CoatingsPro Magazine

JAN 2013

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 77 of 100

JoB at a GLance Project: Abrasive blast and apply epoxy-based lining system to 17 failed 10-foot-diameter (3.05 meter) sections of concrete pressure pipe at a coal fired power plant coatings contractor: Structural Technologies 7455 New Ridge Road, Suite T Hanover, MD 21076 (410) 859-6539 size of contractor: abovE Meanwhile, another robotic cart designer Mike Kronz tested his machine inside a plywood pipeline mockup at his facility, also in Wisconsin. His goal was to pair his robotic cart with a Graco Probler P2 Elite internal mix gun to see how efficiently he could install polyurea onto epoxy pipe, on a test basis. "Sometimes you have to get lucky," says Rozek. "We ran the cart through three, 20-foot-long by 66-inch-diameter (6.10 meters by 167.64 cm) pipes. The first pipe took less than an hour, including cleanup. After all three, we crunched the numbers and found we were averaging 345 square feet (32.05 m2) per hour. In contrast, depending on what other system you used, doing the same work by hand might take six to eight hours." About that time, Structural contacted Rozek about the Southwest power plant. When he and Zaharias arrived on site, everything was set up for them to work their magic. The entire pipeline was drained and dry. Supply and exhaust fans provided air flow. The duo lowered the blast cart and Sponge-Jet equipment into the pipe, reassembled them, and moved nearly 800 feet (243.84 m) to the failed pipe segment farthest away from the air exhaust. They connected pneumatics to their rigs and began blasting. Rozek and Zaharias quickly discovered one of the biggest problems they'd ever encountered. I DIDn't orDer that! "It was supposed to be bare concrete," Zaharias says. "That's what we were told, and that's how the project was originally bid." The power plant had no record that the 40-year-old pipeline, had at one point in time, received a 30- to 40-mil (762- to 1,016micron) epoxy coating. But it had. Judging strictly by looks, it would have been hard to know otherwise. "Because of the hard water, we had layers of limestone and scale," Zaharias says. "We couldn't see there was a coating underneath and we had no reason to suspect there was one, so it wasn't until we started blasting that we found the epoxy. It just looked like dirty concrete. The epoxy changed everything." Prior to the blast attempt, estimates showed that the crew could expect to take bare concrete down to ICRI CSP-3 surface profile at a rate of 22 to 23 square feet (2.04 to 2.14 m2) per minute. If they could finish two sections an hour, they would be making spectacular progress. One and a half sections per hour would be considered great. One section would be barely acceptable. Two coatings crews worked this project, totaling about 30 men Prime client: Power plant in the Southwest that wishes to remain unnamed substrate: 40-year-old concrete pipe with steel casings and tension wire sandwiched inside substrate condition: Seventeen 20-foot-long (6.10 meter) sections failed inspection size: About 10,000 square feet (929.03 m2) duration: 28 days unusual factors: ¢ Plant could be taken off line only 28 days ¢ Extensive use of robotic carts ¢ Crews encountered mysterious preexisting 30 – 40 mil (762- to 1,016-micron) epoxy coating that was not part of original bid materials/Process ¢ Use motorized cart to blast Sponge-Jet encapsulated media to achieve ICRI CSP-3 surface profile ¢ Spray apply single pass of 3 - 5 5 mil (76.20 - 127 micron) (DFT) Structural VWrap 700 epoxy primer ¢ Hand trowel 20-mil (508-micron) (DFT) layer of VWrap 700 thickened with fumed silica to fill voids and create a tack coat ¢ Hand apply saturated strengthening fabric ¢ Lay down 130 mils (3,302 microns) (DFT) of thickened epoxy VWrap 700 ¢ Use motorized cart to install in hoop fashion 208 mil diameter steel wire at 2.5 wires per inch (2.54 cm) into still wet VWrap 700 ¢ Hand trowel 20-mil (DFT) layer of thickened VWrap 700 to cover wire ¢ Hand apply wetted saturated strengthening fabric ¢ On one test section, use motorized cart to spray apply three 32 mil (812.80 micron) (DFT) passes of polyurea safety considerations: ¢ Steel-toed boots, hard hats, safety goggles required ¢ When working near loud equipment, double hearing protection (ear plugs and muffs) required January 2013 g 77

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