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Centrifugal Pump Performance Testing

By Joe Honeywell

Introduction

Centrifugal pumps are subject to a wide range of influences that can affect their performance and operational integrity. Beginning with the pump design and manufacturing process and continuing through the installation and operating phase, the pump is predisposed to many factors, whether initial or changes over time, that affect the way it performs. If the original pump design or material selection is inadequate the pump may not hydraulically or mechanically perform as intended. Even if the pump meets the original specifications, unforeseen design and changing operational conditions can cause changes in the pump behavior. In addition, improper installation or lack of attention to maintenance can affect the pump performance. Normal wear, erosion and corrosion can also influence the operational fitness. In essence, a pump is subjected to many factors in its life cycle that will influence its intended purpose.

Pumps are manufactured for a wide range of services and applications. Some specialized pumps may be categorized as having a proven design. They are usually mass produced for a special market and have high reliability. These pumps are often inexpensive, in general service applications, and if they fail are simple to replace. This category of pump does not warrant a high degree of monitoring or performance testing. Another category of pumps have a proven design but are modified by the manufacturer to meet specific project specifications. These pumps are more expensive to manufacture, in non-critical services, and if they fail, will be repaired or replaced. Some degree of shop testing is needed to mitigate the risk of in-service failure. Monitoring devices may be added to assure the operational integrity of the pump. These devices, however, may not monitor the hydraulic performance, so occasional field testing is needed. Critical service pumps are a third category. They are very expensive to manufacture, arduous to install, and if they fail, cause consequential effects to plan production. These pumps may be customized for an application and require a narrow tolerance for hydraulic performance. Closely monitoring the operation of the pump mitigates the risk of mechanical failure. Periodic inspections will help to determine pump wear and provide valuable trending data. However, due to the critical service, field performance testing is probably not conducted. Shop testing for this category of pump is necessary to reduce the various risks associated with design, manufacturer, installation, and mechanical integrity. These three categories of pumps have various types of risks. It is up to the owner to gauge the various risks associated with the pump service and application, and to choose the proper mitigation method, including performance testing.

From the initial installation to continued operation, engineers and operators are frequently confronted with the challenge of verifying the performance and mechanical integrity of a pump. There are many ways to meet this challenge including conducting various types of pump tests, simulation with scaled models, and statistical analysis of similar applications. Each will depend on the objective, purpose and reasons for verifying the pump performance. The pump industry has created standards that provide for the various levels of standardization, performance tolerance, and mechanical integrity. This article will discuss the various standards, reasons for testing, suggestions for accurately conducting a test, and review various owner recommendations. Finally, this article will give an example of a pump performance testing and how to analysis and interpret the results.

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