The markets: Corrosion-resistant applications (2017)

Corrosion-resistant composites are ideally suited to replace metal structures, including tanks, piping, cooling towers, railcars for chemical transport and much more, in this huge sector. The most pressing need is still in the area of underground pipe.

The annual cost of metallic corrosion worldwide is staggering. Considering the cost of maintenance, prevention, replacement of parts and interruption of services due to maintenance, the World Corrosion Organization (New York, NY, US) says that the annual cost of corrosion worldwide is US$2.2 trillion, more than 3% of the world’s gross domestic product (GDP). The US Department of Defense has estimated the annual cost of corrosion in military applications alone at more than US$10 billion per year.

Corrosion-resistant composites are ideally suited to replace metal structures, including tanks, piping, cooling towers, railcars for chemical transport and much more, in this huge sector.

The most pressing need is still in the area of underground pipe. The US Environmental Protection Agency’s (EPA, Washington, DC, US) report, titled State of Technology for Rehabilitation of Water Distribution Systems says “The impact that the lack of investment in potable water infrastructure will have on the performance of aging underground infrastructure over time is well documented and the needed funding estimates range as high as US$325 billion in the coming 20 years.

            The 18th Annual Underground Construction Municipal Sewer and Water Survey, conducted by Underground Construction magazine (Oildom Publishing Co., Houston, TX, US) reported in February 2015 that, for the first time in many years, municipal sewer and water personnel are somewhat optimistic about spending plans for 2015 and beyond. “Municipal authorities report spending plans for sewer/water/storm sewer piping systems of US$10.3 billion in new construction and US$7.8 billion for rehabilitation, an increase of 6.1% over actual 2014 spending.”  Almost 52% of survey participants prefer to use trenchless methods in lieu of open-cut techniques for construction and rehab projects and for those respondents, CIPP is by far the most preferred trenchless rehab method, cited by 52%.

            In the underground pipe market, like most markets served by the composites industry, customers want high performance — in this case, corrosion resistance, great strength and long-term reliability to reduce or eliminate costly repairs — without a high upfront price tag.

That makes good design essential. And that begins with material selection. As is the case in most markets, traditional materials here — iron, steel, concrete and more recent arrivals thermoplastics — currently rule the large-diameter water and wastewater piping market. That’s because “potential customers using traditional materials today fear that fiber-reinforced plastic [FRP] composite pipes may be damaged during transport and installation underground, possibly because the first cast FRP pipes on the market in the 1970s tended to be brittle,” says Nick Crofts, managing director of pipe manufacturer Amiantit Europe (Mochau, Germany), which acquired Flowtite Technology and its composite pipe design engineers from Owens Corning Composite Solutions Business (Toledo, OH, US) in 2000, after having been its principal licensee.

“We wanted to come up with a new product,” Croft maintains, “tougher than even the best FRP pipes available today, at a comparable or lower price point to these traditional materials.” The goal was a pipe product that, especially in large diameters, “could better withstand in-ground installation and handling — that’s been the Achilles heel for composite pipe.”

Toward that end, Amiantit recently introduced Flowtite Grey pipe for water, sewage, waste and raw material management. Envisioned as a way to expand the existing Flowtite product line, Grey would be much more resistant to rough installation and transport practices, better able to handle unexpected debris within the pipe and, especially, able to resist pressure-jet cleaning — a practice typical in concrete, steel and iron pipelines to control slime buildup. And, it would be engineered to withstand a range of loads imposed by underground burial, which are typically much greater than the loads on a pipe in above-ground installations. Essentially, the pipe wall structure is, a structural I-beam, built up in layers as the pipe mandrel continuously advances. After application of a polyethylene terephthalate (PET) release tape, the first layer placed onto the mandrel is a corrosion-resistant, boron-free fiberglass veil supplied by Owens Corning, wet out with a toughened PET to form a resin-rich, corrosion-resistant pipe liner that is resistant to pressure jet forces.

Over the liner are placed continuous glass rovings wet out with PET resin, in the hoop direction, together with chopped glass rovings that are sprayed simultaneously as the hoop fibers are applied, to form the beam’s inner “flange.” Crofts says the continuous hoop fibers provide hoop strength for pressure resistance, while the chop, although discontinuous, yields required axial strength. In some design cases, the chop can be oriented axially for greater resistance to axial contraction forces, as required.

The pipe wall’s “core” or center is a mixture of a fine-grained sand filler and chopped fiber, resin and more hoop fibers. Next, the outer “flange” is formed like the inner, with hoop and chop. Finally, another boron-free C-glass veil impregnated with the toughened PET forms the pipe’s outermost wear layer, providing a resin-rich protective seal.

At diameters greater than 400 mm, the company maintains, FRP pipe can be less expensive than that produced from plastic or ductile iron, yet deliver better corrosion performance, good flow characteristics and offer reduced weight as well to ease shipping and onsite handling. To accomplish this, the properties of the produced FRP pipes often vary. Because each project’s design is unique, based on installation-specific pressures, pipe stiffness class, burial depth, in-pipe vacuum, and handling, each is built to provide the necessary performance but also minimize cost. Flowtite Grey’s improved performance has been verified in tests conducted by Flowtite Technology’s R&D laboratory, in Sandefjord, Norway. Impact performance was measured via drop testing in accord with industry standards, and in some tests using heavier weights and longer fall heights than the standards. The tests showed no leaks after impact during sustained pressurization, at 1.5 times design pressure for 168 hours. Ultimate burst pressure was recorded at 75.6 bar. Says Crofts, “We’ve shown a 60% increase in abrasion resistance and a four- to 10-time improvement in impact resistance than original Flowtite FRP pipe, at a similar price point as competing materials, thanks to the design and materials used.”

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