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In 1650, Otti von Guericke invented a vacuum pump for removing gas molecules from a sealed volume and leaving behind a partial vacuum. From sealed and confined spaces, this device pulls out the air and gases. In applications like sealing and cleaning, this device is majorly used.
Performance Measures :-
Pumping speed is the factor of measuring performance. The pumping speed is identified by the volume flow rate of the pump at the inlet. This speed is measured in volume per unit of time. The pumping rate often varies for all pumps and the gases being pumped. The average volume flow rate of the pump varies, based on the chemical composition of the gases remaining in the chamber.
The other factor in the determination of performance level is throughput, which is measured by multiplying pumping speed by the gas pressure in the inlet. Throughout is the number of molecules pumped out of per unit time at a constant temperature.
How Does It Operate ?
In order to create a vacuum in an enclosed space, this device is used for removing the air by suction ans progressively reduce the air density. As the air contained within the system, it evacuates the air, and converts the mechanical input energy of a rotating shaft into pneumatic energy. This lowers down the internal pressure level in a sealed volume, as compared to the outside atmosphere. The volume of removed gas or air, and produced pressure difference between internal and external atmosphere are factors for determining the amount of energy produced.
Vacuum pump has several scientific and medical applications in industries such as chemicals, pharmaceuticals, treatment plants, cement, pulp & paper, sugar mills, process industries & power plants, etc. Any industry generally uses two or more kinds of pumps to create high level of vacuum in a confined space.
Here are some of the industrial uses of vacuum pump:
a. Automobile Industry.
b. In the production of electric lamps and tubes, during which the device is evacuated and is refilled with specific kind of gas or mixture of gases.c. Medical processes whose requirement is suction.
d. Analytical instrumentation that analyzes surface, gas, solid, liquid and bio materials.
e. Semiconductor processing, like dry etching, ion implantation, and in the deposition of CVD, PVD, ALD and PECVD.f. Electron microscopy.
g. Medical applications that need suction like radiopharmacy, radiotherapy, and radiosurgery.
h. Ophthalmic coating.
i. Vacuum coating and engineering are needed for decoration, durability and energy efficiency.
j. Glass coating.
k. Mass spectrometers that can generate ultra high vacuum levels between the ion source and the detector.l. Sewage systems.
Several kinds and applications are there of this equipment in a number of industries. The three kinds of vacuum pumps include the following:
There are many vacuum pumps with a common function of removing air, gases and vapour from a confined space and there creating a vacuum. The three types of vacuum pumps are explained in details here :-
Positive Displacement Vacuum Pumps
The positive displacement vacuum pumps are useful in creating low vacuums. This vacuum pumps works to expand a cavity and allows out flow of gases from a sealed environment or chamber. Following the process, cavity is sealed and results in exhausting it to the atmosphere. Positive displacement vacuum pump is principally used for creating a vacuum by expanding the volume of a container. For instance, deep vacuum is created in a manual water pump when the mechanism expands a small sealed cavity. The pressure pushes some fluid from the chamber into the small cavity of the pump. The cavity of the pumps is then sealed from the chamber, opened to the atmosphere and squeezed back to a minute size. The working of the positive displacement vacuum pump can be explained by the working of a diaphragm muscle that expands the chest cavity and causes the volume of lungs to increase. This expansion creates a partial vacuum and reduces the pressure, which is then filled by atmospheric air pushed in by atmospheric pressure. Positive displacement vacuum pumps, like liquid ring vacuum pumps and roots blower are widely used in several industries for creating vacuum in confined space.
Momentum Transfer Vacuum Pumps
Momentum transfer pump is where gas molecules are increased from the vacuum side to the exhaust side. According to the fluid dymamics laws, flow of matter is different at different pressure. Viscous flow is generated when the molecules interact with each other in the atmospheric pressure and mild volumes, and push on their neighboring molecules. When the distance between the molecules increases, they start interacting with the walls of the chamber frequently rather than other molecules. This stage is known as high volume, which is said to be more effective than positive displacement. This kind of pump can be further divided into diffusion pump and turbomolecular pump. These two pumps blow out gas molecules that are diffused into the pump. The difference between the two pumps is that diffusion pump blows out molecules with jets of oil, while the turbomolecular pump makes use of high speed fan. Both types of pumps will stall and fail to pump when exhausted directly to atmospheric pressure.
Entrapment pumps use chemical reactions for operation and are said to perform better as they are generally placed inside the container to be vacuumed. A thin film created by the molecules in the air is removed by the entrapment pumps as they chemically react to the pump's internal surfaces. Gases are condensed to solid or absorbed state by this type of vacuum pump making use of cold temperatures. Entrapment Pumps are used with displacement vacuum pumps and momentum transfer vacuum pumps for creating ultra high vacuum chambers.