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About Vacuum Pumps
Vacuum pumps are basically devices used to create a
vacuum. The vacuum pump changes the mechanical force of a rotating shaft
to pneumatic force by removing air and other gases and releasing them
into the atmosphere or holding them on surfaces within the pump. The
amount of energy produced depends on the force for all vacuum applications.
Vacuum pumps are either positive displacement or non-positive displacement.
A positive displacement pump pulls a constant volume of air despite variations
in the vacuum levels. Nonpositive displacement vacuum pumps use changes
in kinetic energy to remove air from a system. The most important advantage
of this design is its ability to supply very high volume flow rates that
are much higher than possible with any of the positive displacement designs.
Both types of pumps mentioned could be either or oil-free.
The oil lubricated types have advantages in that they are able to provide
a higher level of vacuum because the oil provides a greater seal between
moving parts. Oil-free pumps are useful for pumps that will be mounted
in inaccessible or remote locations. They are also used in the food and
pharmaceutical industries where it is necessary to keep the product free
from contaminants.
The standard types of positive displacement pumps are the piston, diaphragm,
rocking piston, rotary vane, lobed rotor and rotor screw designs. Piston
pumps 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. Rocking piston pumps are basically a
combination of diaphragm and piston pumps. Rotary vane pumps have an
impeller made of rigid material and are useful for high-pressure or low-shear
applications. Lobed rotor pumps have lobe-shaped rotors that gently fill
with and dispense fluids containing soft particles, solids and highly
viscous fluids. Rotary screw pumps have capabilities that are similar
to the piston pumps in terms of vacuum, but air removal is pulse-free.
The standard type of nonpositive displacement vacuum pumps are the centrifugal,
axial-flow and 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.
All of us benefit from vacuum technology, whether wearing a pair of glasses,
watching TV, listening to music, using a PC or driving a car. The manufacturing
of semiconductors, CDs and DVDs, eyeglasses and the coating of heavy-duty
mechanical tools are a few examples in which vacuum technology is applied.
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 used for industrial gripping and chucking, laboratory degassing
and purification in the fields of chemical and semiconductor processing.
Featured
Articles
http://www.massvac.com/pages/resource_article01.html
http://www.graham-mfg.com/downloads/28.pdf
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.
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