Sunday, July 14, 2024

New overland piping system for German paper mill

Primus Line uses overland piping system to return treated wastewater

Rädlinger Primus Line GmbH utilised its self-developed and reusable Primus Line® Overland Piping system to return treated wastewater from a German paper mill to an above ground river.

Low water levels and aquatic ecology are a major issue throughout Europe. As a result, the constraints on businesses that rely on water extraction from rivers, streams and lakes, such as this paper mill in southern Germany, are also increasing.

The mill operator takes water from a mid-mountain stream for paper production and had returned it to a canal several hundred metres below the point of withdrawal. For environmental reasons, the paper mill was instructed to return the purified process water to the extraction spot. In order to achieve this the company approached Rädlinger primus line GmbH who were able to offer a suitable solution employing the Primus Line® Overland Piping system.

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What is Primus Line® Overland Piping?

Primus Line® Overland Piping is a reusable solution specifically designed for above-ground pipelines in order to safely transport demanding and potentially hazardous media such as industrial wastewater, brine, process water etc.

The system consists of two components: an aramid-reinforced liner and specially developed connectors.

Up to 4,000m of the flexible pipe can be supplied on a reel, unrolled and laid directly – even in difficult terrain. (Figure 1) The pipe naturally conforms to the surface structure. Depending on the diameter (nominal widths from DN 150 to DN 350), the maximum operating pressure ranges from 56 to 20 bar. The inner layer is made of thermoplastic polyurethane (TPU), which is corrosion resistant and offers a high abrasion and chemical resistance that even withstands contact with highly corrosive hydrocarbons. The Kevlar® fabric reinforcement gives Overland Piping its high tensile strength, enabling it to completely absorb very high operating pressures. The TPU outer layer protects against UV radiation and abrasion and provides the flexibility required for multiple installations and the ability to roll up the reusable system.

The connectors ensure a leak-free joint. Specially designed high-pressure end fittings with flanges or special quick couplers are used to connect the pipework. They can also be connected to pumps or other pipework.

Project planning for wastewater recirculation with Primus Line®

The wastewater recirculation line of the mill had a total length of 690m 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 consider the ongoing operation and traffic on the mill site which had to be maintained while the winch and reels were put in place. In the end, three sections with lengths of 440m, 200m and 50m were defined.

Pipeline in the river bed

After intensive preplanning, safety training for the installation 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 had to first remove any logs and branches from the canal. This clearing work was done using a boat and a winch.

A boat and a winch were also then 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. The pull of the winch then gradually unwound the liner and placed it in the canal. In this way, Primus Line laid the three sections one after the other: 200m under the hydropower plant, 50m near the lock and 440m up to the wastewater intakes.

A total of six connectors was  necessary to link and connect the pipelines. 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. 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 wood.

Advantages over HDPE pipes

Primus Line® Overland Piping is the result of consistent 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, including 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, for several reasons. These include significant advantages in terms of mobilisation and equipment requirements. The fabric-reinforced liner is transported on reels, saving space. Installation only requires a mini-excavator or winch and simple hand tools. There is no need for machinery, manpower or time to be spent on complex welding to make the connection. Installation and dismantling times are correspondingly shorter. Primus Line normally take one or two days to lay 6km of their liner. Lengths of 1,000m and more in one section reduce the number of joints and weak points. The liner easily adapts to the unevenness of the surface. By comparison, installing the same length of HDPE pipe takes about 25 to 30 days, with increased additional labour costs. Dismantling the same length of pipe also takes only one to two days with Primus Line® Overland Piping, as the liner is simply rolled up, compared with seven to ten days for HDPE. The subsequent storage requirements for HDPE pipes are up to ten times greater than for liners on reels. In addition to storage and transport costs, operating costs are on average also lower due to minimal mobilisation and demobilisation costs and lower manpower requirements.

In addition to cost and efficiency, the low use of machinery also contributes to the environmental friendliness of the Overland Piping system. It can be installed in sensitive environments such as protected areas, nature parks or rivers without major environmental impact. This avoids emissions and reduces the carbon footprint.

The middle layer of the three-layered Primus Line® Overland Piping system ensures the safety of the flexible pipe: It is made of seamlessly woven Kevlar®. This synthetic fibre is up to ten times stronger than steel and twice as strong as glass fibre or nylon. The flexible pipe therefore has a very high factor of safety (FoS). The burst pressure is at least 2.5 times higher than the allowable operating pressure. The entire production process is closely monitored. Sensors and cameras continuously capture the process parameters and provide the basis for extensive wall thickness and consistency control mechanisms. In addition, every liner produced is subjected to an in-house pressure test before being delivered to the construction site.

Fast installation in emergency cases

Primus Line® Overland Piping also provides a solution in the event of catastrophes such as landslides, floods or forest fires that cause pipeline damage or failure. A single container can hold two to four kilometres of flexible pipe with the appropriate fittings. In case of an emergency, the flexible and spoolable Primus Line® above-ground pipe can be installed immediately and – depending on the environmental conditions – within a short period of time. In addition, the Primus Line® Overland Piping system has a very long service life – depending on the type of use and the conditions.

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