The Roots blower is one example of a vacuum pump

A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. The Roots type Supercharger or Roots blower is a positive displacement pump which operates by pulling Air through a pair of meshing lobes not This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. The vacuum pump was invented in 1650 by Otto von Guericke. Otto von Guericke (originally spelled Gericke ˈgeːʁɪkə ( November 20, 1602 &ndash May 11, 1686 ( Julian calendar)

Types

Pumps can be broadly categorized according to three techniques:^[1]

• Positive displacement pumps use a mechanism to repeatedly expand a cavity, allow gases to flow in from the chamber, seal off the cavity, and exhaust it to the atmosphere.
• Momentum transfer pumps, also called molecular pumps, use high speed jets of dense fluid or high speed rotating blades to knock gaseous molecules out of the chamber.
• Entrapment pumps capture gases in a solid or absorbed state. This includes cryopumps, getters, and ion pumps. A cryopump is a Vacuum pump that traps Gases and Vapours by condensing them on a cold surface Getters are reactive materials used for removing traces of gas from vacuum systems An ion pump works by creating an Electric field across a fluid containing ions

Positive displacement pumps are the most effective for low vacuums. Momentum transfer pumps in conjunction with one or two positive displacement pumps are the most common configuration used to achieve high vacuums. In this configuration the positive displacement pump serves two purposes. First it obtains a rough vacuum in the vessel being evacuated before the momentum transfer pump can be used to obtain the high vacuum, as momentum transfer pumps cannot start pumping at atmospheric pressures. Second the positive displacement pump backs up the momentum transfer pump by evacuating to low vacuum the accumulation of displaced molecules in the high vacuum pump. Entrapment pumps can be added to reach ultrahigh vacuums, but they require periodic regeneration of the surfaces that trap air molecules or ions. Due to this requirement their available operational time can be unacceptably short in low and high vacuums, thus limiting their use to ultrahigh vacuums. Pumps also differ in details like manufacturing tolerances, sealing material, pressure, flow, admission or no admission of oil vapor, service intervals, reliability, tolerance to dust, tolerance to chemicals, tolerance to liquids and vibration.

Performance measures

• Pumping speed refers to the volume flow rate of a pump at its inlet, often measured in volume per unit of time. Momentum transfer and entrapment pumps are more effective on some gases than others, so the pumping rate can be different for each of the gases being pumped, and the average volume flow rate of the pump will vary depending on the chemical composition of the gases remaining in the chamber.
• Throughput refers to the pumping speed multiplied by the gas pressure at the inlet, and is measured in units of pressure-volume/unit time. At a constant temperature, throughput is proportional to the number of molecules being pumped per unit time, and therefore to the mass flow rate of the pump. Mass flow rate is the movement of Mass per Time. Its unit is mass divided by Time, so Kilogram per Second in SI When discussing a leak in the system or backstreaming through the pump, throughput refers to the volume leak rate multiplied by the pressure at the vacuum side of the leak, so the leak throughput can be compared to the pump throughput.

Positive displacement and momentum transfer pumps have a constant volume flow rate, (pumping speed,) but as the chamber's pressure drops, this volume contains less and less mass. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface So although the pumping speed remains constant, the throughput and mass flow rate drop exponentially. Mass flow rate is the movement of Mass per Time. Its unit is mass divided by Time, so Kilogram per Second in SI Meanwhile, the leakage, evaporation, sublimation and backstreaming rates continue to produce a constant throughput into the system.

Positive displacement

The manual water pump draws water up from a well by creating a vacuum that water rushes in to fill. In a sense, it acts to evacuate the well, although the high leakage rate of dirt prevents a high quality vacuum from being maintained for any length of time.

