Pipe relining represents a significant advancement in the renewal of district heating pipes. Combining cost savings, minimal disruption, and environmental benefits, the cutting-edge solution of relining pipe systems is proving its worth in installations worldwide. As its technology advances and market acceptance grows, trenchless pipe renewal is poised to transform infrastructure upgrades, offering network owners a fast, simple, and sustainable solution for the future.
By Andreas Martsman, CEO at Pressure Pipe Relining Sweden AB
Published in Hot Cool, edition no. 1/2025 | ISSN 0904 9681 |
Introduction to Trenchless Pipe Renewal
Through two small openings in the pipe, a section of, for example, 200 meters of DN400 pipe can be replaced within 24 hours. This significantly reduces the time required for planning, obtaining approvals, and excavation, enabling quick and cost-effective pipe renewal. The trenchless method also reduces the carbon footprint of pipe replacement by about 90% compared to traditional excavation and replacement methods.
Historical Context and Adoption
Relining sewage and drinking water pipes has been used since the late 1960s and is now widely adopted globally. In some cities, more than 50% of sewage and water pipe renewals are done trenchless through relining. This method saves time and money for network owners and reduces societal costs. Roads, businesses, and stores remain open, and other underground networks can continue operating.
Relining involves repairing the pipe from the inside while it remains in the ground. Typically, access to the pipe is needed at two points: an entry and an exit point. In most cases, relining involves producing and pulling in a new pipe to replace the old one. After installation, the new pipe, or liner, functions as a standalone pipe, rendering the condition of the old pipe irrelevant.
Development of Relining
The high temperatures and pressures of district heating pipes have posed significant challenges for liner manufacturers. Until recently, no product was available for relining district heating pipes. Some network owners tried traditional liner products but found they deteriorated within months or even weeks.
Combining extensive material knowledge with expertise in liner manufacturing, Oxeon AB from Sweden and BKP Berolina from Germany developed CarboSeal, a relining product for district heating pipes. A special epoxy combined with carbon fiber allows for an expected lifespan of 40 years, even in the harsh environment of a district heating network. The unique materials have been chosen, modified, and extensively tested to ensure that no hydrolysis is taking place and that the product will last for a long time.
The project commenced in 2011 and was initiated by HWQ-Group, which formed a subsidiary called Pressure Pipe Relining Sweden AB (PPR Sweden AB). Initial funding came from Vinnova, Vattenfall, and what is now Energimyndigheten, enabling early trials. Material experts from the Research Institutes of Sweden (RISE) and support from suppliers were crucial. It took about ten years to develop the necessary materials and refine the production process, but on June 1, 2021, the relining product was introduced to the market.
Global Installations and Case Studies
Since then, the relining of district heating pipes has been installed in 16 locations worldwide. Network owners in 7 countries have used relining for pipes ranging from DN100 to DN500. Currently, relining is available in sizes up to DN800. The longest single section installed so far is 192 meters, but the technology has no length limitations. Two of the 16 installations were test sections that were removed and analyzed after being in service for a few years to verify functionality and expected lifespan, while the remaining 14 are in full operation and performing well.
The installation in Örebro, Sweden, is a prime example where trenchless pipe renewal saved about 70% of costs compared to directional drilling under the city center’s train tracks. The network, owned and operated by Eon, is aging and needs repair and replacement. The project to renew the pipes under the train tracks was planned and designed by Fjärrvärmebyrån (FVB), which reported that the total cost of the trenchless pipe renewal project was about 30% of the expected cost for pipe replacement through directional drilling.
Network owners can realize substantial savings in complex excavation situations. For instance, in Norrköping, where pipes crossed a major road, drilling was not feasible. The alternative would have been to block one lane at a time and replace the pipes traditionally. Eon Norrköping estimated the cost of traditional replacement to be at least €900.000, while the trenchless pipe renewal project cost €350.000).
”By using trenchless pipe renewal, we were able to keep the major road E22 open with no disruption or traffic congestion. Changing these pipes in a traditional way by digging and replacing them would have taken weeks or maybe months, with severe traffic congestion and frustrated citizens as a result.”—Maria Ohlsson, maintenance engineer, Eon.
