A vacuum pump is a device that removes gas molecules from a sealed volume to create a partial vacuum. The performance of a vacuum pump is the production of a relative vacuum in a given volume. Otto von Guericke invented the first vacuum pump in 1650 and a suction pump was dating back to antiquity.
Vacuum pumps are classified according to their operating pressure range. They are classified as primary pumps, booster pumps or secondary pumps. There are different types of pumps in each pressure range, each with different technology, and each has unique advantages in terms of flow capacity, flow, cost and maintenance needs.
Regardless of its design, the basics of operation are the same.
The function of the vacuum pumps is to remove air molecules and other gases from the vacuum chamber (or from the outlet of a series connected to the upper vacuum pumps). As the pressure in the chamber decreases, it becomes more difficult to remove excess molecules.
Therefore, industrial vacuum systems must be able to operate in a very wide pressure range, typically 1 to 6-10 Torr. In research and scientific applications, it can be increased to 9-10 Torr or less. To achieve this, different types of pumps are used in a typical system, each of which covers part of the pressure range and sometimes operates in series.
Types of vacuum pumps
1) Gas transfer pumps
The transfer pump delivers the gas molecules with a shock pulse (escape action) or positive displacement. The number of gas molecules discharged from the pump is the same as when it enters the pump, and the gas pressure at the outlet is slightly above atmospheric pressure. The density ratio is between the outlet pressure (outlet) and the lowest value obtained (inlet).
2) Centrifugal Pump
A centrifugal pump uses an impeller to transfer fluid from one location to other. This vacuum pump creates a vacuum due to the movement of the impeller blades.
3) Kinetic Vacuum pumps
The kinetic vacuum pump uses high-speed blades or introduced steam to direct gas to the outlet, and the principle of operation is shock transfer. These types of pumps can achieve high compression ratios at low pressures but generally do not have a sealed volume.
4) Positive displacement
A pump that works by mechanically taking a certain volume of gas and moving it around the pump is called a positive displacement pump. Usually, in several stages on a crankshaft, the separated volume is compressed to a smaller volume under higher pressure. Finally, the compressed gas is discharged into the next air or pump. These vacuum pumps are commonly used to create a higher level of vacuum and suction.
As mentioned above, the positive displacement vacuum pump is used to produce a low vacuum. This type of vacuum pump enlarges the cavity and allows the gas to escape from the atmosphere or the sealed chamber.
Subsequently, the cavity is sealed and transferred to the air. The principle of a vacuum pump is positive displacement by creating a vacuum by increasing the volume of the container. For example, in a manual water pump, a mechanism expands a small sealed cavity to create a deep vacuum.
Due to the pressure, some liquid is pushed out of the chamber into the small cavity of the pump. Next, the pump cavity in the sealed chamber is opened to air and then compressed to a small size.
Another example of positive displacement of the vacuum pump is the diaphragm muscles, which dilate the chest cavity and increase lung volume. This expansion leads to a slight vacuum and a decrease in pressure, then filled by atmospheric pressure.
Examples of positive displacement vacuum pumps are liquid ring vacuum pumps and root blowers, which are widely used in various industries to produce vacuum in confined spaces.
5) Entrapment Pump
The pump that traps the gas molecules inside the vacuum system is unsurprising if the pump is trapped in the explosion. These pumps run on less flow than vacuum pumps (such as transfer pumps) but can produce very high vacuum levels below 10-12 Torr.
The suction pump uses cryogenic density, ion reaction or chemical reaction for operation and has no moving parts so that it can create an oil-free vacuum.
The chemical reactions of entrapment pump traps are more effective because they are usually placed in containers that require a vacuum. The air molecules form a thin layer which is removed when a chemical reaction operates the pump on the internal surface of the pump.
The adsorption pump was used in combination with a volumetric vacuum pump and a transmission vacuum pump to produce an ultra-high vacuum.
Application of Vacuum Pumps
Vacuum pumps are also used for decorative vacuum coatings on metals, glass and plastics, energy-saving and glass life, ophthalmic coatings, hard coatings for Formula One engine parts, milking machines and other dairy equipment windings of engines or wood.