T07: Shop Rotordynamic Testing Options, Objectives, Benefits and Practices

Abstract

Understanding the lateral rotordynamic behavior is critical indetermining the reliability/operability of rotating equipmentWhether examining a centrifugal pump or compressor, steam orgas turbine, motor or generator, rotating machinery share thesame need to accurately predict and measure dynamic behaviorIndustrial specifications determining fit for purpose rely on theaccuracy of rotordynamic predictions where direct measurementis impractical or otherwise impossible in an industrial settingTesting to confirm rotordynamic prediction and behaviorprovides both the purchaser and vendor the confidence that thedesign will meet project expectationsRotordynamic shop testing has several options available tothe project during acceptance tests at the vendor’s shop Theseoptions include mechanical run, string and full load/Type 1testing as well as verification testing to validate unbalanceresponse and stability predictions Such testing has numerousadvantages; the most important being the avoidance ofproduction disruptions involved with testing at the job site Eachtest option has associated costs as well as limitations as to whatlateral vibration characteristics are revealed Understandingthese factors is vital to efficiently mitigate the risks associatedwith the purchased equipmentApplying best practices and an understanding of theindustrial (API) test requirements are needed to derive themaximum benefit of each test option The best practices not onlyinvolve the test procedure but also the associated analyticalmethods used to post process the measurement informationWhether performing a simple mechanical run test or morecomplex stability verification during ASME Type I testing,ensuring that a logical, repeatable and proven methodology isfollowed produces reliable evidence to confirm the rotordynamicmodel and lateral vibration performance The rationale behindthe API test requirements provides an understanding of why thattest is being performed and its correct application to the dynamicbehaviorTest options can be separated into two categories; tests thatreveal portions of the dynamic behavior of the equipment tospecific operating conditions and those used to verify theanalytical predictions of that behavior API mechanical, stringand Type I (or full load) tests reveal the rotordynamic behaviorof the equipment to a given set of conditions These are usedspecifically to determine acceptability of the design Unbalanceand stability verification testing is used to confirm (or provideconfidence in) the rotordynamic model Confidence in themodel permits extrapolation of the design (vendor) and operation(purchaser) beyond the machine’s as-built and specific shop testconditions