Moisture-Cured Coatings for a Water Filtration Plant


Written by:
Randy Kerans, The Sherwin-Williams Company

Pumps & Systems, August 2008 

Polyurethane coating technology is commonly chosen for demanding exterior applications such as bridges, stadiums and other large structures. When maintenance was required inside the Hammond Water Filtration Plant in Hammond, Ind., a moisture-cured polyurethane system proved the only way to coat more than 35,000- sq ft of piping and valves.

The plant, which was built in 1936 and renovated in 1950 and 1970, posed numerous repainting challenges. Some of the pipes had never been coated, producing major corrosion problems. There were no records for the surfaces that had been coated, but it was likely that lead was present. Naturally, it was imperative to remove the rust and any lead-based paint before any recoating took place. In addition, conditions inside the plant were highly unusual. Very cold water piped into the plant caused significant condensation that made coating extremely difficult. There was no chance of shutting down or taking any of the pipes out of service since the plant filtered 70-mgd of water.

In October 2004, Hammond called upon Dixon Engineering of Lake Odessa, Mich., to evaluate the project and make recommendations. According to Dixon Vice President Ira Gabin, "Performance and aesthetics were the major considerations-they wanted the job to last and look good 15 to 20 years from now. It was a huge project, and it was going to take a really experienced coatings contractor. The crew would be limited to working in winter months when pipe sweating is minimal. In late spring and summer, you'd get huge differentials in water temperature, and it would be like walking through a waterfall in there."

Can the Contractors Take the Heat?

Dixon Engineering specified a moisture-cured urethane (MCU) system formulated from raw materials manufactured by Bayer MaterialScience. They called on Sherwin-Williams, who agreed to deliver the paint within a week. The system consisted of two different Corothane primers to be used on two different types of pipes, plus an intermediate coat and aliphatic topcoat. Given the conditions inside the plant, Gabin noted that "The MCU system opened a bigger painting window for us."

Specifications were sent to 17 paint contractors, and 14 came to the site for a mandatory pre-bid walk-through. Everyone needed to know the extent of the project and the complications. Eight companies submitted a bid. In January 2005, Era Valdivia (Chicago, Ill.) was awarded the job. According to Project Manager Greg Bairaktaris, "We walked this plant twice just to make sure we were comfortable with the logistical challenges. The bottom line was going to be proper planning and execution."

From Surface Prep to Topcoat

Work was scheduled to be completed in two phases so that the painting contractor could work in the cooler months. Era Valdivia began Phase I in March 2005. Access to certain areas was difficult. There were only two entrances to the plant, and work was required upstairs and downstairs. The painting crew had to carefully stage their hoses and other equipment around the plant staff's work area. Plant Superintendent Gary Williams admits he was nervous about protecting valves, controls and other vulnerable equipment. If any parts were damaged, he would have operations problems and major expenses.

Bairaktaris notes that the surface preparation was particularly challenging. Dehumidification was necessary to remove condensation from the pipes in order to hold the blast. If dehumidification was not used, flash rusting would have occurred.

The substrate was mostly steel, which needed to be blasted to SP10 specification before it was coated. Cast iron pipes were prepped to SP6, then coated. The moisture-cured system actually compensated for some of the onsite problems because it could be applied if the pipes were damp and could handle some flash rusting. "It was hard to get the surface clean enough and moisture-free," says Bairaktaris. "You couldn't get that cast iron to near-white. But the moisture-cured system solves problems on the engineering side, as well as on the application side."

Once the primer was applied, the intermediate and topcoats followed. Since all the pipes needed to be color-coded, the topcoats were made with six different pigments. Since the aliphatic topcoat emitted a low (3.5) VOC, the plant could remain in operation even during the final stages of the maintenance project. "It was a difficult application," continues Bairaktaris. "We needed to use a combination of brush, roller and spraying techniques. We'd spray the piping system first, then cut around it for the color-coded piping. It wasn't a straightforward job."

On Time, On Target

Era Valdivia completed one room at a time during Phase I before tackling Phase II in January 2006. Both phases were completed on time, with minimal disruption to normal plant operations and minimal damage to vulnerable equipment. In all, the project spanned two years and required 900 gallons of coating. "We're very happy with the way it turned out," commented Hammond's Williams.

"This was the only project of this scope that we had done with MCUs," says Gabin of Dixon. "But in an environment like this, I would spec this MCU system again without concern."

For more information, contact Thomas Erdner at Bayer MaterialScience LLC, 100 Bayer Road, Pittsburgh, PA 15205-9741, 412-777-5200

 

The Sherwin-Williams Company, 1-800-524-5979

 

Dixon Engineering, 616-374-3221

 

Era Valdivia Contractors Inc., 773-721-9350

 

Hammond Water Filtration Plant, 219-853-6439


See also:

Upstream Pumping Solutions

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