An overview on high vacuum technology  

vacuum technology  

Vacuum is a utility used in a vast array of industrial manufacturing processes  including packaging, bottling, drying, degassing, pick and place to name but a few.  An industrial vacuum pump is used for creating, improving and maintaining vacuum  in these processes. There are many types of industrial vacuum technologies  available and this article will explore those technologies. To understand which type of  vacuum is most suitable for you and your application, it is crucial to understand the  features, benefits and operating principle each type of technology. This article will  review the most common types of industrial vacuum pump, how they work and in  what types of applications they are best suited. 

If you want to discover more about the full range of vacuum technologies we suggest  you visit Agilent Vacuum Technology. Agilent Technologies Inc. is a company leader  in life sciences and diagnostics, and provides many laboratories worldwide with its  own instruments and services. Agilent makes top quality vacuum pumps, systems,  and components and has extensive expertise in the field. 

Basic Operating Principle of an  Industrial Vacuum Pump 

The basic operating principle of an industrial vacuum pump remain the same no  matter the technology type. 

Vacuum pumps remove air molecules (and other gases) from the vacuum chamber  (or the outlet side in the case of a higher vacuum pump connected in series). As the  pressure in the chamber is reduced, removing additional molecules becomes  increasingly harder to remove. Therefore, an industrial vacuum system (Fig. 1) must 

be able to operate over a portion of an extraordinarily large pressure range, typically  up to 10-9 Torr. To accomplish this, different types of pumps are used in a standard  vacuum system, each covering a proportion of the pressure range, and operating in  series at times. 

Pressure Ranges of Industrial  Vacuum System 

Industrial Vacuum systems can be placed into the following groups of pressure  ranges: 

  • Rough/Low Vacuum: 1000 to 1 mbar / 760 to 0.75 Torr 
  • Fine/ Medium Vacuum: 1 to 10-3 mbar / 0.75 to 7.5-3 Torr 
  • High Vacuum: 10-3 to 10-7 mbar / 7.5-3 to 7.5-7 Torr 
  • Ultra-High Vacuum: 10-7 to 10-11 mbar / 7.5-7 to 7.5-11 Torr 
  • Extreme High Vacuum: < 10-11 mbar / < 7.5-11 Torr 

Different types of pumps for these vacuum ranges can then be divided into Primary  (Backing) Pumps, Booster Pumps and secondary (High Vacuum) Pumps: High, very  high and ultra-high vacuum pressure ranges. 

There are two basic categories of vacuum pump: Gas Transfer Pumps and  entrapment or capture pumps:

Gas Transfer Pumps  

Transfer Pumps transfer gas molecules by either momentum exchange (kinetic  action) or positive displacement. The same number of gas molecules are discharged  from the pump as enter it and the gas is slightly above atmospheric pressure when  expelled. The compression ratio is the ratio of the exhaust pressure (outlet) to the  lowest pressure obtained (inlet). 

Kinetic Transfer Pumps 

Kinetic transfer pumps use high speed blades or introduced vapor to direct gas  towards the outlet, working on the principle of momentum transfer. These types of  pump can achieve high compression ratios at low pressures but typically don’t have  sealed volumes. 

Positive Displacement 

Pumps which work by mechanically trapping a volume of gas and moving it through  the pump are known as positive displacement pumps. Often designed in multiple  stages on a single drive shaft, the isolated volume is compressed to a smaller  volume at a higher pressure, and finally the compressed gas is expelled to either  atmosphere or the next pump. To provide a higher vacuum and flow rate two transfer  pumps are often used in series. 

As mentioned previously, positive displacement vacuum pumps are used to create  low vacuums. This type of vacuum pump, expands a cavity and allows the gases to  flow out of the sealed environment or chamber. After that, the cavity is sealed and  causes it to exhaust it to the atmosphere. The principle behind positive displacement  vacuum pump is create a vacuum by expanding the volume of a container. For  example in a manual water pump, a mechanism expands a small sealed cavity to  create a deep vacuum. Because of the pressure, some fluid from the chamber is  pushed into the pump’s small cavity. After that, the pump’s cavity is then sealed from  the chamber, opened to the atmosphere and then squeezed back to a minute size.  Another example of positive displacement vacuum pumps is like a diaphragm muscle  expands the chest cavity, causing the volume of lungs to increase. This expansion  results to creating a partial vacuum and reducing the pressure, which is then filled by  air pushed in by atmospheric pressure. The examples of positive displacement  vacuum pumps are liquid ring vacuum pumps and roots blower which are highly used  in various industries to create vacuum in confined space. 

Entrapment Pumps 

Pumps which capture gas molecules on surfaces within the vacuum system are  unsurprisingly known as, Capture or Entrapment Pumps. These pumps operate at  lower flow rates than vacuum pumps such as transfer pumps, however, they can  provide extremely high vacuum, down to 10-12Torr. Capture pumps operate using  cryogenic condensation, ionic reaction, or chemical reaction and have no moving  parts, therefore creating oil-free vacuum. 

Those Entrapment Pumps that work using chemical reactions, perform more  effectively as they are usually placed inside the container where vacuum is required. 

Air molecules create a thin film which is removed as the pumps operation cause a  chemical reaction to the internal surfaces of the pump. Entrapment pumps are used  along with positive displacement vacuum pumps and momentum transfer vacuum  pumps to create ultra-high vacuum. 

What else? 

The vast range of products and techniques shows that high vacuum technology plays  a significant part in numerous industrial applications and in the research and medical  fields. For example vacuum technology is pivotal for the sterilisation of medical  equipment as well as the use of x-ray tubes in high vacuum conditions. 

Visit website to discover more applications of vacuum technologies. 

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