Steel expansion joints
Steel expansion joints – general information
Steel compensators are composed of one or several multilayer, corrugated steel bellows and appropriate connections such as flanged, weld-in or other connections. To form the bellow, a couple of adjacent sheet metal layers is shaped into corrugations. A single stainless steel sheet metal piece is e.g. from 0,2 to 0,5 mm thick. This multilayer design of the bellow ensures much higher flexibility than the single layer design with the same overall thickness and height of corrugations – as, for instance, in the case of corrugated steel hoses. Therefore, the corrugated steel hose cannot substitute the compensator – it cannot accommodate comparable deformation with the same flexibility.
The steel compensators are available with an internal steel sleeve to guide the fluid flow. The bellows and internal sleeves are made of the following types of steel: 1.4541 (AISI 321), 1.4571 (AISI316Ti) and other. Flanges and connecting parts are made of carbon steel, stainless steel, acid-resistant steel and other materials. Working temperature range: from -270°C to 600°C. Working pressure: from full vacuum up to several tens of bar. Nominal diameter range: from DN40 to DN6000.
SaniComp compensators are far more effective in absorbing displacement than U-shaped pipelines used in some cases. They are essentially designed for sanitary installations, where hygiene plays an important role. SaniComp compensators are certified by EHEDG – European Hygienic Engineering Group (SaniComp compensators can be applied in utility installations all across Europe). Working temperature up to 200°C (80°C as standard).
Chamber expansion joints is comprised of two bellows in one inside the other configuration: inner bellow – of smaller diameter and outer bellow – of bigger diameter. A chamber formed between them allows for circulation of the heating agent of higher temperature (e.g. oil, water, steam), which heats up the inner bellow conveying the proper medium.
Compensator type:
Steel expansion joint axial
Steel expansion joint axial
Steel expansion joint angular
Type of compensator:
Steel expansion joint flanged fixed
Steel expansion joint flanged swivel
Steel expansion joint weld-in
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FAQ – Steel expansion joints
Steel expansion joints come in countless design and material options, so they can operate at feasible operating parameters reaching very high values.
When the expansion joints with multi-layer bellows are used, their working pressure may exceed 100 bar, depending on the expansion joint diameter.
The same applies to the working temperature, which can even reach values close to +1000°C when certain materials are used, for example, Inconel alloys.
Depending on their design, steel expansion joints can accommodate movement in several directions:
| axial | lateral | angular |
 |  |  |
| along the axis of an expansion joint: compression or extension | perpendicular to the longitudinal axis of an expansion joint | displacing an expansion joint angularly from its longitudinal axis |
Obviously, in the actual operating conditions of a system, the real directions of displacement to which an expansion joint is exposed to may be a combination of these above-mentioned basic directions.
Steel expansion joints can be made from a variety of steel alloys, depending on the conditions (pressure, temperature) in which they will operate and the type of medium that will flow through them.
The working components of the expansion joints, i.e. bellows, are usually made of standard stainless steel and acid-resistant steel: 1.4541(ASI321), 1.4404(AISI316L), 1.4571(AISI316Ti) or 1.4301(AISI304). The other components of the expansion joints, including pipe stubs, flange connectors, tie rods and other accessories, can be made both from the same steels as above and different types of carbon steel alloys, suitable for the conditions in which the expansion joint works.
An extra layer of zinc plating or anti-corrosive paints can be applied on expansion joint components made of carbon steel.
The compensators designed to operate at high temperatures (e.g. above +500°C) are made of alloys with increased temperature resistance, e.g. 1.4828(AISI309), 2.4816/INCONEL 600 or 2.4856/INCONEL 625.
Apart from that, the compensators or just some of their components exposed to the mechanical action of the medium, e.g. abrasion, are often made of alloys, such as Hardox offering increased resistance to this damaging impact.
The bellow of a steel expansion joint can be made as both multi-layer (most common) and single-layer (less common).
The number of layers in a steel bellow depends on the parameters of the expansion joint, which include design pressure, temperature and value of design displacement.
The multi-layer bellows can have from 2 up to 10 layers.
The thickness of a single bellow layer is from 0.2 mm up to several millimetres.