High Speed Coupling Failure related to Torsional Vibration

Abstract

This case study presents compressor high speed coupling failure where torsional natural frequency is excited. The case study examines a repeat high speed coupling failure that excited 2�ᵈ torsional natural frequency of the compressor train. The mature unit had operated successfully for more than 15 years with no changes that would affect fundamental natural frequencies within compressor train until a series of compromising events created gears degradation which triggered natural frequencies excitation. Results are presented herein of the evidence of the failure mode of the couplings which show fatigue fractures leading to catastrophic failure due to high alternating torsional stress. An examination of bull gear modal analysis showed the possibility of excitation frequency. Limitation of existing equipment monitoring (radial vibration measurement) cannot detect torsional vibration. Root cause failure analysis to be discussed