Shells up to 24-in. OD are fabricated from pipe using standard pipe nominal diameters. Standard pipe diameters and wall thicknesses are given in Volume 1, Tables 9-5 and 9-9 (1st edition: 9-4 and 9-7), Shells
larger than 24-in. in diameter are fabricated by rolling steel plate. The wall thickness of the pipe or plate used for the shell is normally determined from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, TEMA standards also specify some minimum wall thicknesses for the shell.
