Prediction of vibration responses in a reciprocating compressor interstage piping system using the modal expansion method

Reciprocating compressors are sources of vibration excitation in hydrotreating units used in the oil refinement industry. Due to their operating principle, these compressors can produce high levels of vibration in the pipes connected to it, which can affect their structural integrity and life span. Continuous vibration monitoring can be a difficult task due to the limited number of sensors and poor accessibility of the places with higher risk of failures. In this work, a methodology is proposed for predicting vibration responses in non-instrumented locations. For this, an output-only modal analysis of the interstage system was carried out and a finite element model of the system was developed to calibrate the numerical mode shapes or, in other words, to smooth the experimental mode shapes. The System Equivalent Reduction Expansion Process (SEREP) was used to reduce the numerical degrees of freedom and the Local Correspondence Principle for Modes and Coordinates (LCMC) was used in the smoothing process. Finally, the smoothed version of the experimental modal matrix was expanded using the modal expansion method and used to predict the vibration responses. Results showed high accuracy between the measured vibration data and the predicted ones.