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Posts Tagged ‘vacuum’

Vacuum Terms and Definitions


Before diving into the world of vacuum chuck workholding there are some basic definitions that are helpful to know.

  • Air Consumption – The volume of compressed air required to power a venturi style vacuum generator.
  • Atmospheric Pressure – The atmosphere that surrounds the Earth can be considered a reservoir of low pressure air. Its weight exerts a pressure that varies with temperature, humidity and altitude.
  • Barometer – A device usually filled with mercury that measures atmospheric pressure.
  • Vacuum Flow – The volume of free air induced by a vacuum pump per unit of time, expressed as standard cubic feet per minute – SCFM or LPM (liters per minute).
  • Vacuum Level – The magnitude of the suction created by the vacuum pump.  The unit of measure is inches of Hg (“Hg).
  • Vacuum Force – Equal to the vacuum level multiplied by the surface area of the vacuum surface, i.e. vacuum cup, vacuum chuck surface.
  • Vacuum Fade – For each 1,000 of elevation, vacuum level decreases by 1″ of Hg.

What is a Vacuum


No, we’re not talking about floor care here, but rather one of the most versatile yet misunderstood forces on Earth.

A perfect vacuum is a region of space that contains no matter including air or gasses. In practice, there is no such thing as a perfect vacuum. Scientists may speak of vacuums as having no matter, but partial vacuums are the only things that truly exist. A vacuum’s quality refers to its proximity to the characteristics of a perfect vacuum. The closest thing to a perfect vacuum is in outer space. None of the modern technology available can match the vacuum of outer space. Vacuums are most ofter associated with their commercial uses. The most common is the household vacuum cleaner. Light bulbs and car brakes are a few other objects that utilize vacuum power.

When humans are in vacuo, the term for being exposed to a vacuum, they will lose consciousness after a few seconds and die in minutes. At different altitudes in the atmosphere, the pressure differs. The farther from the Earth, the less pressure there is and the surroundings are more like a vacuum. This is the reason humans must wear flight suits above 100,000 ft and space suits outside of the atmosphere. While short-term exposure to a vacuum has no effect, exposure longer than a few minutes will cause death. Also, if a person who has been in a low-pressure atmosphere comes into a high-pressure atmosphere too quickly, the effects can be more damaging than the effects from the vacuum. The alveoli of the lungs can be ruptured or the eardrums shattered.

The measurement of barometric pressure is “inches of mercury”. Its abbreviation is inHg or “Hg. This standard is used almost exclusively in the United States. Weather reports and aircraft use altimeters, which give the pressure in “Hg. The origin of the term “inches of mercury” comes from mercurial barometers, which work like thermometers except that air pressure is measured instead of temperature. The air pressure at sea level fluctuates around 30″ Hg and roughly decreases by 1″ Hg (0.5 PSI) per 1,000 ft of elevation.