Failure of reformer tube of an ammonia plant

✍ Scribed by S.K Bhaumik; R Rangaraju; M.A Parameswara; T.A Bhaskaran; M.A Venkataswamy; A.C Raghuram; R.V Krishnan

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 374 KB
• Volume: 9
• Category: Article
• ISSN: 1350-6307
• DOI: 10.1016/s1350-6307(01)00039-5

✦ Synopsis

The present article describes the failure of a primary reformer tube in an ammonia plant. The failure took place at the stub end of the reformer tube where a SS 321 flange was joined to a HK 40 catalyst tube by welding. Detailed metallurgical examinations indicated that the failure was due to stress corrosion cracking. Both longitudinal and transverse cracks were observed at the region of fracture. The cracks originated at the interface of the weld and HAZ at the inner surface and progressed to the outside of the tube in the transverse (thickness) direction. Microstructural study revealed chromium carbides precipitation at the grain boundaries in the heat affected zones on either sides of the weld. The results clearly indicated that the steel had undergone sensitisation which subsequently led to failure of the reformer tube by stress corrosion cracking.