Solution for the torsional vibration of the compressor shaft system with flexible coupling based on a sensitivity study

This paper presents the root cause analysis and solving process of the torsional vibration problem in a reciprocating compressor shaft system. The field measured data showed that the fifth-order torsional resonance occurred in the shaft system. The lumped-mass method was adopted to calculate the torsional natural frequencies (TNFs) and mode shapes of the shaft system. A sensitivity study was conducted to investigate the effect of each inertia and stiffness in the calculation model on the first TNF of the shaft system. The uncertainties of the primary data of the calculation model were discussed, and the mass-elastic model was modified by adjusting the stiffness of the flexible disc coupling. After adding an inertia of 4.68 kg·m², torsional resonance was avoided, and the speed fluctuation of the shaft system was significantly reduced. The compressor package has been operating normally for nearly one year after modification. The analysis methods and conclusions given here can provide guidance for trouble-shooting torsional vibration problems.