Diagnosis and Solution of High Noise and Vibration Issues After a Propylene Refrigeration Compressor Re-Rate

Abstract

High noise and vibration levels were experienced in a propylene refrigeration centrifugal compressor piping system. The noise and vibration problems began after an ethylene plant re-rate that accomplished its aero-thermal performance expectations. The high noise and vibration was measured as a discrete source with the peak noise and vibration frequency occurring near 480 Hz. Fatigue failures of small bore piping appurtenances had also occurred. Comprehensive site measurements were performed to diagnose the root cause of the noise and vibration. In-pipe pressure pulsations, piping vibration, pipe wall strain levels, external sound pressure, and pipe surface sound intensity were measured to identify the excitation source. Analysis of the measured data indicated that the 480 Hz acoustic source originated within the compressor, upstream of the side stream discharge nozzle. Typically centrifugal compressors tend to produce dominant noise at the blade passing frequency and its harmonics. The blade passing frequency (1544 Hz) was well above the 480 Hz measured dominant frequency. Further analysis of the data lead to the belief that an acoustic standing wave inside the compressor flow path was responsible for the noise and vibration. This paper will discuss the source of the issue, how the issue was diagnosed, and what solution was implemented to address the issue. A considerable amount of data gathering and analysis will be described in the paper to support the diagnosis of the root cause of the noise and vibration. After the excitation source was correctly identified, a duct resonator array was designed and installed upstream of the discharge pipe to minimize the acoustic energy entering the pipe. The noise and vibration solution was validated with actual field data measured before and after the installation of the duct resonator array.