Diagram H displays the use of a pressure balanced Expansion Joint to absorb the thermal expansion of equipment such as turbines & compressors. The Expansion Joint is used primarily to minimize loading upon the equipment casing. Take note that only an intermediate anchor is required at the change of piping direction. However, no guiding is necessary if the Expansion Joint is located immediately adjacent to the machine.
Extra care & effort must be taken to provide sufficient flexibility in both the flow bellows and the balancing bellows to ensure that the forces required to compress the Expansion Joint do not exceed loading limits for the equipment as established by the equipment manufacturer.

The selection and proper application of Expansion Joints for lateral deflection, angular rotation and combined movements is dependent on a number of considerations, which includes load limitations upon piping and equipment, the surrounding conditions, the piping configuration, the targetted cyclic life, and available supporting structure etc. There will also be cases where two or more types of Expansion Joints are required for a particular application. In this case, the selection then becomes purely an economic one. Often, one or the other of the available designs will carry certain unique characteristics which make it particularly suitable for a given application.

Single Expansion Joints
The Single Expansion Joint is considered first for any application mainly because of its low cost. Diagram I shows the application of a single Expansion Joint absorbing combined axial movement and lateral deflection. The system closely follows the arrangements shown for axial movement only in the preceding section. The Expansion Joint is located at one end of the long piping control and protection of the piping against buckling. The anchor at the left end of the line is a directional main anchor (DMA). The anchor permits thermal expansion of the short piping leg to act upon the Expansion Joint as lateral deflection while it absorbs the main anchor loading in the direction of the Expansion Joint axis. The anchor at the end of the shorter piping leg is an intermediate anchor as this main anchor loading exists only in the piping segment containing the expansion joint.

Diagram J displays an alternative arrangement where the Expansion Joint is installed in the short piping leg and the principal expansion is absorbed as lateral deflection. The longer the piping length is free of compressive pressure loading requires only an intermediate anchor and directional guiding. The functions of the directional main anchor and the pipe guide can combined in a single device.

Diagram K & L illustrates modifications on Diagram J where the main anchors at either end of the Expansion Joint are replaced by tie rods. When applicable, the use of tie rods adjusted to prevent axial movement usually eases installation and lowers cost. However, because of these tie rods, the Expansion Joint is unable of absorbing any axial movement other than its own thermal expansion. As a result, the deflection of the piping in the shorter leg imposes deflection on the longer piping leg. In cases where the longer piping leg is not sufficiently flexible or where the shorter leg is dimensionally unsuitable, tie rods can be installed spanning the entire short leg to ensure no deflection is imposed.

Shortening of the Expansion Joint can result from the displacement of the tie rods when certain amounts of lateral deflection are imposed upon the Expansion Joints (as shown in Diagram K). Extra effort and care must be taken to ensure that sufficient piping flexibility exists to absorb this deflection of the piping. Minimizing the amount of this deflection is possible by cold springing the Expansion Joint in the lateral direction.

The limited amout of lateral deflection which such an Expansion Joint can absorb is the main restriction upon the use of single Expansion Joints for lateral deflection or combined axial movement and lateral deflection. The allowable lateral deflection is directly proportional to the ratio of convoluted length to diameter which, in turn, is restricted by considerations of stability and manufacturing limitations.

Universal Expansion Joints
The universal Expansion Joint is ideal for the absorption of lateral deflection. This design may also be used to absorb axial movement, angular rotation or any combination of the three. Using the universal Expansion Joint is its use as a tied Expansion Joint in a 90 degree piping offset with the tie rods adjusted to prevent external axial movement is one of the most typical application used.

Diagram M illustrates a tied universal Expansion Joint being used to absorb lateral deflection in a single plane Z bend. Where dimensionally feasible, the Expansion Joint is designed to fill the entire offset leg to ensure that its expansion is absorbed within the tie rods as axial movement. The tie rod should also be extended to the elbow center line whenever practical. The thermal movement of the horizontal lines is absorbed as lateral deflection by the Expansion Joint.

Since the pressure loading is absorbed by the tie-rods, both anchors are considered intermediate anchors. As the compressive load on the pipe consists only of the force necessary to deflect the Expansion Joint, only directional guiding is needed. Any thermal expansion of the offset leg external to the tie-rods, i.e. the elbows at either end, must be absorbed by bending of the horizontal pipe legs. Considerations must be taken in the design of the guides to allow for both this deflection and the reduced length of the Expansion Joint in its deflected position. For long universal Expansion Joints under high pressure particularly, additional allowance might be necessary to compensate for stretching of the tie rods under load. Consulting the Expansion Joint manufacturer for recommended minimum guide clearances is strongly advised.

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