Here are the TOP TEN “Rules of thumb” for compressed air, designed to answer the questions most asked by users of industrial air compressors.
1. CFM delivery per horsepower expected at 100 PSIG:
o For “homeowner” type air compressors — 2 to 2.5 CFM per HP
o For air-cooled 2-stage industrial air compressors —- 3.5 CFM per HP
o For small vane and screw air compressors (25 HP or less) 4 CFM per HP
o For large piston, screw and centrifugal air compressors: 4.5 to 5 CFM per HP
NOTE: MORE CFM PER HP – LESS ENERGY USED.
2. Air receiver size required for these types of inlet control:
o Modulation Control ————— 0 to 1 gallon per CFM
o Online / Offline —————– 3 to 4 gallons per CFM
o Stop-Start / Variable Speed - 4 to 6 gallons per CFM
NOTE: MORE AIR STORAGE, LESS ENERGY USED
3. Amperage per horsepower:
115 volts ——- 1 phase ——– 10 amps per horsepower
230 volts ——- 1 phase ——– 5 amps per horsepower
208 volts ——- three phase ——– 3 amps per horsepower
230 volts ——- three phase ——– 2.5 amps per horsepower
460 volts ——- three phase ——– 1.25 amps per horsepower
574 volts ——- three phase ——– 1 amp per horsepower
NOTE: THE MORE ENERGY EFFICIENT THE MOTOR IS, THE LESS ENERGY IS USED.
4. Air Line Size by CFM and Pressure Drop:
o Compressor room header — 0.25 PSIG pressure drop per 100 feet of tubing
o Main Line —————– 0.5 PSIG of pressure drop per 100 feet of pipe
o Loop Line —————– 1 PSIG of pressure drop per 100 feet of pipe
o Branch ————— 2 PSIG pressure drop per 100 feet of pipe
NOTE: LESS AIR PRESSURE DROP – LESS ENERGY USED.
5. Size your compressed air line filters to be twice (2x) the CFM flow rate of your compressor.
o This will reduce your pressure drop by 2-3 PSIG and save an additional 1% on electrical energy costs.
o Items will last twice as long (2x) and this can save on your maintenance costs.
6. Reducing the air compressor pressure settings by 2 PSIG will result in 1% energy savings.
7. Lowering the air compressor inlet air temperature by 10 ° F will result in 2% energy savings.
8. The average energy cost to operate an air compressor is approximately $ 0.10 per horsepower 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 in electrical power annually.
10. Using synthetic compressor lubricants can save you up to 9% of the energy cost of operating your compressor compared to using a non-synthetic lubricant.
DEFINITIONS OF COMPRESSED AIR:
CFM = cubic feet per minute – volumetric air flow.
Inlet Pressure = The actual pressure at the compressor inlet flange.
PSIG = gauge pounds per square inch
AMPS = Abbreviation of the plural of Ampere, a unit of electric 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 in air.
Inlet Temperature = The total temperature at the compressor inlet connection.
Knowing these “rules of thumb” can help you understand many of the basics of compressed air. Applying these tips can help you save time, energy, and money.