Dimensions of the pipe and coupling before starting welding operations

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Red arrows (pos. 1) show the areas of polypropylene melting. Next comes the stage of joining and compression

Next comes the stage of compression of the mating parts – this is czech republic mobile database by applying mechanical force, with counter vectors directed strictly along the pipe axis. As a result, in the places of polypropylene melting, a diffusion effect occurs – mutual penetration of the polymer (pos. 2). Then follows the necessary technological pause to ensure complete polymerization and obtain a monolithic connection (pos. 3)

Stages of interpenetration of molten polypropylene and final polymerization of the butt joint

The technology seems simple enough, but in reality it is not quite so. As noted, special requirements are imposed on the quality of processing of pipe ends, their strictly coaxial arrangement, and the magnitude of the applied force. It is almost impossible to achieve this without special equipment, and the cost of such welding units is very high. Therefore, this type of polypropylene welding is usually not used in domestic conditions - it is more in demand in the professional environment when laying main communications.

Socket welding
But this is precisely the technology that is available for use in any conditions. The requirements for careful alignment of the mating parts and ensuring the necessary compressive force do not go away, but their implementation is achieved in a completely different way - through carefully thought-out dimensions of the pipe and coupling.


The outer diameter of the pipe (Dнт) is always slightly larger than the inner diameter of the coupling (Dвм), that is, in the normal state, the connection is simply impossible.

To ensure the connection, the external surface of the pipe and the internal surface of the coupling are heated simultaneously. In this case, the length of the heated sections relative to the edge of the parts is approximately equal.