Mechanism of a scroll pump

Fluids cannot be pulled, so it is technically impossible to create a vacuum by suction. Suction is the movement of fluids into a vacuum under the effect of a higher external pressure, but the vacuum has to be created first. The easiest way to create an artificial vacuum is to expand the volume of a container. For example, the diaphragm muscle expands the chest cavity, which causes the volume of the lungs to increase. For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle This expansion reduces the pressure and creates a partial vacuum, which is soon filled by air pushed in by atmospheric pressure

To continue evacuating a chamber indefinitely without requiring infinite growth, a compartment of the vacuum can be repeatedly closed off, exhausted, and expanded again. This is the principle behind positive displacement pumps, like the manual water pump for example. Inside the pump, a mechanism expands a small sealed cavity to create a deep vacuum. Because of the pressure differential, some fluid from the chamber (or the well, in our example) is pushed into the pump's small cavity. The pump's cavity is then sealed from the chamber, opened to the atmosphere, and squeezed back to a minute size.

More sophisticated systems are used for most industrial applications, but the basic principle of cyclic volume removal is the same:

• Rotary vane pump, the most common
• Diaphragm pump, zero oil contamination
• Liquid ring pump
• Piston pump, cheapest
• Scroll pump, highest speed dry pump
• Screw pump (10 Pa)
• Wankel pump
• External vane pump
• Roots blower, also called a booster pump, has highest pumping speeds but low compression ratio
• Multistage Roots pump that combine several stages providing high pumping speed with better compression ratio
• Toepler pump

The base pressure of a rubber- and plastic-sealed piston pump system is typically 1 to 50 kPa, while a scroll pump might reach 10 Pa (when new) and a rotary vane oil pump with a clean and empty metallic chamber can easily achieve 0. A rotary vane pump is a positive-displacement Pump that consists of vanes mounted to a rotor that rotates inside of a cavity A diaphragm pump is a positive displacement pump that uses a combination of the reciprocating action of a Rubber, Thermoplastic or teflon A liquid ring pump is a rotating positive displacement pump They are typically used as a Vacuum pump but can also be used as a Gas compressor. A reciprocating compressor is a compressor that uses Pistons driven by a Crankshaft to deliver gases at high pressure A scroll compressor (also called spiral compressor, scroll pump and scroll vacuum pump) is a device for compressing air or refrigerant Felix Heinrich Wankel Hon DEng (August 13 1902 &ndash October 9 1988 was a German Mechanical engineer and the inventor of the Wankel engine. The Roots type Supercharger or Roots blower is a positive displacement pump which operates by pulling Air through a pair of meshing lobes not Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products 1 Pa.

A positive displacement vacuum pump moves the same volume of gas with each cycle, so its pumping speed is constant unless it is overcome by backstreaming. The volume of any solid plasma vacuum or theoretical object is how much three- Dimensional space it occupies often quantified numerically

Momentum transfer

A cutaway view of a turbomolecular high vacuum pump

In a momentum transfer pump, gas molecules are accelerated from the vacuum side to the exhaust side (which is usually maintained at a reduced pressure by a positive displacement pump). Momentum transfer pumping is only possible below pressures of about 1 kPa. Matter flows differently at different pressures based on the laws of fluid dynamics. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion At atmospheric pressure and mild vacuums, molecules interact with each other and push on their neighboring molecules in what is known as viscous flow. When the distance between the molecules increases, the molecules interact with the walls of the chamber more often than the other molecules, and molecular pumping becomes more effective than positive displacement pumping. This regime is generally called high vacuum.

Molecular pumps sweep out a larger area than mechanical pumps, and do so more frequently, making them capable of much higher pumping speeds. They do this at the expense of the seal between the vacuum and their exhaust. Since there is no seal, a small pressure at the exhaust can easily cause backstreaming through the pump; this is called stall. In high vacuum, however, pressure gradients have little effect on fluid flows, and molecular pumps can attain their full potential.

The two main types of molecular pumps are the diffusion pump and the turbomolecular pump. Diffusion pumps use a high speed jet of vapor to direct gas Molecules in the pump throat down into the bottom of the pump and out the exhaust A turbomolecular pump is a type of Vacuum pump, superficially similar to a Turbopump, used to obtain and maintain high Vacuum. Both types of pumps blow out gas molecules that diffuse into the pump by imparting momentum to the gas molecules. Diffusion pumps blow out gas molecules with jets of oil or mercury, while turbomolecular pumps use high speed fans to push the gas. Both of these pumps will stall and fail to pump if exhausted directly to atmospheric pressure, so they must be exhausted to a lower grade vacuum created by a mechanical pump.

