Pressure balanced expansion joints are designed to absorb movements from a pipe system. They can accommodate axial and lateral movements where anchoring of the pipe system is difficult or impractical due to structural or economic considerations. Pressure balanced expansion joints do not transfer the internal pressure thrust on to the fix points, adjacent equipment, or structures. Fix points are usually not required, only guides can ensure the turning of thermal expansion into a controlled movement.
Therefore, pressure balanced expansion joints can offer signiﬁcant advantages, where pipe systems are connected with turbines, pumps, valves or other equipment, that are unable to withstand pressure thrust loads.
Although pressure balanced expansion joints eliminate pressure thrust, it’s important to note that the existing load on the surrounding equipment is the total sum of the spring rates of both the flow bellows and balancing bellows. The movement absorbed by a pressure balanced expansion joint should be understood as follows:
If the thermal movement in the connected pipe is 20 mm, the flow bellows of the pressure balanced unit will contract by 20 mm and the balancing bellows, with twice the effective area of the flow bellows, will expand by 20 mm.
Pressure balanced expansion joints can be designed to any speciﬁc requirement with tie rods, with cover, and also for the absorption of lateral and or angular movements (universal type).