Rotary Vacuum Pump
#1

Submitted By
S.Ganesan
S.Karthick
Ashwin Vadhulya
Thirumalaiah

[attachment=9478]
Rotary Vacuum Pump
synopsis

 In most of the industries available in the country, the pumps are used for many purposes.
 For pumping water,
 For pumping oil,
 For pumping air and
 For creating vacuum
 Such pumps have to be lubricated. But in the vacuum pump we can’t provide oil holes, because of the difficulty of attaining the absolute vacuum.
 The crisis involved in the above pumps can be overcome by this project. Because are used. So, there is no need for providing oil holes and oil rings. Also, the main criteria are to make it a self lubricated pump. This type of vacuum pump is used to produce and maintain vacuum in a system by removing matter from the space involved to a degree dependent upon the type of system. This type of pump is generally used in printing presses.
introduction
 Life in the world has become faster due to the development of science. In this fast moving world to avoid chaos and confusion, an effective means or mode of communication is essential.
 Of-course communication has also developed to its peak with the invention of telephone, radio, television, pagers etc. inspire of these developments, newspapers, magazines etc. Play an important role in communication.
 In case of newspapers large number of copies must be printed in a short span of time and must reach the public in time. For this purpose offset printing machines are used.
 The heart of newspaper industries are heart beat of the printing machines. These pumps are mostly used in thin machine for delivering papers inside are mostly used in thin machine for delivering papers inside and taking the printed papers outside automatically. However the pumps currently used in these industries cause a lot of trouble and have to be maintained periodically.
 Our project “The Self Lubricated Vacuum Pump” is an attempt to eradicate almost all the difficulties pointed out by experts and technicians working with these pumps, to the possible extent.
Advantages
 Since, the pump is self lubricated (Carbon blades) there is no need for oil.
 Since oil lubrication is not used in this pump it is maintenance free.
 The fabrication of the pump also becomes easier with elimination of the eccentric oil ring.
 The cost of the oil used for lubrication is saved and hence it is economical.
 Prevention measures used in oil lubricated pumps for leakage are not needed
Disadvantages
 Initial cost of the pump is high, since the cost of the carbon blades are high.
 The carbon blades must be changed or replaced in proper time when worn out.
Applications
Many of the principal industrial process involve the use of sub atmospheric pressures. The applications are listed below:

 It is used in printing presses for lifting the sheet and taking the sheet to the printing process.
 It is used in water vapor refrigerating units for air conditioning and process work.
 It is used in vacuum distillation and crystallization units for various chemical and refinery products etc.
 It is also used in evaporative freezing units for a various food products etc.
 It can also be used for free drying or in dehydrating equipment for sublimation drying of food specialties, Blood plasma, Penicillin, Vitamins, Special drugs, etc.

