Since 2005, POLYPLASTIC Group has been producing non-pressure pipes with a structured wall for drainage systems. Initially limited to a diameter of 1200 mm, quite soon it became clear that larger diameters were also needed.

The ability to manufacture a variety of pipes with different profile types, including pressure ones, makes KRAH equipment for the production of polymer pipes the most versatile and multifunctional on the world market both at that time and now. And in 2007, POLYPLASTIC Group signed a contract for the purchase of a complete KRAH line for pipes of large diameters using the profile winding technology. The line was installed at the Group‘s largest plant, Klimovsk Pipe Plant, which already at that time had a capacity of more than 50,000 tons. CORSYS brand name (originated from CORrugated SYStems) had already been registered by POLYPLASTIC for smaller diameter twin-wall corrugated pipes, so large sizes received the brand name CORSYS PLUS. The commissioning of the line took place in close cooperation with KRAH, in addition to experienced commissioning personnel, all necessary auxiliary equipment and components were provided, as well as detailed instructions for the production and welding of CORSYS PLUS pipes. The implementation progressed very intensively and the first projects were not long in coming. The first large facility appeared already in 2008 - a 9000 meters long DN/ID1400mm public sewer collector in the resort area of Caucasian Mineralnye Vody. Giving up traditional reinforced concrete was due to its obvious flaws, which do not allow to talk about the stability and durability of the sewer system to preserve the unique environment of the area.
Thanks to the variety of profile types, KRAH pipe system is highly competitive. Flexible and lightweight pipes withstand high static loads. The unique process of conjugated coextrusion makes it possible to produce pipes with a special inner layer, for example, light-colored - convenient for teleinspection, colored for identification of applications or technical characteristics, light-resistant and non-flammable - for culverts, etc. The main method used for connecting CORSYS PLUS pipes is electrofusion connection which provides a high quality welding, giving the pipeline homogeneous properties and flexibility.

Advantages of the CORSYS PLUS system

It is the electrofusion connection, coupled with the wide possibilities for the strength characteristics of the pipe wall, that provides the advantages of CORSYS PLUS system over SPIROLINE pipe made of spirally wound profile and CORSYS ARM pipe reinforced with steel tape, of the same pipe sizes. The main areas of application for KRAH pipes are non-pressure and low-pressure water disposal, drainage, and irrigation systems. In addition, several marine outfalls have been commissioned recently. These pipelines are also widely used in the construction of airfields, where reliability issue comes first.

A large number of sudden and non-standard tasks arise at construction sites. For instance, at the “Technopark Grabtsevo” facility, it was necessary to weld in a manhole into the existing pipeline made of CORSYS PLUS pipes with a diameter of DN/ID2000 mm. For this, repair electrofusion liners were manufactured and tested, which allow not only to repair CORSYS PLUS pipeline by connecting the ends of the pipes without a socket, but also to make cut-ins into the pipe, which was required at the aforementioned facility. The branch pipes of the tangential manhole, which was also made of CORSYS PLUS pipe, were welded with two liners. The experiment on insertion into the existing CORSYS PLUS collector, of course, should be considered successful.
The proposed technology has proven itself in the field both in terms of connection reliability and installation speed. And since inserting a manhole into a large-diameter CORSYS PLUS pipe in principle is no different from inserting a pipe segment, this experiment is a brilliant proof of the promise of CORSYS PLUS pipeline repair technology using electrofusion sleeves-liners.
In 2011, in cooperation with KRAH specialists, the line underwent a total modernization. As a part of this modernization, the range of pipe sizes was significantly expanded with the possibility of using DN/ID90mm and DN/ID110mm PE coated PP corrugated pipes, which increased the efficiency of the structure to achieve maximum ring stiffness of the pipe.

Capabilities for pressure applications

Increasingly, the question arose about the capabilities of CORSYS PLUS pipes for pressure applications. Work experience was proving that a standard socket and one welding spiral cannot withstand a high working pressure, especially with an increase in diameter. As a result, a solution was worked out to extend the socket and install a double spiral welding. Such a solution was implemented for the public sewer in Cheboksary, where the normalized working pressure of the pipeline is declared up to 0.6 MPa for diameters up to 2000 mm. In order to test pressure pipes and fittings for a constant internal pressure at a temperature of 80°C, a unique test equipment for pipes with a diameter of up to DN/ID2200 mm was developed and installed - equipment which, according to our data, is still the only one in the world. Despite the fact that in Europe the standard classes for structured wall pipes are usually SN2 or SN4 ring stiffness, in the realities of the Russian market, especially for megapolis cities, a pipe with greater ring stiffness turned out to be in demand. Thus, in Moscow there is a technical regulation that defines the requirements for pipes for various laying methods, so CORSYS PLUS pipes up to DN/ID2200mm with ring stiffness up to SN16 appeared in the production range.

Wastewater treatment plant with various CORSYS PLUS pressure pipes

In 2021-2022, a wide range of pressure CORSYS PLUS with diameters of DN/ID1200-2200 mm was used at the Schelkovo wastewater treatment plant, and a variety of fittings were also used, most of which were produced for the first time specifically for this project. Those included standard elbows and stub flanges, as well as pressure reducers, including eccentric ones, and tees.

More than 15 years of successful Krah technology

The products of POLYPLASTIC Group based on KRAH technology have been successfully used throughout the country for more than 15 years. One of the recent projects (2022) was the use of CORSYS PLUS pipes with a DN/ID3500 mm in the project for the reconstruction of the Akulovsky water channel in the Moscow region. The total length of the pipeline from CORSYS PLUS pipes was 1.2 km.

The project was the first application of CORSYS PLUS pipes with a diameter of 3.5 meters in the construction of water conduits. The experience will be scaled up during the implementation of similar projects and the reconstruction of reclamation canals - by replacing them with pipelines based on CORSYS PLUS.

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