Metallic
Metallic expansion joints are the elements designed to absorb relative movements in pipe systems transporting fluids under high pressure and/or at high temperatures. The basic element of an expansion joint is the bellows, which must be strong enough to withstand the circumferential pressure, and flexible enough to absorb the design deviations as often as necessary.
The balance between strength and flexibility is the problem which, according to the service conditions, is solved by the engineers on the basis of the bellows design (number of waves, thickness, height, number of layers, etc.) and the elasticity of the material used (AISI 304, 316, 321, 400, INCONEL, etc.).
Using special equipment for welding and deforming the metal plates, we manufacture the metallic expansion joints following the plans established for each design by our engineering department.
Our expansion joints can normally work up to 64 bars, although in special cases, using reinforcement rings, they can exceed said pressure. It is necessary to bear in mind that the pressure values will depend on the working temperature, diameter and corrugations.
Temperature affects the strength of the materials and must be taken into account when designing the resistance to wave pressure, and the thickness of the different components. Movements also depend on the temperature. Depending on the material, from -196º C to 800ºC.
The BIKAR metallic expansion joints included in our standard programme range from DN 50 to DN 2000, with the possibility of manufacturing larger sizes for special cases, with both a circular and rectangular form.
Types
Simple
This expansion joint is simply a bellows with connections at the ends.
- The most economic.
- Can absorb axial, angular and small lateral movements.
- Does not absorb the force produced by pressure.
- Must be suitably fixed and guided.
- The total installation cost may be higher than other types.
- Available with flanged or weldable ends or a combination of both.
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Lateral
This type of double joint is supplied with strap or control unit between ends. These can be a set of 2 or more units, distributed equidistantly around the circumference.
When only two are applied at 180º, the joint can absorb angular movements and warp, as well as absorbing lateral movements; but with a larger number (3 or more), only lateral movements.
This type of joint is not designed to withstand any external axial movement, but it is designed to absorb the movement generated by its length between ends.
- Absorbs large lateral movements in any direction.
- Does not require fixtures.
- Absorbs the expansion of the pipe between the ends of the straps.
- Available with flanged or weldable ends.
Universal
Consists of two bellows separated by a sleeve or spool of piping.
The main purpose of this arrangement is to absorb greater axial and lateral movements than with the simple joint.
For a given set of bellows, the capacity to absorb greater or lesser lateral movements will depend on the length of the central sleeve. If the pipe requires a large quantity of movements, the sleeve must be increased to the suitable length.
Withstands all movements, as with the simple joint, not forgetting the comments regarding fixtures.
- Absorbs large axial and lateral movements in any direction.
- Suitable for low pressure services.
- Does not absorb the force produced by pressure.
- Must be suitably fixed and guided.
- Available with flanged or weldable ends or a combination of both.
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Angular
Consists of two bellows separated by a sleeve or spool of piping. The main purpose of this arrangement is to absorb greater axial and lateral movements than with the simple joint.
For a given set of bellows, the capacity to absorb greater or lesser lateral movements will depend on the length of the central sleeve. If the pipe requires a large quantity of movements, the sleeve must be increased to the suitable length.
Withstands all movements, as with the simple joint, not forgetting the comments regarding fixtures.
- Absorbs large axial and lateral movements in any direction.
- Suitable for low pressure services.
- Does not absorb the force produced by pressure.
- Must be suitably fixed and guided.
- Available with flanged or weldable ends or a combination of both.
Spherical Angular
Basically the same as the angular type, except that instead of restricting movements to just one plane, it can withstand warping, buckling or angulations in any plane.
Contains two sets of articulations or pivots, the axis of each set being perpendicular to the other, being connected with a central gimbal ring.
This joint provides the same type of impediment and resistance to axial thrusts as to the pressure thrust.
- Permits angular movements in all planes.
- Excellent control of bellows movement.
- The articulated device contains the forces caused by pressure.
- No fixtures required.
- Bellows are protected from torsional loads.
- Can be designed to bear the weight of the pipe.
- Induces low forces in the pipeline.
- Available with flanged or welded ends.
Self-compensating
Used in applications where the space limitations rule out the use of set fixtures.
The pressure induced force acting on the bellows is balanced by the compensation bellows via a system of straps.
The only forces transmitted to the unit are the bellows deformation forces, which are generally very low.
- Absorbs axial and lateral movements.
- Restricts the thrust caused by pressure.
- Eliminates the main fixtures.
- Requires minimum guides.
Rectangular
 Rectangular expansion joints are generally made to fulfil certain specific applications.
BIKAR designs and manufactures a wide range of rectangular joints to compensate axial and lateral movements of different sections and for different service conditions.
Rectangular joints are available with four different types of corners and two basic profiles (see diagrams). |
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