Coating the exterior of a large steel tank is never an easy endeavor, but add to that lead paint removal and a Class 1 explosive jobsite and things get complicated. This was the situation faced by the Yankee Fiber Control team when working at an energy manufacturer in the northeastern United States that wishes to remain unnamed.
The substrate was a large carbon steel tank that would remain active during the entire surface prep and coating process. “The tank was constantly being filled with liquefied natural gas that eventually will go into pipelines and be used to heat homes,” explained Chris Gagnon, project estimator for Yankee Fiber. “We did the work on the exterior during the summer months, and the tank needed to remain in service so that there was not a supply problem during the winter months when demand is high.”
The job specifications called for applying a new coating system on the tank, caulking on the roof skirt, and an epoxy caulk/sealant on the bottom chine and concrete base. “We prepped and coated 100,000 square feet [9,290.3 m²], including shell exterior, support rings, welded stairs, catwalk, and rails and concrete base,” explained Ron Gagnon, vice president of Yankee Fiber and Chris’s brother.
The team arrived on the job in the spring, as the cold Northeast weather made any other start time nearly impossible. “A third party erected the scaffolding, but they had to wait until the snow melted and the ground thawed enough to support the scaffolding,” explained Ron Gagnon. With the height of the tank, especially the dome, the crew was often working 125 feet (38.1 m) off the ground. The scaffolding was fully planked with toe boards and guard rails, and the crew was 100 percent tied off. “The team also had training in fall protection prior to the job,” he said.
According to the Yankee Fiber team, the jobsite property is bordered by an organic farm and protected wetlands, so keeping the surrounding environment free from any lead contamination was of the utmost importance. The team put up a Monarflex containment system to ensure that fugitive lead was not released during the abrasive blasting process, and they used pre- and post-soil sampling.
The containment system was non-permeable; however, there had to be a way for a gas pressure relief valve to be installed. “We engineered the containment system to accommodate duct work and an external gas pressure relief valve. This way, if the interior of the tank ever became over-pressurized, the excess gas pressure could be safely vented into the air outside the containment system,” said Yankee Fiber President Jim Hutzler.
Inside the containment area, the crew set up an Industrial Vacuum Hurricane high-efficiency particulate air (HEPA) waste vacuum and two 20,000 cfm (566.3 m³/min.) Industrial Vacuum dust collection systems. They were used to keep the area clean during the blasting process.
According to Hutzler, the air in the breathing zone was constantly monitored. “In accordance with the lead compliance plan, there was third party OSHA [Occupational Safety and Health Administration] personnel monitoring, and all team members had lead exposure training and were medically monitored. Also, full blast suits and NOVA 2000 blast hoods were worn during the blasting,” said Hutzler. The blast hoods had cooling nozzles attached to ensure that each member of the crew was kept comfortable during the blasting process. For the coating application, the crew wore Tyvek suits and powered air-purifying respirators.
Because the job was considered a Class 1 explosive site, the crew also grounded their equipment and wore personal electronic gas detectors to monitor the levels of gases inside the containment. The containment was tested upon shift start and after breaks for explosion hazards, as well.
On top of all of that, the crew had to contend with the effects of the intensely cold temperature of the tank’s interior. According to Hutzler, Yankee Fiber quickly learned that dehumidification was an absolute necessity. Without dehumidification within the containment area, the temperature gradient between the tank’s internal core of -250° F (-156.7° C) and external shell temperatures would cause excessive condensation on most nights (and randomly throughout the day), cause flash rust on the blasted steel, affect paint curing times, and reduce suitable blasting and coating conditions. “The three 6,000 cfm [169.9 m³/min.] Polygon DX 30-ton [27,215.5 kg] dehumidifiers with air conditioning kept condensation to a minimum and controlled the environment within the containment,” stated Hutzler.
Having a Blast
For the exterior of the tank, the crew brought in one four-pot and one six-pot ARS Recycling Systems blasting/grit recycling systems with 75 drums of Winoa Abrasives W G40 steel grit media. As stated by Hutzler, using the recyclable media reduced hazardous waste from 1,200,000 pounds (~554,000 kg) of spent conventional media to less than 20,000 pounds (~9,000 kg) of spent recycled media.
The abrasive blasting process not only removed the old lead paint layers, but it also prepared the steel surface to receive Sherwin-Williams’ three-coat system. All coats were applied to the tank’s exterior using two Graco King airless spray pumps, along with two Ingersoll Rand compressors.
The crew first installed a recoat-able epoxy at an average dry film thickness of 4 mils (101.6 microns). “We would spend two, three, or four days blasting, and then we’d prime the area,” said Ron Gagnon. Because of the long recoat window — up to one year — the crew primed the entire tank prior to beginning the intermediate coat application, Macropoxy 646. This fast-cure, high-solids polyamide epoxy is designed to protect steel in industrial exposures; it was applied at an average dry film thickness of 4 mils (101.6 microns). Once cured, the crew applied Sherwin-Williams’ high-solids urethane topcoat at an average dry film thickness of 3 mils (76.2 microns). This coating is designed for abrasion and weathering resistance, and it offers color and gloss retention.
Throughout the entire coating process, any pinholes and weld scars on the tank’s exterior were repaired with epoxy putty. In addition, the crew applied Sika Flex 2C caulk on the roof skirt of the tank. “This ring on the edge of the dome ensures that any water goes over the sides and does not stay on the dome of the tank,” explained Chris Gagnon.
On the bottom tank chine and concrete base, the crew applied Unicoat’s Polysulfide Epoxy caulk/sealant. The concrete base was spalled and had cracks, so the crew wanted to encapsulate the concrete and ensure that no further cracking would occur. According to Hutzler, the Unicoat product dries in a matter of minutes and is flexible enough to handle the movement of the concrete during freeze/thaw cycles. On the tank’s exterior, the Yankee Fiber Control team used DeFelsko PosiTector 6000 coating thickness gages.
Safe to Say
Yankee Fiber Control is happy to report that even with the hazardous conditions, there were no safety issues at all on the job — no injuries and no release of fugitive lead into the environment. “We did a lot of front-end work to make sure that all safety protocols were in place. During the job, safety was the top priority, and our crew was well-versed in all procedures and the use of safety equipment,” said Chris Gagnon. It’s safe to say this job could be considered a feather in the cap for Yankee Fiber Control.