In 2017, GasNet in the Czech Republic started investigations on a trenchless rehabilitation technology for high-pressure natural gas pipelines. A DN 250 PN 25 steel pipe with a length of 1,581 m in Adamov near Brno in the Czech Republic is located in a forestry area with difficult access. Large parts of the pipeline were laid between a narrow forestry path and a river. Furthermore, a section of about 400 m was built into an inaccessible steep, wooded area.
The technical department of operator GasNet, a member of Innogy, was informed about the self-supporting Primus Line® system – certified by the DVGW (German Association for Gas and Water) – for the rehabilitation of high-pressure gas pipelines. Three different Primus Line® options were reviewed and GasNet decided to continue with the Primus Line® system DN 150 PN 35. At Primus Line, a qualified quotation was created based on a detailed construction schedule.
In cooperation with GasNet, Primus Line instructed a local Czech construction company for camera inspection, pipe cleaning and pipeline construction. Employees of the construction company as well as from GasNet were trained and certified for the installation of the Primus Line® system at the manufacturer’s headquarters in Germany.
On preparing the installation of the Primus Line® system in 2018, the Czech construction company created access points to the forest and the pipeline, laid a bypass, cleaned the pipeline and removed wrongly made welding seams protruding into the inner diameter of the host pipe by using a cutter. Before the installation, a calibration pig was pulled through the host pipe.
The installation of the Primus Line® system – consisting of three sections of Primus Line® DN 150 PN 35 including six connectors Primus Line® DN 150 PN 25 – was accomplished in three weeks. After the 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.
