Simply, a double gimbal expansion joint is consisted of two single gimbalexpansion joints and an intermediate pipe con- nects them each other. The advantage of this arrangement is the ability to absorb a large lateral movement in any plane at each end.
The double expansion joint is comprised of two individual joints that are joined together with the use of what is referred to as the common connector. The common connector is anchored to a certain part of the structure that is typically very rigid with respect to the anchor support base. They are also available with or without the anchor support base, which usually depends on what the customer prefers. In any case you’ll find a need to use the double expansion joint whenever the actual movement that needs to be absorbed is too big to be supported by use of the single expansion joint.
The anchor that appears on the center of the nipple, which is referred to as the intermediate anchor, creates a divide to the movement, which causes each of the bellows within the double joint to absorb its proper proportion of the movement.
You’ll also find that the double expansion joints are normally located in the middle of the pipe run, whereby each of the ends is exposed to the same level of movement – and each having the same amount of corrugations.