Vacuum pumps are devices that create a vacuum by removing gasses from a sealed space. A perfect vacuum is a space in which there is no matter. No naturally-occurring perfect vacuums exist, and it is impossible to create one. Industrial vacuum pumps, or vac pumps as they are often called, can be used to create partial vacuums of varying intensities; high vacuum pumps can evacuate enclosures to very low pressure levels, and small vacuum pumps create less intense vacuums.
VACUU·LAN® vacuum networks make it possible to supply several different applications with one vacuum pump; this is a money- and space-saving solution when a lot of users are working with vacuum in one laboratory. This also avoids the numerous drawbacks of a central ("house") vacuum supply. These very versatile modules for single workplaces can be subsequently upgraded. All of the components are available for new laboratory furnishings or for installation in existing or renovated laboratories. All of the subassemblies are very resistant to chemicals and have built-in check valves to ensure that adjacent applications do not contaminate or interfere with one another.
There are many contexts throughout industry and commerce in which the creation of a vacuum is necessary. Laboratory vacuum pumps create carefully controlled environments for electron microscopy and other tests and experiments. Medical vacuum pumps are used for suction during surgical procedures and for radiotherapy. Vacuum forming, eyeglass lens fabrication, light bulb manufacturing, plastic molding, lamination, hard coating, safety glass fabrication, photolithography and a host of other processes make use of vacuum pumps. Chemical and corrosive gas suppliers, food processors, manufacturers, packagers and many other companies need vacuum pumps for their operations. Vacuum pump systems are designed in varying configurations; liquid ring pumps, dry pumps, oilless pumps and rotary vane pumps are just a few possibilities. All vacuum pumps are air pumps; they work by directing air out of an enclosure and preventing it from re-entering.
Different vacuum pumps direct airflow in different ways, and three main categories of pump systems account for most of those methods: positive displacement pumps, momentum pumps and entrapment pumps. Positive displacement pumps create a vacuum by repeatedly expanding and exhausting a closed cavity; rotary vane pumps, scroll pumps, piston pumps, diaphragm pumps and liquid ring vacuum pumps are all positive displacement pumps. Most positive displacement pumps feature simple designs and are used to create low-intensity vacuums. Momentum transfer pumps expel air molecules from a sealed vacuum pump by accelerating the molecules using high speed gas jets or fans. Diffusion pumps and turbomolecular pumps are examples of momentum vacuum pumps and can be used to create very low-pressure vacuums. Entrapment pumps trap gasses using a heating or cooling process that makes them easier to catch. Some vacuum pumps are not easily categorized. A piston vacuum pump, which is a type of regenerative pump, consists of rotating pistons of varying stroke lengths that pump fluids through check valves. Diaphragm pumps feature one or two flexible diaphragms that pulsate to displace fluid, while check valves control fluid flow direction.
Though vacuum pump system configurations can vary wildly, the concept of vacuum creation is the same in every design and application. Vacuums can only be created in enclosed spaces. The first artificially created vacuums were intended for use in demonstrations and research. Their enclosures were usually glass and were not much larger than a large glass jar. The glass enclosure would be placed upside-down on a surface after its edges had been coated with some kind of liquid sealant. Air would then be removed by an air pump through an outlet in the surface. The first vacuum pumps were simple, low-capacity fans. Every time a fan blade spun near the vacuum enclosure's outlet, it would push air away from the outlet and through an exhaust port located elsewhere in the pump, creating a small vacuum. Air pressure imbalances correct themselves naturally, so some of the air from the enclosure would flow out to correct the imbalance. This air would be pushed away by the spinning fan, and the process would repeat itself until much of the air from the enclosure had been evacuated. Today, many pump systems still resemble this model, though great improvements in vacuum pump efficiency and effectiveness have been made since then. Many options are available to the great diversity of industries and processes for which the use of vacuum pumps is necessary.
All vacuum pump systems can be categorized as either wet or dry. Wet systems are any vacuum pumps that make use of a liquid at any point in a pumping process. Wet systems can make use of oil as a lubricant or sealant. Liquid seal vacuums use liquids within their mechanical enclosures to create air-tight compression seals. Dry systems are the opposite; at no point during a dry vacuum pumping process is any liquid used. Different applications call for either dry or wet vacuum systems. Oil-sealed vacuums are used when high-intensity vacuums are needed because oil provides a good seal between moving parts. When oil-seals are used, a downstream oil separator must be employed to ensure that neither the enclosure nor the exhaust areas are contaminated with oil. Dry vacuum pumps eliminate this problem, but they do so at the cost of effectiveness. Wet vacuum pumps generally achieve lower vacuum pressures, but they also require more frequent maintenance and can cripple operations if they fail. In applications like aircraft instrumentation in which long-term, failure-free performance is absolutely critical, dry vacuum pumps are almost always preferred over wet pumps. Industry professionals are careful to consider the potential costs and benefits of choosing a wet or dry vacuum pump.
