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Instrument Quality Air Requirements

In accordance with the Instrument Society of American Standards (ANSI/ISA-57.3-1975)(R1981) are:

1. Maximum Particle Size-3 micron
2. Oil content-1PPM w/ w/ or v/ v or less under normal operating conditions.
3. Pressure Dew Point-At least 10°C or 18°F below the lowest ambient temperature.
4. 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 it's 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
Temp°F
C2
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° 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 PSIG
Step 2-
Calculate the atmosperes at 100 PSIG
Step 3-
Determine ratio between pressures
Step 4-
Convert volume to its equivalent at 100 PSI
200 SCFM x 3.86 ratio = 772 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. PULLEY 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. =

Cost Of Air Leaks To Atmosphere At 100 PSIG

Assumptions
1. Cost of compressed air $0.30/1000 SCFM
2. 24 hour/day operation 50 wks/year

Equivalent Orifice Size
Cost/Year
1/32
$244.94
1/16
$718.28
1/8
$3,931.12
1/4
$15,724.80

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.
DIAMETER OF ORIFICE
1/64"
1/32"
1/16"
1/8"
1/4"
3/8"
1/2"
5/8"
3/4"
Discharge in cubic feet of free air per minute
6
7
9
12
15
.068
.073
.083
.095
.105
.272
.293
.331
.379
.420
1.09
1.17
1.32
1.52
1.68
4.34
4.68
5.30
6.07
6.72
17.4
18.7
21.2
24.3
26.9
39.1
42.2
47.7
54.6
60.5
69.5
75.0
84.7
97.0
108
109
117
132
152
168
156
168
191
218
242
20
25
30
35
40
.123
.140
.158
.176
.194
.491
.562
.633
.703
.774
1.96
2.25
2.53
2.81
3.10
7.86
8.98
10.1
11.3
12.4
31.4
35.9
40.5
45.0
49.6
70.7
80.9
91.1
101
112
126
144
162
180
198
196
225
253
281
310
283
323
365
405
446
45
50
60
70
80
.211
.229
.264
.300
.335
.845
.916
1.06
1.20
1.34
3.38
3.68
4.23
4.79
5.36
13.5
14.7
16.9
19.2
21.4
54.1
58.6
67.6
76.7
85.7
122
132
152
173
193
216
235
271
307
343
338
366
423
479
536
487
528
609
690
771
90
100
110
120
125
.370
.406
.441
.476
.494
1.48
1.62
1.78
1.91
1.98
5.92
6.49
7.05
7.62
7.90
23.7
26.0
28.2
30.5
31.6
94.8
104
113
122
126
213
234
254
274
284
379
415
452
488
506
592
649
706
762
790
853
934
1016
1097
1138