As with positive displacement pumps, the base pressure will be reached when leakage, outgassing, and backstreaming equal the pump speed, but now minimizing leakage and outgassing to a level comparable to backstreaming becomes much more difficult.

• Diffusion pump
• Turbomolecular pump

Entrapment

Entrapment pumps may be cryopumps, which use cold temperatures to condense gases to a solid or adsorbed state, chemical pumps, which react with gases to produce a solid residue, or ionization pumps, which use strong electrical fields to ionize gases and propel the ions into a solid substrate. Diffusion pumps use a high speed jet of vapor to direct gas Molecules in the pump throat down into the bottom of the pump and out the exhaust A turbomolecular pump is a type of Vacuum pump, superficially similar to a Turbopump, used to obtain and maintain high Vacuum. A cryopump is a Vacuum pump that traps Gases and Vapours by condensing them on a cold surface Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals An ion pump works by creating an Electric field across a fluid containing ions A cryomodule uses cryopumping. A cryomodule is that section or sections of a Linear particle accelerator composed of superconducting RF cavities used in a Linear accelerator, or linac

• Ion pump
• Cryopump
• Sorption pump
• Non-evaporative getter

Other pump types

• Venturi vacuum pump (aspirator) (10 to 30 kPa)
• Steam ejector (vacuum depends on the number of stages, but can be very low)

Techniques

Vacuum pumps are combined with chambers and operational procedures into a wide variety of vacuum systems. An ion pump works by creating an Electric field across a fluid containing ions A cryopump is a Vacuum pump that traps Gases and Vapours by condensing them on a cold surface The sorption pump is a Vacuum pump that creates a Vacuum by adsorbing molecules on a very porous material like Molecular sieve which is cooled by a Getters are reactive materials used for removing traces of gas from vacuum systems An aspirator, also called an Eductor-jet pump or filter pump is a device that produces Vacuum by means of the Venturi effect. An injector, ejector, steam ejector or steam injector is a pump-like device that uses the Venturi effect of a converging-diverging Sometimes more than one pump will be used (in series or in parallel) in a single application. If two or more circuit components are connected end to end like a daisy chain it is said they are connected in series. If two or more circuit components are connected end to end like a daisy chain it is said they are connected in series. A partial vacuum, or rough vacuum, can be created using a positive displacement pump that transports a gas load from an inlet port to an outlet (exhaust) port. Because of their mechanical limitations, such pumps can only achieve a low vacuum. To achieve a higher vacuum, other techniques must then be used, typically in series (usually following an initial fast pump down with a positive displacement pump). Some examples might be use of an oil sealed rotary vane pump (the most common positive displacement pump) backing a diffusion pump, or a dry scroll pump backing a turbomolecular pump. There are other combinations depending on the level of vacuum being sought.

Achieving high vacuum is difficult because all of the materials exposed to the vacuum must be carefully evaluated for their outgassing and vapor pressure properties. Outgassing (sometimes called offgassing, particularly when in reference to indoor Air quality is the slow release of a Gas that was trapped Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium For example, oils, and greases, and rubber, or plastic gaskets used as seals for the vacuum chamber must not boil off when exposed to the vacuum, or the gases they produce would prevent the creation of the desired degree of vacuum. Although the word grease originally described the rendered fat of animals the term is now applied more broadly to mean a Lubricant of higher initial Viscosity Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products A gasket is a mechanical seal that fills the space between two objects generally to prevent leakage between the two objects while under compression. A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage (e The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Often, all of the surfaces exposed to the vacuum must be baked at high temperature to drive off adsorbed gases. Adsorption is a process that occurs when a gas or liquid Solute accumulates on the surface of a solid or a liquid (adsorbent forming a film of molecules or atoms (the

