When thinking of industrial coatings, the first thing that comes to mind isn't usually conservation. But when it comes to repairing as opposed to replacing a structure, a quality coating can add years if not decades to its existence, saving a company thousands of dollars in build cost and lost time. However, repairing comes with its own set of pitfalls and challenges, and in the case of an aging riveted storage tank, this meant stripping the existing substrate and a rigorous check for leaks.
Needing a complete overhaul in just a matter of weeks, the massive 160-foot (49 m) diameter structure in Portland, Ore., had to be stripped, sealed, and coated. According to Dayton Thorpe, associate estimator at Dunkin and Bush, the coatings contractor on this job, “When abrasive blasting the tank, you have to watch for weep holes small pinholes that cause minute amount of product to leak through, especially around the rivets) and take that into safety consideration. You'll notice that more so when you apply the product because it will leak through the coating itself, and we’ll need to ping it with nonferrous metal to fill the hole before you re-coat it.”
At the NuStar Energy facility, Thorpe and his team repeated this time-consuming process throughout the 60-foot-tall (18 m) tank in just three weeks, pushing for 10-hour days while also repairing other pipes to help get the entire facility up and running. The client had a tight timeline to keep their business going, but Dunkin and Bush also had numerous safety conditions to address in addition to the use of the non-sparking metal. Balancing the two and still getting the job done proved to be a type of challenge made for the skilled Dunkin and Bush team, including Pete Weise and Jacob Melton, project managers and estimators.
Blast. Prime. Coat.
While it may seem to be a simple process, re-coating the tank was not only a large job, but it also required significant attention to detail to make sure not a single crack or speck of rust went unattended. The process involved power-washing with at least 3,500 psi (24,132 kPa) and using a machine with a turbo tip. The crew washed the entire tank before and after blasting away the old coating, which eliminated any organic material, foreign objects, and debris. “After that,” noted Thorpe, “we blasted to SSPC-SP-10 [the Society for Protective Coatings surface profile 10, also known as the National Association of Corrosion Engineers No. 2] Near-White Blast Cleaning standard. And once it was prepped, we made sure that if there was an extended period of time between that, we generally did brush-off blast to make sure there were no rust blooms and then sealed with a primer.”
The primer, which was applied at 2 to 3 mils (51–76 microns) per coat, was then left to cure overnight on the tank that was still contained in tarps and scaffolding. Since Dunkin and Bush is one of the nation's largest painting contractors, everything was coordinated and supplied in-house, allowing for a smoother work process. Even then, it still took nearly three full days to set up the containment of the site, which consisted of scaffolding and a tarpaulin boom hoisted over the protective concrete wall surrounding the tank.
When it came to applying the coating — Mascoat’s Industrial-DTI (MI-DTI) thermal insulating coating — the crew utilized Graco’s King Airless Pumps on the majority of the tank. This allowed the coatings to go on “like butter,” according to the Dunkin and Bush applicators. The coating will not only “hinder any further corrosion of the older tank, but it will also aid in energy retention and personnel protection,” said Mascoat’s Marketing Director Will Conner. In addition to the coating, the crew was mindful to allow just the right amount of hose to allow the crew to move around easily, but not so much that kinks that could lead to expensive waste of equipment and materials could occur.
The crew spray-applied 60 mils (1,524 microns) of the MI-DTI coating in three 20-mil (508 microns) passes. On any smaller areas, they used pressure pots for touchups, which allowed for easy and thorough coverage of the entire structure. “Mascoat is pretty easy application as far as insulation goes, which I found surprising,” explained Thorpe. “We watched the equipment carefully, especially the intake. You want to be actively checking all your coatings as they’re going along and you do have to adjust your equipment for insulation coatings as well and be careful to follow manufacturers’ instructions as listed on most product data sheets.” Sometimes all the crew needed was a little bit of heat or a new filter.
Getting the Lead Out
Handling potentially dangerous fuel vapors was just one element the Dunkin and Bush team needed to be diligently aware of at all times. According to Thorpe, “[NuStar] wanted to get product going. They wanted to be able to store anything, but with safety concerns, we had to try to keep the tank at minimal pressure, especially when blasting.” In addition to monitoring the volatility of the fuel, the team rigorously tested for lead. This included blood tests, which were used to ensure that there was no lead poisoning. The crew also wore proper personal gear during lead abatement. After blasting off the old coating, lead tests were conducted to ensure that no hazardous materials were released during any stage of the restoration process.
Thorpe detailed the process explaining, “We can start at higher levels when we’re painting, but we try to [blast] so it doesn’t interfere with any of the coating. Generally, when blasting we work from the bottom up; while painting we work from the top down.” The crew used a Vector Vac, an industrial vacuum for the disposal of abrasive blast media, and took test samples. “We generally use at least 15 to 20 percent Blastox on all lead jobs to ensure that the Blastox particles in the blast attaches to the lead and renders it inert, making the blast non-hazardous waste. We don’t want our employees getting hurt or having their children gett hurt when they come home.” In terms of safety gear, everyone was wearing H2S monitors and Tyvek suits. And, regardless of conditions, NuStar required 100 percent tie-off.
Overall the project has been a rousing success. According to Thorpe, “For any product, the success of any coating comes down to proper surface preparation and following manufacturer’s instructions.” By also taking care of any structural or rust issues with the tank, Dunkin and Bush maintained a valuable asset for NuStar. Thorpe also stressed “attention to detail and clear communication with the customer, and a good manner of professionalism.” The deadline was met on time, met NuStar’s specific needs, and most importantly was done with the highest standards of safety monitoring. With a symbiotic business partnership, this tank job may have just helped to pave the way for coatings projects in the future.