As the name suggests, a hinged expansion joint has a bellows, can be unbalanced or self-balancing, and is designed to allow angular rotation in only one plane through the use of a pair of hinges attached to the ends of the expansion joint. The hinge pins have a common axis that is perpendicular to the longitudinal centerline of the bellows and is located exactly in the center of the length of the bellows. The hinge must be designed to withstand full compression thrust loads as well as any other external forces that will be applied, such as the weight of the pipe, wind loads, deflection forces, etc. Hinged expansion joints should be used in pairs or groups of three to work properly.
The use of hinged expansion joints not only reduces the thrust loads imposed on the anchor, but also allows the anchor to be installed in a more favorable location. However, their use does not eliminate the need to install enough alignment rails.
Swing expansion joint:
A swing expansion joint is a modification of an articulated expansion joint in which two bellows are connected to a common center joint, and the outboard ends of the assembly are joined together by hinge pins connected to two swing rods at the ends. This type of unit Designed to absorb lateral deflection and/or limited angular rotation in only one plane.