Angular expansion joints allow angular movements only, contrary to axial expansion joints which elongate and compress in the pipeline axis. The angular expansion joints move in an angular rotation in one or several planes, controlled by a pair of hinges or a gimbal. The angular expansion joints are as standard delivered with either hinges or gimbals, and can be manufactured with any end connections such as welding ends, welded flanges, or loose flanges or combinations thereof, depending on client requirements.
DIMENSIONS OF ANGULAR EXPANSION JOINTS
Belman designs and manufactures a wide range of angular expansion joints.
As customised solutions angular expansion joints are available in all sizes up to DN 12.000, all designs and all materials.
As standard solutions angular expansion joints are available in size range DN 50 – 2200.
TYPES OF ANGULAR EXPANSION JOINTS
Comprehensive technical data and selection criteria for +3500 standard metallic expansion joints.
CUSTOMISED ANGULAR EXPANSION JOINTS
TECHNICAL DESCRIPTION OF ANGULAR EXPANSION JOINTS
Hinged angular expansion joints
Hinged angular expansion joints are equipped with hinges, to absorb angular movement/rotation in one plane only. The hinges are designed to resist the pressure thrust from the pipe system. Single hinged angular expansion joints are generally used in pairs or threes with a connecting pipe system between, and widely used in irregular and complex pipe systems.
Gimbal angular expansion joints
Gimbal angular expansion joints are designed to absorb angular movements in several planes without transferring pressure thrust on to the fix points. A gimbal expansion joint is more flexible than a hinged expansion joint as the gimbal enables multiple angular rotations.
Angular expansion joints in general
Angular expansion joints offer a wide range of options, and when built into two or three pinned pipe systems, they can accommodate very large movements with very low reaction forces, without the need for fix points and structures. As angular expansion joints are fully restrained, they require only inexpensive guides or intermediate guides. This gives an economic advantage in large diameter, hot piping systems, even if the movements are complex and in several planes. Further, the hinges or gimbal can be designed to support the dead weight loads from the adjacent pipes and connected equipment, and to carry wind loads, snow loads, and any other external loads from the pipe system, minimizing the need for fix points and structures.
The hinge can also be designed to eliminate torsion forces acting on the bellow. The bellow does not allow any torsion, and this should be counteracted against in all cases. When the angular expansion joints are installed in two hinged or three hinged systems, the distance/intermediate pipe between each unit should be as large as possible, as this allow maximum lateral deflection or movement to be absorbed. If the thermal growth of the intermediate pipe is significant, a three hinged system is required.
Angular movement is an angular/rotational displacement of the expansion joint where its longitudinal axis is displaced as an arc from its initial position. This is to be understood as an angulation of the expansion joints two end planes relative to each other, which results in the longitudinal centerline becoming an arc, like a pipe bend. The convolutions are uniformly compressed along the inside of the bellows longitudinal centerline, and uniformly elongated along the outer radius of the arc. Torsion or twisting of one end with respect to the other end about its longitudinal axis, and is not to be understood as angular rotation.
Angular movement is shown as AN and stated in degrees. Angular rotation is indicated as negative (-) and positive (+) respectively.
Angular movement positive +5 and negative -10 will be stated as: AN +5/-10°. An equal angular rotation over the bellows longitudinal centerline are stated as AN +/-10° (2αN).
ADVANTAGES & REQUIREMENTS
What are the advantages of using Angular expansion joints?
- Absorb angular movements in single or multi plane
- Use of normal guides
- Reduced loads on all fix points
What are the requirements for using Angular expansion joints?
- Changes in flow direction/pipe direction is required
- More space consuming than axial expansion joints
- Two or three expansion joints are required for a system
PIPE WORK GUIDELINES
Hinges in a system
Hinged angular expansion joints can, in sets of two or three, be used for absorbing large lateral and axial movements. In general, there should not be more than three angular expansion joints installed between two fix points, of which a maximum of two can be gimbal angular expansion joints.
Two gimbals in a three-dimensional system
Just as hinged angular expansion joints offer great advantages in single plane applications, gimbal angular expansion joints are designed to deliver similar benefits in multi-plane systems. The gimbal angular expansion joints ability to absorb angular rotation in any plane is most frequently achieved by utilising two such units to absorb lateral deflection. An application of this type is shown in the illustration. Since the pressure loading is absorbed by the gimbal structure, fix points only are provided. Guides are provided to restrict the movement of each piping leg. As in the case of hinged angular expansion joints, the location of pipe supports is simplified by the load carrying ability of the gimbal structure. Since, in a two gimbal system, the growth of the vertical pipe leg will be absorbed by bending of the longer legs, spring supports (SP) may be required on either or both of these. Guides must be designed to allow for the thermal expansion of the leg containing the expansion joints and for the shortening of this leg due to deflection.
Angular Expansion Joints (Gimbal)
Angular Expansion Joints (Gimbal)