This case study presentation is about startup support services on a 135 MW steam turbine-generator set after major overhaul. Vibration data and relevant process variables were remotely monitored to assess machine condition in real-time. Vibration amplitudes measured at high-intermediate pressure (HIP) turbine were significantly fluctuating with subsynchronous vibration frequency and unstable orbit shape when the unit is loaded more than 103 MW. Vibration amplitudes were significantly increased when load increased and it tripped at 134 MW just before reaching full load due to excessive vibration amplitudes at bearing#2 of HIP turbine. Plant operator decided to restart the unit again but limit operating load at around 100 MW only until next opportunity available. Vibration amplitudes were stable at this load and it can be run for a few months before it was shutdown to adjust steam seals clearances and perform realignment. The subjected unit was then restarted again with vibration monitoring during startup and load variation test. Vibration appeared to be stable with acceptable amplitudes upto baseload operation.

Takeaways

Cause of steam whirl and its phenomena
Vibration characteristics of steam whirl
Practical solutions and consideration to cure steam whirl

Roengchai Chumai is founder and technical director of Machinosis Company Limited, a consulting and engineering company in the field of machinery condition monitoring and diagnostics located in Rayong, Thailand. He started his career with Bently Nevada (Thailand) Limited in 1999 as a machinery diagnostics engineer before the company was taken over by General Electric in 2002. He is responsible for machinery vibration testing, analysis and troubleshooting, field balancing, rotordynamics modeling and analysis. He was a technical leader of machinery diagnostics group for Asia region including Australia and New Zealand in 2008 until he left the company in 2015. He holds a bachelor degree in mechanical engineering from King Mongkut’s University of Technology Thonburi and a master degree in management science from Asian University. He is a certified vibration analyst Cat. IV according to ISO standard.