CENTRIFUGAL-COMPRESSOR MODIFICATIONS AND THEIR EFFECT ON HIGH-FREQUENCY PIPE WALL VIBRATION

High-frequency pulsation generated by centrifugal compressors, with pr essure wavelengths much smaller than the attached pipe diameter, can c ause fatigue failures of the compressor internals, impair compressor p erformance, and damage the attached compressor piping. There are numer ous sources producing pulsation in centrifugal compressors. Some of th em are discussed in literature at large (Japikse, 1995; Niese, 1976). NGTL has experienced extreme high-frequency discharge pulsation and pi pe wall vibration on many of its radial inlet high-flow centrifugal ga s compressor facilities. These pulsations led to several piping attach ment failures and compressor internal component failures while the com pressor operated within the design envelope. This paper considers seve re pulsation conditions at an NGTL compression facility which resulted in unacceptable piping vibration. Significant vibration attenuation w as achieved by modifying the compressor (pulsation source) through rem oval of the diffuser vanes and partial removal of the inlet guide vane s (IGV). Direct comparison of the changes in vibration, pulsation, and performance are made for each of the modifications. The vibration pro blem, probable causes, options available to address the problem, and t he results of implementation are reviewed. The effects of diffuser van e removal on discharge pipe wall vibration as well as changes in compr essor performance are described.