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What is vacuum?

In technical literature vacuum stands for "a space that is empty of matter" and "pressure free space". In other words vacuum is "the state of a gas in which the pressure is lower than the atmospheric pressure". While in the world vacuum is generated by using special equipment, the space is a natural vacuum zone.
Vacuum was discovered in 1641 by Italian physicist Toricelli. Toricelli discovered that if a long tube filled with mercury was sealed at one end and then stood up in a bowl of mercury, with the open end in the bowl, a vacuum was created in the top of the tube. This is because the mercury flowed out of the tube until the weight of the column of mercury equaled the air pressure that was exerted on the surface of the mercury in the bowl by the weight of the column on air on top of it. The height of the column of the mercury was noted and he discovered that as the air pressure increased so did the height of the column of the mercury. Thus the first barometer was created.
The standard atmospheric pressure at the sea level is 760 mmHg or 760 torr. This unit of measurement is still widely used.

What are the vacuum measurement units?

In addition to Toricelli's work on atmospheric pressure, in 1646 the famous French mathematician Pascal discovered that if a barometer was climbed up on a mountain the height of column of mercury would drop due to decreasing air pressure with height. Today we have the units pascal "pa", hektopascal "hPa" and kilopascal "kPa" in his honour.
The most commonly used vacuum and pressure measurement units bar and millibar "mbar" were introduced in 1909 by British meteorologist William Napier Shaw based on Toricelli's work. The standard atmospheric pressure is 1,01325 bar or 1013,25 mbar (roughly 1033).
The measurement units discovered by Pascal are usually used for relatively more precise measurements. Column of mercury "mmHg" and millibar are rather used in rough or middle precision measurements. Apart from that, water column "mmH2O" and in countries that employ imperial units system inches column of mercury "inHg" are used in measurement of vacuum.

How is vacuum created?

As the atmospheric pressure is continuously exerted everywhere in the world, vacuum can only be created by utilizing special equipment. These devices that are used to generate vacuum are called Vacuum Pump. There are various types of vacuum pumps among them are rotary vane, side channel blower, rotary lobes and dry screw. Oil circulated, liquid ring or dry running vacuum pumps are chosen according to the requirements of the working environment. When the vacuum pump starts the air taken from the inlet port is pressurized and then discharged into the exhaust port. As the vacuum pump is installed in a closed vacuum chamber, continuously works to decrease the density of air molecules in the chamber. Depending on the vacuum pump type, the final vacuum level will change dramatically. We will discuss how to choose the pump type and capacity according to the working conditions in another article.

How is vacuum measured?

Just as in pressure measurement, vacuum is measured by using mechanical or electronic gauges. A suitable gauge is chosen according to the precision level of measurement and working conditions. The most commonly used vacuum gauges are mechanical with a spring action, which provide less precise measurement. This type of vacuum gauges are common due to their low price and ability to work without an energy source.
Mechanical gauges are usually capable of measuring the difference between the atmospheric pressure in their work location and the vacuum in the chamber which they are installed. Thus measurements taken at the sea level and above this level will not give the same results. This is the reason why various measurement results are obtained from the same vacuum system in different locations. In order to overcome this problem absolute vacuum gauges are utilized. This type of gauges use a vacuum tube that is calibrated in laboratory environments to measure the vacuum, thus independent from the height from the sea level the measurements for the same system will give the same exact results. Absolute vacuum gauges usually employ electronic components so they require an energy source to operate and provide more precise results.

Where is the vacuum used?

Vacuum technology has a very wide application area. Most products that are used in daily life cannot be manufactured without vacuum. One of the most well-known applications is vacuum packaging. It is possible to preserve food and non-food products for much longer time in a hygienic environment under vacuum.
Plastic industry is another main employer of vacuum technology. Plastic sheets extrusion and thermoforming applications use vacuum. Similarly in chemical industry many processes require vacuum. Homogen mixing, moist removing and reaction accelerating are done by vacuum.
In electric/electronic industry vacuum pumps are used on impregnation drying and coating applications. Vacuum is also vital for composites manufacturing. Today aircraft components, boat mainframes, land vehicle parts and outdoor use products are succefully manufactured from composite materials. Another application area of vacuum is vacuum lifting units (vacuum lifters). Metal plates of 10-10.000 Kgs, natural stone and marble, glass sheets and wood panels are easily lifted with maximum security measures available. Vacuum lifting is also applied in automation systems, allowing much faster and precise production. In metallurgy vacuum is used in casting of precious metals, jewelry manufacturing and vacuum heat treatment ovens.
In hospitals central vacuum systems are used to remove unwanted body liquids at the operation and maternity rooms. Many processes in pharmaceutical industry require vacuum. Precise mixing chemicals, vacuum transportation and final packaging are just some of those processes.

Apart from the examples listed above, vacuum technology has many more applications. For more information on your specific application please contact Zinisan Vakum

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