Cracking of a Closing Weld in a Secondary Autothermal Reformer in a Mega Methanol Plant

摘要

After six years of operation a major leak was detected in May 2010 in a very large water jacketed Autothermal Secondary Reformer (ATR) made to ASME Section VIII Div1 in the Atlas 5000 MT/d methanol plant in Trinidad. The cracked weld was a "closing weld" that had been locally post weld heat treated. Inspection revealed that the cracking was present around the entire circumference of the vessel on the inside. Metallurgical examination revealed that the cracking had initiated at the inside of the vessel as a result of CO-CO2-H stress corrosion cracking, primarily in the heat affected zone and weld. This case is the first known ATR or secondary reformer to crack as a result of stress corrosion cracking at a locally post weld heat treated closing weld.