Compressed Air Best Practices - September 2008 - (Page 40) | 09/08 Focus Industry FOOD PACKAGING & PROCESSING | EIGHT FACTORS TO CONSIDER FOR EFFICIENT BLOW-OFF AIR 2 & 3. Space, Weight and Noise Level Space limitations can automatically discount the use of one technology over the other. Blower-operated systems (like air knives) require far more space and weigh more than compressed air amplifiers. Blower-operated systems create more noise than compressed air amplifier systems. Silencers can be added to blower systems, but this adds to the cost. 4. Application Particulars Applications where the blow-off must be continuous tend to favor blower-operated systems above 12” in length. Blower systems are typically constant running systems. This air nozzle design is popular on blow guns because it conserves compressed air while converting the pressure to flow and maintains a strong blow-off force with dead-end pressure still under 30 psi for safety. If the application calls for intermittent use of blow-off air, compressed air amplifier systems become much more economical. For example, if an item is on a conveyor, a compressed air operated air amplifier air blade (air knife) may be cycled on and off ONLY when the item is there to be dried. A blower-operated system, on the other hand, is constantly running. If the requirement for drying is intermittent, a blower system may actually use more energy than an amplifier. The distance between points in a blow-off system is important as to which technology is best. Blowers may have heated air and one must examine the product being dried — some do not allow the presence of heat (like packaged meat products). Some metals may have stains if the moisture is evaporated-off rather than blown-off. 5 & 6. Reliability & Energy Cost If the blower motor or the blower goes down, the production line goes down in a blower-operated system. Therefore spare parts and service response becomes a critical factor. Compressed air amplifier systems have no spare parts and run off stored compressed air and are intrinsically more reliable as a result. Smaller-size applications which are critical tend to use compressed air amplifiers for this reason. Blower-operated systems, used for constantduty systems, are far more energy efficient than compressed air amplifiers. FILTER A compressed air operated air knife is used to blow off the extra sugar on muffins before it goes into an oven. The application uses very little compressed air at low pressure and is tightly controlled to blow off the extra sugar. This eliminates the presence of burnt sugar in the oven and makes for perfect muffins. 40 www.airbestpractices.com http://www.airbestpractices.com
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