Here's an "insider's" explaination of compressed air industry's top ten "rules of thumb"...explaining lot of terms and formulas that many people may not be very familiar with.
Here are our TOP TEN Compressed Air "Rules of Thumb" that we have come up with throughout our 25-plus years of experience. These are the areas of interest that our air compressor customers seem to ask about most.
1. CFM delivery per Horse Power expected at 100 PSIG: • For "home owner" type of air compressors---2 to 2.5 CFM per HP • For Industrial Air-cooled 2-stage air compressors----3.5 CFM per HP • For Small Vane & Screw air compressors (25 HP or less) 4 CFM per HP • For large Piston, Screw & Centrifugal air compressors--4.5 to 5 CFM per HP
NOTE: THE MORE CFM PER HP - THE LESS ENERGY USED.
2. Air Receiver Size needed for these types of inlet control: • Modulating Control---------------0 to 1 gallon per CFM • On-Line/Off-Line----------------- 3 to 4 gallons per CFM • Stop-Start/ Variable Speed-- 4 to 6 gallons per CFM
NOTE: THE MORE AIR STORAGE - THE LESS ENERGY USED
3. Amperage per Horse Power: 115 Volts------- 1 phase-------- 10 amps per horse power 230 Volts------- 1 phase-------- 5 amps per horse power 208 Volts------- 3 phase-------- 3 amps per horse power 230 Volts------- 3 phase-------- 2.5 amps per horse power 460 Volts------- 3 phase-------- 1.25 amps per horse power 574 Volts------- 3 phase-------- 1 amp per horse power
NOTE: THE MORE ENERGY EFFICIENT THE MOTOR - THE LESS ENERGY IS USED.
4. Air Piping Size by CFM and Pressure Drop: • Compressor Room Header---0.25 PSIG pressure drop per 100 feet of piping • Main Line-----------------0.5 PSIG pressure drop per 100 feet of piping • Loop Line-----------------1 PSIG pressure drop per 100 feet of piping • Branch Line---------------2 PSIG pressure drop per 100 feet of piping
NOTE: THE LESS AIR PRESSURE DROP - THE LESS ENERGY USED.
5. Size your Compressed Air Line Filters to be twice (2x) your compressor CFM flow rate. • This will lower your pressure drop 2-3 PSIG and save an additional 1% on electrical energy costs. • Elements will last twice (2x) as long and this can save on your maintenance costs.
6. Lowering Compressor Pressure settings 2 PSIG will result in a 1% energy savings.
7. Lowering Compressor Inlet Air Temperature 10° F will result in a 2% energy savings.
8. The average energy cost to operate an air compressor is approximately $0.10 per horse power per hour.
9. Compressed Air system leaks totaling the size of a 1/4" orifice, at 100 PSIG, running 24 hours a day will waste approximately $15,000 worth of electrical energy a year.
10. Using Synthetic Compressor Lubricants can save you up to 9% of the energy cost of operating your compressor as compared to using a non-synthetic lubricant.
DEFINITIONS: CFM= Cubic Feet per Minute - Volumetric air flow rate. Inlet Pressure = The actual pressure at the inlet flange of the compressor. PSIG= Pounds Per Square Inch Gauge AMPS=Abbreviation of the plural for Ampere, a unit of electrical current
Tommy McGuire Owner of McGuire Air Compressors "Real People with Real Air Compressor Experience" 1-888-229-9999 Email: compressors@mcguire.biz
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Tommy McGuire has owned McGuire Air Compressors, located in a 10,000 square foot facility in the heart of Piedmont NC, since 1981. His knowledge of air compressor systems & related equipment is extensive.
