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The inside story on moisture-cured coatings

Published on 2007-11-21. Author : SpecialChem

Pittsburgh -- It's common knowledge that polyurethane coating technology is an excellent choice for demanding exterior applications such as bridges, stadiums and other large structures. But when maintenance was required inside the Hammond Water Filtration Plant in Hammond, Ind., a moisture-cured polyurethane system proved to be the only way to go to coat more than 35,000 square feet of piping and valves.

Originally built in 1936, with additions in 1950 and 1970, the Hammond Water Filtration Plant in Hammond, Ind., houses more than 35,000 square feet of pipe and valves that needed to be recoated - without interfering with plant operations.

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 being piped into the plant caused significant condensation, making coating extremely difficult. There was no chance of shutting down or taking any of the pipes out of service since the plant filtered 70 million gallons of water per day.

Only minimal maintenance was performed on the pipes prior to the repainting project in 2006, and rust and corrosion were significant.

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 15-20 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."

Conditions inside the plant caused pipes to sweat, especially in the warmer months. Two different moisture-cured urethane primers were specified because they could be applied even if the pipes were damp.

Can the contractors take the heat?

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

The moisture-cured urethane coating system, manufactured by Sherwin-Williams using raw materials from Bayer MaterialScience looks great - and should perform well for the next 15 years, in spite of harsh moisture conditions inside the plant.

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 they would be facing. Eight companies submitted a bid. In January, 2005, Era Valdivia from Chicago 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 - no sweat.

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 of 2005. Access to certain areas was difficult, to say the least. There were only two entrances to the plant, and work needed to be done 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 expense.

Greg 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 with Corothane I GalvaPak. Cast iron pipes were prepped to SP6, then coated with Corothane I MIO Zinc. The moisture-cured Corothane system actually compensated for some of the on-site 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 Corothane intermediate and topcoats followed. Since all the pipes needed to be color-coded, the topcoats were made with six different pigments. And because the Corothane I 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 with MCU system.

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

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

Bayer MaterialScience LLC is one of the leading producers of polymers and high-performance plastics in North America and is part of the global Bayer MaterialScience business with nearly 14,900 employees at 30 sites around the world and 2006 sales of 10.2 billion euros from continuing operations. Our innovative developments in coatings, adhesive and sealant raw materials, polycarbonates, polyurethanes and thermoplastic urethane elastomers enhance the design and functionality of products in a wide variety of markets, including the automotive, construction, electrical and electronics, household and medical industries, and the sports and leisure fields. Our inorganic basic chemicals unit produces chlorine and related essential products for the chemicals industry. Let us give life to your vision.

Bayer MaterialScience - Where VisionWorks.

Bayer Corporation, headquartered in Pittsburgh, is a subsidiary of Bayer AG, an international health care, nutrition and innovative materials group based in Leverkusen, Germany. In North America, Bayer had 2006 net sales of 7.8 billion euros and employed 17,200 at year end. Bayer's three subgroups, Bayer HealthCare, Bayer CropScience and Bayer MaterialScience, improve people's lives through a broad range of essential products that help prevent and treat diseases; protect crops and enhance yields; and advance automobile safety and durability.

This news release contains forward-looking statements based on current assumptions and forecasts made by Bayer Group management. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. Th ese factors include those discussed in our public reports filed with the Frankfurt Stock Exchange and with the U.S. Securities and Exchange Commission (including our Form 20-F). The company assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.

Source: Bayer MaterialScience


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