Vacuum pumps are those devices which remove gas molecules from a sealed environment or chamber, leaving a partial vacuum in their wake.
History of the Vacuum Pump
The vacuum pump was first invented by Otto von Guericke in 1650. Later, in the 19th century, Nikola Tesla built an apparatus that used a Sprengel pump to create a high amount of exhaustion, which helped create a strong vacuum.
The vacuum pumps which were built before 1980 used oils that contained a mixture of many dangerous PCBs or Polychlorinated Biphenyls. It was discovered that these PCBs were very toxic and also carcinogenic (can cause cancer).
Types of Vacuum Pumps
Positive Displacement Pumps
These pumps expand a cavity which causes the gases from the chamber to flow in, seal off the cavity, and exhaust these gases to the atmosphere. When this process occurs repeatedly, a partial vacuum gets created within the chamber. These pumps are most useful for creating low vacuums. Examples are, diaphragm pump, piston pump, and scroll pump.
Momentum Transfer Pumps or Molecular Pumps
These pumps use high speed jets of dense fluids or rapidly rotating blades to knock off the gas molecules from the sealed environment or chamber. They are often used along with positive displacement pumps to create high vacuum chambers. Examples are, turbomolecular pump and diffusion pump.
These pumps are used to capture gases in either a solid or absorbed state. They are used along with positive displacement pumps and molecular pumps to create ultra high vacuum chambers. Examples are, ion pumps and cyropumps.
Industrial Vacuum Pump Uses
Due to their specific capabilities, different types of vacuum pumps find uses and applications in a variety of industrial environments. Some of these are:
- In the production of electric lamps and vacuum tubes, where the device is left evacuated, and is then refilled with a specific gas or a mixture of gases.
- In medical processes where suction is needed.
- For semiconductor processing such as ion implantation, dry etching, and in the deposition of PVD, ALD, CVD, and PECVD.
- In analytical instrumentation, to analyze solid, liquid, gas, surface, and bio-materials.
- In vacuum coating for decoration, energy saving and durability.
- In electron microscopy
- For creating ultra-high vacuum levels between the ion source and the detector in mass spectrometers.
- In medical applications such as radiotherapy, radio-pharmacy and radio-surgery.
- For trash compacting.
- For ophthalmic coating.
- For glass coating.
- In vacuum engineering.
- In sewage systems.
- In automobile industries.
Normally, two or more different types of vacuum pumps are used, either in parallel or in series, to create a high level of vacuum. It is difficult to achieve a high level of vacuum, because the materials used must be capable of withstanding the large levels of heat and pressure that is generated.
Therefore, materials such as greases, oils, plastic, and rubber gaskets which are used to seal the chambers where vacuum is to be created, must be appropriately chosen.
The surfaces of the chambers which are to be used for vacuum creation are heated at high temperatures, so that all the absorbed gases are removed. Alternatively, some vacuum creation systems use liquid nitrogen to cool the chambers below room temperature, so that the residual out-gassing is shut down, while running the cyropump system at the same time.