2010 Volume 51 Issue 2 Pages 389-393
Serious deformation on the pipe transporting hot water for heating was occurred by the cyclic heat impact during trial operation. Non-destructive inspection (RT, UT, MT, PT) and continuous indentation test were carried out to observe the flaw on the pipe and the variation of mechanical property for pipe material respectively. It was newly found by radiographic test that incomplete penetration flaws exist on every welding zone, which had been generated during the process of production. Ultrasonic test showed the length of incomplete penetration flaw reached 2/3 of circumference and its depth reached up to 60% of width. The mechanical property of material was found to be well uniform along the tube by the continuous indentation test. The incomplete penetration flaw was assumed to be a keen notch, and fitness for service was examined to observe the possibility of breakage crack and spread of crack in incomplete penetration area. As a result, it was observed to be usable under current operating condition, considering safety factor.