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Vacuum

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 .

Vacuum Ranges

• atmospheric pressure - 760 torr
• low vacuum - 760 to 25 torr
• medium vacuum - 25 to 10-3 torr
• high vacuum - 10-3 to 10-9torr
• ultra high vacuum - 10-9to 10-12 torr
• extremely high vacuum - < 10-12 torr
• perfect vacuum - 0 torr <

Related Topics

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Properties of air, LNG, LPG and other common gases. Pipeline capacities and sizing of relief valves.

Related Documents

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Elevation above sea level - in feet and meter - with barometric and atmospheric pressure - inches mercury, psia, kg/cm2 and kPa.
• 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 - Flow Measurement

Measure air volume flow in vacuum.
• Vacuum - Pressure Units Converter

Converting between vacuum units like % vacuum - mm Mercury - psi - torr - micron - kPa.
• 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.
• Water - Boiling Points at Vacuum Pressure

Online calculator, figures and tables giving the boiling temperatures of water in varying vacuum, SI and Imperial units.

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Citation

• The Engineering ToolBox (2005). Vacuum. [online] Available at: https://www.engineeringtoolbox.com/vacuum-d_837.html [Accessed Day Month Year].

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