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Technical Tips & Information
Air Knife Systems Can Cut Compressed Air Costs 65%
Drying, contrary to some beliefs, is a critical and often costly process integral to many manufacturing industries from potato chips to micro chips. Some of the options include using compressed air, warm air, and infrared to name a few. Most of these options are expensive to operate and prone to problems. For many applications, the combination of a suitable blower combined with an adjustable air knife incorporated into a system presents the best opportunity to achieve your drying results. Simplicity and low operating costs are added benefits.Many plant applications for compressed air use involve drying or cleaning of products and equipment. Compressors typically generate about 4.3 cfm per horsepower. For most drying, cleaning, solvent evaporating, and similar applications use the velocity of air to achieve the desired result. Nozzles and air knives can be provided with the required air from a high speed belt driven blower.
A properly selected blower will provide large volumes of air which will also be heated by the blower as a byproduct of the blower operation. This high volume of warm air is a perfect solution to affect drying of many types of products in a cost effective manner. When combined with an air knife system to properly manage and direct the air at the product, high speed effective results are easy to achieve.
Typical systems include a 3 hp-20 hp blower combined with 2-4 stainless steel adjustable air knives to achieve the desired results. The blower when combined with the air knives delivers a precise curtain of air which “squeegees” liquid off the surface of a part. High impact air velocities of 10,000-35,000 FPM is achieved by the blower and when combined with a natural heat of compression of the air of 25-80 F aids in drying effectiveness.
Air knives come in a variety of styles and configurations. The most common style is a rectangular slot. The “work” done by the air is really a function of the air velocity exiting from the slot.
Air consumption is a function of the air knife slot width and length of the knife. As an example, assume we wish to dry a 24” wide conveyer using four air knives, two up and two down. For best drying results we are going to use a 30,000 discharge velocity from a .045” wide slot. Consulting Chart One, air consumption is 9.4 cfm per inch of air knife. Each 24” air knife would consume 225.6 cfm of air (9.4 x 24). Four air knives would consume 902.4 cfm of air. Using a conventional air compressor at 4.3 cfm per horsepower, 209.9 horsepower would be required to perform the drying task.
Using a air knife blower, selection would be a 15 hp blower operating at 18,000 rpm. Horsepower saved in this example is 195. Power saved is 145 KW. Using a cost of $.05 per KW and 40 hours of operation per week, electrical savings is $1,160 per month. A system as described would cost about $7,000 depending on accessories and installation details. Payback in this example is about 6 months.
Call for information and a proposal for an air knife system to meet your cleaning or drying needs.