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Engineers often specify a pressure balanced expansion joint in the piping connecting the boiler feed-pump turbine exhaust to the condenser in conventional fossil-fueled electric power generating plants. [1] Variations in operating conditions cause frequent changes in temperature, pressure and steam quality. Condensers are designed to withstand steam generator overloads without causing significant loss of electric power, but the piping system must accept the forces associated with these variations.

The major advantage of a pressure balanced joint is its ability to absorb externally imposed axial movement without imposing additional pressure loading on the system, so it should be considered when additional pressure loading is objectionable. [2] The force resulting from the bellows spring rates is not eliminated, but it is relatively small when compared to the pressure thrusts.

Examples included in the EJMA standards [2] point out the relation of the guides to the function of the anchors and guides to the function of the pressure balanced expansion. Figure below illustrates an example using a pressure balanced universal expansion joint installed at a change of direction between two anchors. The pipes are guided so expansion of both pipes is toward the joint. In this example the bellows which are components of the universal joint accommodate movement in both the horizontal and vertical directions.

[1] Sibblies, Melbourne B. "A Fundamental Guide and Reference in Designing Piping Systems". 2nd Edition, SIMBE International, New York, U.S.A. 1995.
[2] "Standards of the Expansion Joint Manufacturers Association, Inc."., Sixth Edition 1993.

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