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JOB AT A GLANCE PROJECT: Abrasive blast, repair weld, and recoat interior and exterior of 5,000,000-gallon (18,927,058.9L) water tank in the city of Houston COATINGS CONTRACTOR: Blastco Texas 5514 East Hampton Drive Houston, TX 77039 (281) 590-3200 www.blastco-texas.com SIZE OF CONTRACTOR: An 8- to 10-man crew worked this project ABOVE The interior blast- ing revealed unforeseen prob- lems, mainly at the tank's cen- tral high point where chlorine fumes accumulated over the years. The 48"-wide (121.92cm), 45'- long (13.7m) beams were too far gone to take paint. With the portal cut, Blastco used a 10,000-pound/4,535.92kg- capacity JLG Industries forklift to bring in scaffolding. Forklifts, boom cranes, compact tractors, and other self-powered machin- ery entering the tank were equipped with catalytic converters by Canada-based CEP. Nobody wants to breathe carbon monoxide, and believe it or not, some coating manufacturers don't want their products curing in polluted air. For scaffolding, Blastco uses a modified version of a commer- cially available wedge-lock system. The Blastco system rides atop a wheeled carriage so the scaffold can be moved without disassembly. That saves time! "We took a typical wedge-lock system and placed it atop a carriage that rolls around," says Soper. "That way, we also have a bigger platform. Each scaffold is 10'-by-20' (3.05m-by-6.09m) and accommodates four blasters. On this project, we put four scaffolds in there." For safety's sake, such modifications should be designed by qualified engineers. "You have to make the initial investment and have it engineered and stamped," Soper says. "Ours come with outriggers that prevent them from tipping over if a tire goes flat. You can't just go in there with a farmer's wagon." BLAST HOSES GALORE Outside, Blastco fired up their ARS Super Unit, a self-contained mobi le blast and vacuum rig that recycles spent abrasives like crazy. Soper estimates that conventional blasting on the 80,000-square-foot (7,432.24m2 PRIME CLIENT: City of Houston Drinking Water Operations 901 Bagby Street Houston, TX 77002 (713) 837-0311 www.houstontx.gov SUBSTRATE: 1970s-era steel tank SUBSTRATE CONDITION: Generally good but with excessive interior corrosion at top of domed roof SIZE: About 80,000 sq. ft. (7,432.24m2 DURATION: Four-month project UNUSUAL FACTORS: ¢ Tenacious drought meant city in hurry to get tank back in operation ¢ Extreme size of tank required 10'x10' (3.05m x 3.05m) access door cut into side ¢ Approximately forty 45' (13.72m) steel beams needed replacement ¢ Large expanses of rooftop and exterior walls invited use of robotic abrasive blaster MATERIALS/PROCESS: Exterior ¢ Abrasive blast to NACE No. 3/SSPC-SP6 Commercial Blast Cleaning with a 2.5-mil (63.5 microns) anchor profile ¢ Spray-apply 2- to 3-mil (50.8 microns to 76.2 microns) DFT layer of Carboline Carbozinc 11 base coat ¢ Spray-apply 4- to 6-mil (101.6 microns to 152.4 microns) DFT interme- diate coat of Carboguard 893 in a single pass ) project would have produced approximately 400 tons (362,873.9kg) of spent paint and blast media (enough to fill about forty 20-yard/18.29m dumpsters). By recycling blast media and tossing out only spent coatings, the ¢ Spray-apply 2- to 3-mil (50.8 microns to 76.2 microns) DFT topcoat of Carbothane 134 HG in a single pass ¢ Interior ¢ Abrasive blast to NACE No. 2/SSPC-SP10 Near White Metal Blast with 3-mil (76.2 microns) anchor profile ) July 2012 J www.coatingspromag.com 57