Properties of the Secondary Steam Pipelines with Welded Joints Operating under Creep Conditions in the Assessment of Suitability for Long-Term Service

Abstract

The research aimed to assess the condition of the main steam pipelines and peripheral welded joints after long-term exploitation under creep conditions that operated for a time significantly exceeding the design time. Secondary steam pipeline elements made of 10CrMo9-10 steel operated for 240,000, 280,000, and 308,000 h were under investigation. The mechanical properties of the welded joint areas were determined in destructive tests. In particular, the brittle transition temperature and mechanical and plastic properties at room and elevated temperatures were determined. The effect of long-term operation on the tested pipelines’ strength, plastic properties, and impact strength was also investigated. Based on the completed creep tests, the extrapolation method determined the residual life. The available residual life was estimated, which is the safe period of further operation for the operating parameters of stress σr and temperature Tr. The applied methodology and the adopted procedure will be used to assess the condition and further operation time prediction of welded joints of power equipment pressure parts operating under creep conditions.