Excessive pipe vibration brings a series of serious problems, especially for hyper compressors used by LDPE production. Therefore, the pipeline vibration issues should be handled with care as the process gas reaches pressures up to 350 MPa (50,000 psi). This paper focuses on how to analyze the hyper compressor pipe vibration during operation and maintenance. Taking the outlet pipe vibration of an ultra-high pressure ethylene compressor for example, firstly the vibration level was assessed by the site measurement and signal processing. Then the acoustical analysis was executed based on the plane wave theory and the finite element theory. After that, the modal analysis of pipelines was made with the finite element method. Finally the analyses of all the obtained results made it possible to identify the true reason for pipeline vibration — gas pulsation with large amplitude instead of gas column resonance and structure resonance. Based on the integrated analyses of the results, the retrofit measures were proposed and verified.

No abstract