In Malmö, Sweden, energy company E.ON operates a district heating system in the area around Södra Grängesbergsgatan. The pipe system had previously undergone rehabilitation, and the trenchless method of controlled drilling had been chosen to minimize the impact on the traffic-intense intersection. However, the new pipe, a PE foam-insulated twin pipe holding two DN 100 district heating pipes, had sustained damage in the section joints of the polymer jacket. Thus, groundwater had been degrading the pipes, causing leakage. E.ON was forced to stop using the pipe for five years. Installing a CarboSeal liner would allow the company to recommission it.
The steered drilling process had positioned the twin pipe in an arc shape with a ca 5-m vertical deviation between the lowest and highest points, with the lowest point located about halfway into the section. As steam condensates during the steam-curing cycle, water naturally accumulates at the lowest point. This water must be removed continuously during the curing process so that the curing is not affected. During the manufacture of the liner, a thin draw wire was placed inside the liner, which allowed the condensate hose to be pulled into the low point, 25 m into the liner from the exit, without causing damage.
The AMEX type 10 end seals, which are normally used together with CarboSeal, have a minimum diameter of DN 150. Thus, they were too large for the DN 100 pipes. In collaboration with the end seal manufacturer, AMEX Sanivar, a new, narrower end seal was developed. To test and verify this product, a small test rig was made to cure the DN 100 liner and subsequently test the new type of end seal.
Following successful testing and verification of the DN 100 liner and end seal, the actual installation was planned. During four days in November 2021, the feed and return in the twin pipe were cured at the same time without disturbing the intersection traffic above. The pipes were pressure-tested, and the pipe section was recommissioned by the network owner.