Hinged expansion joint is a flexible device consisting of a bellows, two sets of hinged plates connected with end pipes and a pair of pin shafts. Hinged expansion joint is generally used as a group of two or three to absorb lateral displacements in one or more directions of single-plane pipe system. In such a system, each expansion joint is restricted by its hinged plate, producing a pure angular displacement, whereas each pair of hinged expansion joints separated by the tube segment cooperate to absorb transverse displacement. The angular displacement of single expansion joint is proportional to the distance between hinge pin shaft and the lateral displacement absorbed by each pair of hinge expansion joint. Therefore, in order to give full play to the application of expansion joint, the distance should be increased as far as possible.
The hinged plate of the expansion joint is usually used to withstand all the pressure thrust acting on the expansion joint, and can also be used to withstand the weight of pipes and equipment, wind load, etc.
1) figure 6 is plain noodles with double hinge system absorbs the main thermal expansion, "Z" shaped bend due to pressure thrust is the hinge on the expansion joint to bear, just in the midst of piping at both ends fixed bracket, because of the expansion joint is conditioned by hinge can produce pure angular displacement, cannot scale, containing the expansion joint in the middle of the tube must be made with its vertical thermal expansion of the arm arm bent tube to absorb, two long arms bending deflection by proper design of the guide bracket and the bracket to control.
(2) if the intermediate arm of the single-plane "Z" pipe system is too long, a system of three hinged expansion joints can be adopted. Figure 7 shows A three-hinged expansion joint system in A single-plane curved pipe. The thermal expansion of the vertical pipe segment will be absorbed by the actions of two expansion joints, B and C, while the thermal expansion of the horizontal pipe segment will be absorbed by two expansion joints, A and B. Obviously, the angular displacement of expansion joint B is the sum of A and C.
Like the previous example, in the middle of the pipe ends only fixed bracket to fixed, in this case, all of the thermal deformation is absorbed by expansion joint, due to the thermal deformation of the pipeline on the fixed bracket of the load is very small, if the fixed bracket and the first on the left of the hinged expansion joint spacing is bigger, the guide bracket shall be set up near the expansion joint, the bracket to bear the force of expansion joint rotation, thus reducing the expansion joint between C and on the left side of the fixed bracket part of pipe bending, in order to keep the piping system is located in the plane, and eliminate potential produced by external load ACTS on the hinge of the bending force, could add one or more of the guide bracket, The support of the pipe system can be adopted in a variety of ways. When the pipe between expansion joints is supported without impeding its free movement, the spring support hanger can be adopted.
3) FIG. 8 is an example of using hinged expansion joint when bend Angle is not equal to 90°.
Hinged expansion joint's main advantage is its compact size, easy to install, and can make its stiffness and strength of the hinge plate was so great that can use them usually irregular topography of compensation for the thermal expansion of the complex pipeline, and use other expansion joint on the pipeline often doesn't work, because the hinge structure can load, hinged expansion joint of the pipe is applied to the reaction between the fixed bracket is very small, this system can not get in the way of system activity in the support of any position, it gives the design of the system has brought a lot of freedom.
