Dehumidification control helps spread soft-touch paint

May 10, 2000
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Buyers of the 2000 Mercedes M-Class SUV (sport utility vehicle) will love the look and feel of its trendy soft-touch paint on the instrument panels and consoles, but they’ll have no idea of what it took to achieve the exacting application.

The coating used by plastics molding-assembler Arkay Industries, Miamisburg, OH, at its Arkay Plastics plant in Prattville, AL, is a special two-part application of water-soluble paint compounds that produces a soft-touch finish. However, application of the formula, color accuracy, and proper curing depend on precise environmental conditions of 55% relative humidity (rh) and 75°F temperature in the twin, 1,200-sq-ft paint booths.

“It’s temperature and humidity control in the application process that decides between a product that’s of the utmost quality and one that is less than acceptable and [has to be] produced again,” said Tim Henion, Mercedes model year 2000 program manager for Arkay Plastics.

Arkay is a tier-two injection molding producer-assembler for tier-one supplier Delphi Automotive Interior Lighting Systems, Vandalia, OH.

To maintain tight humidity and temperature tolerances of 5% or less, Arkay put together a design-build team led by mechanical contractor Capital Refrigeration, Montgomery, AL; engineers from hvac equipment manufacturer Dectron Internationale, Roswell, GA; manufacturer’s representative Derek Brown, president of Air Dynamics, Birmingham, AL; and consultants from Alabama Power Co. — A Southern Company, Birmingham, AL.

Key to Arkay Plastics' new paint booth for the 2000 Mercedes SUV interior components is the computer-controlled dehumidifier mounted above the booth.

Put on a coat

The production line of instrument panels, consoles, and other components are sprayed with the two-part coating as they are conveyed through paint booths between separate 3- by 8-ft entrance and exit openings. But these openings, which could potentially introduce contaminated air from the surrounding 50,000-sq-ft factory floor or from the flash tunnels and infrared ovens down the line, complicate the system design.

Arkay designed the application equipment for the booths, but the hvac system was designed by Brown and Bonner Patrick, P.E., president of Capital Refrigeration. The key unit of the hvac system is Dectron’s Dry-O-Tron® Series Model DK-450, typically used in office buildings, hotels, and other structures.

The DK-450, which is actually two systems packaged in one unit, has a capacity of 150 tons of refrigeration, 28,800 cfm, and 440 lb/hr of moisture removal. It is designed to introduce 100% outside air, which is dehumidified and cooled in the summer and heated in the winter months.

During Alabama’s seasonably dry winter season, a humidifier from Nortec Industries, Ogdensburg, NY, custom-installed in the DK-450 at the factory, raises the humidity when needed.

Although a paint booth might seem like a once-in-a-lifetime project for an hvac contractor, Capital has designed and engineered several paint booths for other manufacturers such as Lockheed Martin. However, unlike past projects where Capital combined different components to accomplish the job, Dectron supplied the firm with a complete package where all components were factory installed and tested.

“We’ve done plenty of paint booths in the past, but this is the most impressive because of the sophistication and high quality, from the coils on down to the doors and control systems,” said Patrick, whose firm recently merged its $12 million mechanical contracting firm with consolidator Comfort Systems USA, Houston, TX.

Cut the scrap

So far, there have been minimal scrap and remakes, due to the hvac system’s engineering. Henion said the dual paint booths, which cost approximately $250,000 to build, are state-of-the-art and unique for Arkay.

Few other applicators of the soft-touch paint, made by Red Spot Paint & Varnish Co., Evansville, IN, control humidity and temperature so accurately.

Capital and Henion did have challenges with airflow within the booth, however. Ongoing daily statistical studies will determine whether automated damper systems, monitored by airflow sensors, will be needed to maintain the engineered target velocity of 150 ft/min.

Currently, airflow is accomplished manually with one inlet and one relief damper installed in each booth’s supply duct. Regulating the damper openings for greatest airflow efficiency was accomplished through test-and-balance metering.

The booths presently are maintaining a positive pressure and excess air is relieved (via the relief dampers) into the factory, which improves the general IAQ of the surrounding open paint areas.

Sidebar: Building contractor standardizes on project mgmt software

Manhattan Construction Co., Tulsa, OK, has selected Prolog Manager 5.0 from Meridian Project Systems, Sacramento, CA, as its company project management software.

Manhattan Construction has purchased 70 licenses and will be fully standardized on the software by the middle of the year.

The firm also uses the software to help track all correspondence and logs and manage punch lists.

Manhattan Construction is currently using the software on jobs including the Williams Technology Center, MCI/Worldcom Northern Virginia Operations Center, Doubletree Hotel and Conference Center, and Electronic Data Systems (EDS) office building at Lincoln Park.

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