PSI - Issue 57

Malik Spahic et al. / Procedia Structural Integrity 57 (2024) 833–847 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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On-site machining was performed to remove the cracks. Finite element calculations have shown that the remaining lifetime after repair is strongly reduced at the first stage slot bottom as the new geometry introduces an important stress increase compared to the original one. As mitigation actions to prevent reoccurrence of severe cracking, following actions have been implemented: • a reduction of the operational gradients • borescope inspection to detect cracks at crack location 2 • correction of the calculation by the RSE

Figure 9: The first stage blades had to be removed to detect the crack in the slot bottom

4. Fleet risk assessment The ENGIE fleet within Europe consists of around 25 CCGT units in many different configurations, including single shaft units with and without clutch, but also 1:1 and 2:1 configurations. A wide variety of steam turbine rotors is present with designs of di fferent OEM’s including Siemens, Mitsubishi, Ansaldo, GE and also former Alstom, forming a very interesting benchmark. In a first phase, all these units have been assessed based on the parameters shown in Figure 10. The parameters have been divided into four segments, namely design, operations, maintenance and protection. They are further detailed in what follows. For units assessed to be at risk, mitigation actions were implemented. These are described in Section 5.

Figure 10: Parameters used in the fleet risk assessment