THE MAGAZINE FOR THE DRAINAGE, WATER & WASTEWATER INDUSTRIES
CASE STUDIES
Fig 2 & 3: Clearing work in the riverbed prior to installation
pumps or other pipework. Project planning for wastewater recirculation with Primus Line®
The wastewater recirculation line of the South-German paper mill has a total length of 690 metres and was to be installed above ground via a raft water canal. The volume of recirculated wastewater varies between 600 and 1,200 cubic metres per hour. Due to its temporary use during the summer and autumn months, the original plan was to roll up the system, store it for the rest of the year and then roll it out again – a classic use case for the reusable Primus Line® Overland Piping system.
However, during an on-site visit, the project team decided to leave the pipeline permanently in the canal due to the difficult access in some areas. The Primus Line F-Liner that is used as Overland Piping system was also suitable for this case of application and met all the requirements in terms of service life, temperature, UV and abrasion resistance. It also withstands the alternation between several months of operation and shutdown. In addition, its shape remains stable whether the canal is filled with water or not.
As a result of the flow rate calculation, an F-Liner with a nominal diameter of DN 350 was selected, operating at a pressure rating of PN 10. Due to its low friction coefficient (k = 0.028 millimetres), it can also handle the highest flow rates.
One of the challenges of project planning was determining the installation sections. The curved course of the canal as well as structures that had to be passed such as a lock and a building containing the mill’s own hydropower plant prevented installation in one section. Primus Line’s engineers also had to take into account the ongoing operation and traffic on the mill site which had to be maintained during placing the winch and reels. In the end, three sections with lengths of 440, 200 and 50 metres were defined.
Pipeline in the river bed After intensive preplanning, the safety training for the installation
FOLLOW US
team from Rädlinger primus line GmbH and setting up the construction site, work could begin.
In order to place the liner in a safe and stable manner, both during installation and in future operation, the Primus Line installation team first of all removed timber from the canal (logs and branches). This clearing work was done using a boat and a winch. (Figures 2 and 3)
A boat and a winch were also used to lay the pipeline. The team placed the end of the liner with the installed connector in the boat and attached the end of the winch line to the connector. In this way, the pull of the winch gradually unwound the liner and placed it in the canal. In this way, Primus Line laid the three sections one after the other: 200 metres under the hydropower plant, 50 metres near the lock and 440 metres up to the wastewater intakes.
A total of six connectors was necessary to link and connect the pipelines. (Figure 4) Some were mounted on pontoons and some were pre-installed before the liner was laid. The liner was then pressurised with water, set up and brought into its circular shape. (Figure 5) This allowed the liner to sink to the bottom of the canal. After a final pressure test, the pipeline was returned to service after a three-week construction period. About half of this time was taken up with the removal of the timber.
Advantages over HDPE pipes
Primus Line® Overland Piping is the consistent further development of a technology that Rädlinger primus line GmbH has been using for more than 20 years for the trenchless rehabilitation of pressure pipes. The Bavarian company’s above-ground solution is now also being used all over the world, for example in France, Canada and Norway, to reliably transport brine, domestic sewage and process water.
In all of these projects, the flexible pipeline based on the aramid- reinforced liner has prevailed over above-ground HDPE pipes, albeit for different reasons.
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