Vacuum Pump System - Agilent Technologies
Industrial vacuum pump - Vacuubrand, Inc.
Laboratory Vac Pumps - Vacuubrand, Inc.
Vacuum Pump System - Agilent Technologies
Rotary Vacuum Pump - Vacuubrand, Inc.
Vacuum Pump System - Agilent Technologies
Vacuum pumps, inarguably the most widely used equipment in ranges of industries, have roots in the 17th century. With time, as the technology evolved, various types of pumps mushroomed, each designed for specific purposes. Nowadays, vac pumps are used in a variety industries, which range from development of composite plastic to flight controls to uranium enrichment.
There are many ways to classify vacuum pump systems; however, categorizing them based on mechanisms gives an insight into the functioning, which proves essential while making buying decision.
Momentum Transfer Pump
In momentum transfer pump, molecules in the chamber are blown out-by either high-speed rotating blades or jets-to the exhaust side. As the name suggest, the pump adds momentum to the gas molecules that are diffused in. Molecular pumps are designed as an alternative to mechanical pumps to sweep up larger area. As they are capable of higher pumping speeds, they sweep the area more frequently.
Two types of molecular pumps are available: turbo-molecular and the diffusion pump. Diffusion pump employs jets of oil or mercury to blow out gas molecules, whereas turbo-molecular pump are fitted with high-speed fans to impart momentum to the gas molecules. These pumps cannot work independently, as the exhaust from molecular pumps cannot be released directly to the environment with standard atmosphere pressure. They need a partial vacuum at the exhaust line or they will stall. Therefore, they work in conjunction with mechanical pumps.
Positive displacement pump
In a positive displacement pump, a vacuum is created by expanding or increasing the volume of a sealed off cavity; this results in lower pressure in the cavity than the atmospheric pressure. As the pressure goes down, gas or other material, for which the pump is designed, flows in from the chamber, then the cavity is sealed off, and afterwards, through an outlet, the material is exhausted out. However, through this pump, only partial vacuum is achieved. The manual water pump is an example of positive displacement pump.
Various forms of positive displacement industrial vacuum pumps are on the market, including, rotary vane vacuum pumps, diaphragm pump or dry vacuum pumps, liquid ring vacuum pumps, piston pump, scroll pump, screw pump and Wankel pump. Each of these pumps has their own advantages, like contamination free (oil-less vacuum pumps are used when contamination is an issue), environmentally friendly, high speed etc.
They mainly are of two types of entrapment pumps: Cryo and ion pumps. These types of pumps use fundamentally different approach to create vacuum. Cryo pumps make use of cold temperatures to entrap gases in to a solid state; it practically freezes gases on arrays, which are cold surfaces.
Ion pumps are used for achieving ultra-high vacuum levels; they react with gases in the chamber and bury gases on the wall of the pump. Both of these pumps need regeneration process, including various pumps and valves to work efficiently. As they are used to attain ultra-high vacuum, they require a combination with other getter pumps, including evaporable barium getters and non-evaporable getters.
Vacuum pumps systems are extensively used in a wide range of process plants. Vacuum pumps eliminate or remove gas from a sealed, enclosed space to create a partial or full vacuum. Otto Von Guericke invented the vacuum pump in 1650, which could achieve far lower pressures in comparison to his processors. He proved the efficacy of his pump by conducting Magdeburg hemispheres experiment, in which two teams of horses are pitted against each other to separate two hemispheres that are joined together by evacuating the air between them. No horse team could separate the hemispheres. This started a new field, altogether. However, its modern day application was realized only in the end of the 19th century.
Nowadays, vacuum pumps have application in industrial and scientific fields.
Given the wide varieties and alternatives available, it is daunting task to select the vacuum pump that suits your requirements. Understanding the terms related to pumps can help you to make a right decision.
