Failure Analysis of Expansion Joint Bellows of Gas Pipelines

Some expansion joints bellows used in buried gas pipeline in east China cities cracked after 1∼2 years service, the cracks usually located at top of the bellows, they expand nearly 48% of total circumference and the whole thickness. The material of the bellows was austenitic stainless steel plate. In order to research the crack causes, one typical failure bellows was chosen in this work, the specimen cut near the crack were analyzed by the macro-analysis, micro-analysis, chemical composition analysis, optical microscopy and electron microanalysis. The results showed that the chloride ion and sulfide in water of pipeline well and the high additional stress due to deviation of alignment of the two side pipeline ends were the main causes, the interaction effects of aggressive and high stress lead to stress corrosion crack of the top of bellows.