The many types of couplings and adaptors seem to overlap with each other with regard to application and installation. To help gaining a better understanding of the different options the couplings and adaptors can be divided into two main categories – dedicated and universal – which again can be divided into tensile and non-tensile types, resulting in four main categories.
Dedicated couplings without tensile resistance
These couplings are the most simple in design and can only be used on specific pipe materials with a specific outside pipe diameter. In other words, the couplings do not allow for tolerances on the outside pipe diameter. Given the simplicity of the design, these couplings are mostly used in situations where the customer has no demand for a tensile coupling, typically in new installations where the pipeline is connected to other pipes or stabilized in another way e.g. by means of backfilling with concrete. The limited application and the simple design will in most cases result in a low pricing.
Dedicated couplings with tensile resistance
The dedicated couplings in this category are quite similar to the non-tensile couplings. However, the tensile couplings are designed to withstand the pull in the pipe arising from the internal pressure and the mechanical pull originating from the installation. This type of coupling is normally equipped with grip segments placed in conjunction with the gasket unit. The grip segments compress around the pipe when the gasket compresses, providing full resistance against the pull in the pipe. Typically, the dedicated tensile couplings are the preferred choice when customers install new pipes in an open trench without using backfilling and want to pressure test the complete pipeline before covering it with soil.
AVK products in this category are combi-flanges series 05/60 for PE/PVC and 05/26 for ductile iron pipes, Supa Plus™ series 621 straight couplings, series 623 flange adaptors and series 624 end caps, as well as Repico® Grip couplings series 745/01 and series 745/03.
Universal couplings without tensile resistance
A universal coupling offers flexibility with regard to the choice of pipe material and thus also with regard to the outside diameter of the pipe. Typically, the outside tolerance of the pipe may vary from 20 to 40 mm depending on the size of the coupling. In most markets this type of coupling is the customer’s preferred choice in situations where pipes need to be repaired or replaced in small sections. Since old pipes installed underground in most cases are repaired with new pipe materials, the couplings must accept different outside pipe diameters within each DN range. The old pipes are kept in place by the soil, thus there is rarely a need for tensile resistance.
AVK products in this category are Supa® couplings series 601 straight couplings, series 602 step couplings and series 603 flange adaptors, as well as Repico® Slip couplings series 745/20 and series 745/28.
Universal couplings with tensile resistance
These couplings are the absolute top products within couplings. They offer both the flexibility needed with regard to the outside pipe diameter and they also withstand the pull in the pipe from the internal pressure and the mechanical pull from the installation. These two features make the product ideal as a repair product for large renovation projects, as the coupling seals around most pipe materials and prevents the pipe from moving during pressure tests. Many customers are switching from universal non-tensile couplings to universal tensile couplings even on small renovation projects, to avoid carrying stock of both types.
AVK products in this category are Supa Maxi™ couplings with series 631 straight couplings, series 632 step couplings, series 633 flange adaptors, series 634 end caps and series 635 transition couplings.