Metal Finishing Guide Book


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With surface area known, solution drag-out and water consumption is calculated and expressed in gallons per hour. Water treatment experts suggest every gallon of dragout requires approximately 600 gallons of rinse water to maintain appropriate dilution levels. Total annual water consumption can then be calculated. Be aware rinses may require RO water, a process that is approximately 75% efficient. The 25% loss should be added to total water consumption calculations. Machines should be designed to reduce solution drag-out by any/every means possible. Opportunities include efficient rack, barrel, basket, or rotating basket design, long drain dwells, up-barrel rotation (Figure 2), largest possible round or slotted barrel perforations, tipping, tilting, or vertically oscillated racks (Figure 3), recirculating spray clean and/or multiple cleaners, over tank top sprays, and engineered flow in rinse tanks all contribute to drag-out reduction (Figure 4). Clearly, machine design should be a cooperative effort. * It is important to note that water treatment is an Figure 3. Vertical rack oscillation reduces dragevolving science. Federal, out (Photo credit: Photography by Colleen Sadlik, state, and local environmental regulations regarding water use and treatment — and the methods and cost of treatment and disposal of spent process chemistry and/or sludge — are beyond the scope of this article and should be addressed with a competent water treatment supplier. VENTILATION & AIR MAKEUP MANAGEMENT While the latest technical advancements are installed on new machines, older systems suffer due the perceived high cost of installation and associated downtime. As a result, air management too often remains a footnote in the energy reduction portfolio. It deserves closer review as improvements can be installed in phases to save finishers energy and cost. The least invasive improvement is to install VFD controls for the ventilation blower, which is slaved to tank temperatures. This offers the opportunity to slow ventilation output as tanks cool during overnight or weekend shutdowns, or may be shut down completely when temperatures fall to a predetermined 700

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