Failure analysis on the inner cylinder explosion of a gas producer water jacket

• There was a 115 mm high steam at the top of the water jacket.
• The maximum equivalent stress was higher than the yield stress of the material.
• There were non-metallic inclusions and banded structure in the material.
• The cracking started from the weakest parts where were under high stress.

A large area of the inner cylinder wall in a gas producer turned inside while exploded in the trial running for 16 days. The failure analysis of the accident was presented in this paper. Firstly, on-site tests reveal that the installation location and type of the steam outlet caused 115 mm high steam at the top of the water jacket. Then, finite element simulation indicates that the maximum equivalent stress of the water jacket was higher than the yield stress of the material, even if the gas producer was in normal operating conditions. Furthermore, it was found that there were non-metallic inclusions and banded structure near the initial cracking area, which reduced the mechanical strength of the steel plate. It is concluded that the cracking started from the weakest parts of the material where were under high stress. The inner cylinder of the water jacket burst under the internal pressure, and turned inside due to the shock of the steamed water in the water jacket. Finally, some suggestions were proposed to improve the stress state of the water jacket and prevent similar accidents.