Eliminating A Rub-Induced Startup Vibration Problem In An Ethylene Drive Steam Turbine.

Abstract

A 16 megawatt ethylene drive steam turbine built in 1973 experienced rub related startup vibration problems for many years. The turbine would lock into a rub as it accelerated through the rotor’s first critical speed causing high vibration and often damage to components. Many possible causes of the rub were identified including casing distortion from bound keys, a steam leak at the horizontal joint flange, and a deteriorated foundations after many years of operation subjected to high vibration. Finally, the sensitivity of the rotor’s first critical speed was a concern. This paper describes how these problems were attacked in a concerted effort to eliminate the rub-induced vibration. The horizontal joint seal face was redesigned to address the steam leak; all sliding keys were removed, cleaned, and lubricated; the foundation repaired and regrouted; the original labyrinth seals replaced with retractable packing; and a squeeze film damper added to reduce the critical speed response sensitivity.