This is the simplest assembly in family of expansion joint. It consists of a bellow element with end connections. It is used for axial movement only in pipe configurations. However, it can also absorb small amounts of other two types of basic movements viz. lateral and angular.
Unrestrained Axial expansion joint
This type of bellow, without any restraints or guides, cannot resist deflections other than those due to spring rate of the bellow elements. The pipe configurations should be adequately guided and anchored to avoid unexpected movements and proper functioning of the expansion joint.
Advantages
• Inexpensive
• Absorbs all three types of movement.
• Easy to install
• Low maintenance.
Restrained Axial Expansion joint
It inherits all the characteristics of the unrestrained expansion joint with addition of tie-rods to restrain the pressure thrust and to restrict the movement of expansion joint. The tie-rods are arranged in opposite to each other or at an interval of 90 degrees.
Advantages
• Inexpensive.
• Absorbs all three types of movement.
• Easy to install
• Low maintenance.
• Absorbs system pressure thrust.