FlexEJ Bellows Finder

A. Spring rate is the reaction force of the bellows when it is moved. It is a different force to pressure thrust – both forces act together on the piping. For technical assistance contact us or use our Live Chat facility.

A. This is a metal bellows term : ply refers to the number of sheets of metal used in the forming of the bellows, so a 2 ply bellows is made from two sheets of material. A multi ply bellows is generally more flexible that an equivalent single ply bellows. For technical assistance please contact us

A. In this field, the terminology can be confusing, often with no universally accepted meaning. We tend to use the following definitions but the terms “bellows” and “expansion joint” are typically considered as interchangeable:

> Expansion Joint – an expansion joint is a complete unit with metal bellows or rubber bellows and end fittings, plus, optionally, liner, cover and external hardware. Other terms used : compensator, flexible connector.

> Rubber Bellows – the flexible element within a rubber expansion joint

> Metal Bellows – the flexible element within a metal expansion joint

> Liner – The liner fits within the expansion joint under the metal bellows or rubber bellows to prevent the flowing media directly impinging on the bellows. This this reduces flow disturbance and allows the temperature of the bellows to be controlled in the design.

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A. A tie rod is a simple pressure thrust restraint. It will allow reasonable lateral movement but not axial extension; it can allow axial compression if the pressure thrust is overcome by the piping movement. See the movements and pressure thrust FAQs for definitions. For technical assistance please contact us or use our Live Chat facility.

A. All expansion joints exert a force, pushing the pipe ends apart – pressure thrust – which is proportional to the operating pressure and diameter of the bellows. If the expansion joint is unrestrained the piping system must withstand the force, or, alternatively, the expansion joint may have restraints built in to constrain the pressure thrust force. For instance types, tie rod, hinge or gimbal.

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A. To design or select a rubber bellows or metal expansion joint we need to know: nominal bore, end type, service, temperature, pressure and required movements. You may also specify in addition your requirements for external hardware – tie rods, hinges, gimbals – internal liner, external cover and instrumentation. Material selections should also be specified to suit the service and associated system piping. For technical assistance please contact us or use our Live Chat facility.

A. The EJMA is the Expansion Joints Manufacturers Association. Their bellows calculation method is most frequently used for metal bellows expansion joint design. EJMA does not cover rubber bellows or metal hose design. For technical assistance please contact us or use the LIVE CHAT link on this page.