Patent ID: 7580802

Claim:
In a compressor having a series of turbine blades that are housed in a casing and rotate at a blade pass frequency, wherein certain movements of the turbine blades generate pressure waves that propagate to the casing and thereby cause the casing to vibrate, a method of estimating the operable life of turbine blades in the compressor, said method comprising the steps of: monitoring blade pass frequency of the turbine blades; sensing fluctuations in said blade pass frequency to identify a developing condition of rotating stall; sensing vibrations in the casing caused by movement of the turbine blades; correlating the sensed vibrations to a frequency value representative of the vibration frequency of the casing; identifying when the turbine blades are subjected to a condition of rotating stall by determining when said frequency value is outside of a known range of frequency values of the casing during normal turbine blade operation; and factoring the identified developing condition of rotating stall and the identified condition of rotating stall into an estimation of the operable life of a turbine blade in the compressor.