BOA Expansion Joints

The BOA Group offers a wide range of expansion joints, suitable for numerous specific applications.

According to their physical properties, most metals expand with increasing temperatures and contract with decreasing temperatures. In pipeline systems, this phenomenon causes a variation in the length of the individual sections of the pipeline. As pipelines are normally anchored at least on two connection points, any variation in length will result in thermal strain in the material and enhanced forces and moments at these terminal points. As far as possible, one will utilize the inherent flexibility of a pipeline to compensate for the pipe expansion (natural compensation). Should the expansion, however, exceed the inherent flexibility of the pipe, expansion joints are necessary to compensate these movements. Additionally, mechanical vibrations of pumps, compressors, turbines and motors should be dampened to avoid any damage to adjoining pipelines, their supports or any installed instruments. Forces and moments on nozzles of compressors, turbines, vessels and other plant components are limited and must not be exceeded. In all these cases, expansion joints can be utilized.

BOA Group Metal Expansion Joint    BOA Group Rubber Expansion Joint

The central component of each expansion joint is the metal bellows (exceptions are rubber expansion joints.) that, due to its shape and thin wall, acts as a spring. The bellows, however, have to meet the following basic criteria to qualify for its use as an expansion element:

  • withstand the operating and test conditions (pressure, temperature) of the pipe system,
  • ensure corrosion resistance against internal (flow) and external (atmospheric) conditions,
  • provide sufficient flexibility to compensate thermal expansion and mechanical vibrations with the requested durability (life expectancy)
  • include sufficient squirm stability.

Expansion joints with stainless steel bellows

We offer a wide range of expansion joints, suitable for numerous specific applications.

The BOA expansion joints portfolio basically consists of three main series:

  1. Standard series: expansion joints up to DN 150 (6″)
  2. Industrial series: expansion joints up to DN 1.000 (40″)
  3. Special series: expansion joints >DN 1.000

The heart of all expansion joints is the metal bellows. Thanks to modern design and manufacturing facilities, all BOA expansion joints offer the following advantages:

  • High flexibility
  • Short build length
  • Large movement capacity
  • Durability and excellent chemical resistance

We use almost every type of bellows forming to offer the best possible solution to its customers: Hydraulic and elastomer forming, punching as well as mechanical rolling.

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Characteristics of Expansion Joints

Axial expansion joints

These expansion joints are designed to take up axial movements in a piping system. The advantage of axial expansion joints is the fact that they take up relatively little space and no directional changes in the piping are required. When installing axial expansion joints, proper fix points and guidance are required. Please consult our engineers for more information.

BOA Group Axial Expansion Joint

We offer two ranges of axial expansion joints:

  • Standard series: (axial) expansion joints up to DN150 (6″)
  • Industrial series: expansion joints > DN150 (6″)
  • Depending on the required type, sizes in the industrial series go up to DN1.000 (40″).

Besides our standard and industrial program, we also manufacture special expansion joints according to customers’ specifications. Diameters of several meters are no exception!

Axial Expension Joints

Lateral expansion joints

A lateral expansion joint works in the same way as a hinged expansion joint does. It utilizes the ability of a bellows to rotate in an angular direction. The lateral movement capability is the result of the angular rotation of the bellows and their centre to centre distance. The longer the distance between the bellows, the larger is the movement.

BOA Group Lateral expansion joint

A longer centre to centre distance also results in lower displacement forces of the expansion joint. Lateral expansion joints are independent expansion systems in contrast to single hinged expansion joints. They are practically a two pin system. Lateral expansion joints are usually installed with a 50% pre-stressing. This is accomplished by pre-stressing the entire pipe system after the expansion joint is installed.

Lateral Expension Joints

Angular expansion joints

Angular expansion joints are used for large angular movement in one or two planes.

BOA Group Angular expansion joint

Angular (or hinged) expansion joints are used for large pipe elongations. A system of expansion joints is made of standard elements. This requires two or three expansion joints. The application of angular expansion joints always requires a change in the direction of the piping. Therefore, they are preferably located where a 90° bend has originally been foreseen. The elongation absorption of hinged expansion joint systems is practically unlimited. It is determined by the allowable movement‘s angle of the hinged expansion joints and the length of the pipe section between two angular expansion joints.


  • almost unlimited elongation absorption
  • reduced load on anchor points
  • modular concept application
  • use of normal guides

Angular Expension Joints

Rubber / PTFE expansion joints

Rubber and PTFE expansion joints are commonly used in industrial and HVAC applications.

BOA Group Rubber Expansion Joint

Typical examples are:

  • Chemical and petrochemical industry
  • HVAC installations
  • Shipbuilding
  • Piping

The main difference between rubber and PTFE expansion joints is the corrosion resistance and temperature resistance which are significantly higher with PTFE expansion joints.

BOA rubber and PTFE expansion joints are suitable for:

  • Absorption of vibrations
  • Taking up axial or lateral expansion
  • Taking up installation tolerances
  • Noise reduction

Rubber Expension Joints

How can we help you?

If you want any information or if you need any help? Just visit our online expert center. Here you find information on all our products or you can contact one of our engineers about your challenge. We will be glad to support you.

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