Elbow Pressure Balanced Expansion Joints
An Elbow Pressure Balanced Expansion Joint is designed to absorb externally imposed axial movement without imposing pressure loading on the system. This is accomplished by using two bellows both at line pressure tied together and acting in opposite directions. It is used where pressure loading on piping or equipment is not acceptable.
To move the joint itself is not balanced. Both the flow bellows and balancing bellows must be compressed or elongated in operation and the combined axial spring force acts on the piping or equipment. Since the forces needed to move the bellows of these joints are of low magnitude these are usually not objectionable.
These expansion joints are usually installed at change of direction. They may also be designed for in line operation. In case of single Elbow joints when it is subjected to both axial and lateral movements both the anchors at the end of the piping run and the one on the machine are intermediate anchors and only directional guiding is required. By proper design the guide directly above the equipment can be made to absorb the axial movement forces of the expansion joint without imposing these on the equipment. The only force imposed on the equipment is the force which is required to deflect the expansion joint.