Air Compressors.pptx , types of air compressor

compressor its deifinition & types of air compressor

1. AIR COMPRESSORS

2. CONTENTS Introduction Uses of Compressed Air Types of Air compressor Terminologies in Air compressor Air Dryers Air Receivers Advantages of air power Vs Electric power Advantages of air power Vs Hydraulic power.

3. INTRODUCTION Definition: Compression is a process of increasing the pressure of any state of matter . Air compression is the process of increasing the air pressure above the atmospheric pressure. The value of atmospheric pressure is given as ‘1 atm’ or ‘101,325 Pa (Pascals)’. The mechanical device used to compress air is called an ‘Air compressor’. Thus, the air compressor is a mechanical pneumatic device powered by IC engines or electric motors to convert the kinetic energy of air to potential energy. The compressed air from the air compressors is usually stored in a high-pressure vessel.

4. INTRODUCTION Definition: Air compressor is a device that increases the pressure of a gas by reducing its volume and converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in a tank or air receiver (i.e., compressed air). The pressurized compressed air in the cylinders has kinetic energy when released and can be used in various applications Every air compressor obeys Boyle’s Law which states, “The product of pressure and volume of the mass of a confined gas is constant and proportional to the temperature.” Mathematically, PV∝T

5. INTRODUCTION Pressure (P) is the force per unit area applied in a direction perpendicular to the surface of an object. Celsius (C): (also known as centigrade) at 0°C is defined as the freezing point of water, the temperature at 100 °C is defined as the boiling point of water and 1.033 Kg/cm² is defined as the standard atmospheric pressure. pressure units : 101,325 Pa = 1.013 bar = 1.033 kg/cm² abs = 760 mm of Hg = 14.7 psia C° = (F – 32) / 1.8 5.The temperature Fahrenheit at 32°F is defined as the freezing point of water, the temperature at 212°F is defined as the boiling point of water and 14.7 psi is defined as the standard atmospheric pressure. F° = 1.8 C° + 32

6. Uses of Compressed Air Compressed air powers many different kinds of devices. It can be used to push a piston , as in a jack hammer ; It can go through a small air turbine to turn a shaft, as in a dental drill ; It is used in striking type pneumatic tools for concrete breaking, clay or rock drilling, chipping ,caulking, riveting etc. It is used as an atomiser in paint spray and insecticides spray guns. It is used in rotary type pneumatic tools for drilling, grinding, hammering etc. Pneumatic lifts and elevators work by compressed air. It is used for cleaning purposes Pile drivers, extractors, concrete vibrators require compressed air. Air-operated brakes are used in railways and heavy vehicles such as buses and lorries. Sand blasting operation for cleaning of iron castings needs compressed air.

7. Types of Air Compressors

8. Types of Air Compressors Positive Displacement Air Compressors 1.Reciprocating Air Compressors: The reciprocating type is a positive displacement (meaning that they increase the pressure of the air by reducing its volume) air compressor that is similar to IC engines. These have a piston connected to the crankshaft reciprocating inside a cylinder. The suction and delivery valves are at the top of the compressor cylinder. Single-stage: When the entire compression is accomplished with a single cylinder or a group of cylinders in parallel generally used for pressures in the range of 70 psig to 100 psig. Double-stage: Is when two ore steps of compression are grouped in series generally used for pressures in the range of 100 psig to 250 psig. Single acting: Is when the compressing is accomplished using only one side of the piston. Double acting: Are those using both sides of the piston.

9. Types of Air Compressors 1.1 Single acting Air Compressors:

10. Types of Air Compressors 1.1 Double acting Air Compressors:

11. Types of Air Compressors 1.2 Diaphragm Air Compressors: A Diaphragm Compressor is a variant of the classic reciprocating compressor with backup and piston rings and rod seal. The compression of gas occurs by means of a flexible membrane, instead of an intake element. The back and forth moving membrane is driven by a rod and a crankshaft mechanism. Only the membrane and the compressor box come in touch with pumped gas. For this reason this construction is the best suited for pumping toxic and explosive gases. The membrane has to be reliable enough to take the strain of pumped gas. It must also have adequate chemical properties and sufficient temperature resistance.

12. Types of Air Compressors 1.2 Diaphragm Air Compressors:

13. Types of Air Compressors 2.Rotary Air Compressors Rotary air compressors use the action of gears to compress air. These compressors involve the rotating element developing a liquid seal . This creates a suction at the inlet. The air is displaced positively by the mechanical component in this type of compressor.

14. Types of Air Compressors 2.1 Lobe Type or Roots Blower Rotary Air Compressors There are two rotors in the compressor, and generally one of them is connected to the external drive that drives the other rotor. The shape, technically known as the lobe , of these rotors, follows a cycloid or involute profile. The mating between these two imparts accurate sealing to the delivery side . Low-pressure air is compressed by the action converting it to high-pressure air by the end of the process.

