Session: 21-07 Mechanical Integrity and Materials for Steam Turbines

Paper Number: 103882

103882 - Failures of Steam Turbine Diaphragms and Approaches to Improve Their Structural Integrity 

Diaphragms  are used in steam turbines to regulate the flow of the steam to the rotating blades.  The regulation of  the steam flow is needed to increase the efficiency of the turbine.  The efficiency of the steam turbine also depends on the dimensional accuracy of the geometric parameters of the stationary vanes of the diaphragms.  The fabrication of the diaphragms involves welding together  multiple pieces made of different alloys.  All these aspects make their fabrication somewhat difficult.  Proper design and fabrication are important for the structural integrity of the diaphragms.

Though diaphragms are non- rotating parts, they may experience elevated temperature and they may also be subjected to high stress and or cyclic stresses during service.  As a result, they may develop cracks or and other issues due to long term service.  The vanes of the diaphragms may develop cracks and the diaphragms may develop dishing which is generally a result of creep deformation resulting from long term service at elevated temperature.   Some of the common failures and issues these diaphragms may see in their service life will be discussed in this paper.  These will be illustrated with some recent field examples.  This will be followed by some approaches to mitigate the risk of these failures and issues.        

Presenting Author: Vamadevan Gowreesan Sulzer Turbo Services

Presenting Author Biography: Dr. Gowreesan has been working in the turbo machinery field for the last 17 years. His experience includes metallurgical root cause failure analysis, additive manufacturing, heat treatment, in-service evaluation and rejuvenation, selection and qualification of materials, development of welding procedures and troubleshooting materials and welding related issues in the repair of turbo machineries. He has conducted more than 100 metallurgical root cause failure analysis of different components from turbo machineries.

Authors:

Vamadevan Gowreesan Sulzer Turbo Services
Wayne Greaves Sulzer Turbo Services
Kirill Grebinnyk Sulzer Turbo Services