SPECIAL WORKS
Fig 7. The liner folded into a U-shape and coiled on reels saves transport costs thanks to its small footprint.
went back into operation after successful pressure testing and disinfection to ensure drinking water safety.
New pipe-in-pipe construction for double safety Fig8.
existing shaft on the right bank of the river served as the starting pit so that traffic on the main road could continue to flow unhindered. (Fig. 6) On the opposite side, only a small excavation pit on a car park was required.
The host pipe was not cleaned mechanically during this renovation, but with high-pressure water jetting technology at 1,300 bar and a flow rate of 200 litres per minute. The entire rehabilitation was successfully completed after one week.
New life for leaking drinking water inverted siphon in Winnipeg
A leaking DN 250 steel drinking water inverted siphon crossing under a river in Winnipeg, Canada, was in urgent need of action due to the constant loss of water. The original plan to rehabilitate the pipe using the CIPP method had to be abandoned due to a large number of bends in the pipe. In addition, the pipeline was constantly filling with water due to leaks in the outer area, which jeopardised the curing process in the CIPP method.
This is why the responsible engineering office and the City of Winnipeg opted for the Primus Line® system, which is also certified to Canadian drinking water standards. Thanks to its flexibility, it could be laid through the three 45-degree, 22.5-degree and 11.5- degree bends in the 172 metre long rehabilitation section.
Before the Primus Line® DN 250 system was installed, a CCTV inspection was carried out to detect any deposits, incrustations or unclean weld seams. This revealed several sharp-edged indentations, which were removed with a milling robot before the liner was pulled in so as not to damage the liner during installation. During this inspection, an unmarked 45-degree bend was also discovered around six metres before the end of the pipeline. Despite this, the renovation was executed as planned. The pipeline was then cleaned and a second camera inspection was carried out to check the preparatory measures.
Pulling in the liner itself only took around 30 minutes with the help of a cable winch. To do this, the transport reel with the U-shaped pre- folded liner was positioned at one of the two excavation pits. (Fig. 7)
After the liner had been moulded into its round shape using compressed air, the installation team fitted the connectors at both ends. The installation was completed within a day and the pipeline
60 | May 2025 |
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Primus Line® Rehab is also an interesting alternative for new inverted siphon construction as a double pipe solution in combination with an HDPE pipe. In contrast to steel double pipes or cast steel pipes, this solution allows greater flexibility, requires less space and is more cost-effective. With such double-pipe solutions, the HDPE pipe is first inserted into the ground using an HDD bore and then the liner is pulled into the pipe. (Fig. 8) As Primus Line® Rehab absorbs the entire internal pressure of the pipe, the HDPE pipe only serves as a protective jacket and only requires a small wall thickness. In addition, Primus Line® Rehab does not require any bonding or curing. An annular space remains between the liner and the old pipe. This makes the combination of HDPE pipe and Primus Line® Rehab a cost- effective method for double safety.
The pipe-in-pipe solution is used, for example, in the high-pressure gas sector or for pipelines under critical transport infrastructure such as railway lines or motorways, as this example from Regensburg in Germany shows. A new drinking water subway was laid under the A3 motorway using the HDD flush drilling method and subsequent insertion of Primus Line® Rehab with DN 250 over a length of 110 metres. In this case, the jacket pipe consisted of PE-HD 100 SDR 11 (315 x 28.6 mm). The individual pipe sections were joined using heating element butt welding.
As is usual with conventional Primus Line® Rehab installations, a CCTV inspection and cleaning preceded the installation. In addition, a milling robot removed existing weld seams that could have structurally damaged the liner during installation. After just six working days for the liner installation, including all preparatory and follow-up work, the new pipeline was put into operation.
Even in earthquake-prone areas or in particularly sensitive environments such as water protection areas, the dual containment method can offer added safety compared to rigid pipe solutions.
Bottom line
Primus Line® Rehab enables the efficient and sustainable rehabilitation of pressurised pipes that run under complex infrastructure such as rivers or roads. Thanks to its multi-layer structure and special connection technology, the system offers maximum stability with minimum impact on the environment. This makes Primus Line® the ideal solution for rehabilitation projects with the highest demands on flexibility, load-bearing capacity and service life.
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