THE INFLUENCE OF REPAIR WELDED JOINT ON THE LIFE OF STEAM PIPELINE MADE OF Cr-Mo STEEL SERVICED BEYOND THE CALCULATED WORKING TIME WPŁYW NAPRAWCZEGO ZŁĄCZA SPAWANEGO NA TRWAŁOŚĆ RUROCIĄGU PARY ZE STALI Cr-Mo EKSPLOATOWANEGO POWYŻEJ OBLICZENIOWEGO CZASU PRACY

The aim of the paper was to examine the influence of repair welded joints on the service life of steam pipelines for over 220 000 hours of service in creep conditions. The research included the study of the microstructure using scanning microscopy, the tests on mechanical properties at room and elevated temperature, determining the nil ductility transition temperature, and short-time creep tests to determine the residual life of the material. The tests allowed determining the time of further safe operation of elements of the steam pipeline with a repair welded joint, with reference to the base material, and the welded joint after service. The assessment of residual life and disposable residual life, and at the same time determining the possible time of further safe operation, has an essential meaning in the case of elements serviced considerably beyond the calculated working time.