1) To drive air motors in coal mines. 2) To inject fuel in air injection diesel engines. 3) To operate pneumatic drills, hammers, hoists, sand blasters. 4) For cleaning purposes. 5) To cool large buildings. 6) In the processing of food and farm maintenance. 7) For spray painting in paint industry. 8) In automobile & railway braking systems. 9) To operate air tools like air guns. 10) To hold & index cutting tools on machines like milling.
i) FAD – It is the volume of air delivered under the intake conditions of temperature and pressure. ii) Compression ratio – It is defined as the ratio of absolute discharge pressure to the absolute inlet pressure.
Speed control of any actuator (Cylinders or motors) can be controlled using flow control valves. Varying the rate of flow of oil will vary the speed of the actuator.(Explanation 1Mark) In meter in circuit, rate of flow of oil is controlled at inlet of the actuator. In meter out circuit, rate of flow of oil is controlled at outlet of the actuator. In bleed off circuit, rate of flow of oil is controlled in the by-pass line leading towards the tank.
Oil heaters: When hydraulic circuit works in cold climate, then oil is solidifies below 5 o C temperature. To liquefy the oil electrical heater or thermostatic heater are equipped with oil tank. This increase the operating and maintenance cost of hydraulic system The cost of hydraulic system is higher. It heats the oil so that its viscosity increases and it can flow in the system smoothly. Thermostatically controlled oil heater commonly used
1. Relatively low accuracy: As pneumatic systems are powered by the force provided by compressed air, their operation is subject to the volume of the compressed air. As the volume of air may change when compressed or heated, the supply of air to the system may not be accurate, causing a decrease in the overall accuracy of the system. 2. Low loading: As the cylinders of pneumatic components are not very large, a pneumatic system cannot drive loads that are too heavy. 3. Processing required before use Compressed air must be processed before use to ensure the absence of water vapour or dust.
