November 2024 Vol. 79 No. 11
Features
New HDPE composite pipe replaces welded steel at potash mine
To update the brine transfer line at its Rocanville potash production facility in Saskatchewan, Canada, Nutrien, a Canadian fertilizer company, selected a steel-reinforced, high-density polyethylene (HDPE) pipe.
The project utilized 3,937 feet (1,200 meters) of a new spoolable pipe design: FlexSteel’s 10-inch MXL steel-reinforced composite product.
Nutrien opted for the new pipe design as it needed a high-pressure rated, API Specified 15S pipe. Able to handle up to 1500 psi, and designed and tested in accordance with API Specification 15S, the FlexSteel pipe fills the bill. The pipe design features helically wound carbon steel strip reinforcements that are sandwiched between an HDPE liner and an HDPE shield.
The undertaking was named 2022 Project of the Year by the Energy Piping Systems (EPSD) Division of the Plastics Pipe Institute Inc. (PPI). The award was presented to the PPI-member company and manufacturer of the pipe, FlexSteel Pipeline Technologies LLC, Houston, Texas, during PPI’s annual meeting held in May 2023. PPI’s membership votes on project of the year for each of the five PPI divisions.
Nutrien is the largest producer of potash, or potassium chloride (KCl), in the world. Its Rocanville mine is a conventional underground potash mine that uses long room and pillar mining techniques to extract ore. The mine is 3,150 feet (960 meters) below the Saskatchewan prairie and extends as far as 7 miles north and 4.3 miles south from the mine shafts. The shafts carry employees down to the mining level and lift ore up to the mill.
Generally, potash comes from underground evaporated sea beds and is mostly used as fertilizer to improve crop yield and quality. Mining operations employ continuous mining (boring) machines to produce a granular product for agricultural use. Nutrien`s annual capacity in Canada is more than 15 million tons of KCl, and Rocanville Potash is its largest asset. At the milling plant, crushed ore is sped into agitation tanks or scrubbers filled with a brine solution.
During this process, called ‘de-sliming,’ the mix goes through screens, cyclones and other specialized equipment to remove clay particles, leaving behind potash and salt. Through flotation and drying, potash is separated from the salt crystals. During flotation, a reagent is added to the mixture and causes air bubbles to form around the potash crystals. The crystals then rise to the surface and are skimmed. To remove excess moisture, the slurry of potash crystals and brine is fed into large centrifuges that pull the brine away from the potash. The potash is then fed into dryers that take out the remaining moisture by heating it to a minimum of 122 degrees F (50 degrees C).
Time for a change
Traditionally, Nutrien, like other mining companies, would use cement-lined carbon steel pipe for brine transfer pipelines. This, however, limits the pressure containment capability and presents challenges to maintaining the integrity of the lines. Recently introduced to the marketplace, the 10-inch 1500 psi MXL FlexSteel pipe provided the means to convey the brine and increase the flow rate by 50 percent, compared to the 8-inch steel-reinforced design.
FlexSteel pipe is a steel-reinforced composite pipe with concentric HDPE liner and HDPE shield that are reinforced by layers of helically wrapped steel strips. The sections of the pipe are quickly connected with reliable steel fittings that are hydraulically compressed onto the pipe to ensure the long-term seal and integrity. Each pipeline requires only a handful of fittings, which enables quick installation. The 10-inch diameter is the largest currently available in the spoolable pipe market.
“This project marks the first known installation and operation of a 10-inch steel-reinforced spoolable composite pipeline,” said Randy Knapp, Ph.D., engineering director of the PPI Energy Piping Systems Division. “Less than a decade ago, the same material set the standard as the first 8-inch product in the market.
“This FlexSteel pipe combines the advantages of HDPE pipe with the strength of steel pipe. It is fast, safe, and easy to install in any environment with minimal resources and can serve numerous applications, from energy to mining and industrial. The 20-year design life and simplified integrity management ensure the long-term integrity of the FlexSteel pipelines and reduce the total cost of ownership.
“Typically, the large-diameter reinforced thermoplastic pipe (RTP) pipe is used in the energy industry for hydrocarbon production and produced water injection and disposal,” added Knapp. “This project is also the first known application of FlexSteel pipe for the potash production industry. It expands the application envelope for the high-pressure, large-diameter RTP pipe and pushes it outside traditional oil and gas applications. The large-diameter and high-pressure capability of the pipe permits reliable transportation of corrosive fluids with no corrosion concerns and minimal integrity management.”
The Nutrien pipeline was installed in approximately seven days with a minimal crew of three persons plus two excavators and a bulldozer. Only seven midline fittings and two end fittings were required for the 3,937-foot (1,200-meter) project. The pipe was also easily pulled through several road crossings using HDPE casing. Due to constricted workspace, some sections of FlexSteel pipe were dragged for 1,640 to 2,300 feet to its final location; abrasion was not an issue for the thick outer HDPE pipe shield.
As a result of this successful 2022 pilot project, Nutrien selected FlexSteel pipe for another critical project at the Rocanville facility next year.
FOR MORE INFORMATION:
FlexSteel Pipeline Technologies, 832-531-8555, flexsteelpipe.com
PPI, plasticpipe.org/energypipingsystems
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