Angular bellows expansion joints

Design features of angular bellows expansion joints

Main element of the angular bellows expansion joint, which ensures its functioning, is a bellows welded to the connecting fittings, which, in turn, are connected to each other on both sides by limiting fittings representing a hinged structure.

Hinged design of the limiting fittings, the axis of rotation of which is located in the middle of the bellows, does not allow the expansion joint length change (lengthening, shortening) and allows the bellows to only bend its axis relative to the axis of hinge rotation to one or another side within the elastic deformation of the bellows material.

Specific feature of angular bellows expansion joints is that they only take up angular (rotary, bending) deformations. Limiting fittings connected with the connecting branch pieces take up the separating forces arising from the action of internal pressure on the bellows corrugation walls, as well as loads arising in pipeline systems at thermal deformations, and do not transfer them to the fixed supports and equipment.

The connecting fittings of angular bellows expansion joints can be made in the form of welded neck branch pieces for welding to the pipeline, in the form of flanges, and in combined form: from one end of the expansion joints there is a welded neck branch pipe for welding to the pipeline, and from the other one - a flange.

Angular bellows expansion joints may be equipped with inner guide branch pieces and outer protective casings.

Depending on type of the applied limiting fittings, angular bellows expansion joints may be manufactured as single-plane, taking up angular displacements in only one plane, and spatial (cardan), taking up angular displacements in all directions.

Kompensator SPE, JSC manufactures the following types of angular bellows expansion joints:

single-plane angular bellows expansion joints with welded neck branch pieces, type POPN (ПОПН);
single-plane angular bellows expansion joints with inner guide branch piece and welded neck branch pieces, type POPG (ПОПГ);
single-plane angular bellows expansion joints, type POFN (ПОФН), with flanges.

Angular bellows expansion joints type POFN (ПОФН) and POPN (ПОПН) can be installed directly in pipelines carrying water (delivery and drinking water) under a temperature of up to 150 °С and at a flow rate of up to 8 m/s, oil and oil products under a temperature of up to 450 °С and at a flow rate of up to 8 m/s, as well as steam and gaseous media that do not corrode materials of the expansion joint under a temperature of up to 500 °C and at a flow rate of up to 20 m/s.

Angular bellows expansion joints type POPG (ПОПГ) can be installed directly in pipelines carrying water (delivery and drinking water) under a temperature of up to 150 °С and at a flow rate exceeding 8 m/s, oil and oil products under a temperature of up to 450 °С and at a flow rate exceeding 8 m/s, as well as steam and gaseous media that do not corrode materials of the expansion joint under a temperature of up to 500 °C and at a flow rate up to 80 m/s.

Application of angular bellows expansion joints

Since angular bellows expansion joints take up only angular deformations, to compensate for deformations of the pipeline section, two, and in some cases, a system of three angular expansion joints shall be used to compensate them, providing total compensation for almost any values of lateral displacements of the pipeline system by increasing the length of the straight pipeline section between the angular bellows expansion joints.

It is recommended to install them next to natural (defined by location of the pipeline) turns. Use of angular bellows expansion joints allows to solve the problem of compensation for thermal, dynamic and vibration loads arising in the pipeline, without transferring the separating force to the fixed supports and equipment.

When designing the pipelines using the angular bellows expansion joints, the magnitude of the expansion joint displacement moment shall be taken into account. Displacement moment is the moment of forces applied to one of the expansion joint ends when it is turned through an angle equal to the amplitude of turning, at an internal pressure equal to the rated one.