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Metallic Expansion Joints

Restrained Metallic Expansion Joints

  • Single Tied Pump Connectors
  • Double Tied Lateral
  • Single and Double Hinged
  • Single and Double Gimbal
  • In-Line and Elbow Pressure Balanced

Restrained metallic expansion joints are recognisable by the inclusion of some form of external steelwork or structure, typically taking the form of hinges, gimbal (or cardan) rings or tie-rod assemblies.

These structures form an integral part of the expansion joint design, both in terms of movement capacity and pressure containment, and ensure that when pressurised during operation, only minimal loads and forces are transferred to adjacent pipework, nozzle connections and equipment, thus allowing the use of relatively light system anchors.

Restrained metallic expansion joints can perform multi-plane movement, typically operating where there is a requirement for either lateral travel or angulation, although some restrained metallic expansion joints can also allow axial travel. In many cases, two or three joints are used in combination to create a two, or three pin hinge system.

Unrestrained Metallic Expansion Joints

  • Single Axial
  • Double Axial (often referred to as a 'Universal' Expansion Joint)

A single axial expansion joint is characterised by a single bank of convolutions and typically with flanged or schedule pipe end connections, although we can accommodate pretty well any termination requirement. Although single axial expansion joints can accommodate a relatively small amount of lateral and angulation movements, they are predominantly utilised in systems where only axial compression and/or extension are required.

A double axial expansion joint is recognisable by two banks of convolutions connected by a central pipe section or spool. Although these joints can accommodate both axial and angulation movements, they are predominantly installed where appreciable amounts of lateral, or sideways travel, are required.

Although unrestrained joints can be found in higher pressure applications, such as heat exchangers and process pipework, they are more commonly found in lower pressure environments, such as exhaust manifolds, flue gas systems, or in building services carrying LTHW, steam and condensate in relatively small diameter pipework.

Particularly relevant to long straight runs of pipework, when pressurised, unrestrained metallic expansion joints transfer forces onto adjacent pipework, plant items and equipment through what is known as ‘pressure thrust force’, which is a function of internal pressure multiplied by the effective area of the expansion joint convolutions, or membrane as it is commonly referred to.

In such cases, care should be taken to ensure that suitable termination anchors are installed to overcome the effects of pressure thrust force on the wider system.

Specifications and Build Options


25mm – 3000mm DN


To suit application

Movement Type

Axial, lateral or Angular, movement capacity specified prior to purchase

Typical Flow Media

Exhaust Gas
Flue Systems
Process Gasses
Water, Steam, Condensate
Waste Water

Membrane Materials of Construction

Austenitic & Martensitic 300 series stainless steels

Inconel, Incoloy, Monel, Hastelloy and other exotic alloys available

End Fittings

Flanges: Carbon and stainless steels in standards BS10, BS EN10912 PN series, ANSI, JIS (other materials and non-standard drilling patterns as required, square flanges and other profile shapes available on request, please contact us to discuss)

Pipe-Ends: Plain Schedule pipe-ends in carbon or stainless steel with squared, butt-weld prep or screwed end finish

Other end fitting options are available on request, please contact us to discuss

Operating Temperatures and Pressures

Our products operate in a wide variety of environments where temperatures vary between Cryogenic applications to high temperature exhaust at ~1000 Degrees C. Similarly, pressure requirements can vary right through from full vacuum to significant positive pressures. Please contact us to discuss your requirements and our engineers can advise on the best solution for your application.

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