A compressor impeller was submitted for investigation of what was reported to be a corrosion failure. Laboratory analysis determined that the cause of metal wastage was not corrosion. Failure of the impeller was due to fatigue cracking caused by plate mode (edge) vibration between the vanes. Vibration testing determined that two specific frequencies excited the impeller in this manner. The source of these excitation frequencies was never determined. However, a new impeller with a modified geometry was designed so that it was "de-tuned"; i.e., the vibration nodes were moved away from the known excitation frequencies. The compressor with the modified impeller has been running for over four years with no further problems.
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