all about vacuum

1. What is Vacuum?
1
Reduction
of air
pressure in
container by
Vacuum
pumps

2. Units of Pressure
mm
(Hg)
Pascal
(N/m2)
Bar Torr
lb/in2
(psi)
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Relations between units
1 Pascal = 1 N/m2= 0.01 mbar
1 atm= 105 Pascal= 1.013 bar = 1013 mbar = 760 Torr = 14.70 lb/in2
1 torr = 1.33 mbar = 1330 Pascal = 1mm Hg
1 mm Hg = 1330 Pa
1 psi = 0.068 atm = 51.71 Torr

5. Broad Pressure range
Rough vacuum (RV) 1000 – 1 mbar
Medium vacuum (MV) 1 – 10-3 mbar
High vacuum (HV) 10-3 – 10-7 mbar
Ultrahigh vacuum (UHV) 10-7 – 10-14 mbar
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6. Vacuum is utilized in ……
• Food and Packaging industry
• Beverage Industry
• Cleaning purposes
• Thermal Insulation
• CRT
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7. Food & Packaging Industry
• Vacuum packaging
evacuates air from the
package before sealing to
remove oxygen from the
container to extend the shelf
life of foods and, with
flexible package forms, to
reduce the volume of the
contents and package.
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8. Packaging
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9. Beverage industry
Bottle Filling Machines in
Breweries and Soft Drink plants
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10. Deaeration of Mineral Water
Mineral water and other beverages should contain a
precise quantity of dissolved carbon dioxide.
The CO2 is first extracted from the source water
by a vacuum Deaeration system, then cooled
and liquefied, and finally reintroduced in exact
quantities to the final product at the bottling
stage.
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11. Vacuum Cleaners
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12. Thermal Insulation
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13. Production
of
Vacuum
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14. Units or gas pressure
• mm of Hg
• Pascal
• Bar
• Torr
• Lb/in2
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15. In order to obtain sufficient vacuum(required range of vacuum) different types of pumps are
used. Here, different pumps are “Like gears on a car”.

16. Categories of Vacuum Pump
Gas Transfer
Vacuum pump
Positive
Displacement
Rotary Pump
Kinetic
Vacuum pump
Drag
Fluid
Entrainment
Diffusion
Pumps
Jet pumps
Ion transfer
Entrapment
Vacuum Pump
Getter Pump
Sublimation
Pump
Cryopump
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18. Rotary Pump(Rotary Vane Pump)
• Capacity – 760 Torr – 10-4 Torr
• Speeds ranging from 0.25 L/s to more than 80 L/s
• Known as a roughing pump (to get rough vacuum)
• Also known as roughing pump as it creates rough vacumn
• Principle
Gas Transfer by rotor from inlet to outlet
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21. Limitations
• Rotary pump requires some routine maintenance. The oil level must be checked
regularly and maintained at the proper level.
• The oil must be chemically stable as the stability of oil depends on the type of
vapour passing through it.
• oil is lost during the process of pumping.
• Vapours that condense in the system can pollute oil, hich may lead to the corrosion
of pump or degradation of oil.
• Expensive synthetic oil is needed for smooth working
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22. Diffusion Pump (100mT- 10-10 mTorr)
• Fluid entrainment gas transfer
pump.
• 10-4 to 10-10 Torr
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23. Diffusion Pump
• Vapour from a boiler passes
through a series of nozzles in
a downward direction,
carrying residual atoms in
the vacuum chambers with
it.
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Cross sectional
View

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Procedure
• High purity oil at the bottom of the pump is heated of about 250◦C and
evaporates.
• oils have reasonable high speeds of about 300 m/s.
• The stack confines the oil, and when the oil leaves the stack it moves in a
downward direction, colliding with gas molecules and driving them towards
the bottom of the pump.
• At the bottom of the pump the gas pressure is high enough that a rotary
pump can remove the gas to atmosphere. The oil Vapor hits the sides of the
pump that are cooled by water pipes, and the condensed oil runs to the
bottom of the pump to be reheated.

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Sputter Ion Pump
• Is a gas entrapment type of vacumn pump
• Using a combination of an electric and magnetic field the ion pump
provides a method of ionizing atoms of gas and then trapping them.
• Sputter-ion pumps are gas capture type vacuum pumps that function
without pump fluids or any moving parts.
• They offer a clean, quiet, and safe way to achieve ultra-high vacuum (10-11
Torr).
• Principle
• Sorption processes

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Working
The influence of the magnetic field is small because of the ion’s relatively large atomic mass compared to the electron mass.
The usual result of a collision with the electron is the creation of a positive ion that is accelerated to some kV by the anode voltage and moves
almost directly to the cathode.
Electrons are emitted from the cathode due to the action of an electric field and, due to the presence of the magnetic field, they move in long
helical trajectories which improves the chances of collision with the gas molecules inside the Penning cell.
The magnetic field is orientated along the axis of the anode.
The cathode plates positioned on both sides of the anode tube are made of titanium, which serves as the gettering material.
The anode is usually cylindrical and made of stainless steel.
A sputter-ion pump consists basically of two electrodes, anode and cathode, and a magnet

31. Ion Pump
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32. Cryosorption pump
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33. Vacuum Measurement
• Pirani Gauge
• Ion Gauge
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34. PIRANI GAUGE
• Range: 0.5 Torr – 10-3 Torr (CAN NOT WORK > 1 Torr)
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35. Pirani Gauge
(Thermal Conductivity Gauge)
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• R2 is exposed to vacuum chamber
• R1 serves as a reference resistance which is also kept in
high vacuum
• Both R1 and R2 heated up by passing constant current (10-
100mA) through them
• Other resistances of the bridge are adjusted for getting
null point
• At higher pressure, temperature of R2 decreases because
of thermal conductivity of gas
• Therefore, the resistance of R2 decreases and current
through unbalanced bridge indicates the change in
pressure.

36. How Pirani Gauge Works?.....
• R2 is exposed to vacuum chamber
• R1 serves as a reference resistance which is
also kept in high vacuum
• Both R1 and R2 heated up by passing
constant current (10-100mA) through them
• Other resistances of the bridge are adjusted
for getting null point
• At higher pressure, temperature of R2
decreases because of thermal conductivity
of gas
• Therefore, the resistance of R2 decreases
and current through unbalanced bridge
indicates the change in pressure.
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