Investigation of Steam Turbine Blades Damage and Reliability in a Power Plant

This work presents an experimental case study of 200 MW low-pressure steam turbine rotor blades damage after 310 thousand hours of operation and 404 start-ups on the power plant. Damaged blade material was analysed by experimental testing of mechanical properties as well as crack initiation and micr...

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Bibliographic Details
Published in:Key engineering materials 2019-04, Vol.799, p.89-94
Main Authors: Molodtsov, Artjom, Dedov, Andrei, Mikli, Valdek, Lausmaa, Toomas, Kommel, Lembit, Klevtsov, Ivan
Format: Article
Language:English
Subjects:
Case studies
Chemical composition
Crack initiation
Crack propagation
Fatigue cracks
Fracture mechanics
Fragmentation
High cycle fatigue
Impact damage
Low pressure
Martensitic stainless steels
Mechanical properties
Microscopes
Microstructural analysis
Microstructure
Organic chemistry
Plant reliability
Power plants
Rotor blades
Rotor blades (turbomachinery)
Scanning electron microscopy
Steam turbines
Thickness
Turbine blades
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Summary:This work presents an experimental case study of 200 MW low-pressure steam turbine rotor blades damage after 310 thousand hours of operation and 404 start-ups on the power plant. Damaged blade material was analysed by experimental testing of mechanical properties as well as crack initiation and microstructure in the damaged area by using optical and scanning electron microscopes, and investigation of chemical composition by the SEM-EDS method. Results of the investigation show that the material was die forged martensitic steel 20Cr13. The mechanical properties of the blade steel were in accordance with standard technical requirements for new material. The cross-sections of damaged and undamaged blades were investigated and compared. It was found that thickness of damaged blades was significantly less than undamaged ones. SEM-EDS analysis has shown the presence of brass fragment on the surface of one damaged blade. The microstructural analysis has shown that one of the cracks was initiated due to impact of brass fragment. Based on the given case study results it is concluded that the reason of the blade damage was a combination of at least two factors: accelerated high cycle fatigue due to increased stresses caused by excessive vibration of damaged blades with lower thickness and impact of brass fragment against blades.
ISSN:1013-9826
1662-9795
1662-9795
DOI:10.4028/www.scientific.net/KEM.799.89