The universal expansion joint consists of two bellows separated by a pipe section or spool. The primary purpose of this arrangement is to have a unit which will accept large amounts of lateral deflection. The amount of lateral deflection they can accept is a function of the amount of angulation each bellows can absorb and the distance between the bellows. For a given bellows element, the amount of lateral deflection capability can be increased or decreased by simply changing the length of the center spool. In this catalog three standard overall lengths are given with their lateral movement capability. If the piping problem requires greater capability, then the overall length can be increased to suit.

Since deflections are usually the result of piping thermal expansion, and universal expansion joints are usually long, our units are designed so that the thermal expansion of the entire unit's length is accepted as compression by the two bellows elements. In this way, the overall length of the unit does not change when the piping is heated. The standard units in this catalog have all been designed to accept the thermal expansion of their length when the temperature is up to the design temperature shown.

Universal types can be supplied with or without tie rods. Tie rods connect the ends of the unit to each other and restrain the pressure thrust load. This unit is normally not expected to accept any externally applied axial deflections. The thermal expansion of the distance between the tie rods ---within the expansion joint--- will be handled by the bellows element, as described above. The tie rods usually come in sets of two or more, equally distributed around the circumference of the expansion joint. When only two are provided, 180 degrees apart, the expansion joint is free to bend, or deflect angularly, as well as laterally. With three or more tie rods, since rods are loaded equally by the pressure thrust, only lateral deflections are possible without significant forces being applied by the adjacent piping. Without tie rods, the universal expansion joint will accept all of the deflections that a single type will, and the pipe guiding and anchoring needs discussed for the single type above also apply.

Many times the universal expansion joints will be attached directly to pipe elbows as shown below. As discussed in more detail in the Applications Section, this arrangement, because of the large lateral deflection capability, accepts the thermal expansion of relatively long runs of heated pipe. So that the distance between the elbows does not change due to thermal expansion, the tie rods can be connected to the elbows themselves. This catalog offers this type of arrangement as one of the standards, and can be seen on each of the Universal expansion joint pages, along with their dimensions and performance characteristics.