Metallic Expansion Bellow Types


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Single Bellows  Assembly

The simplest type of expansion joint consists of a single bellows element welded to end fittings, normally flange or pipe ends. The single bellows can absorb small amounts of axial, lateral and angular movement with ease, but adequate anchors and guides must be provided.



Universal Expansion Joint Assembly

This assembly consists of two bellows connected by a center spool piece with flange or pipe ends. The universal arrangement allows greater axial, lateral and angular movements than a Single Bellows Assembly. Increasing the center spool length produces increased movement capability. Like for the single Bellows adequate anchors and guides must be provided.



Hinged  Bellows Assembly

When a Hinged Expansion Joint is used, movement is limited to angulations in one plane. Hinged Assemblies are normally used in sets of two or three to absorb large amounts of expansion in high pressure piping systems. Only low spring forces are transmitted to the equipment. The hinge hardware is designed to carry the pressure thrust of the system, and often is used to combat torsional movement in a piping system. Slotted hinged Expansion Joints are a variant of the standard Hinged Expansion Joints that allow axial and angular movement. Be careful; once a slotted Hinge is introduced, torsion in the piping system is still resisted but the hinge no longer carries pressure thrust.



Gimbal Bellows Assembly

The gimbal restraint is designed to absorb system pressure thrust and torsional twist while allowing angulation in any plane. Gimbal Assemblies, When used in pairs or with a single hinged unit, have the advantage of absorbing movements in multi-planer piping systems. The gimbal works the same as an automobile's universal drive shaft.



Externally Pressurized Assembly

Line pressure acts externally on the bellows by means of a pressure chamber, This allows a greater number of convolutions to be used for large axial movements, without fear of bellows instability. Externally pressurized expansion joints have the added benefit of self-draining convolutions if standing media is a concern. Anchors and guides are an essential part of a good installation.



Pressure Balanced Elbow Assembly

These assemblies are used in applications where space limitations preclude the use of main anchors. Pressure thrust acting on the line bellows (bellows in the media flow) is equalized by the balancing bellows through a system of tie rods linkages. The only forces created by the axial, lateral, or angular movements. An elbow must be present in the piping network to install this style of expansion joint.



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General Information
Operating Principle
Metallic Expansion Bellow Types
Metallic Expansion Bellow Accessories
Installation Instructions
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