Rehabilitation of pressure pipes under rivers and lakes with Primus Line®

Flexible, fibre-reinforced pipelines are the optimal solution for the challenging rehabilitation of pressure pipes under rivers and lakes: they combine stability and flexibility, require only a short rehabilitation time and protect the environment and surroundings. This is also demonstrated by a project in the Canadian city of Winnipeg.

River crossings are often characterized by long lengths with bends in their course and are only accessible from the two banks of the watercourse. This brings many trenchless rehabilitation methods to their limits. New construction is time-consuming, disruptive, costly and often associated with geotechnical and hydrogeological problems as well as construction risks.

Primus Line®, the technology for trenchless rehabilitation of pressure pipelines, was developed in Germany over 20 years ago and is produced there up to a diameter of DN 500. The system is based on a multi-layer, flexible liner and specially developed connectors. The Primus Liner can be pulled into pipeline sections up to 2,500 metres long and pass through bends of up to 45 degrees. The distribution for North America's water market is organized by MTC, a company of the Aegion Group, with a comprehensive stock of Primus Line products in Batesville, Missisippi, USA.

 

New life for 172-metre potable water river crossing in Winnipeg

The steel potable water line crossing a river in Winnipeg, Manitoba, Canada, was in urgent need of rehabilitation. The original plan to rehabilitate the pipe using the CIPP (cured-in-place pipe) method had to be discarded due to a large number of bends in the pipe. In addition, the pipe was constantly filling with water due to leaks in the outer area, which endangered the curing process in the CIPP procedure.

Engineering firm AECOM and the City of Winnipeg therefore considered the NSF/ANSI 61 certified Primus Line® system. Its flexibility allowed it to be installed through the three 45-degree, 22.5-degree and 11.5-degree bends along the 172-metre rehabilitation length. No bonding or curing is required. An annular space remains between the liner and the old pipe. The contracted company Tri-Core Projects Ltd. received support during the installation from the trained Primus Line installation partner LV Trenchless from Calgary.

Prior to the installation of the Primus Line® system DN 250, a CCTV inspection was carried out to detect deposits, incrustations or unclean weld seams. This revealed several sharp protrusions that had to be removed before the liner was pulled in with a milling robot to avoid damaging the liner during pull-in. In addition, an unrecorded 45-degree bend was found about six metres before the end of the pipeline. The actually planned low-pressure connector therefore had to be replaced by a medium-pressure connector. Subsequently, the pipeline could be cleaned and a second camera inspection could be carried out to check the preparatory measures. 

To insert the liner, the transport drum with the liner pre-folded in a U-shape was placed at one of the two excavation pits. With the help of a winch, it was then pulled in at a speed of about ten metres per minute.

After the liner was brought into its round shape with the help of compressed air, the connectors could be installed on both sides. Within a day, the installation was completed and the pipeline could be put back into operation after successful pressure testing and disinfection to ensure the safety of the drinking water. The service life of the water main was thus extended by at least 50 more years.  

 

Follow-up project already planned

After the successful and satisfactory completion of the measure for the city of Winnipeg, the next project there is already being planned and will be implemented in August this year. This time, too, it is about the rehabilitation of a siphon. A 220-metre potable water pipeline DN 600 will be rehabilitated with the Primus Line® System DN 500 (operating pressure 232 psi).

These projects are not the first river crossing measures with Primus Line® in Canada. Among others in Canmore, Alberta, a Primus Liner DN 250 was installed over a length of 193 metres in an HDPE pipeline DN 300 with two 42-degree bends. The aim of the measure was to convert the pipeline from wastewater to potable water.

 

New pipe-in-pipe construction for dual containment

For the construction of new siphons, Primus Line® as a pipe-in-pipe solution together with an HDPE pipe is also an interesting alternative to double steel pipes or cast steel pipes, which, due to its flexibility and pliability, also allows pipe runs with bends. First, the HDPE pipe is inserted into the ground via an HDD borehole and then the liner is pulled in. Since Primus Line® absorbs the complete internal pressure of the pipe, the HDPE pipe only serves as a protective cover and only requires a small wall thickness. Thus, the combination of HDPE pipe and Primus Line® is a cost-effective method for double safety.

The pipe-in-pipe solution was therefore used, for example, in the high-pressure gas sector or for pipelines under critical traffic infrastructure such as railway lines or highways. This solution can also offer more safety in areas with seismic activity (compared to rigid pipe solutions) or in particularly sensitive environments such as water protection areas (e.g. at crossings of sewage pipes).

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