Burst Failure Analysis of Pipe in High Temperature Superheater

After working for 150 000 h, a pipe in the high-temperature reheater of a boiler burst. In order to find out the failure cause, field investigation, macroscopic inspection, mechanical properties testing, metallographic examination, hardness testing, and wall thickness and diameter measurement were carried out. The results show that the pearlite in the failed tube-like metallographic structure is completely globalized, and the carbides have been distributed in a chain shape, which resulting in a significant decrease in mechanical properties . The measurement results of the inner and outer wall oxide scale thickness exceed the relevant standard requirements. The burst reasons of the elbow pipe of the outlet header of the high temperature reheater are as follows: the aging of the material led to the deterioration of the mechanical properties of the material and the occurrence of micro-cracks in the material. Due to the larger stress at the elbow, the crack expanded, resulting in the thinning of the wall thickness. When the wall thickness was thinned enough, the pipe burst.