While comparing pumps, you often will see the term Cubic Feet per Minute (CFM), which tells the speed of the vacuum flow. The term is relevant to electric rotary vane pumps and piston pumps, also known as reverse air compressors. The CFM is pivotal to how fast the pump can remove the air from a refrigeration system or tank.
Another major term that you should know about is Inches of Mercury (Hg). It is a measure of power, which can be compared to horsepower. The term plays a big role when holding power is the most important factor, regardless of the time it takes to reach the full vacuum. Holding power is key attribute of a pump in machining metals and plastics industry.
How to achieve partial pressure and higher vacuum
Positive displacement pumps, which move gas from an inlet port to an exhaust, are considered suitable only for achieving partial vacuum. As they have mechanical limitations, pumps achieve a partial vacuum.
Higher vacuum can be achieved by joining pumps in series, commonly a combination of a fast pump and positive displacement pump. Similarly, rotary vane pump works with a diffusion pump, and a dry scroll pump with turbo-molecular pump. Depending on the level of vacuum being sought, different combinations are also available.
- The process involving the penetration
of a gas or vapor beyond the surface of a solid or liquid, usually by
some kind of diffusion and its subsequent binding or capture.
- The sum of atmospheric and gauge pressures, it is the total force per unit area exerted by a fluid and the pressure above a perfect vacuum (zero pressure) in vacuum systems. U.S. units for absolute pressure are pounds per square inch absolute (psia).
- Gas or vapor bonding on, or "sticking" to, a solid or liquid surface.
- Device installed at the intake port of a compressor or vacuum pump that is used to capture insoluble contaminants from a fluid with porous material.
- A vacuum heat treatment process in which a material is relaxed and uneven or heterogeneous regions of a substrate, which result from the application of internal stress, are homogenized.
- Unit of pressure that will sustain a column of mercury of 29.92" at 0°C, sea level. Actual daily atmospheric pressure fluctuates about this value.
- Pressure exerted by the atmosphere in all directions, equal at sea level to about 14.7 psi. Also the force exerted on a unit area by the weight of the atmosphere.
- Resistance to flow in the system.
- The movement of the vapor of the operational fluid of a pump in the direction of the area being depleted.
- A system of cold surfaces placed between the inlet of a pump and the area on which it is pumping to condense backstreaming vapor and return it to the pump.
- The heating of vacuum system components during the pumping process for the purpose of degassing. The bake-out process increases the evolution of adsorbed and absorbed gases.
- Mechanism for calculating atmospheric pressure, given in inches of mercury (in. Hg) at a precise point.
- A plate that supports a belljar along with its enclosed materials or components subjected to a vacuum, providing mechanical, electrical and other connections to components within the vacuum system.
- A cylindrical vacuum compartment with a detachable seal supported by a baseplate.
- The negative electrode in an electron device. A cathode is the most negative electrode in an ion pump, which can discharge electrons and accumulate positive ions.
- A two-way directional valve that allows free flow in one direction and blocks flow in the other direction. Check valves can act as either directional or pressure control apparatuses.
- The process of a vapor becoming a liquid or solid.
- Under steady-state conservative conditions, the ration of throughput to the pressure differential between two specified cross sections inside a pumping system.
- The pressure at which pumping is transferred from one pump to another, providing a higher speed and/or a lower pressure.
- The deliberate removal of gas from a material, usually done by heating the material under vacuum.
- An absorption material that eliminates moisture from air.
- Switch with a low-pressure and high-pressure adjustment. Fluid pressure activates an electric switch to perform work.
- The process of particles moving from an area of higher concentration to one of lower concentration.
- Meaningful only in positive displacement compressors, the entire volume that is swept by the repetitive motion of the pumping element. Displacement per revolution depends on the size of the pumping chamber or chambers, and displacement per minute is determined by compressor speeds.
- Also known as "pass-through," it is a device used to transmit electrical current, fluids or mechanical motion through the walls of a vacuum system.
- A measurement of the amount of fluid at a point per unit of time, commonly represented by cubic feet per minute (cfm).
- Energy controlled and transmitted through utilization of a pressurized fluid within an enclosed circuit.
- A measurement of the force per area applied by a fluid with atmospheric pressure as the zero reference.
- Often used to indicate gauge pressure, this is energy per pound produced by pressure, elevation or velocity. Expressed in linear units, it is the height of a column or body of fluid above a given point.
- The exertion of pressure in all directions equally at points within an enclosed gas or liquid at rest.
