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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.
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