Vacuum - Flow Measurement
Sponsored Links
For standard or normal pressure it is common to measure flow in
- standard cubic feet minute - scfm - imperial units
- normal metric liter per second - nl/s - metric units
In vacuum the air or gas is expanded and it is common to use
- actual cubic feet minute - acfm - imperial units
- actual metric liter per second - al/s - metric units
Since the gas is expanded, actual volume flow is greater than standard volume flow for the same amount of gas.
The flow volume can be converted from standard volume flow to actual volume flow by the expression:
qa = qs (29.92 / p) ((t + 460) / 520) (1)
where
qa= actual volume flow (acfm)
qs= standard volume flow (scfm)
p= actual pressure (in Hg)
t= temperature (oF)
For full table - rotate the screen!
| Pressure | Conversion Factor from scfm to acfm (or nl/s to al/s) | |||||||
|---|---|---|---|---|---|---|---|---|
| Temperature(oF) | ||||||||
| in Hg absolute | in Hg gauge | kPa absolute | 0 | 30 | 60 | 90 | 120 | 150 |
| 29.92 | 0.00 | 101.42 | 0.88 | 0.94 | 1.00 | 1.06 | 1.12 | 1.17 |
| 28.92 | 1.00 | 98.03 | 0.92 | 0.97 | 1.03 | 1.09 | 1.15 | 1.21 |
| 27.92 | 2.00 | 94.64 | 0.95 | 1.01 | 1.07 | 1.13 | 1.20 | 1.26 |
| 26.92 | 3.00 | 91.25 | 0.98 | 1.05 | 1.11 | 1.18 | 1.24 | 1.30 |
| 25.92 | 4.00 | 87.86 | 1.02 | 1.09 | 1.15 | 1.22 | 1.29 | 1.35 |
| 24.92 | 5.00 | 84.47 | 1.06 | 1.13 | 1.20 | 1.27 | 1.34 | 1.41 |
| 23.92 | 6.00 | 81.08 | 1.11 | 1.18 | 1.25 | 1.32 | 1.40 | 1.47 |
| 22.92 | 7.00 | 77.69 | 1.15 | 1.23 | 1.31 | 1.38 | 1.46 | 1.53 |
| 21.92 | 8.00 | 74.31 | 1.21 | 1.29 | 1.36 | 1.44 | 1.52 | 1.60 |
| 20.92 | 9.00 | 70.92 | 1.27 | 1.35 | 1.43 | 1.51 | 1.60 | 1.68 |
| 19.92 | 10.00 | 67.53 | 1.33 | 1.42 | 1.50 | 1.59 | 1.68 | 1.76 |
| 18.92 | 11.00 | 64.14 | 1.40 | 1.49 | 1.58 | 1.67 | 1.76 | 1.86 |
| 17.92 | 12.00 | 60.75 | 1.48 | 1.57 | 1.67 | 1.77 | 1.86 | 1.96 |
| 16.92 | 13.00 | 57.36 | 1.56 | 1.67 | 1.77 | 1.87 | 1.97 | 2.07 |
| 15.92 | 14.00 | 53.97 | 1.66 | 1.77 | 1.88 | 1.99 | 2.10 | 2.20 |
| 14.92 | 15.00 | 50.58 | 1.77 | 1.89 | 2.01 | 2.12 | 2.24 | 2.35 |
| 13.92 | 16.00 | 47.19 | 1.90 | 2.03 | 2.15 | 2.27 | 2.40 | 2.52 |
| 12.92 | 17.00 | 43.80 | 2.05 | 2.18 | 2.32 | 2.45 | 2.58 | 2.72 |
| 11.92 | 18.00 | 40.41 | 2.22 | 2.37 | 2.51 | 2.65 | 2.80 | 2.94 |
| 10.92 | 19.00 | 37.02 | 2.42 | 2.58 | 2.74 | 2.90 | 3.06 | 3.21 |
| 9.92 | 20.00 | 33.63 | 2.67 | 2.84 | 3.02 | 3.19 | 3.36 | 3.54 |
| 8.92 | 21.00 | 30.24 | 2.97 | 3.16 | 3.35 | 3.55 | 3.74 | 3.93 |
| 7.92 | 22.00 | 26.85 | 3.34 | 3.56 | 3.78 | 4.00 | 4.21 | 4.43 |
| 6.92 | 23.00 | 23.46 | 3.82 | 4.07 | 4.32 | 4.57 | 4.82 | 5.07 |
| 5.92 | 24.00 | 20.07 | 4.47 | 4.76 | 5.05 | 5.35 | 5.64 | 5.93 |
| 4.92 | 25.00 | 16.68 | 5.38 | 5.73 | 6.08 | 6.43 | 6.78 | 7.13 |
| 3.92 | 26.00 | 13.29 | 6.75 | 7.19 | 7.63 | 8.07 | 8.51 | 8.95 |
| 2.92 | 27.00 | 9.90 | 9.06 | 9.66 | 10.25 | 10.84 | 11.43 | 12.02 |
| 1.92 | 28.00 | 6.51 | 13.79 | 14.68 | 15.58 | 16.48 | 17.38 | 18.28 |
| 0.92 | 29.00 | 3.12 | 28.77 | 30.65 | 32.52 | 34.40 | 36.27 | 38.15 |
| 0.82 | 29.10 | 2.78 | 32.28 | 34.38 | 36.49 | 38.59 | 40.70 | 42.80 |
| 0.72 | 29.20 | 2.44 | 36.76 | 39.16 | 41.56 | 43.95 | 46.35 | 48.75 |
| 0.62 | 29.30 | 2.10 | 42.69 | 45.47 | 48.26 | 51.04 | 53.83 | 56.61 |
| 0.52 | 29.40 | 1.76 | 50.90 | 54.22 | 57.54 | 60.86 | 64.18 | 67.50 |
| 0.42 | 29.50 | 1.42 | 63.02 | 67.13 | 71.24 | 75.35 | 79.46 | 83.57 |
| 0.32 | 29.60 | 1.08 | 82.71 | 88.11 | 93.50 | 98.89 | 104.29 | 109.68 |
| 0.22 | 29.70 | 0.75 | 120.31 | 128.15 | 136.00 | 143.85 | 151.69 | 159.54 |
| 0.12 | 29.80 | 0.41 | 220.56 | 234.95 | 249.33 | 263.72 | 278.10 | 292.49 |
- T (oC) = 5/9 (T (oF) - 32)
- The calculation above is available as an excel file - vacuum.xls
- Altitude and pressure
Sponsored Links
Related Topics
• Gases and Compressed Air
Properties of air, LNG, LPG and other common gases. Pipeline capacities and sizing of relief valves.
Related Documents
Vacuum
Vacuum is defined as air pressure below atmospheric pressure.
Vacuum - Air Expansion Ratio
Convert vacuum air volume to standard air volume
Vacuum - Evacuation Time
Vacuum pumps - calculate flow rate and required evacuation time.
Vacuum Pipes - Flow Velocities
Air velocity diagrams for vacuum pipe lines.
Vacuum Pipes - Pressure Loss vs. Air Flow
Calculate pressure drops in vacuum pipe lines.
Vacuum Pumps - Exhaust Pipe Capacities
Capacities of vacuum pump exhaust pipes.
Sponsored Links
Search Engineering ToolBox
Search is the most efficient way to navigate the Engineering ToolBox!
Privacy
We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.
Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.
Google use cookies for serving our ads and handling visitor statistics on the AMP pages. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.
AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.