Vibration and Destabilizing Effects of Floating Ring Seals in Compressors,
ALLIS-CHALMERS CORP MILWAUKEE WI COMPRESSOR AND CUSTOM PUMP DIV
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Operating experience on a compressor commissioned 12 years ago has presented an interesting history of sporadic increases in shaft vibration. Initial operation was satisfactory with low levels of vibration. However, after some time the shaft vibration level increased to several mils. Initially this was believed to be due to rotor unbalance from deposits formed in the passages due to process upsets. After cleaning up the rotor, operation was again satisfactory. In time the vibration level again increased. It was then found that the rotor vibration was primarily subsynchronous. Further investigation revealed that the original seal design was subject to wear and was no longer properly pressure balanced. A modified seal design was installed and it has operated successfully for the past six years. Subsequent analysis has provided a better understanding of the seal destabilizing effects on the rotor and motion of the seal which has been confirmed by test data on the current seal design.