ULTRASONIC STRESS EVALUATION IN A COMPRESSOR ROTOR

The run-out report for a compressor rotor showed an almost continuous bow between the two bearings. The maximum run-out of 0.03 mm (0.0012 i n.) occurred at the inlet to the fourth stage impeller. The steel comp ressor rotor was just over 3 m in length. It had been removed from ser vice for maintenance. Each of the seven compressor stages was mounted on the rotor at the time of the stress measurement. An evaluation of t he residual stress at the inlet locations in the shaft using criticall y refracted longitudinal, L-CR, ultrasonic waves showed compressive st ress on the bowed side of the rotor, supporting the conclusion that re sidual stress is the cause of the bow.