Outgassing can also be reduced simply by desiccation prior to vacuum pumping. Desiccation is the state of extreme dryness or the process of extreme drying High vacuum systems generally require metal chambers with metal O-ring seals such as Klein flanges or ISO flanges, rather than the rubber o-rings more common in low vacuum chamber seals. The system must be clean and free of organic matter to minimize outgassing. All materials, solid or liquid, have a small vapour pressure, and their outgassing becomes important when the vacuum pressure falls below this vapour pressure. As a result, many materials that work well in low vacuums, such as epoxy, will become a source of outgassing at higher vacuums. In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a With these standard precautions, vacuums of 1 mPa are easily achieved with an assortment of molecular pumps. With careful design and operation, 1 µPa is possible.

Several types of pumps may be used in sequence or in parallel. In a typical pumpdown sequence, a positive displacement pump would be used to remove most of the gas from a chamber, starting from atmosphere (760 Torr, 101 kPa) to 25 Torr (3 kPa). Then a sorption pump would be used to bring the pressure down to 10^-4 Torr (10 mPa). A cryopump or turbomolecular pump would be used to bring the pressure further down to 10^-8 Torr (1 µPa). An additional ion pump can be started below 10^-6 Torr to remove gases which are not adequately handled by a cryopump or turbo pump, such as helium or hydrogen. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1

Ultra high vacuum generally requires custom-built equipment, strict operational procedures, and a fair amount of trial-and-error. Ultra high vacuum (UHV is the Vacuum regime characterised by Pressures lower than about 10−7 pascal or 100 nanopascals (~10−9 Ultra-high vacuum systems are usually made of stainless steel with metal-gasketed conflat flanges. In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 The system is usually baked, preferably under vacuum, to temporarily raise the vapour pressure of all outgassing materials in the system and boil them off. If necessary, this outgassing of the system can also be performed at room temperature, but this takes much more time. Once the bulk of the outgassing materials are boiled off and evacuated, the system may be cooled to lower vapour pressures to minimize residual outgassing during actual operation. Some systems are cooled well below room temperature by liquid nitrogen to shut down residual outgassing and simultaneously cryopump the system. Liquid nitrogen (liquid density at the Triple point is 0707 g/mL is the liquid produced industrially in large quantities by Fractional distillation of

In ultra-high vacuum systems, some very odd leakage paths and outgassing sources must be considered. The water absorption of aluminium and palladium becomes an unacceptable source of outgassing, and even the absorptivity of hard metals such as stainless steel or titanium must be considered. WikipediaNaming Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Some oils and greases will boil off in extreme vacuums. The porosity of the metallic chamber walls may have to be considered, and the grain direction of the metallic flanges should be parallel to the flange face.

The impact of molecular size must be considered. Smaller molecules can leak in more easily and are more easily absorbed by certain materials, and molecular pumps are less effective at pumping gases with lower molecular weights. A system may be able to evacuate nitrogen, (the main component of air,) to the desired vacuum, but the chamber could still be full of residual atmospheric hydrogen and helium. Vessels lined with a highly gas-permeable material such as palladium (which is a high-capacity hydrogen sponge) create special outgassing problems. Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1

Uses of vacuum pumps

Vacuum pumps are used in many industrial and scientific processes including:

• The production of most types of electric lamps, vacuum tubes, and CRTs where the device is either left evacuated or re-filled with a specific gas or gas mixture
• Semiconductor processing, notably ion implantation, dry etch and PVD, ALD, PECVD and CVD deposition and soon in photolithography
• Electron microscopy
• Medical processes that require suction
• Medical applications such as such Radiotherapy, Radiosurgery, Radiopharmacy
• Analytical instrumentation to analyse gas, liquid, solid, surface and bio materials
• Mass spectrometers to create an ultra high vacuum between the ion source and the detector
• Vacuum Coating for decoration, for durability, for energy saving
• Glass coating for low e glass
• Hard coating for engine (as in Formula One)
• Ophthalmic coating
• Trash compactor
• Vacuum engineering
• even in sewage system see EN1091:1997 standards

