Imagine the stopwatch starting before you even get to the jobsite for a steel tank lining and coating job. Imagine on top of that, when you arrive on site, there are enough holes in the steel to make it look a bit like Swiss cheese.
With three days to get the town of Pollack, Louisiana’s water tank back up and running, that was exactly the set up for the three-man crew from Global Coat. But for this seasoned crew, even those steep challenges were winnable. It was nothing but net!
A Better Option
Even though the steel tank was heavily corroded, the client decided that coating and lining the tank would be the best option. “The only other option before they found us was replacing the tank,” explained Global Coat’s President Steve Doxey. “That was going to cost them over $100,000, and they really didn’t have that in their budget.” In addition to being less expensive, the solution also had to be a fast one.
“They only had a tiny other tank in which to use and store water, so when they emptied this one, time was of the essence,” Doxey said. “A lot of people were without water and extremely low water pressure. We just couldn’t do it fast enough for them.”
The polyurea system from Rhino Linings, it seemed, made a great option. “The material that we selected has a 4-second gel time and has 80 percent cure in just a couple of hours,” Doxey said. “I don’t know any other material that has a gel of 4 seconds; once we were done they could be returned to service within a couple of hours.”
In addition to a fast-set material, the three-person coatings crew on this project helped move things along. “The crew has lots of experience applying polyurea, and with something with such a fast gel time you really need to know what you’re doing,” Doxey said. The lead foreman on this job has 12 years’ experience working with polyureas and the other two crew members have 5 years each under their belts.
“Time was of the essence,” Doxey said. Having the right crew and the right materials set up, things were looking good. On top of that, for the duration of the three days onsite, the crew had “good weather,” according to Doxey. There was no rain and no wind, two potential elements that can throw a wrench in the schedule, especially when working with sprayed materials. “The stars aligned for us on that one,” he said.
“Once they drained it, we jumped on the inside right away,” Doxey said.
“The focus was on getting the inside done — all hands on deck for the interior,” Doxey explained. The interior took two days to finish, and the first step was surface prep.
The crew blasted most of the steel to remove any rust and mill scale and to achieve NACE No. 2/Society for Protective Coatings (SSPC) Surface Preparation (SP) 10: Near-White Blast Cleaning. They wore blast hoods during this stage.
But due to the “hundreds of finger-sized holes in the bottom ring of the tank,” as Doxey explained, the crew had to “take great care” in that area. “That’s one thing that slowed us down. If we’d done the regular blasting, we’d have blown holes in that and taken finger-sized holes into fist-sized or larger.”
On the bottom ring, the crew used dual action (DA) sanders. “The only reason we had to use that was in the areas that were very thin; we would have just blown that bottom ring to pieces,” Doxey explained.
“There was a lot of scale and rust that came out from the inside of the tank,” Doxey said. The client had a receptacle on site for the crew to use. “There was already a lot of scale in the bottom of the tank from settling. Then once we sanded and blasted, more came off so we just removed that.”
Stripe, Coat, Repeat
Wielding Graco Fusion guns, the crew applied the primer the next morning and the polyurea a few hours later. They started with a full coat of Rhino Linings’ 1500 primer. They followed that with a stripe coat of the same — with a little extra finesse.
This was “not just the typical stripe coat but from all angles,” Doxey explained. “Right side, left side, top, and bottom — we stripe coated bolts and rivets from four angles to ensure full encapsulation and full seamless liner.”
They used the same stripe coat strategy with the polyurea too, which was Rhino Linings’ HiChem 11-70. The polyurea was applied with a Graco E-XP2 Reactor and a #01 tip applied at 80‒100 mils (2,032.0‒2,540.0 microns) on the floor and 60‒80 mils (1,524.0‒2,540.0 microns) on the walls. According to Doxey, the system adds “structural integrity back to the bottom ring.”
“Once they got the door on and bolted up then the crew focused on the exterior,” Doxey said. Remember, time was of the essence! So much so that “in effect they were putting water back on the inside while we were coating the outside,” he said.
Wearing Tyvek suits and full-face respirators, they used the same primer and polyurea system to the walls on the outside of the tank. There was no need for forced air. “So in effect, we’re sandwiching the heavily corroded and weak substrate in between our rugged and structural coating,” Doxey explained.
Fulfilling a Need
This small community was in dire need of access to its potable water. “From the time they emptied the tank, 72 hours later they had water back in it,” Doxey said. Working 10-hour days, the qualified crew completed the ~4,200-square-foot (390.2 m²) project on time and met that need.