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Technical Tips & Information
Cut Compressed Air Costs 65% with Air Knives
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.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.
This chart correlates air consumption with typical slot widths commonly used in air knives. Air consumption is a function of the air knife slot width and length of the knife.
Inches H2O CFM/Inch Velocity -ft/min
28.0 6.3 20,000
41.5 8.3 26,700
55.0 9.4 30,000
69.0 10.0 32,000
83.0 10.8 34,700
97.0 11.7 37,300
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 the information above, 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 high spped 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.