Vacuum may be used to power mechanical devices. Lighting includes both artificial Light sources such as lamps and natural illumination of interiors from Daylight. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Ion implantation is a Materials engineering process by which ions of a material can be implanted into another solid thereby changing the physical properties of the An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles Low-emissivity (Low-E Coatings are microscopically thin virtually invisible Metal or metallic Oxide layers deposited on a Window or skylight Vacuum engineering deals with technological processes and equipment that use Vacuum to achieve better results than those run under atmospheric Pressure. In diesel-engined automobiles, a pump fitted on the engine (usually on the camshaft) is used to produce vacuum. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum The camshaft is an apparatus often used in Piston engines to operate Poppet valves It consists of a cylindrical rod running the length of the Cylinder bank In gasoline-powered automobiles, instead, vacuum is obtained as a side-effect of the operation of the engine and the flow restriction created by the throttle plate. A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction This vacuum may then be used to power:

• The booster for the power brakes
• Motors that move dampers in the ventilation system
• The throttle driver in the cruise control servomechanism
• Controlling other devices (such as turbo geometry, EGR, etc. A damper is a valve or plate that stops or regulates the flow of air inside a duct, Chimney, VAV box, Air handler, or other air handling equipment A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction Cruise control (sometimes known as speed control or autocruise) is a system that automatically controls the rate of motion of a Motor vehicle. A servomechanism, or servo is an automatic device which uses error-sensing Feedback to correct the performance of a mechanism )

In an aircraft, the vacuum source is often used to power gyroscopes in the various flight instruments. A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum. To prevent the complete loss of instrumentation in the event of an electrical failure, the instrument panel is deliberately designed with certain instruments powered by electricity and other instruments powered by the vacuum source.

History of the vacuum pump

The vacuum pump was invented by Otto von Guericke. Otto von Guericke (originally spelled Gericke ˈgeːʁɪkə ( November 20, 1602 &ndash May 11, 1686 ( Julian calendar)

Nikola Tesla designed the apparatus, imaged to the right, that contains a Sprengel pump to create a high degree of exhaustion. There have already been discussions about Tesla's ethnicity on the talk page

Hazards

Old vacuum-pump oils that were produced before circa 1980 often contain a mixture of several different dangerous polychlorinated biphenyls (PCBs), which are highly toxic, carcinogenic, persistent organic pollutants. Polychlorinated biphenyls ( PCB s are a class of Organic compounds with 1 to 10 Chlorine atoms attached to Biphenyl which is a molecule composed Toxicity is the degree to which a substance is able to damage an exposed organism The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation Persistent organic pollutants ( POP s are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic ^[2][3]

See also

• An Experiment on a Bird in the Air Pump
• Vacuum engineering
• Vacuum flange

References

1. ^ Van Atta, C. An Experiment on a Bird in the Air Pump is a 1768 oil-on-canvas painting by Joseph Wright of Derby, part of a series of candlelit scenes that Wright painted Vacuum engineering deals with technological processes and equipment that use Vacuum to achieve better results than those run under atmospheric Pressure. A vacuum flange is a Flange at the end of a Tube used to connect Vacuum chambers tubing and Vacuum pumps to each other M. ; and M. Hablanian (1991). "Vacuum and Vacuum Technology". Encyclopedia of Physics (Second Edition). Ed. Rita G. Lerner and George L. Trigg. VCH Publishers Inc. . pp. 1330-1333. ISBN 3-527-26954-1.  
2. ^ Martin G Broadhurst (October 1972). "Use and Replaceability of Polychlorinated Biphenyls". Environmental Health Perspectives 2: 81-102. doi:10.2307/3428101. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
3. ^ C J McDonald and R E Tourangeau (1986). PCBs: Question and Answer Guide Concerning Polychlorinated Biphenyls. Government of Canada: Environment Canada Department. ISBN 0-662-14595-X. Retrieved on 2007-11-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1492 - The Ensisheim Meteorite the oldest Meteorite with a known date of impact strikes the Earth around noon in a Wheat  

External links

• Instructables: Make a Manual Vacuum Pump for Under $20 by Converting a Bicycle Pump