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GRP joining elements

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Joining elements are special parts (couplings) used to join two pipes. There are two main types of joining elements: unrestrained and restrained. The unrestrained couplings are not bonded to the ducts, therefore these offer the pipes degrees of freedom for axial and radial movement. Restrained couplings are bonded to the pipes, therefore the pipes have no degree of freedom of movement after the coupling (connection) has been completed.

For uniaxial pipelines, unrestrained joints are usually used, and it is necessary to use thurst blocks. These take up the loads that occur when there are directional changes. Only restrained joining elements are used for biaxial pipes.
Rorex offers several types of GRP pipe joining elements.

Reka couplings
Reka couplings are standard GRP couplings used for joining uniaxial pipes, and the sealing is done with elastomeric rubber (EPDM) seals. They have been used successfully for over 50 years and can be installed on slopes or in different soil conditions. They are available for a wide range of diameters (DN 100 mm – DN 4000 mm) and pressure classes (PN 1 bar – PN 32 bar). These couplings allow an angular deflection of up to 3o depending on the pipe diameter, and pressure class, thus reducing the number of elbows required in the pipe network.
Further details on Reka coupling sizes can be found in the ROREX General Presentation Catalogue in the “Downloads” menu.

Further details on Reka coupling sizes can be found in the ROREX General Presentation Catalogue in the “Downloads” menu.

Mechanical steel couplings

Mechanical steel couplings are usually used when joining a GRP pipe with a pipe made of another material or when work is being carried out on an already installed pipe and there is not enough space to install a Reka coupling. In the latter example, flexible mechanical couplings are used. Their installation requires qualified personnel.

These couplings consist of a steel mantle with an interior sealing rubber sleeve. The steel mantle can be made of stainless steel, galvanised steel or epoxy-protected steel.

For mechanical steel couplings, ROREX collaborates with the Spanish company ARPOL. They are manufactured in three versions: ARPOL INSTAL, ARPOL REP and ARPOL TRANS.

An alternative to these couplings is the use of a special, custom-made steel joining part. The steel casing is machined on the lathe to have the same outside diameter as the GRP pipe. One end of this piece is welded to the steel pipe and the machined end is joined to a Reka coupling.

Further details of ARPOL mechanical steel couplings can be found in the ROREX General Presentation Catalogue in the “Downloads” menu.

Laminated joints

Laminated joints are manufactured from GRP. The number of layers in the joint and their length, configuration or type varies according to the diameter and pressure rating of the pipe. They are mainly used where pipe joints must transmit axial forces from the internal pressure due to directional changes, without thrust blocks, or as a repair method. Their installation requires qualified personnel.

Flanges

The flange is a mechanical joining method, used for either joining two pipes together, a pipe to a fitting, or a pipe to a valve. It can also connect GRP with GRP or GRP with other materials. Flanges are used to create a watertight connection that can be disassembled and reassembled if necessary. The flange disc is a circular surface that has a standard pattern for bolting based on the pipe outside diameter and pressure rating.
Adhesive-bonded couplings (COMBI)
Adhesive-bonded couplings (combi couplings) are used to connect two biaxial GRP pipes and are equipped with four sealing gaskets. Usually, they are installed on one end of the pipe from the factory. Their length and diameter vary according to the pipe’s nominal diameter and pressure rating. The space between the two sealing gaskets from each end of the pipe is filled with a special resin that bonds the coupling to the pipe.
Further details on COMBI coupling sizes can be found in the ROREX General Presentation Catalogue in the “Downloads” menu.