The application of bellows is determined by the need to avoid, stabilize or minimize the occurrence of undesirable factors resulting from environmental exposure or the service conducted and as a result of the device operation. These factors may include stress in metal, pipeline supports, etc.The main sites of application of expansion bellows are systems with liquid and vapor service operating at high pressures and high temperatures. They are widely used in power generation, chemical, petrochemical, oil, gas and other industries.
Expansion bellows are made of different types of steel: Ст3сп5, Ст20, 09Г2С, 08X18H10T, 12X18H10T, as well as titanium, molybdenum and others.
The main element of the expansion joint is the bellow. The bellow is an elastic asymmetric corrugated metal cover made of several layers of stainless metal sheet by method of hydraulic sheet rolling or with the help of a special press.
The design of the bellow allows the expansion joint under the influence of the longitudinal, lateral and angular momentum to stretch, shrink, deform in the transverse direction and to bend with considerable displacements (up to tens of centimeters and degrees), retaining tightness.
The main types of expansion bellows are:
- Axial expansion joints.
Consist of one or a pair of bellows plus low-carbon fittings. They are used in the areas with possible thermal expansion of the piping. Bellows elastically deform and absorb all the changes of pipe dimensions.
- Lateral expansion joints.
Consist of rods (guide and restraining), ropes, flanges and internal baffles. The device dampens transverse displacement to its axis, but cannot offset axial expansion and contraction.
- Angular expansion joints.
Designed for connecting non-straight pipelines and can be mounted in several planes. The task is to eliminate the possibility of changing the geometry of the pipeline as a consequence of thermal expansion and thus emerging bending moments at the pipe bend.
- Universal expansion joints.
Able to offset not only angular displacement but also a shift. Installation of piping joints of this design makes it unnecessary to install additional components that have to offset tractive force. Universal joints can provide sustained and stable positioning of the pipeline in space without the use of fastening systems.