IQS Newsroom Articles on Vacuum Pumps
About Vacuum Pumps and Vacuum Pump Manufacturers Including: Air
Pumps, Dry
Vacuum Pumps, High Vacuum Pumps, Liquid
Ring Vacuum Pumps, Rotary
Vane Vacuum Pumps & Small Vacuum Pumps.
Vacuum pumps are devices used to create a vacuum by removing air molecules from a sealed volume. The vacuum pump changes the mechanical force of a rotating shaft, piston, diaphragm, scroll or rotary vane to pneumatic force by removing air and other gases from a specific space, creating suction and subsequent pneumatic or hydraulic flow. Vacuum pumps come in many styles designed for very different applications, and all vacuum pumps fall into one of three categories: positive displacement pump, momentum pumps or entrapment pumps. Positive displacement pumps create an artificial vacuum by continually expanding and exhausting a closed cavity. Rotary vane pumps, scroll pumps, piston pumps, diaphragm pumps and
liquid ring vacuum pumps all fall under this category; these are all mechanical-type pumps typically used for low vacuum applications, and they are the simplest and most cost effective. Momentum transfer pumps may be diffusion pumps or turbomolecular pumps; both these
air pumps expel air molecules from a sealed vacuum pump by accelerating the molecules using high speed gas jets (diffusion pumps) or a series of high speed fans (turbomolecular pumps), and both are considered high vacuum or ultrahigh vacuum pumps. Entrapment pumps, such as cryopumps, use condensation created by artificial rapid heating and cooling to compress and/or trap specific gases.
Vacuum technology is used in processes from the manufacturing of everyday consumer items to radiotherapy and electron microscopy. Vacuum pumps may provide pneumatic or hydraulic power in flight instruments, plastic molding and air conditioning, or they may provide the vacuum pressure necessary for laminations, hard coatings, safety glass fabrication or photolithography. TVs, DVDs, PCs, cars, eyeglasses and the coating of heavy-duty mechanical tools are a few examples of applications dependent on vacuum technology. Vacuum pumps are used for vacuum distillation and the processing of food and in devices such as vacuum tubes, vacuum bottles, barometers and research equipment. Industries in which vacuum pumps and vacuum generators are commonly used include chemical and corrosive gas, food processing, manufacturing processing, medical and laboratory, packaging, power generation, pharmaceutical/sanitary and semiconductor manufacturing industries. Vacuum pumps are also used to improve the efficiency of steam heating systems. Different types of pumps are created by vacuum pump manufacturers and are used for industrial gripping and chucking, laboratory degassing and purification in the fields of chemical and semiconductor processing. Small vacuum pumps are particularly critical in aircrafts, where they power the gyroscopes which drive various flight instruments; vacuum-powered instruments will continue to function in an aircraft even if aircraft electricity has failed.
Piston pumps, a type of regenerative pump, consist of rotating pistons of varying stroke lengths that pump fluids through check valves. Diaphragm pumps consist of one or two flexible diaphragms that pulsate to displace fluid, while check valves control the direction of the fluid flow.
Rotary vane vacuum pumps have an impeller made of rigid material and are useful for high-pressure or low-shear applications. Rotary screw pumps have capabilities that are similar to the piston pumps in terms of vacuum, but air removal is pulse-free. Momentum transfer pumps, or nonpositive displacement pumps, are usually centrifugal, axial-flow or regenerative designs. Centrifugal pumps have a rotating vanned disk that is attached to a drive shaft. As it spins, the drive shaft moves fluid without pulsation. The outlet can be restricted without damaging the pump. Axial-flow pumps are designed to have a fluid flow parallel to an axis of rotation, similar to a turbine. Regenerative nonpositive displacement pumps consist of a series of pumps joined together to increase and maintain pressure. Another common classification of vacuum pumps describes whether pumps are assisted by an oil or other liquid sealing agent or not. Wet vacuum pumps include liquid ring pumps and some rotary vane pumps; in liquid ring pumps, water is pumped in to the vacuum and becomes a sealing ring around the internal rotating vanes. Rotary vane pumps often pump oil into the vacuum to act as a lubricating sealant, and diaphragm valves commonly use hydraulic fluid on the compressing side of the diaphragm.
