Failure analysis of process gas boiler tubes

Samples from the failed process gas boiler tubes of hydrogen-2 unit were sent to the laboratory for analyzing the cause of failure. Examination revealed that the boiler tubes have failed by pitting corrosion. The reason for pitting corrosion was identified to be high concentration of KOH in the process gas. Analysis suggests that the source of excess K in the process gas was the catalyst that was used for reforming naphtha. A failure in the elbow flange of the boiler feed water preheater was investigated in this laboratory in the year 2004 wherein the process gas contained excess amount of KOH due to failure in the catalyst beds (refer NAL report No. MT-FA-871-09-2004). The present failure of the boiler tubes appears to have caused due to similar reasons