Extended service life and lower operating costs were the targets when Hankuk Fiber Glass Co. Ltd. (HFG, Kyungnam, Korea) developed a composite alternative to cast iron ash-transfer pipes for coal-burning electric power plant customers. Traditional iron pipes rust quickly and suffer erosion and subsequent failures from an abrasive slurry of water and residual ash (expected service life is typically two years). Further, the pipes are heavy and difficult to install.
The company developed an in-house, high-throughput filament winding process, using its own E-glass wet out with recently developed and trademarked EPOVIA KAYAK KRF-1001 epoxy vinyl ester resin (a low-foam, prepromoted and high heat- and abrasion-resistant grade of bisphenol-A epoxy acrylate resin) supplied by Cray Valley (La Defense, Paris, France). The material was used to produce composite pipe with diameters from 150 to 3,000 mm (6 inches to 10 ft) and wall thicknesses of 15 to 20 mm (0.6 to 0.8 inch). Plies that form the pipe’s slurry-exposed inner surface are wound using the KRF-1001 resin, modified with abrasion-resistant fillers, including alumina and silicon carbide. The outer pipe plies are produced using the same, but unfilled, resin. Although the filler initially tended to interfere with fiber wetout, HFG notes that this issue was addressed by Cray Valley, via improvements in the resin, and by HSG, via adjustments to the winding process.
The pipes have proven themselves in service. While HFG warrants them for two years, some installations already have seen four years of use with minor erosion, but no leakage or failure — a service life double that of cast iron. And, says HFG, they actually cost less than iron pipes. HFG conducted laboratory testing, in accordance with the ASTM D 4060 (abrasion resistance by Taber Abrasion) test method, which specifies that less than 40 mg/0.0014 oz of weight loss can occur in the test specimen during the 1,000-cycle test. Legacy iron pipe experienced a 72-mg/0.0025-oz loss in weight while the composite pipe lost only 7 mg/0.0002 oz, a ten-fold difference.
Based on this success, HFG is applying the technologies to large-diameter pipes in a growing number of thermoelectric power plants in Korea, and sees opportunities in the nuclear power industry as well as potable water and sewage applications.