Oil lubricated vacuum pumps are able to provide a higher level of vacuum because the oil provides a greater seal between moving parts; whenever oil pumps are used, however, a downstream oil separator must be employed to ensure that no contamination will occur within the application. Oil-free pumps, or dry pumps are use in applications which require pumps to be mounted in inaccessible or remote locations. Oilless pumps, which include dry scroll pumps and most piston pumps and rotary vane pumps, are simpler and more cost effective because they require no downstream oil separators. Although
dry vacuum pumps are far more common within the industry, many manufacturers consider wet vacuum pumps to have superior performance and durability, despite wet pumps' higher cost. This is particularly true in the aviation and aerospace industries, where long-term, failure-free performance is absolutely critical. Still, for easily accessible applications in which cost-effectiveness and lack of contamination are paramount, such as in the food and pharmaceutical industries where it is necessary to keep the product free from contaminants, dry vacuum pumps are very effective.
Types of Vacuum Pumps
- cause a gas to flow against a pressure,
converting mechanical force and motion into pneumatic fluid power.
- ,
also called "cryopumps," are
gas binding vacuum pumps that work by the condensation and/or sorption
of gas at
surfaces maintained at temperatures, kept low enough through refrigeration,
for the vapor pressures of the condensed gases to be insignificant.
Cryogenic pumps, which are vacuum pumps working in a range below 120°
Kelvin, cause
the vapor pressures to be lower then the vacuum pressure.
- are vacuum pumps in which heated
oil or another substance is pushed through jets as a vapor that collides
with gas molecules
and carries them out of the compartment being evacuated.
- operate without fluids, such as steam or water,
eliminating environmental worries and the cost of contaminant disposal.
Dry vacuum
pumps, which can be configured to operate either hot or cool depending
on the application, reduce emissions and ease solvent recovery.
- are vapor pumps in which the vapor streams primarily
under viscous flow conditions.
- have the ability to operate under the most
difficult conditions, such as when highly saturated vapors form in
or solid particles
get into the inlet stream.
- are heavy-duty pumps used in to create a vacuum in industrial settings.
- are "capture and hold" pumps
in which ionization removes gas at a significant rate.
- , used in many industries for the evacuation
of both dry and wet gases, have the capability to deal with condensable
vapors or even small slugs of liquid entrained in the incoming gas.
The condensing effect, occurring at the liquid ring as the incoming
gas makes
contact with it, can greatly enhance the upstream capacity of the
pump.
- have moving parts such as pistons, rotating vanes
or eccentric rotary members used for pumping vapor or gas.
- utilize kinetic energy to produce
pressure gradients (slopes) for air in motion.
- move an exact volume of air for every
cycle of operation.
- are reliable industrial-grade, heavy-duty
pumps that are used in high contaminate applications.
- are oil-sealed, air-cooled, direct-drive
pumps with a small footprint that are used for pumping
clean, dry, non-reactive
gases. With regular oil and vane/filter changes, the reliability
of rotary vane vacuum pumps, as far as maintaining maximum
up-time, is
moderate
- consist of many circular hollow rings, half of
which are in the upper and lower side of the pump housing
and the other half
in either side of the impeller, which has scoops on both
sides. Side channel pumps generate very low pulse suction air,
making them ideal
for a wide variety of industrial applications that require
precisely defined functions.
- are axial-flow
turbines designed for operation in the molecular flow range. Turbo
molecular pumps
consist of a series of alternate circular rotor and stator disks,
both of which
have
inclined blades designed to impart momentum change
to
gas molecules in a preferential
direction from the pump inlet to the outlet.
Vacuum Pump Terms
- 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. (http://www.iqsdirectory.com/check-valves/)
- 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. (http://www.iqsdirectory.com/pressure-switches/)
- 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%.