Pressure balanced expansion joints are used in the piping systems where the flow direction occurs to change counteracting the pressure thrust and absorbing axial and lateral movements..
Installation Instructions !
FIGURE 1: As depicted in the fi gure, the pressure acting on the bellow ”A” is absorbed by the bellow “B” on the same axial line. The pressure thrust applied by the internal pressure of the pipe to the expansion joint is balanced by an equal and opposite directed force transmitted by limit rods (D) connected to the blank end (C) at the side of the bellow “B”. Pressure balanced expansion joints are used mainly at the systems like turbines, etc. This type of expansion joints is a good solution to balance the forces caused by internal pressure thrust, because the forces caused by high pressure and big diameter expansion joints are also strong.
FIGURE 2: As it can be seen in the fi gure, Effective Area of the Balancing Bellows (EABB) is twice that of the Effective Area of the other two Small Bellows (EASB). At this type of pressure balanced expansion joints as the small bellows are compressed, the balancing bellow is extended. Thus the internal pressure of the expansion joint remains unchanged.
FIGURE 3: As depicted in the fi gure, pressure balanced expansion joints are placed between the intermediate anchor and the equipment, thus the thermal expansion occurring there can be absorbed. The axial movement at the system compresses the bellow (A). At the same time, internal pressure acting through limit bars elongates the bellows (B) providing a balanced system.
FIGURE 4: As it can be seen in the fi gure, pressure balanced expansion joints can absorb lateral and axial movements. Intermediate anchors and pipe alignment guides should be installed as shown in the fi gure. Here, the bellow “A” has the required capacity to absorb both the axial and lateral movements. The bellow ”B” needs only to absorb the axial movement at the horizontal pipe run.
Other Expansion Joint Installations !
AXIAL TYPE FIGURE 1: This figure shows the simplest and most basic application of an axial expansion joint. The sequence of installation steps to pay attention to follows:
- Only one expansion joint may be installed between two main anchors.
- Main anchors are located in the direction of pipeline.
- An expansion joint is located next to each main anchor.
- The fi rst pipe alignment guide is located within the distance of 4 pipe diameters next to the axial expansion joint.
- The second pipe alignment guide is located within the distance of 14 pipe diameters next to the fi rst pipe alignment guide.
- The distances between the other pipe alignment guides to be located are determined according to the Pipe Guide Spacing Chart by EJMA (Expansion Joint Manufacturers Association).
LATERAL TYPE FIGURE 1: As depicted in the fi gure, pressure thrust is compensated by using limit rods installed at lateral expansion joints and intermediate anchors are used instead of main anchors. A planer pipe guide is used providing the thermal expansion in the vertical pipe leg to be taken as natural fl exibility in the horizontal pipe run.
ANGULAR TYPE FIGURE 1: As it can be seen in the fi gure, thermal expansion in both the horizontal and vertical legs can be absorbed by using hinged expansion joints. Following points should be taken into consideration by locating expansion joints to such piping systems:
1) The distances L1 and L2 should be made the maximum possible,
2) The distance L3 should be made the minimum possible.
In order to keep offset and frictional forces affecting the expansion joints and anchors small, the hinges should be designed in the way to compensate the pressure thrust and weight of the pipe between the two expansion joints.
