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Vacuum is defined as air pressure below atmospheric pressure.
The vacuum level is the difference in pressure between atmospheric pressure and pressure in the evacuated system:
- 0% vacuum = 760 torr = 14.7 psia = 29.92 inc mercury abs = 101.4 kPa abs
- 50% vacuum = 380 torr = 7.3 psia = 15 inc mercury abs = 50.8 kPa abs
- 99.9% vacuum = 1 torr = 0.01934 psia = 0.03937 inc mercury abs = 1.3 kPa abs
For perfect vacuum (100%) - the pressure is 0 torr, 0 psia or 0 Pa abs.
Vacuum versus Absolute Air Pressure
Example - Vacuum
If the absolute pressure is 60 kPa the vacuum according the diagram above is approximately 40% - or approximately 450 Torr.
- atmospheric pressure - 760 torr
- low vacuum - 760 to 25 torr
- medium vacuum - 25 to 10-3 torr
- high vacuum - 10-3 to 10-9 torr
- ultra high vacuum - 10-9 to 10-12 torr
- extremely high vacuum - < 10-12 torr
- perfect vacuum - 0 torr
- Air, LNG, LPG and other common gas properties, pipeline capacities, sizing of relief valves.
- Elevation above sea level - in feet and meter - with barometric and atmospheric pressure - inches mercury, psia, kg/cm2 and kPa.
- Convert vacuum air volume to standard air volume
- Vacuum pumps - calculate flow rate and required evacuation time.
- Measure air volume flow in vacuum.
- Converting between vacuum units like % vacuum - mm Mercury - psi - torr - micron - kPa.
- Air velocity diagrams for vacuum pipe lines.
- Calculate pressure drops in vacuum pipe lines.
- Capacities of vacuum pump exhaust pipes.
- Online calculator, figures and tables giving the boiling temperatures of water in varying vacuum, SI and Imperial units.
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