Instrument Quality Air Requirements
In accordance with the Instrument Society of American Standards (ANSI/ISA-57.3-1975)(R1981) are:
- Maximum Particle Size-3 micron
- Oil content-1PPM w/ w/ or v/ v or less under normal operating conditions.
- Pressure Dew Point-At least 10C or 18F below the lowest ambient temperature.
- Air shall be free of all corrosive contaminants and hazardous substances.
How to Estimate Compressed Air Capacity
Generally, the compressed air capacity of an air compressor is related to its horsepower (HP). A good rule of thumb is: 4.5CFM per HP@100PSI.
Correction Factor for Sizing a Dryer
- FA=FRxC1xC2xC3xC4
- FA-Actual flow requirement
- FR-Nominal flow rating of a dryer
C1-Inlet Air Pressure Correction Factor
Pressure
(PSIG)C1
| 40 | 60 | 80 | 100 | 120 | 140 | 150 | 180 | 200 |
| .67 | .83 | .94 | 1.00 | 1.03 | 1.05 | 1.08 | 1.09 | 1.11 |
C2-Inlet Air Temperature Correction Factor
TempF
| 60 | 70 | 80 | 90 | 100 | 110 | 120 |
| 2.73 | 1.94 | 1.50 | 1.21 | 1.00 | 0.84 | 0.69 |
C4-Pressure Dew Point Correction Factor
P.D.P.
C4
| 35° F to 39° F | 45° F to 50° F |
| 1 | 1.2 |
You Can't Afford Water In Compressed Air
Ambient air at 75F and 75% relative humidity carries 18 gallons of water/day into a compressor of 100 SCFM at 100 PSIG. An after-cooler will remove approx. 50% of that amount or 9 gallons. A properly sized dryer will remove the balance.
Low Pressure Calculation For Equivalent At 100 PSI
Blower at 200 CFM @ 15 PSI.
Step 1
Calculate the atmosphere at 15 PSGI
Step 2
Calculate the atmosphere at 100 PSGI
Step 3
Determine ratio between pressures
Step 4
Convert volume to its equivalent at 100 PSI
200 SCFM x 3.86 ratio = 722 SCFM
Step 5
Size dryer/filters/equipment for that which is rated for 775 CFM @ 100 PSI
Comp. R.P.M. =
MOTOR PULLY p.d. =
COMP. PULLY p.d. =
MOTOR R.P.M =
PISTON DISPLACEMENT IN CU. FT. MIN. =
CU. FT. COMPRESSED AIR =
CU. FT. FREE AIR =
CU. FT. FREE AIR REQ'D. TO RAISE REC. FROM 0 GUAGE
TO FINAL PRESSURE =
GALLONS =
CU. FT. =
LOSS OF AIR THROUGH AN ORIFICE
In cubic feet of free air per minute at standard atmospheric pressure of 14.7 lb per square in. absolute and 70 F.
|
Gauge Pressure before Orifice in Pounds per sq in. |
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||