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Green isn’t a color normally associated with a top-selling car, but Volkswagen is hoping its eco-friendly paint shop at a new $1 billion Chattanooga, TN assembly plant will make inroads with car buyers.
The $120 million paint shop, which the company is expecting to start testing its operation this month, claims to be the most advanced in the automotive industry, and certainly one of the most sophisticated in North America when it begins producing about 150,000 vehicles annually starting in 2011.
“In terms of technology, we're the best,” says Lothar Grensemann, general manager of the VW paint shop, which is three levels tall to save space and to also utilize the heat that rises to the top of the expansive facility.
“We're trying to build the most eco-friendly process in the world,” says Donald Jackson, president of manufacturing for VW's Chattanooga operations.
The secret to the facility’s green success will be virtually no waste from the coatings by the time the vehicle moves through the 382,000sf2 shop, which is about the size of seven NFL fields. Overall, the VW production facility will be about 2 million sft2
More importantly, the paint shop will use 60% less energy than it normally would need thanks to innovative engineering and built-in technology controls.
“Volkswagen is a green company,” says Leslie Williams, a process engineer in the paint shop. “We’re always looking for ways to have less impact on the environment.”
Williams says the paint shop will re-circulate most of the air it uses rather than venting it and then replenishing it with fresh supplies. Volkswagen will also not apply a primer coat to it's vehicles since they have adopted new techniques that eliminate this need.
“We put on a second pass of the metallic paint, and then we use additional UV blockers and additional film build to eliminate the primer,” Williams says. “Other automotive companies are using a similar technology, but this will be the first for Volkswagen, and the customer won’t notice the difference.”
The process will be almost fully automated with 56 robots doing the work on the VW brands. The shop will have three drying ovens to burn off excess solvents before they can be emitted through exhaust systems, the largest at just over 425 feet long and reaching temperatures close to 320 degrees.
“With our new processes, the film builds of your base coats are critical for the UV protection of the ecoat layers,” Williams says. “We have two robots that do a 100% in-line check of that basecoat thickness in the paint booth immediately after it’s sprayed.”
After the vehicles go through the flash off oven, two additional robots check the film build at 100 points on each car. Totaled, it will take one vehicle about 39 minutes to make the trip through the paint system from start to finish, Grensemann says.
The Volkswagen plant is expected to create 2,000 direct jobs, and almost 12,000 indirect jobs in the region, according to independent studies. The new plant is expected to generate $12 billion in income growth for the Tennessee area.
The Chattanooga plant will build a new midsize sedan specially designed for the North American market. Approximately 30% of these cars will be powered by Volkswagen's TDI Clean Diesel Technology.
The paint shop construction is overseen by German-based Eisenmann AG with help from sub-contractors Southern Fabrication Contractors (Chattanooga), IMF Inc. (Greeneville, TN) and Complete Automation (Lake Orion, MI).
Eisenmann has installed its new ‘E-shuttle’ system that swings the car body into the dipping bath. Another German-based manufacturer, Dürr, installed its new EcoDryScrubber system to collect the excess wet paint particles and overspray.
“There is a lot of new technology going into this facility and in the course of the bidding process we introduced new technologies and Volkswagen was convinced it's the right way to do it,” says Ralf Voellinger, executive director at Eisenmann.
The EcoDryScrubber system will be where most of the plant’s eco-friendliness comes from.
On the market since 2008, the EcoDryScrubber at VW will be the first time it is used by an automotive OEM. European auto supplier and polymer specialist Rehau has been using it on bumpers at its German and South African plants for several years, producing about 500,000 products annually.
Dürr will be installing the complete top coat line for VW, which includes robotic and application equipment, as well as the PVC area for underbody, cavity and seam sealing.
“At the customer’s request, the EcoDryScrubber has been made even more fail safe,” says Jim Pakkala, engineering manager for Dürr. “We added an improved drainage surface that will ensure that liquids drain directionally away, thereby making provisions for dealing not only with the consequences of hose bursts should they occur, but also with activation of the sprinkler system.”
On top of energy usage savings, environmental impact benefits of the EcoDryScrubber includes reduced usage of natural resources and less air pollution. For example, the new Volkswagen top coat spray booth energy usage will be about 14,000 megawatts per year less than of a traditional spray booth, which is about a 62% reduction.
Included in the savings will be a reduction of roughly 45 million ft? per year in natural gas usage, Pakkala says. And because the greenhouse gas CO2 and smog forming gas NOX are by-products of natural gas combustion, the plant will see a reduction in those emissions by 2,800 tons per year and 3,800 pounds per year, respectively, he added.
In addition, Pakkala says the elimination of water as a scrubbing medium will reduce process air humidification requirements, cutting down on the spray booth water usage by nearly 4 million gallons annually.
