GasNet used a flexible Primus Liner® system to rehabilitate a natural gas pipeline in a sensitive area of the Czech Republic..
In 2017, Czech Republic energy operator Innogy’s subsidiary, gas distributor GasNet, started investigating trenchless rehabilitation technologies suitable for application on high pressure natural gas pipelines. The section of pipe to be rehabilitated – a DN 250 steel pipe with a length of 1,581 m and a PN of 25 – was located in Adamov near the country’s second largest city Brno.
The region features a landscape of flat highland, divided by deep valleys and steep slopes, including a forestry area with difficult access. Due to the hilly terrain, Adamov’s lush forests have not disappeared, although wood mining has impacted their health. At the beginning of the 20th century, extensive restoration was carried out in the forest area and care is taken to preserve the area.
A case for Primus Line
In this unique topography, large parts of the pipeline were laid between a narrow forestry path and a river. Further complicating the project was that a section of about 400 m was built into an inaccessible and steep wooded area.
During research for an appropriate trenchless technology, the technical department of GasNet was informed about the self-supporting Primus Line system – certified by the German Association for Gas and Water (DVGW) – for the rehabilitation of high pressure gas pipelines.
Primus Line values maximum sustainability and this drives the way the technology is designed and applied. To achieve a sustainable system, the lining technology uses the existing infrastructure and small construction zones, protecting nature and the environment by minimising impact and machine deployment.
The Primus Line system is referenced in the international standard ‘DIN EN ISO 11295:2018-06 Classification and information on design and applications of plastics piping systems used for renovation and replacement’ and also complies with the technical standard ‘DVGW VP 643 Flexible textile-reinforced plastic inliner for piperelining of gas high pressure pipes’.
The system itself comprises a Kevlar®-reinforced liner and specifically developed end fittings, which accommodates the operating pressure of the pipe due to the reinforcement layer and because it does not bond to the host pipe. The liner is seamlessly manufactured at an ISO 9001 certified production plant in Germany and transported on reels to the site.
Other advantages include the liner’s flexibility, allowing installation at angles of up to 45° and in lengths of more than 1,000 m in one pull, as well as installation speeds of up to 600 m/h.
Three different Primus Line options were reviewed by GasNet before it decided to proceed with the DN 150 PN 35 Primus Line system. Following this selection, Primus Line put together a qualified quotation based on the detailed construction schedule.
In cooperation with GasNet, Primus Line instructed a local Czech construction company to complete a camera inspection, pipe cleaning and pipeline construction. Construction company and GasNet employees were trained and certified for the installation of the Primus Line system at the manufacturer’s headquarters in Germany. During the course, attendees acquire the know-how to plan, manage and supervise projects with the innovative system for trenchless rehabilitation.
In 2018, to prepare for the installation of the Primus Line system the Czech construction company created access points to the forest and the pipeline, laid a bypass, cleaned the pipeline and removed malformed welding seams protruding into the inner diameter of the host pipe using a cutter.
Before the installation, a calibration pig was pulled through the host pipe. The installation of the Primus Line system – comprising three sections of Primus Line DN 150 PN 35 including six connectors Primus Line DN 150 PN 25 – was accomplished in three weeks.
After a successful pressure test with 33 bar and the acceptance by the Czech Technical Inspection Authority, the renovated pipeline was handed over to GasNet and integrated into the network.
This article was featured in the Spring edition of Trenchless International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
For more information visit the Primus Line website.
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