Compressed Air Best Practices - September 2008 - (Page 58) | 09/08 Compressed Air Industry FOOD PACKAGING & PROCESSING | REAL WORLD BEST PRACTICES UTILIZING VENTURI VACUUM GENERATORS With the same operating conditions we now have the following operating electrical energy cost analysis for compressed air use. p p p What is an integrated E-Stop Venturi vacuum generator with Air-Economizing Feature? This product, taking advantage of modern electronics, is completely equipped as a single unit with integrated control. No other controls are needed and it can be installed and operated without the utilization of machine controlled software. Venturi generators integrate pressure sensors, vacuum valves, blow-off valves and check valves, vacuum filters and E-Stop functions in a single assembly. The vacuum pilot valve is toggled “ON” and “OFF” for air economizing. The check valve holds the degree of vacuum in the cup when the air-economizing system is conserving air consumption. When a part is adhered to the cup, the vacuum pilot-operated valve is in the passing state. When power is lost, the E-Stop valve shifts. This air signal passes through the vacuum pilot-operated valve, which shifts the normally closed master valve to create vacuum flow. No matter what state of air economizing, this sequence will create vacuum flow to maintain the part on the cup because the emergency-stop unit circuit is separate from the air-economizing function. Use of an integrated Venturi vacuum generator with automatic control in many applications will allow the oversizing of the venture vacuum generator to cover higher cycles, unexpected leaks, etc. without interrupting production and still only using the minimum compressed air required. Control circuits to accomplish the same goals can be built onsite by qualified personnel and in addition to the proper design, the optimum vacuum sensors, control valves, check valves, blow- off valves, vacuum filter and e-stop components must all be located and installed. Many operators today feel much more comfortable with the new integrated units utilizing modern, quick response reaction. For more information contact Hank Van Ormer, tel: 740-862-4112, email: hankvanormer@aol.com, www.airpowerusainc.com Production Hours — 6,240/yr Power Rate — $.115 kWh One E-Stop Venturi vacuum generator with built-in automatic control system (air economizer) and full load flow — 9.4 kW at 60 psig Suction time — 85% of 6,240 hrs/year = 5,304 hrs/year Generator on time — .7 seconds / (÷ 50 seconds) = .012 minutes Air on time during production = .012 minutes x 60 minutes = .72 minutes per hour .72 minutes per hour = (.72 ÷ 60) .012% hours 5,304 production hours suction or (5,304 x .012) = 64 hours/year air on p p p p p Average scfm flow: p p Full load flow — 9.4 scfm Actual flow .012 minute = 9.4 scfm x .012 = .113 scfm each Total for six units = .678 scfm = (÷ 4-hp/cfm input power) = .170 average hp (x .746 ÷ .9 ME) = .141 average kW input Annual electrical energy cost of operating six units (.141 kW x $.115 kWh x 64 hours) = $1.04/yr p p The applications went from an annual electrical energy operating cost of $7,908/year for six units to $1.04/year for six units. Or, from a significant to an almost insignificant cost by changing to a more appropriate type vacuum generator for the conditions including proper, well-sealed cups. There are some instances where the savings might not be so dramatic such as when an extremely porous material needs to be held. However, many Venturi vacuum generator processes, particularly with robotic parts, transfer after significant opportunities. The more cups involved with the more extended time, the greater the potential savings. Obviously, when properly maintained, this type of product also should enhance productivity. 58 www.airbestpractices.com http://www.airpowerusainc.com http://www.airbestpractices.com
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