Reasons for and nature of weld joints failure in hot reheat steam lines of 800-MW power units

The nature of and reasons for weld joint failure in the hot reheat (HRH) steam lines of an 800-MW power unit are analyzed. It is shown that the weld joint destruction happened in the softened area and is typical for the weld joints operating for a long time under creep conditions. Numerical simulation demonstrated that the weld joint exhausted its lifetime due to the impact of equivalent stresses that exceeded design values, this being the reason for the failure.