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Polyurethane Elastomer System Extends Service Life of HVAC Cooling Towers at Competitive Cost

Bayer MaterialScience AG : 26 February, 2001  (Company News)
Keeping people comfortable - through heat waves, blizzards and every temperature in between - is a primary concern for facilities managers and requires regular attention to a building's heating, ventilation and air conditioning (HVAC) system.
This also includes the cooling towers often used in conjunction with these industrial systems. That's because the continuous evaporation and addition of water inside the towers leaves deposits, which cause corrosion and, consequently, leads to premature deterioration and costly replacement.

Fortunately, MAGNA-Coat Industrial Coatings, Georgetown, Texas, has developed an effective and less expensive alternative. MAGNA-Coat can greatly extend the life span of new and existing cooling towers by spraying the inside of the towers with elastomeric polyurethane materials from Bayer Corporation. The result: significant cost savings - as well as fewer headaches - for building owners and managers.

Bayer's Baytec« SPR Holds Harsh Environments at Bay

With 25 years experience in the industrial HVAC industry, Mike Swearingen, President of MAGNA- Coat, saw how the inside of cooling towers could corrode prematurely. He also noted how attempts to protect towers had mixed results, in part because the linings used had difficulty withstanding harsh conditions inside the tower and adhering for an extended period of time. 'Adhesion is the key,' he explained.

Swearingen experimented with several polyurethane products, surface preparation techniques and spraying conditions. He found the optimum material solution in the Baytec« SPR polyurethane spray elastomer system from Bayer's Polyurethanes Division. With a Shore hardness of at least 66A, as well as added ultraviolet (UV) stabilizers, the Baytec SPR system is used in spray applications to improve the corrosion, weather and abrasion resistance of metal, concrete, wood and plastic materials. Typical uses include protective layers for wood and industrial surfaces, and liners pipes and tanks.

The long- term corrosion protection and adhesion of the Baytec SPR system has been proven. The deck of a Norwegian fishing vessel sprayed with the Baytec system in 1967 was still intact and preventing corrosion 17 years later in 1984. In Germany, sheet steel profiles on a sea wall were still in good condition 14 years after they were lined with the Baytec system, even beneath layers of algae and barnacles.

'In addition to its excellent adhesion properties, it is also easier to apply. In fact, I haven't found a polyurethane product that is as forgiving as Baytec SPR in regard to the ambient conditions, such as humidity, dew point and temperature, under which you can spray,' said Swearingen. 'And not only does Bayer supply a great product, they also provide me with great technical support. On a scale of one to ten, they're an eleven.' Swearingen applies the polyurethane elastomer to the inside of new or existing cooling towers using a computerized, metered spraying system equipped with electronic temperature control. While spraying time varies by project, Swearingen said it typically takes three to four hours to coat the inside of a cooling tower. The polyurethane dries to the touch in just a minute or two, and fully cures in approximately 24 hours, he said.

While the Baytec SPR system is a constant in the equation, Swearingen evaluates other variables (such as tower age, condition and manufacturer) on a project-by-project basis, tailoring his proprietary preparation method accordingly. 'No two towers are exactly alike,' he explained.

Customers Save Mega- Bucks with MAGNA-Coat

According to Swearingen, his polyurethane elastomer lining process can markedly extend the service life of deteriorated cooling towers for approximately a quarter of the cost of installing a new tower.

Ken Anderson, Chief Engineer at Regency Office Center in Austin, Texas, called upon Swearingen when the complex's 360-ton, two- cell cooling tower started to pit and deteriorate less than six months after installation.

The facility drained the 12- foot-by-15-foot tower, and Swearingen sprayed the polyurethane elastomer inside. Now, more than a year later, the polyurethane lining is holding up very well, according to Anderson. This will extend the life of the tower and save thousands of dollars in the years ahead.

'The beauty of this elastomer system is that you can take something that is rusting and greatly extend its life,' he said, adding that lining the 22-year-old evaporator coil drain pan of the complex's cooling tower is now under consideration.

In fact, Swearingen, recently completed this type of project for Dobie Center, a multi-use facility incorporating a 30-story dormitory, retail complex and six-story parking garage on the University of Texas campus. The Factory Service arm of Carrier Corporation contacted Swearingen to line the condensate pan for the 30-year-old air handling unit in the dormitory's cafeteria.

'In places, the pan was rotted through and was leaking,' explained Jack Preston, Carrier Service Manager.

The pan was cleaned, patched, then sprayed, saving Dobie Center the expense of replacing the entire unit. As a preventive measure, Swearingen also sprayed the water basin and associated parts of two new outside make-up air units that service the cafeteria's kitchen.

Larry Dougherty, Chief Facility Engineer for Dobie Center, is pleased with the results. 'I was especially impressed with how the polyurethane adhered to the corroded pan,' he said, adding that he plans to have MAGNA-Coat apply the elastomer to the pans for the Center's 20-year-old cooling tower during the next scheduled maintenance shutdown. 'For patching and repairing, I don't think you could find a better product.'

Illustrating the versatility of Bayer SPR and his proprietary lining process, Swearingen also sprayed the drain pan of Tarrytown Baptist Church's nearly 50-year-old wooden cooling tower, in Austin, Texas. Other contractors considered the tower a lost cause, but Swearingen had faith in the polyurethane system. 'He was the first to tell us that it was worth saving,' said Beth Frank, Minister of Education and Administration.

Swearingen lined the pan in May 1999, and it has held up 'incredibly well, and saved us a huge expenditure,' said Frank, adding that, as a preventive measure, the church may ask MAGNA-Coat to spray the wooden slats around the cooling tower, as well.

The latest application of this technique was a 400-ton cooling tower that served 80 percent of a hospital's HVAC system in the Austin, Texas, area. Over the course of a single weekend, Swearingen drained and cleaned the tower, then lined it with the polyurethane elastomer.

Swearingen estimates that the tower had approximately three years of service life remaining due to heavy corrosion. By coating the tower with the Baytec SPR system, Swearingen estimates the tower could remain in service 'for as long as 25 more years.'

'Facilities that have purchased a new cooling tower recently, or that plan to purchase one soon, should also consider coating the new tower to help prevent corrosion from developing,' Swearingen said.
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