Failure analysis of steam reformer waste heat recovery boiler tubes

A waste heat recovery boiler used to cool process gas as part of a steam reforming process at a hydrogen production facility experienced tube leaks after operation for four years. A thermal and stress analysis of the boiler was conducted to evaluate stresses experienced by the tubes, in addition to a metallurgical evaluation of tube samples. The metallurgical analysis revealed the tubes had experienced caustic stress corrosion cracking (CSCC) due to the configuration of the tubes at the tubesheet. The results of the thermal and stress analysis of the boiler indicated that the CSCC initiated a chain of events that also resulted in circumferential cracking of the tubes at the tube to tubesheet welds. The circumferential cracking produced more leaks that compromised refractory intended to protect the tubesheet from thermal damage. A discussion of repair issues will also be presented.