We are replacing a carbon steel Amine Absorber in Hydrocracker unit with a 316L s.s clad vessel. The vessel is in wet H2S service and the design pressure is around 20,000 kPA. Am I correct in assuming that since the vessel is clad I don't have to worry about HIC testing the SA-516 Gr.70 plates used for fabrication. Also, is there any issues with hardness requirements, since the carbon steel base metal is not being exposed to the wet H2S environment, due to the cladding. The vessel will be PWHT. What kind of hardness I should accept on the 316L Cladding/weld overlay?

Yes! The design pressure fro thjese vessels is 20002 kPa, and they operate around 17,700 kPA. Hydrocracker typically is a high pressure unit and the amine absorber is in the high pressure circuit.

Ram: Re HIC testing, the need for that should be based on the type of 316SS lining. A loose lining will not promote diffusion of H+ ions into the CS base metal, a mechanically bonded lining might contribute to H+ ions in the base metal where HIC might be a potential concern. Maximum hardnesses of the 316SS cladding should not be an issue with respect to hydrogen damage. Hope this helps! David Hendrix The Hendrix Group Inc.