ACFM AND SCFM CORRECTIONS FOR ALTITUDE OIL-FLOODED SINGLE-STAGE TORARY SCREW AIR
COMPRESSOR
| Altitude Above MSL Feet |
PSIA |
ACFM
Correction Factor |
Ambient Temp. Deg. F |
Ambient R.H. Percent |
Inlet
Pg, H2O
PSIA |
SCFM
Correction Factor |
Total Correction Factor |
Reduction in BHP Percent |
| 0 |
14.7 |
1.0000 |
68 |
36 |
.3389 |
1.0000 |
1.0000 |
0 |
| 1000 |
14.18 |
.9984 |
64 |
36 |
.2995 |
.9718 |
.9703 |
1.8 |
| 2000 |
13.66 |
.9969 |
61 |
36 |
.2641 |
.9438 |
.9409 |
3.5 |
| 3000 |
13.17 |
.9954 |
57 |
36 |
.2325 |
.9164 |
.9122 |
5.2 |
| 4000 |
12.69 |
.9940 |
54 |
36 |
.2042 |
.8899 |
.8845 |
6.9 |
| 5000 |
12.23 |
.9926 |
50 |
36 |
.1791 |
.8636 |
.8572 |
8.5 |
| 6000 |
11.78 |
.9912 |
47 |
36 |
.1567 |
.8383 |
.8309 |
10.1 |
| 7000 |
11.34 |
.9989 |
43 |
36 |
.1368 |
.8133 |
.8124 |
11.6 |
| 8000 |
10.90 |
.9887 |
39 |
36 |
.1191 |
.7878 |
.7789 |
13.1 |
| 9000 |
10.49 |
.9874 |
32 |
36 |
.1035 |
.7638 |
.7542 |
14.6 |
| 10000 |
10.10 |
.9862 |
32 |
36 |
.0898 |
.7408 |
.7305 |
16.1 |
*Typical ambient at elevated altitude. For different temperatures and R.H.'s,
see formula page.
ACFM CORRECTION DUE TO ALTITUDE
Ambient pressure drops as altitude increases, increasing the pressure ratio
across the compressor. The increased pressure ratio reduces the volumetric
efficiency slightly, reducing the ACFM, as shown in Tables 1. Table 1 is for a
single-stage, oil-flooded rotary screw compressor, while
SCFM CORRECTION DUE TO ALTITUDE AND TEMPERATURE EFFECTS
The reduced pressure at altitude decreases the density of the inlet air,
reducing the amount of "standard air" delivered. In addition, ambient
temperature drops as altitude increases. Temperature effects two aspects of a
compressor's throughput of air. First, it effects the density of the air at
intake, varying the amount of standard air delivered. Secondly, cooler inlet air
holds less moisture than standard air does (68 deg. and 36% humidity), and
warmer air holds more, effecting the amount of delivered standard air.