Heat treating, vessel shell

Larger clean-steam generator designs typically employ a pressure vessel (shell) containing a U-shaped tube bundle. The heat source is primary steam supplied to the shell side (which may be amine treated), and secondary clean steam is generated within the tubes. 

DOT specification TC/MC-331 prescribes fabrication from steel under Section VIII of the AS ME Boiler and Pressure Vessel Code, and a minimum design pressure of 265 psig (1830 kPa) is required [14]. Steel of a thickness less than 3/16 inch (4.8 mm) must not be used for the shell, heads, or protective housings. Each cargo tank used for ammonia must be post-weld heat treated. The post-weld heat treatment must be performed as prescribed by the ASME Code. See 49 CFR 178.337-1, (f) [9]. 

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