Md Jewel Rana
Mechanical
- Nov 17, 2024
- 1
Recently, our plant experienced a shutdown due to a leakage in the waste heat boiler inlet line, where converted ammonia gas passes through. The nozzle material is 2¼ Cr, and the inlet material is 800HT. Upon inspection, a crack was found in the buttering layer on the 2¼ Cr side, caused by disbonding of the metal. The entire buttering layer was cut in three stages. After the first stage of cutting, De hydrogenation (DHT) was applied before the first repair welding at the first stage cut portion. However, after the second stage of cutting, no DHT was applied before welding. Why was DHT not applied before welding after the second cut?