Expansion joints connect two fixed assemblies or pipes and allow movement due to service load, shock, or thermal cycles. They are made of elastomer, fabric or metal materials and feature a bellows-style construction. Convolutions permit misalignment, movement or isolation of the components that are joined together. Expansion joints can have a round, square, or rectangular cross-section. Rounded products often have a neck or collar that permits attachment with a hose clamp. Expansion joints with a flanged end usually attach to components with screws or bolts. Some expansion joints are used in plumbing or piping applications. Others are designed for vacuum or process-gas systems in which vacuum flanges and fittings connect runs of pipes or tubes to other sections of pipes or tubes, as well as to hoses, valves, pumps, chambers and vacuum components. Expansion joints for electrical conduits are also available.
Size is an important parameter when specifying expansion joints. Shape, application, and units of measure are related considerations. For round expansion joints, enter the size as the diameter. For square or rectangular expansion joints, enter the size as the width. Do not, however, use the diameter or width for plumbing or piping applications. Instead, use the standard pipe-size options. In terms of scale, expansion joints can use English or metric units of measure. English products are measured in inches (in.) or fractions of inches. Metric products are measured in millimeters (mm). English pipe and electrical conduit sizes include: 1/8 in., 1/4 in., 3/8 in., 1/2 in., 3/4 in., 1 in., 1 1/4 in., 1 1/2 in., 2 in., 2 1/2 in., 3 in., 3 1/2 in., 4 in., 5 in., 6 in., 8 in., 10 in., 12 in., 14 in., 16 in., 18 in., 20 in., 22 in., 24 in., 26 in., 28 in., 30 in., 32 in., 34 in., and 36 in. English sizes that are less than or greater than 36 in. are also available. Metric pipe sizes are specified by range and include: 10 mm – 20 mm, 20 mm – 30 mm, 30 mm – 40 mm, 40 mm – 50 mm, 50 mm – 100 mm, 100 mm – 200 mm, 200 mm – 500 mm, and 500 mm – 1000 mm. Metric pipe sizes that are less than 10 mm or greater than 1000 mm are also available.