In recent years, the focus of many products has shifted toward a more sustainable, environmentally friendly model. Fluid transfer is no different, with engineers, project managers and contractors alike seeking new ways to improve reliability, limit leaks or pipeline failure, and deliver environmentally sound results.

Figure 1: The marine donut is a sea-based enclosed, donut-shaped structure. Source: McElroy

High-density polyethylene (HDPE) pipe, when butt fused with quality equipment and following a recognized standard, easily meets all of those requirements. As the benefits of thermoplastic pipe become more widely accepted, its use for fluid transfer and flow control has grown in popularity and scope.

If performed correctly, thermoplastic pipe fusion results in a pipeline that surpasses traditional iron pipe in both longevity and reliability. While metallic systems’ output is expected to reduce over its lifespan through corrosion and tuberculation, service using HDPE is typically unaffected by inner diameter loss. Where welding and bolt-up fusion processes of steel pipe require massive amounts of time, thermoplastic pipe provides an option that allows for more efficient and secure connections that can last for more than a hundred years.

Figure 2: The marine donut is a closed-system fish farm that works to reduce the footprint of traditional fish farming methods. Source: McElroy

Two of the many benefits to thermoplastic pipe are its flexibility and durability. For that reason, thermoplastic pipe is becoming the material of choice for harsh working conditions. McElroy, headquartered in Tulsa, Oklahoma, is the world’s leading producer of thermoplastic pipe fusion equipment. Alongside thermoplastic pipe, McElroy equipment has become known for being the industry’s choice for rugged and reliable pipe fusion equipment.

One of McElroy’s most recent fusion machines, the TracStar iSeries, has been part of a project in Norway that is taking a new approach toward conventional fish farming.

Bluegreen Fusion AS, McElroy’s Scandinavian distributor, is part of a team pioneering the “marine donut,” a closed-system fish farm that works to reduce the footprint of traditional fish farming methods. The butt fusion for piping systems in the donut is being performed using TracStar iSeries machines.

The marine donut is a sea-based enclosed, donut-shaped structure. The “donut” part of the structure sits underwater, with a large platform that sits on top and above the water. The platform is used primarily for maintenance and other access purposes.

The donut itself is constructed with HDPE, which acts as a tight barrier against external environmental factors. The structure is stabilized with float tubes, bracing tubes and vertical ballast tanks that allow it to be raised and lowered. It is built to withstand high exposure to both waves and currents.

Once completed, the outer portion of the donut will stand 57.5 feet (17.51 m) tall, with a 48 foot (14.64 m) tall inner portion. Its total diameter, including the jetty, will be 180 feet (55 m). In all, it has a 22,000 cubic meter capacity and will be able to support 1.1 metric tons of biomass.

The Norwegian Directorate of Fisheries, a Norwegian government agency that promotes sustainable management of marine resources, has issued development licenses for the marine donut concept, noting that the project contributes to solving several environmental and area challenges facing the commercial fish farming industry. The project, the agency added, involves new and “significantly improved” production technology.

Figure 3: McElroy’s most recent fusion machine, the TracStar iSeries. Source: McElroy

The marine donut’s construction is fine-tuned to address several of the challenges that face the commercial fish farming industry. Because it is a closed containment facility, it allows for significant temperature control, reducing the risk of fish lice and preventing escape. The flow system exercises the fish and can be adjusted alongside the pressure, according to the needs of the species housed inside. For example, if salmon are being raised inside the donut, a river-like environment can be created to closely match what the fish would experience if born and raised in the wild.

The donut is equipped with a system that accounts for the animals’ waste, as well. A sludge collection system allows that waste to be reused for fertilizer, natural gas or other products.

Because of thermoplastic pipe’s ability to withstand harsh conditions and outlast traditional iron and steel pipe materials, its use was an easy choice for this project. Butt-fused thermoplastic pipe has a 0% allowable leakage rate, giving the users of the marine donut peace of mind when it comes to the durability of its piping systems.

Recent technological improvements in thermoplastic pipe have allowed for even better control and quality of piping materials. As a result, the pipe and pipe fusion industries are expected to continue a pattern of sustained growth. At the same time, new and exciting uses for thermoplastic pipe continue to appear, as more and more engineers and contractors realize the benefits of the piping material and the time and money saved by utilizing quality materials, quality fusion equipment and quality fusion operators.