An Inline pressure balance expansion joint is designed to absorb axial, lateral and angular deflection, while restraining the pressure thrust exerted by the internal pressure and without a change in direction of the piping. The pressure thrust is restrained by the tie rods arrangement, which connects the line bellows and the balancing bellows. It is a constant volume system, so the Main Anchors can be designed as intermediate anchors, and function only to direct the thermal expansion of the pipe towards the expansion joint.
An Inline Pressure Balance expansion joint consist of two line bellows and a balancing bellow having effective area twice than that of line bellows. The line bellows absorb the axial and/or lateral movement while restraining the pressure thrust by the means of the tie devices interconnecting the balancing bellow, which is also subjected to the line pressure. Each bellows are designed to absorb the axial movement while the line bellows are designed to absorb the lateral deflections also.
Operation: The effective area of the balancing bellow is twice that of the line bellows. The thermal expansion causes the line bellows to compress and due to the tie rods assembly the balancing bellows is extended and vice-versa. As a result, the volume contained at any instant in the expansion joint remains constant. So the forces, exerted on the pipe anchors or the attached equipments is eliminated. Thus, these types of expansion joints are used in straight runs of pipe connecting two load sensitive equipments, where main anchoring is not practical or pressure thrust loads are too high.