Pressure Balanced Expansion joint Movement

Pressure Balanced Expansion joint Movement

        The pressure thrust produced by low pressures can be tremendous in large diameter systems,just as it can be at normal pressure ratings in small pipes.To avoid expensive anchors,to keep long pipe runs in tension,to prevent buckling,or reduce reaction forces on equipment,the pressure in the pipe can be used to generate balancing forces within the expansion joint.These combinations of belows and thrust restraining structural components can accept almost any combination of movements,as shown in the following examples.

        The pressure balanced elbow is ideal for absorbing the thermal expansion of equipment,such as tubines,pumps and compressors,which reply upon low reaction forces on their inlet and exhaust flanges.In this example,only an intermediate anchor is provided at the elbow,to isolate the equipment from any forces produced in the remaining piping.The pressure thrust force produces tension on the equipment flange,but the only forces produces by the deflection, are the spring resistance of the bellows within the expansion joint.The spring rate of these units is the sum of the spring rates of the bellows on each side of the elbow,and care must be taken to provide a unit which produces spring forces low enough to satisfy the equipment maximums as stated by the equipment manufacturer.Bellows may also be cold sprung to reduce these forces even lower.