Abstract: Leakage on the welded joint of tube to tubesheet occurs due to cracking in high pressure tube bundle with plug header of carbon steel air-cooled heat exchanger in wet H₂S service in refinery. Aiming at such problem, this paper carried out research and analysis in terms of material selection, tube joint hardness, welding process, post-welding heat treatment and so forth by combining the structural characteristics of the tubes and tube boxes of plug-channel air cooler. The analysis concluded that the hardness of the welded joint exceeding the standard was the main cause of cracking.In view of the above reasons, the paper proposed more practical and reliable recommended requirement to prevent wet H₂S stress corrosion cracking on the welded joint of tube to tube and the recommended requirement was implemented in enterprises. This has achieved good results.

Key words: air-cooled heat exchanger, welded joint of tube and tubesheet, wet H₂S environment, stress corrosion cracking/SCC, heat affect zone/HAZ, cooling time t_8/5