Numerous factors, including actual chemical composition, heat treatment, microstructure, dimensions, and service conditions, determine the lifetime of creep-exposed components. This creates a wide gap between the real condition of a given steel pipe and its project specification. For a 141MW unit main steam line, the remaining life calculated according to the German Boiler Code TRD 508 was found to be almost exhausted. It was recommended to remove a pipe sample with a circumference weld for laboratory examination. Stress rupture tests were performed on three types of specimens: tangential, longitudinal, and longitudinal with a heat-affected zone in the middle of the gauge length using the isostress testing method. Metallographic examination of the broken specimens was conducted. Linear extrapolation of the rupture times to the service temperature yielded a residual service life of more than 100,000 hours.

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