noted it likely was knocked out of alignment during reinstallation.
Because the alignment disturbance was not obvious in the process data, the issue would have likely gone unnoticed until irreparable injury to the equipment had occurred were it not for the near real-time diagnostics implemented by Sygnology which uncovered the imbedded precursors to damage. Minor pump shaft alignment issues generally prematurely wears pump shaft seals and bearings causing leaks and mechanical failure. As a result of Sygnology's information the pump was taken out of service for repairs. After the motor and pump shafts were realigned and the pump returned to service, all traces of signatures were no longer present. The client was able to implement appropriate equipment adjustments rather than encountering unexpected repair costs and delays.