15. Types of Air Compressors 2.2 Screw Type Rotary Air Compressors The screw type rotary air compressor uses a rotary type positive displacement mechanism. The compressor comprises closely meshing rotors of spiral shape to compress the air. In practical scenarios, while running the system dry, a pair of timing gears are used to ensure precise alignment. This also ensures resistance to rapid wear. The lubricating oil forms a connection in the space between the rotors in an oil-flooded rotary screw air compressor. This oil acts as a transfer medium of mechanical energy between the rotors to aid in the rotation of one powered by the other.

16. Types of Air Compressors 2.3 Vane Type Rotary Air Compressors The vane type compressor consists of a set of vanes mounted on a rotor as shown in the image. The vanes on the rotor inside the chamber are of variable length . They are in contact with the walls of the casing as the rotor rotates. The air from the inlet is drawn and compressed with this action.

17. Types of Air Compressors 2.4 Scroll Type Rotary Air Compressors Air compression within a scroll is accomplished by the interaction of a fixed and an orbiting helical element that progressively compresses inlet air . This process is continuously repeated, resulting in the delivery of pulsation-free compressed air. With fewer moving parts , reduced maintenance becomes an operating advantage. Scroll compressors can be of lubricated or oil-free design.

18. Types of Air Compressors Dynamic Displacement Air Compressors A steadily flowing air is impacted by kinetic energy by the mechanical elements in a compressor of this type, which increases the pressure of the flowing air. 1.Centrifugal Air Compressors The rotational energy is imparted to the air by centrifugal air compressors in the possess of compression. The rotational energy by the vanes is converted into a centrifugal force that pushes the air towards the discharge side. The airflow is normal to the axis of the rotating shaft in this type. The vanes are of two types: Diffuser and Impeller. Impeller vanes are curved which aids the flow of air. Diffuser vanes are fixed and are used to aid in the conversion of the rotational kinetic energy of air coming from impeller vanes to pressure energy. Centrifugal Air Compressors

19. Types of Air Compressors 1.Centrifugal Air Compressors

20. Types of Air Compressors 2.Axial Air Compressors The axial air compressor, a widely known dynamic compressor , is a mechanical device employed to increase the pressure of the air continuously in the system. In comparison with the centrifugal compressor, the axial compressors are small in size and light weight. The compressor has a drum on which the rotating blades are mounted. The fixed blades are to direct the flow and achieve high speeds. The air radially enters the impeller and is discharged axially from the compressor.

21. Terminologies in Air Compressors 1.Free Air Delivery (FAD): The volume of air in the compressor after the reduction of volume , considering the intake temperature and pressure , is called ‘Free air delivery or FAD’. It is expressed in m 3 /min. 2.Volumetric efficiency : The ratio of the actual volume of air drawn by the piston or membrane of the air compressor to the swept volume per cycle of the compression process is called the Volumetric efficiency. 3.Pressure ratio : The ratio of the discharge pressure of the compressor to its suction pressure is known as the pressure ratio.

22. Components of Air Compressor

23. AIR DRYERS 1.Refrigerated Air Dryers : Remove moisture from the compressed air through a mechanical refrigeration system to cool the compressed air and condense water and lubricant vapor . Most refrigerated dryers cool the compressed air to a temperature of approximately 35°F , resulting in a pressure dew point range of 33°F - 39°F. 2.Desiccant Dryers : Utilize chemicals beads, called desiccant, to adsorb water vapor from compressed air. Silica gel, activated alumina and molecular sieve are the most common desiccants used. (Silica gel or activated alumina is the preferred desiccants for compressed air dryers). The desiccant provides an average -40°F pressure dew point performance.

24. AIR DRYERS 3.Deliquescent Air Dryers : Utilize an absorptive type chemical, called a desiccant, to provide a 20°F to 25°F dew point suppression below the temperature of the compressed air entering the dryer. While deliquescent dryers are typically used in applications such as sandblasting and logging operations, they are not recommended for industrial applications since the dried compressed air exiting the dryer may contain small amounts of the effluent which may be corrosive to downstream equipment.

25. AIR TANKS OR AIR RECEIVERS An air receiver is essential to every compressed air system to act as a buffer and a storage medium between the compressor and the consumption system. There are in principal two different air receivers in a compressed air system: 1. Primary Air Receiver : Also designated as air tank, is located near the compressor, after the aftercooler but before filtration and drying equipment. 2. Secondary Air Receiver: Located close to points of larger intermittent air consumptions.

26. Humidity Absolute humidity is the actual amount of water vapor in the air. The higher the amount of water vapor, the higher the absolute humidity. Absolute humidity is expressed as either mass of water vapor per volume of moist air (in grams per cubic meter) Relative humidity measures the maximum amount of water vapor that can exist in the air at its current temperature. It is written as a percent. For example, warm air can hold more water vapor, or moisture, than cold air. So, with the same amount of absolute humidity, cold air will have a higher relative humidity and warm air will have a lower relative humidity. The relative humidity is 100% when the air is completely full of water vapor. The dew point marks the temperature at which water vapor will turn into liquid water droplets. This process is called condensation.

27. Selection of a Air Compressor

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