First gas pipeline renovation with Primus Line®

South Cemetery, Leipzig, autumn 2003: The team from Rädlinger Primus Line GmbH carried out one of the first projects there using the then novel Primus Line® inliner system – the trenchless rehabilitation of a gas pipeline. More than twenty years later, what has become of the rehabilitated pipeline? Is it still in operation? How does the network operator assess the rehabilitation from back then in retrospect? What insights did the manufacturer Rädlinger Primus Line GmbH gain from this project? Here are the answers.

Covering 72 hectares, the South Cemetery in Leipzig is one of the largest park-like cemeteries in Germany. It and its trees are listed as historical monuments. This was precisely one of the challenges facing Leipzig's public utility company in 2003. A DN 300 gas pipeline runs under the cemetery. More than a kilometre of this pipeline was in need of rehabilitation. Due to its listed status, conventional renovation methods, i.e. open construction, were not possible. Netz Leipzig GmbH, a subsidiary of the municipal utilities “Leipziger Stadtwerke”, was very open to the new system, making the Leipzig network operator a pioneer in the trenchless renovation of gas pipes using inliners.

Rädlinger Primus Line GmbH, which had been founded just two years earlier, had developed this inliner specifically for the transport of gas; other media were added later. After various tests, the system, called "Primus Line", was ready for live use. The Leipzig-based company had classified Primus Line® as a "viable method" and used it to renovate the steel pipeline under the South Cemetery. Holger Thieme, then as now head of the Gas Network Operations department at Netz Leipzig, summarises the reasons for this as "fast, uncomplicated and low-cost". Fast, because the rehabilitation could be carried out within a few days; uncomplicated and low-cost, because only a few relatively small excavation pits were required. The old pipe could remain in place. In addition, it was a pipe with few branches and a long length – good conditions for using an inliner process.

The steel pipe, which dated back to the 1950s, had been used to transport so-called town gas during the GDR era. This is a mixture of various gases from lignite mining, including up to 30 percent hydrogen. This town gas had left heavy deposits in the pipe, which meant that intensive cleaning was necessary. "Back then, we didn't have the milling robots we have today," recalls Christian Pollak, who was responsible for construction site management at Rädlinger Primus Line in 2003 and still is today. "The cleaning device looked a bit like an angle grinder." Nevertheless, the cleaning was successful. Afterwards, the Primus Liner was pulled in.

The five renovation sections ultimately required seven excavation pits instead of the six originally planned. During the insertion of the liner, it became apparent that the insertion forces generated by the cable winch were very high. In order to minimise any possible effects on the stability of the liner, the longest insertion section was halved – which meant that an additional excavation pit was necessary. The camera inspection prior to cleaning and liner insertion also revealed an undocumented floor at the water pipe crossing along the route of the pipeline. The municipal utilities renewed this using open construction methods.

Despite the complications, the construction project was completed to the satisfaction of the Leipzig network operators. And the company is still satisfied today. "The renovated gas pipeline is still in operation at a pressure of 3 bar," explains Holger Thieme. "There has been no damage in over 20 years. The pipeline is inspected twice a year at the sniffing pipes in accordance with DVGW regulations. We have not detected any gas leaks, so there is hardly any permeation."

Findings from this project

Rädlinger Primus Line gained the following insights from this first large-scale installation of a gas liner:

Minimising insertion forces

In order to make the liner insertion as gentle as possible and with as little pulling force as possible, Rädlinger Primus Line now folds the liner into a U-shape instead of flat. In addition, deflection rollers reduce the insertion forces. Twist arresters for the cable winch also prevent the cable and thus the liner from twisting during insertion. An optimised insertion angle also helps to minimise insertion forces.

Removing incrustations

Milling robots have also improved significantly over the last 20 years. Sharp-edged weld roots and heavy incrustations can be effectively removed with the latest technology. A clear inner diameter is necessary to protect the liner during pulling.

Conclusion

The gas liner in Leipzig has survived

 almost half of its minimum service life of 50 years without complications, thus confirming the results of long-term tests in practice.

Rädlinger Primus Line has gained valuable knowledge from the challenges encountered in this first project. The company has optimised the installation process to its current level of maturity, which requires only standard equipment.

The trenchless method is also particularly well suited for sensitive environments – such as the listed cemetery in this case.

Main image: The South Cemetery in Leipzig is one of the largest park-like cemeteries in Germany. In 2003, Rädlinger Primus Line carried out one of its first rehabilitation projects there using trenchless technology. © Joachim Köhler / Wikimedia Commons / CC BY-SA 4.0

This article appeared in Issue 332 of Drain Trader magazine, December 2025. You can view it here.