Evaluation of mechanical properties and assessment of residual life of a service-exposed water wall tube

Abstract

This paper is aimed at investigating the residual life, spanning 32 years, of a service-exposed water wall tube from one of the steam generating boilers of a thermal power station. The remaining life prediction and safety assessments were made using destructive accelerated stress rupture and tensile tests at different temperatures, as well as some non-destructive tests. There was no evidence of localised damage in the form of surface cracks, cavitation or dents in the service-exposed water wall tube. So far as the remaining life at 425°C is concerned, it is possible to obtain a life greater than 100,000 h at the hoop stress level of the service-exposed tube, providing that no localised damage in the form of cracks or dents have been developed. It is recommended that a health check may be carried out after 50,000 h of service exposure.