PRO231 single arch (or PRO232 double, PRO233 triple arch) are traditional, hand built, spool type expansion joints that can be customized for a wide range of dimensions, lengths, and heavier materials (available in sizes 1" through 12"). They are commonly seen in more industrial applications such as mining, power, petrochemical, refining, or for slurry. They have 'fixed' rubber flanges built into the joint, so they do not provide as much flexibility when assembling compared to other joints due to possible misalignment of mating flange holes. If light material buildup is a concern, it is better to use the PRO271- wide arch model. When there are 20% or more solids/abrasives being conveyed in the pipe system, to limit internal wear (but less movement), PRO231 can be requested with a 'filled arch' (PROFA230) or towards a rubber pipe (PRO310). The PRO231/232/233 are available in various rubber compounds depending on the media, temperature, etc.; EPDM tube and cover (suffix EE), Neoprene tube and cover (suffix NN), Neoprene cover/Nitrile Tube (NP), Neoprene cover/Natural Rubber Tube (NR), Neoprene cover/Gum Rubber tube (NG), Chlorobutyl (BB), and food grade tubes. We also offer them in jump sizes in order to mate different flange sizes. They are available in sizes 2"-1" up to 18"-12", and in either standard concentric (PRORC231-) or eccentric plane (PRORE231-).