Here are the TOP TEN Compressed Air “Rules of Thumb” – designed to respond to the questions that industrial air compressor users ask about most.
1. CFM delivery per Horse Power expected at 100 PSIG:
o For “home owner” type of air compressors—2 to 2.5 CFM per HP
o For Industrial Air-cooled 2-stage air compressors—-3.5 CFM per HP
o For Small Vane & Screw air compressors (25 HP or less) 4 CFM per HP
o 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:
o Modulating Control—————0 to 1 gallon per CFM
o On-Line/Off-Line—————– 3 to 4 gallons per CFM
o 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:
o Compressor Room Header—0.25 PSIG pressure drop per 100 feet of piping
o Main Line—————–0.5 PSIG pressure drop per 100 feet of piping
o Loop Line—————–1 PSIG pressure drop per 100 feet of piping
o 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.
o This will lower your pressure drop 2-3 PSIG and save an additional 1% on electrical energy costs.
o Elements will last twice (2x) as long and this can save on your maintenance costs.
6. Lowering Air Compressor Pressure settings by 2 PSIG will result in a 1% energy savings.
7. Lowering Air Compressor Inlet Air Temperature by 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.
COMPRESSED AIR 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
Pressure = Force per unit area, measured in pounds per square inch (psi).
Pressure Dew Point = For a given pressure, the temperature at which water will begin to condense out of air.
Inlet Temperature = The total temperature at the inlet connection of the compressor.
Knowing these “Rules of Thumb” can assist you in understanding many of the basics of compressed air. Applying these tips can help save you time , energy and money.
