Problem Diagnostics on High-Speed Centrifugal Compressors Using Vibration Signature Analysis (18 page booklet)
Highlights:
This paper concentrates on the techniques and instrumentation required to detect a multitude of problems experienced by today's high-speed centrifugal air compressors.
Such techniques apply to compressors typically ranging in size from approximately 1,000 to 18,000 CFM with normal discharge pressures of about 100 to 125 psig and usually driven by electric motors ranging from 300 to 6000 HP (occasionally turbine-driven).
These multi-stage compressors have impeller speeds ranging from 15,000 to 70,000 RPM or more.
These units are outfitted with bullgears having high tooth counts, on the order of 250 to 500 teeth, running at nominal speeds of 1800 to 3600 RPM.
This means that the fundamental gear mesh frequency most often ranges from 850,000 to 1,500,000 CPM (or roughly 14,000 to 25,000 Hz).
Therefore, one must be concerned about extremely wide frequency ranges all the way from subsynchronous motor and bullgear frequencies up to approximately 3.5 times gear mesh frequency (or from roughly 600 to more than 4,000,000 CPM)!
This requires several transducers and various analyzers, along with employment of several specialized techniques in order to fully evaluate the "health" of this critical family of machines.
Discussions are included on these techniques, instruments, and programs required to improve the reliability and to prevent costly, unanticipated failure of these machines.
In addition, several case histories are offered for further amplification.
