In plastic pipes for distribution of pressurized water, the socket jointing technique made with the Rieber system is mainly used in PVC-U pipes. In a pipe socket made with the Rieber system, the gasket is integral with the socket wall, and it is no longer removable or even replaceable. On the other hand, in Moleculary Oriented Polyvinyl Chloride (PVCO) pipes, it is customary for a removable and replaceable gasket to be added to the socket joint after the socket is formed.

The Rieber socket shape, despite its known operational advantages, is not used in PVCO pipes and the reason is essentially due to the difficulty of implementing a heated Rieber socket forming process in industrial socketing machines for PVCO pipe. The Rieber socketing process for PVCO pipes is conditioned by compliance with fundamental requirements such as: adhesion of the gasket to the socket wall; preservation of the structural integrity of the gasket during the socketing process; repeatability of the socketing process; increase in the orientation factor of the PVCO material in the socket wall; and guaranteeing the shape and dimensions of the socket suitable for the functionality of the joint.

Recently, a new thermoforming process has been developed that allows the Rieber system socketing of PVCO pipes for the distribution of pressurized water, which guarantees all the requirements described. The procedure is then applicable to all PVCO pipes of different operating pressure classes and to all PVCO pipes of different orientation level of the material. Specifically, it is applicable to ISO 16422 piping systems for pipes with nominal diameters from DN/OD 63 mm up to DN/OD 630 mm; to AS/NZS 4441 (Oriented PVC (PVC-O) pipes for pressure applications) piping systems for pipes with nominal diameters from DN 100 up to DN 450 and to ANSI/AWWA C909 (Molecularly Oriented Polyvinyl Chloride (PVCO) Pressure Pipe, 4 In. (100 mm) and Larger) piping systems for pipes with nominal diameters from DN/OD 4” up to DN/ OD 24”.

The procedure can be applied both to PVCO pipes with orientation obtained by inflation in a tank and to PVCO pipes made and oriented directly in the extrusion line. Special characteristics of the heated Rieber socket forming process are the physical phenomena of PVCO pipe and of the sealing gasket, which are considerably different from those that result in PVC-U pipe. Controlling these phenomena required the development of unconventional but absolutely effective technological solutions. The document contains the description of the Rieber socketing