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.
Classification of steel expansion joints (compensators) according to the type of displacement
Depending on the type of pipeline displacement, steel expansion joints are divided into:
- axial expansion joints, intended to absorb displacement along the axis of the pipeline and minor lateral displacement. The permissible axial movement is directly related to the number of corrugations. These expansion joints are simple and compact, with one corrugated bellow. Short built-in length and easy installation are the advantages that make these expansion joints a very popular, inexpensive choice when it comes to compensating for pipeline displacement, especially due to thermal expansion or contraction. The pipeline, though, must be secured with supports and pipe guides to carry the stress that occurs in the expansion joint.
- general purpose expansion joints, designed to absorb both axial and lateral displacement at the same time; two corrugated bellows are separated with a straight section. They do not contain any tie rods or hinges.
- lateral expansion joints, single or double bellow, intended to absorb movements perpendicular to the pipeline axis in all directions. They are equipped with expansion limiters in the form of tie rods or a set of hinges mounted to the connectors.
- angular expansion joints, intended to compensate for angular deflections, contain straight hinges (enable angular rotation in one plane – hinged angular expansion joints) or are equipped with gimbals – gimbal expansion joints (enable angular rotation in any plane).