Unexpected Vibration on a Centrifugal Compressor Caused by Vibration Probe Support

Abstract

During the commissioning of a Main Air Compressor in an Air Separation Unit, the rotor showed increased radial vibrations at the Non-Drive End probe. The RCA revealed: The vibration resulted from the excitation of a natural frequency of the vibration probe support, triggered by the pressure fluctuation at the suction of the 11 blades-impeller. The probe support was redesigned to increase its stiffness in order to shift the natural frequency. After replacement of the support, no particular vibration appeared anymore. Generally: The vibration probe support requires careful attention, especially if the machine is standardized for a very large operation speed range.