Removing Paint Overspray from Paint Booths
Vanchem manufactures products that aid in removing paint overspray from paint booths
Removing paint overspray is important because vast arrays of manufactured goods purchased by consumers are painted. There are two types of paint used in manufacturing, wet-paint (either solvent-borne or waterborne) and powdercoat (fluidized solid). This article discusses wet-paint only.
In automated wet-paint booth systems, paint is sprayed onto parts traveling on a conveyor. Parts can be anything from small painted widgets to large automotive body frames. Parts receive 50-80% of paint sprayed. This is referred to as paint transfer efficiency. The remaining 20-50% is paint overspray. For example, a paint transfer efficiency of 75% means 75% of sprayed paint goes to the part being painted, while 25% is paint overspray.
Paint overspray lands on walls, robots, fixtures, floor grating, and either onto dry paint filters or into flowing water curtains. Paint overspray is tacky to the touch and referred to as “live paint”. Manufacturing facilities are concerned with removing paint overspray because venting live paint directly to the atmosphere would produce environmental damage. Paint overspray will accumulate in paint booths, paint booth equipment, under booth areas, and exhaust stacks unless it is first chemically treated. Cleaning live paint from these areas is an onerous task that requires extensive downtime to complete. It is highly prudent to prevent such occurrences. Purchasing Vanchem detackifiers and detackification flocculants will ensure proper detackification.
Removing paint overspray is a unique process specific to wet-paint applications. There are two chemical solutions for removing paint overspray. The first solution is protecting paint booth equipment with Vanchem’s paint booth coatings (see article Booth Coatings for more information). The second solution is chemically treating paint overspray captured by flowing water curtains with Vanchem’s paint detackification chemicals.
There are two types of flowing water curtain systems, side-draft and down-draft. Side-draft systems force filtered air through a permeable wall or ceiling past the part into a waterfall. Down-draft systems force filtered air through a permeable ceiling past the part into a flowing water curtain located under the floor grating. Flowing water in both side-draft and down-draft systems travels to a paint-sludge removal process. Utilizing Vanchem’s detackifcation products, chemically treated water reacts with paint overspray for ease of removal. Detackified live paint is referred to as “killed paint”.
Forced air, paint overspray, and flowing water mix in an under booth venturi. The purpose of the venturi is to mass-transfer paint overspray from forced air into flowing water. Air and water are separated in the under booth after the venturi. Forced air travels to a mist eliminator process and in some designs includes a scrubber before exhausted to atmosphere. The flowing water diverts to a paint-sludge removal process.
The forced air passes through a series of inclined baffles in the mist eliminator section to remove water mist and particulate matter. Sometimes, a small amount of paint overspray is carried up and out the exhaust stacks after it has been scrubbed. This occurs when the booth balance (air pressure and water velocity) is misaligned or poorly maintained. Particulate matter can accumulate in the mist eliminator section and in other areas of the under booth. Routine manual cleaning is necessary for removing paint overspray from the under booth area in order to prevent environmental infractions and maintenance downtime.
Gravity carries the flowing water to a paint-sludge removal system normally located outside the paint area. The water contains detackified paint. It is pumped to a separation system where the solids are reacted with a Vanchem flocculant (see Vanchem Detackification Products). The reaction produces large floc particles that float and are subsequently skimmed and removed. The floating blanket of solids is called paint sludge. Paint sludge is then dewatered by a variety of different processes. It is normally disposed of as landfill or in some unique applications, used as an ingredient for other chemical applications, e.g. used in the making of artificial railway ties or drain plugs for automobiles.
Removing paint overspray is an important mechanical-chemical process commonly employed in facilities that paint parts. Industry has worked hard to advance the philosophy of cradle-to-grave manufacturing. Removing paint overspray is one industrial example of this philosophy at work.
Vanchem Performance Chemicals has a full product line of water-based and solvent-based detack technologies formulated to detackify live paint overspray. We also produce a line of paint booth coatings to protect paint booth floors, walls, robots, and other booth areas in order to regulate the maintenance and protection of these surfaces.
Vanchem has the solution for removing paint overspray. Contact Vanchem at our Burlington national headquarters for more information.