Analysis and Improvement Practice for Stream Control Valve Stem Fracture of Back Pressure Steam Turbine

Abstract

During the running of the steam turbine for XyMax recycle hydrogen compressor in an aromatics union plant, the stem of stream control valve had fractured several times. According to the characteristic of structure, assembly, force and the process data, it was thought that when the stream come into chamber from side end, the beam end-face will be struck directly by steam inevitably, the valve disc will be subjected to irregular torque force under the action of steam flow, resulting in vibration frequency difference between the valve beam and the valve disc. When there are some defects in the stem, such as threaded rod was not strength enough, or had some stress concentration, or had low anti-fatigue performance, etc., the rod is highly likely to be fractured. Passed optimizing the force distribution and disturbance gave by steam, reforming the rod structure, and upgrading the material comprehensive performance and anti-cavitation ability, after this final improvement, the problem never happened again.