The rub can cause elastic deformation of the rotor at the point of impact and temporary rotor shaft bending. The forces produced by the impact of the large rotating rotor mass with the poorly functioning stationary seals often impress a layer of metal on the surface of the rotor. Secondarily, there may be a localized temperature increase at the point of contact, causing increased metal temperatures at the point of contact due to friction. This situation commonly occurs when the high-mass rotor at operating speed comes in contact with a stationary surface, typically caused by a too-small clearance between the labyrinth or diaphragm gland seals and the rotor. It almost goes without saying that rubbing in the labyrinths or diaphragms, caused by insufficient clearances, disrupts the end sealing of the rotor. The units were commissioned from 1980 through 1985. The discussion is based on the authors’ experiences at the six-unit, 1,890-MW Ramin Power Plant, located in Ahwaz, Iran. Working from the inside out, we next look at rotor balance issues, followed by rotor and casing misalignment problems, and problems caused by the casing. We begin with mechanical factors related to the rotor, the largest rotating assembly in the turbine. Rotor bending may be caused by a variety of static and dynamic factors, many of which will be explored in this article.
![within the blade steam within the blade steam](https://www.gamingdragons.com/images/game_img/screenshots/skara/2734trj98234jtr93tf92843%20(6).jpg)
Extreme rotor bending problems often involve interaction between the turbine’s rotor and stationary parts.
![within the blade steam within the blade steam](https://assets.rpgsite.net/images/images/000/054/896/original/XC2_Rex.png)
The problems often reduce plant availability by limiting generation and increase plant operation and maintenance cost. Rotor bending that results in premature failure of steam turbine blades and other internal components is one of the most serious problems experienced in power plant operations. An operator of many utility-scale steam turbines shares its extensive field experience identifying the root cause of failures as well as successful solutions. However, bending can cause impact between stationary and rotating parts-often cascading impacts. Steam turbine rotors bend during operation, but the bearing and supports are designed to keep the static and dynamic forces under control.