Prediction and mitigation of common steam line hanger failures

Abstract 

Repeated hanger failures were observed in the steam condenser reject lines of a multi-unit nuclear power station, attributed to shear fractures of the threaded end of the hanger rods. The failures occurred at the same location in the piping run, near a reducer and an elbow where the stream flow changes direction. While condensed steam water slug impact is a possibility, the primary cause is believed to be structural resonance driven by steam flow-induced pipe vibrations. This paper investigates the fluid motion in the pipe, driven by high mass flow rate, pressure drop through the reducer, and flow discontinuity at the elbow. The magnitude and frequency of the steam flow-induced vibrations and impact forces will be computed and compared to the natural frequency of the trapeze hanger to determine if flow-induced structural resonance is the mode of failure.

Partners 

NSI (Canada)