Expansion joints are used in piping systems to absorb thermal expansion where the use of expansion loops is undesirable or impractical. Expansion joints are available in slip, ball, metal bellows, and rubber bellows configurations.
Slip-type expansion joints (Fig. 1) have a sleeve that telescopes into the body. Leakage is controlled by packing located between the sleeve and the body. Leakage is minimal and can be near zero in many applications. A completely leak-free seal cannot be ensured; thus these expansion joints are ruled out where zero leakage is required.