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#2

Presented by:
Debjit adak

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Introduction:
Rotary pumps are pumps that move fluid using the principles of rotation. The vacuum created by the rotation of the pump captures and draws in the liquid. Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed the air from the lines manually.
Rotary pumps make up about 10% of the pumps we use in industry.
Advantages:
Unlike the more common centrifugal design, they are positive displacement (PD) pumps with several advantages:.
They will put out a constant volume of liquid regardless of the pressure they encounter. They put out the constant volume with each rotation of the shaft.
They do not impart velocity to the liquid they are pumping.
The discharge pressure is determined by resistance, and not affected by the specific gravity of the fluid.
There is no radial thrust transferred to the shaft as you move on the pump curve.
Flow is independent of pressure. You can change the flow without upsetting the pump's efficiency.
The pump can handle high viscosity fluids efficiently.
The pump is self priming
You get a smooth pulse free flow of the liquid into the system.
You can get the desirable high head low flow combination that is need in many high pressure applications.
They give you a non-shearing action that will not degrade sensitive petrochemicals and polymers
Limitations:
The head of a centrifugal pump was limited by the diameter of the impeller and its speed. How much pressure will a rotary PD pump produce? It is limited only by:
The strength of the pump casing and the internal components.
The power available from the pump driver (normally an electric motor).
Different types of rotary pumps:
The simplest vane pump is a circular rotor rotating inside of a larger circular cavity. The centers of these two circles are offset, causing eccentricity. Vanes are allowed to slide into and out of the rotor and seal on all edges, creating vane chambers that do the pumping work. On the intake side of the pump, the vane chambers are increasing in volume. These increasing volume vane chambers are filled with fluid forced in by the inlet pressure. Often this inlet pressure is nothing more than pressure from the atmosphere. On the discharge side of the pump, the vane chambers are decreasing in volume, forcing fluid out of the pump. The action of the vane drives out the same volume of fluid with each rotation. Multistage rotary vane vacuum pumps can attain pressures as low as 10−3 mbar
The different other types of rotary pumps are as follows:
 External gear
 Internal gear
 Lobe
 Progressive cavity
 Three screw
 Two screw
 One screw
 Flexible tube
 Sliding vane
 Flexible vane
Table depicting the power of different types of Rotarty pumps:
Weaknesses of Rotary Pumps:
Positive displacement rotary pumps also have their weaknesses. Because of the nature of the pump, the clearance between the rotating pump and the outer edge must be very close, requiring that the pumps rotate at a slow, steady speed. If rotarypumps are operated at high speeds, the fluids will cause erosion, much as ocean waves polish stones or erode rock into sand.Rotary pumps that experience such erosion eventually show signs of enlarged clearances, which allow liquid to slip through and detract from the efficiency of the pump.
Uses:
Common uses of vane pumps include high pressure hydraulic pumps and automotive uses including, supercharging, power steering and automatic transmission pumps. Pumps for mid-range pressures include applications such as carbonators for fountain soft drink dispensers and espresso coffee machines. They are also often used as vacuum pumps for providing braking assistance (through a braking booster) in large trucks, and in most light aircraft to drive gyroscopic flight instruments, the attitude indicator and heading indicator. Furthermore, vane pumps can be used in low-pressure gas applications such as secondary air injection for auto exhaust emission control, and in vacuum applications including evacuating refrigerant lines in air conditioners, and laboratory freeze dryers, extensively in semiconductor low pressure chemical vapor deposition systems, and vacuum experiments in physics. In this application the pumped gas and the oil are mixed within the pump, but must be separated externally. Therefore the inlet and the outlet have a large chamber – maybe with swirl – where the oil drops fall out of the gas. The inlet has a venetian blind cooled by the room air (the pump is usually 40 K hotter) to condense cracked pumping oil and water, and let it drop back into the inlet. It eventually exits through the outlet.
Main Advantage:
Rotary pumps work best with viscous (thick) fluids because the viscous fluid fills the clearance areas as well as the pumping cavities, and the less clearance you have in a rotary pump the better it works.
This means that rotary are more efficient than centrifugal pumps when the fluid is viscous, but less efficient with low viscosity fluids because of "slip" (the cross over point varies from 700 to 1000 SSU).
They also have the advantage of being self priming because they can pump gases as well as liquid.
Pumping Slurries
Tight tolerances means more wear when you are pumping a slurry or abrasive fluids. If you are pumping either of these you should run at pump speeds well below those used for clean lubricating liquids. In slurry applications the wear rate is proportional to the speed. Caution : Be sure to keep the speed high enough to keep all velocities within the pump and system above the critical carrying velocity of the slurry.
Specify pumping elements which combine soft and hard materials to reduce abrasion and provide resistance to the solids imbedding into the pump components.
Since rotary pumps are positive displacement pumps and slurries have an inherent tendency to settle and clog piping, over pressure protection should be part of the system. Slurry service precludes the use of many conventional relief valves, but rupture discs and other options are available.
The corrosion rate of the slurry should be a prime consideration in selecting the pump materials. Most corrosion resistant metals form a protective oxide layer (we use the term "passivated" to describe this), that will be removed by the slurry, increasing the corrosion rate of the metal dramatically.
The Effect Of Viscosity On The Pump And System Performance
The net positive inlet pressure required (NPIPR) increases with increasing viscosity.
The required input power increase with increasing viscosity.
The maximum allowable pump speed decreases with increasing viscosity.
The pump slip decreases with increasing viscosity. This has the affect of a slight increase in the gpm output.
The outlet pressure does not increase with an increase in viscosity.
Working of gear,vane or lobe pump
Though the construction, shape and design of gear, vane and globe pumps are a bit different , they fall under the same category of rotary pumps. The working of all these pumps are based on the same principle, i.e pumping of the liquid with the help of rotating elements. The rotating elements can be gears, screws or vanes. We will understand the basic principle of all these pumps by taking the working system of gear pumps into consideration.
A gear pumps rotating assembly consists of two gears, a driving gear and a driven gear. Pumping in a gear pump takes place when the driving gear meshes with the driven gear to form cavities that moves the fluid.The cavities are the clearances between the gears or lobes and the body of the pump. The mating surfaces of the gears' mesh provide continuous sealing between the the inlet and outlet ports.
As the rotation of the pump continues, the movement of the cavities progresses, thus moving the fluid along the way. After some time, a point is reached where the seal between the captured fluid and the outlet part of the pump is broken. At this point of time the vanes, gears or lobes, forces the volume of the captured fluid out of the pump. A continuous cycle takes place due to the simultaneously opening of new cavities at the inlet port. This leads to a continuous flow of liquid though the suction and discharge ports.
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