Case study: Evaluation of L-1 Steeple Repair Strategy
Stage: L-1 stage in a base load LP steam turbine
Issue: Crack indications have been found in the L‐1 steeples with axial curved entry blade roots
Objectives: FEA analyses to evaluate the stresses resulting from modifications by grinding out cracks in the steeple grooves
Background
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Crack indications have been found in the L‐1 steeples with axial curved entry blade roots.
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Modifications by grinding out cracks with different profiles were proposed.
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FEA was performed to evaluate the impact on stresses and associated risk as a result of modification to repair the damage steeple.
Summary of Analyses
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FEA analysis shows that steady stresses in the original and modified L-1 steeples are NOT excessive to pose a significant threat to the structure integrity under a base load operation.
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Cracking might be associated with corrosion assisted fatigue.
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The proposed modifications were studied and optimal configuration was recommended.