Failure analysis of a low-pressure stage steam turbine blade

• Published in: Nondestructive testing and evaluation 2023-07, Vol.38 (4), p.668-682
• Main Authors: Rani, Pooja, Agrawal, Atul K.
• Format: Article
• Language: English
• Subjects: Catastrophic failure analysis; Chemical analysis; Damage assessment; damage causes; erosion pitting; Failure analysis; Fluid penetrant testing; High temperature; Load fluctuation; Low pressure; Mechanical analysis; Mechanical properties; Metallurgical analysis; NDT; Nondestructive testing; Steam turbine blade; Steam turbines; Tensile tests; Turbine blades; Water drops; X20cr13 stainless steel
• ISSN: 1058-9759; 1477-2671
• DOI: 10.1080/10589759.2022.2156503

Steam turbine blades are regularly damaged because of their harsh working conditions, which include elevated temperatures and fluctuating loads. Most investigations of blade failures end with a metallurgical analysis, which does not provide sufficient positive identification of the mechanisms involved. Hence, in the current research work a mechanical analysis is performed in conjunction with the metallurgical analysis for competent analysis of blade failure. For the purpose of evaluating the damage, non-destructive testing (NDT) was carried out. The purpose of this examination is to qualitatively examine the blade of a 210 MW low-pressure steam turbine after 1,52, 241 h of working to identify the critical locations of damage and the reason behind it. Visual examination, chemical analysis, dye penetration testing, and metallurgical testing are all part of this examination. In addition, mechanical properties were evaluated using hardness and tensile testing. The findings revealed that water droplet erosion accelerated blade failure, preferentially attacking the blade's edges. These erosion pits act as stress concentrators and serve as a potential crack propagator if neglected, which can lead to catastrophic failure of the system. Hence, to increase reliability and to avoid such failures in future, this type of failure analysis is highly recommended.