Vibration Analysis of the Base Structure Supporting a Centrifuge–Motor Assembly in a Petroleum Oil Refinery

Abstract

A structure carrying a centrifuge and motor in a petroleum oil refinery has been vibrating above the alarm limit of vibration. This has been a recurring problem. The maintenance work undertaken at regular intervals on the basis of time waveform and spectrum analysis could provide only a temporary solution. To investigate the causes of vibration above the acceptable limits, pre-stressed modal analysis of the structure was undertaken by using Finite Element Analysis software ANSYS™ and natural frequencies and mode shapes were extracted. Pre-stressing was done by considering the self-weight of the structure, centrifuge and motor. The structure was analyzed using a combination of beam elements, shell elements and mass elements. The operating deflection shape (ODS) technique which helps to observe the deflection pattern of structure in real time at operating or other frequencies from the measured vibration data was employed to validate the analytical results. ME’scopeVES™ software employing the ODS technique was used in this work. Analytical results obtained from ANSYS™ software are compared well with the ODS test results. The analysis of analytical and experimental results has revealed that the structure was operating in the resonance band.