Pakkala added that spray booths are the leading user of energy in most large-volume paint finishing operations, and is especially true for the automotive paint finishing industry, where historically 40-50% of the energy required to manufacture an automobile is consumed by paint spray booths.
“This energy is mostly consumed by equipment used to handle and condition spray booth process air,” Pakkala says. “One of the most effective methods for reducing spray booth energy usage is to recycle process air. By re-circulating a substantial portion of air exhausted from the spray booth back to the painting chamber, the quantity of air that must be fully conditioned is significantly reduced, leading to substantial energy usage reductions.”
An advantage of the EcoDryScrubber compared to traditional wet separation technology is the ease in which spray booth air re-circulation can be implemented, Pakkala says. Traditional wet separations systems -- commonly referred to as wet scrubbers -- utilize a chemically treated water curtain to capture paint overspray particulate. While wet scrubbers have proven to be robust, reliable systems in large volume painting operations, they have two weaknesses which hamper air re-circulation.
“Although wet scrubbers can yield separation efficiencies well above 99%, paint particulate concentrations in wet scrubber exhaust air streams are far above acceptable levels for painting environments,” Pakkala says. “As air passes through a wet scrubber, the air is humidified to near saturation. In order to implement an air re-circulation scheme with a wet scrubber system, high efficiency bag filters as well as de-humidification equipment must be installed downstream of the wet scrubber to further clean and re-condition the process air to acceptable conditions for paint application.”
Pakkala adds that this additional equipment is costly to install, operate and maintain, often negating a substantial portion of the energy cost savings gained by air re-circulation. The EcoDryScrubber overcomes these deficiencies through the use of a regenerative, dry filtration process which yields near HEPA 12 level filtration, allowing for direct air re-circulation of spray booth process air without the need for additional air conditioning equipment.
He says the EcoDryScrubber operates by directing paint laden process air into scrubber chambers located directly below and on either side of the painting chamber. Each scrubbing chamber contains an array of porous plastic filter elements. To protect these filter elements from becoming fouled with tacky paint particles, a process referred to as pre-coating is utilized in which a sacrificial layer of milled calcium carbonate is automatically applied to the exterior of each filter element. As paint laden air is drawn through the scrubber chambers and across the filter elements, wet paint particles are captured within the pre-coat layer rather than on the surface of the filter elements.
Paint solid particulate continues to accumulate within the pre-coat layer until a predetermined pressure loss is measured across the pre-coat layer/filter element, at which point a back pulsing sequence is triggered to release the now fouled pre-coat layer from the filter elements. The fouled material, which is completely dry and free-flowing, is collected and automatically removed from hoppers located below the filter elements. Virgin pre-coat material is then introduced into the scrubbing chamber and the process is repeated.
Tobias Schmedding, VW’s assistant manager for environment, says the paint shop is excited to use a dry filtration process rather than one which is water based.
“Usually, you get wet paint sludge,” says Schmedding. “With the change to dry, you get a dry powder.”
The EcoDryScrubber pre-coat process extends the life of the filter elements to a minimum of 15,000 hours. The process is automatic and is performed online without interruption to production or spray booth air balance. Compared to wet scrubber water treatment, chemical and sludge disposal costs, the costs of supplying and recycling the pre-coat are 20-40% lower, Pakkala says.
EcoDryScrubber was recently recognized by the automotive manufacturing industry, winning the 2010 Automotive News PACE (Premier Automotive Suppliers’ Contribution to Excellence) award.
Dürr is also building the new paint shop at the SGM Dongyue site in Yantai, a joint venture of SAIC and General Motors. The Yantai paint shop is designed for an output of 60 vehicles per hour. Production should begin in mid 2012 with painting for various Buick and Chevy models.
For more information on Eisenmann AG, please call 815-455-4100, or visit www.eisenmann.com. For more information on Dürr Systems, please call 734-459-6800, or visit www.durr.com.
Maximizing paint inspection performance
To read about attempts to achieve zero defects in the first surface, visit http://www.pfonline.com/articles/99sp04.html
Volkswagen Chattanooga Paint Shop
“By The Numbers”
• Total: 21,500 cubic yards
• Enough to fill seven (7) Olympic-size swimming pools
• Poured to date: 5,750 cubic yards
• Total pieces: 240
• Total weight: about 4,287 tons
• Equivalent to about nine (9) 747 jets loaded to capacity
• Installed to date: about 60 pieces
• Total pieces: about 7,000
• Total weight: 4,900 tons
• Equivalent to 2,970 Volkswagen Beetles
• Weight erected to date: 600 tons
• Total: 253,000 square feet
• Equivalent to about five (5) NFL football fields
• Total: 382,000 square feet
• Equivalent to seven (7) NFL football fields
Source: Volkswagen Group of America