New methodology for safety assessment of steel-lined pressure shafts using high-strength steel

Although high-strength steel provides higher tensile yield strength, the fatigue resistance of the steel welded joints is not increased compared with mild, more ductile, steels. Under more severe operational conditions, particularly for pumped-storage plants, the number of starts and shut-downs of the generation units increases. Fatigue of the welded joints may become critical, especially in the case of imperfections and undetected flaws in the welds. This paper proposes a new methodology for safety assessment of the steel liners of pressure tunnels and shafts.