Societal savings and reduced impact on life in the city
There are also significant societal savings, as roads can remain open, businesses can continue serving customers, and other networks are not disrupted when long trenches are avoided. VA Syd, a Swedish utility company operating water and sewage systems in Malmö and Lund, conducted a study on the societal costs of street excavation. They found that the societal cost in the investigated case was about €1.200.000, while the project cost to replace the pipes was only about €100.000.
The reduced societal costs and low impact on life on the streets were the main reasons to turn to trenchless pipe renewal when Stockholm Exergi was to renew a short section of DN150 pipe under Norrlandsgatan in the city center of Stockholm. The ability to keep roads open and businesses operating was a significant factor in their decision.
Even though the replacement cost was similar to traditional methods, the savings for the city were substantial. Entry and exit points for the liner were managed on sidewalks, allowing traffic to flow, shops to stay open, and other underground services to continue uninterrupted.
“We considered different ways to repair the pipe, but relining as a method was a good fit here. We avoided digging up the entire street and closing traffic for a few days,” says Robert Kelava, maintenance engineer at Stockholm Exergi.
Challenges and Future Development
Currently, trenchless pipe renewal can only be used on relatively straight sections. Like relining pressurized water pipes, connections, bends, and valves need to be excavated and replaced traditionally. However, many straight sections under train tracks, bus lanes, buildings, canals, and bridges in city centers worldwide can benefit from this method. The developers hope to start with these sections and expand the business while developing solutions for bends and connections.
One of the major challenges in introducing this new technology is the uncertainty about its lifespan. All testing so far, including by RISE (Research Institute of Sweden), indicates a lifespan of at least 40 years. However, accelerating long-term testing is difficult, as elevated temperatures may not accurately simulate normal district heating network conditions. Gaining long-term experience from more installations and continuing to monitor existing ones is crucial. Additional long-term testing at various labs worldwide is also being conducted to verify and prove the product’s longevity. So far, no evidence of degradation has been seen.
AGFW, the German District Heating Association, has initiated this work, mapping out network owners’ requirements. The next step is to develop test methods to verify that the liner meets these requirements and have it certified.
Market Acceptance and Environmental Impact
Trenchless pipe renewal and its potential to save network owners money, time, and headaches are gaining interest worldwide.
Combining relining with traditional pipe replacement benefits all parties. Network owners get an upgraded pipe network quickly and at a lower cost than a complete traditional replacement. Pipe manufacturers gain more business as network owners can avoid the most costly and time-consuming excavation work, allowing them to invest in network expansion or additional replacements.
Everyone benefits from the positive environmental impact of trenchless rehabilitation compared to traditional methods. For sewage and water, the carbon footprint reduction is at least 80%, and for district heating, avoiding new steel pipe production, PUR foam, and PE coating can reduce the carbon footprint by at least 90%.
Veolia highlighted the positive environmental impact when they used relining to renew a section of DN400 pipes under a bus lane in central Sheffield, UK. According to the installer, CPC Civils, the trenchless method saved the customer about £1.2 million, which could be allocated to other network projects.
Conclusion
Relining represents a significant advancement in the renewal of district heating pipes. Its development and successful implementation in various locations worldwide demonstrate its effectiveness and potential for widespread adoption. The combination of cost savings, minimal disruption, and environmental benefits makes trenchless pipe renewal an attractive solution for network owners looking to upgrade their infrastructure efficiently and sustainably.
As the technology continues to evolve and more installations are completed, the long-term benefits of relining will become even more apparent. The ongoing efforts to standardize and certify the product will further enhance its credibility and acceptance in the market. With continued innovation and collaboration, trenchless pipe renewal has the potential to revolutionize the way district heating pipes are renewed, providing a fast, simple, and sustainable solution for the future.
For further information please contact: Adreas Martsman, andreas.martsman@carboseal.com
“Fast, Simple, and Sustainable Renewal of District Heating Pipes” was published in Hot Cool, edition no. 1/2025. You can download the article here:
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