- A process that occurs by adding or removing electrons to or from an atom or molecule, resulting in the formation of ions.
- Expansion or compression of a gas at a constant temperature. Practically, this is a slow process because of the time required to replace heat absorbed by expansion or to remove heat generated by compression.
- Energy due to motion that is added to a fluid either by rotating it at a high speed or by providing a catalyst in a direction of flow.
- Gas flow of adequate velocity so the gas will flow efficiently over surface obstructions and defects.
- Pneumatic component that lubricates through the injection atomized oil into the air stream.
- An instrument used to measure the pressure of vapors and gases.
- Highest level of vacuum recommended for a vacuum pump.
- The average distance a gas molecule moves without interacting with a surface or another molecule.
- Also called "gauge vacuum" or "vacuum level," it is the pressure drop that results from the system emptying, measured in inches of mercury (in. Hg.). Negative gauge pressure is a term that must be carefully used, because absolute negative pressure does not exist.
- A vacuum gauge intended to be inserted into a vacuum system that does not have its own envelope.
- The volume of air exhausted per minute, expressed in cfm, when there is no pressure or vacuum load on the pump.
- The process of evaporation that substances, such as oil and dirt, undergo after being placed in a low-pressure or vacuum environment.
- The movement of gas through a solid. The process always involves diffusion through the solid and may involve surface phenomena such as dissociation, sorption, desorption and migration.
- The energy that is controlled and transmitted within an enclosed circuit by use of a pressurized fluid.
- The difference in pressure above atmospheric pressure.
- Force per unit area impacting a surface, typically expressed in pounds per square inch (psi) or in MegaPascals (Mpa).
- An electrical switch controlled by fluid pressure.
- Pressure measured from a state of complete absence of air.
- Pressure above or below (vacuum) atmospheric pressure.
- A valve that releases air directly to the atmosphere, bypassing the directional valve, which reduces backpressure resistance.
- Container in which gas is stored under pressure or vacuum as a source of pneumatic fluid power. Receiver tanks accommodate sudden or unusually high system demands, prevent frequent on/off cycling of an air compressor or vacuum pump and absorb pulsations.
- Also referred to as a "partial pressure analyzer" or "partial pressure gauge," it is a device for measuring the amounts and species of various gases present in a vacuum chamber.
- Gas remaining in the vacuum chamber after pump-down.
- A valve that opens to its full capacity to provide a rapid and large reduction in pressure when a predetermined value is exceeded.
- Holes covered with the glass through which the inside of a vacuum system may be observed.
- Any element that controls current without moving parts, heated filaments or vacuum gaps.
- A generic term used to describe the uptake of a gas or vapor by a solid without distinction as to whether the process occurs by adsorption and/or absorption.
- Air at a temperature of 68°F, a pressure of 14.7 psia and a relative humidity of 36%.
- Also referred to as "standard operating conditions," it is a term referring to the temperature and pressure to which all values are referenced for comparison. STP is generally 760 mm Hg (1 atm), 25°C.
- The physical changes of a surface structure to states of less regularity or symmetry, or the chemical changes in its composition.
- A unit of pressure equal to 1/760th of a standard atmosphere.
- A device used to capture and retain vapors and gases on cold and/or adsorbent surfaces.
- Gas flow that is not laminar at high pressures and velocities.
- A space of air or other gas that is less than atmospheric pressure, expressed in inches of mercury (in. Hg).
- The enclosure or container that is evacuated and in which the process or experiment is performed.
- An instrument for determining gas pressure below atmospheric pressure.
- The cfm of free air exhausted by a vacuum pump at rated speed. Usually given for vacuums ranging from 0 in. Hg to the maximum vacuum rating.
- A valve that operates to provide a modulated flow of atmospheric air into the system to control vacuum level of the system.
- A total assembly, comprised of vacuum pumps, valves, chambers, lines and monitoring instruments, used to conduct a vacuum process or experiment.
- A fixed value that typically refers to the saturated vapor pressure at a specific temperature for all substances.
- The resistance to flow of a fluid when subjected to pressure.
- The flow of gas, which may be turbulent or laminar, through a channel under conditions such that the mean free path is very small in comparison with the smallest dimension of a transverse section of the channel. At these pressures, the flow characteristics are determined mainly by collisions between the gas molecules.
- Also known as "volumetric ratio," it is the ratio of the actual delivery of a pump to its calculated delivery multiplied by 100%.