COMPRESSOR ROTOR CRACK CASE
Abstract
The case study describes rotor crack detection using vibration measurements, documented on real case of Induction Motor driven Compressor Unit. The study highlights the complexity of rotor crack diagnostics as the primary problem as it can be often masked by other existing machine malfunctions. In this case indication of the possible rotor crack, led to the Compressor bundle removal and rotor inspection. The rotor problem was confirmed, but not due to rotor crack but luckily only due to rotor thrust collar fit found to be worn and locating pin to be bent. Thrust collar had become eccentric (radial run out measured) causing a mass unbalance on the rotor in one direction, with similar symptoms as rotor crack. The gradual radial vibration increase on the compressor NDE bearing was observed on an export gas Compressor and the increase continued for several weeks. The vibrations were purely synchronous (1X) with a constant unidirectional phase angle. Following transient data comparisons, Lube Oil supply temperature checks, compressor feet / bearing housing vibration measurements and a NDE bearing inspection (no findings) the BN team diagnosed a rotor issue and insisted the compressor rotor was inspected. BN remotely witnessed the compressor inspection where it was discovered the thrust collar to rotor fit was worn and oversized, antirotating pin bended, causing the thrust collar to be eccentric resulting in an unbalance. This was proven on the high-speed balancing machine when the thrust collar eccentricity values could then be correlated with the rotor vibration response using an influence vector from installing a test weight at the thrust collar. Following the initial diagnosis and continued monitoring by the BN SSA team the machine was able to be safely operated for 6 months allowing for a replacement compressor bundle to be prepared and installed minimizing the operational and business impact.
Description
Technical BriefsCollections
Citation
Popaleny, Peter; Blackwell, Joseph; Peton, Nicolas (2022). COMPRESSOR ROTOR CRACK CASE. Turbomachinery Laboratory, Texas A&M Engineering Experiment Station. Available electronically from https : / /hdl .handle .net /1969 .1 /197049.