Abstract: Cracking of weldments between short pigtails and inlet manifold in a steam methane reformer were investigated utilizing different characterizing techniques including optical light microscopy, scanning electron microscopy, chemical analysis techniques, and FEA, to determine the failure mechanism, and contributing factors. The investigation showed that the weldments failure is attributed to stress relaxation cracking, which, surprisingly, happened after about 20 years of operation. Finite element analysis has been performed to find a load condition that could explain the cracking at the observed location. Metallurgical evaluations of similar un-failed weldments show the HAZ of the failed weldments to have a lower degree of grain refinement, which may contributed to the failure. Practical corrective actions were suggested in order to avoid reoccurrence of similar failures.
Authors: Abdulmohsen Al-Sahli, Gys van Zyl, and Abdulaziz Al-Meshari
Keywords: Stress Relaxation Cracking, Weldment, HAZ, FEA, Reformer