SHRI S’AD VIDYA MANDAL INSTITUTE OF TECHNOLOGY

PREPARED BY :- Urvesh Prajapati (140453119029). Aakash Rana (140453119030). Keval Rana (140453119031). Pinakin Rana (140453119032).

SEMESTER :- 5th Sem. DEPARTMENT :- Mechanical DepartmentGUIDED BY :- Dhaval Patel

Topic:- Pneumatic control system and it’s

components

Content1. Basics of Pneumatics2. Advantages & dis-advantages3. Pneumatic Components

Pneumatic CompressorAir ConditionersAir pressure regulatorAir lubricatorAir service unitPneumatic Silencer

4. Pneumatic ValvesPneumatic ActuatorsDirectional control valveShuttle valve

1. Basics of Pneumatics A pneumatic system is a system that uses compressed air to

transmit and control energy. Pneumatic systems are used in controlling train doors, automatic production lines, mechanical clamps.

2. Advantages & Limitations of pneumatic systems

The Advantages of pneumatic systems High effectiveness High durability and reliability Simple design High adaptability to harsh environment Safety Easy selection of speed and pressure

The Limitations of pneumatic systems Relatively low accuracy Low loading Processing required before use Uneven moving speed Noise

3. Pneumatics Components A compressor is a machine that compresses air or another type of

gas from a low inlet pressure (usually atmospheric) to a higher desired pressure level.

This is accomplished by reducing the volume of the gas. Air compressors are generally positive displacement units and are either of the reciprocating piston type or the rotary screw or rotary vane types.

Piston compressor In this type of compressor a cylinder bore encloses a moving

piston. As the crankshaft of the compressor rotate, the piston moves within the cylinder, similar to the piston in a car engine. As the piston is pulled down, the volume increases, creating a lower atmospheric pressure in the piston chamber.

Vane compressor The following figure shows a cutaway view of the sliding-vane-

type rotary compressor. The air inlet is placed where the volume of the compression chamber is greatest, the outlet where the volume is smallest. Consequently, as the vanes turn, the space between them is reduced.

Screw compressor There is a current toward increased use of the rotary-type

compressor due to technological advances, which have produced stronger materials and better manufacturing process.

during the rotation of the rotor, air is drawn through the suction port to fill the space between the male and female rotor lobes.

Lobe compressor In this type of compressor the rotors do not touch and certain

amount of slip exists. This slip increases as the output pressure increases.

It is therefore operated at maximum speed for the highest efficiency. bar is obtainable with this type of constant displacement compressor.

Air ConditionersAir filters:- The air needs to be filtered to be free of moisture and

contamination. Air filter is used to do this job. The filter elements remove the particles and moisture as small as 5 microns.

Air pressure regulator The pressure regulator is used to adjust the desired pressure for the

pneumatic system. This use a piston to sense downstream pressure fluctuations.

As the pressure downstream drops it is sensed by the diaphragm and the popper valve opens. This adjusts the position of the poppet valve, which limits the downstream pressure to the pre-set valve.

Air lubricator A lubricator ensures proper lubrication of internal moving parts

pneumatics components. The proportional increase in oil mist by an increase of air flow is achieved by the spring loaded poppet assembly. As the flow increases and the valve opens, the area is increased and a pressure differential created.

Air service unit Filters, regulators and lubricators can be combined to ensure

optimum compressed air preparation for a specific pneumatic system.

Pneumatic Silencer To decrease the noise of air in the outlet of valves, a silencer can

be used. They are made from the porous plastic or bronze. Some of them are equipped with a control flow valve to control velocity of flow in the outlet of valves as well.

4. Pneumatic Valves

The pneumatic valves are similar to hydraulic valves in terms of physical concepts. They are categorized into three classes:

Pneumatic ActuatorsPneumatic Cylinders:- The cylinders converts the energy of the compressed air into

linear motion which extend or retract the piston rod.

Pneumatic Rotary Actuators:- The rotary actuators converts the energy into a rotary motion.

Most of them is Vane air motor.

Pneumatic Semi-Rotary Actuators:- Limited rotary motion can be achieved by incorporating a rack

and pinion into a linear actuator or as seen opposite by a Vane Mechanism within the body of the cylinder.

Directional control valve Directional control valves ensure the flow of air between air ports

by opening, closing and switching their internal connections. Their classification is determined by the number of ports, the

number of switching positions, the normal position of the valve and its method of operation. Common types of directional control valves include 2/2, 3/2, 5/2, etc.

2/2 Pneumatic Valve 3/2 Pneumatic Valve

4/2 Pneumatic Valve 5/2 Pneumatic Valve

Shuttle valve Shuttle valves are also known as double control or single control

non-return valves. A shuttle valve has two air inlets ‘P1’ and ‘P2’ and one air outlet ‘A’. When compressed air enters through ‘P1’, the sphere will seal and block the other inlet ‘P2’.

Air can then flow from ‘P1’ to ‘A’. When the contrary happens, the sphere will block inlet ‘P1’, allowing air to flow from ‘P2’ to ‘A’ only.

Pressure control valve Pressure is controlled based on the outlet pressure. A feedback is

given from the outlet to the control mechanism which is normally open type.

The exit pressure acts on the controlling diaphragm. the outlet pressure is to be maintained constant.

When the outlet pressure increase, the valve gets closed more and the flow of air is reduced.

When there is a change in outlet pressure, this is communicated to the diaphragm. the diaphragm will move upwards or downwards depending on the outlet pressure.

In case of the outlet pressure reduced, then the valve will get lifted up and the opening of valve will increase the flow rate of air.

Flow control valve A flow control valve is formed by a non-return valve and a

variable throttle.

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