HPS-UNIT 4-PNEUMATICSHPS-UNIT 4-PNEUMATICS.pptx.pptx

HPS-UNIT 4-PNEUMATICS.pptx

1. Unit 4 - Basics of pneumatics, air compressors and fluid conditioners, Pneumatic valves and actuators, Fluid power circuit design( Cascade method, Classic or intuitive method, Step counter method,Karnaugh-Veitch (K-V) mapping method, Combinational circuit design), Presented By D r . N. rajamani , Lecturer/MEE Dept. UR – CST, Rwanda. MEE 3161: Hydraulic and Pneumatic Systems

2. 2 Indicative Content: Unit 1 - Introduction to Fluid power systems . Fluids and their properties, Hydraulic Transmission Lines, Fluid power symbols. Unit 2 - Hydraulic pumps and motors: Basic types and constructions. Positive displacement machines, limited and continuous travel devices, Schematic diagram of double-acting piston actuators (Single or double rod) Limited rotation actuators (Single or double vane). Unit 3 - Hydraulic control valves: Valve configuration, Two-land-four-way spool valve. Three-land-four-way spool valve, etc. Characteristic a valve, Flow gain, General Flow equation, etc. Hydraulic power elements: Hydraulic actuation devices (linear and rotary). Valve controlled Motors. Electro-hydraulic. Accumulators and intensifiers, Unit 4 - Basics of pneumatics, air compressors and fluid conditioners, Pneumatic valves and actuators, Fluid power circuit design( Cascade method, Classic or intuitive method, Step counter method,Karnaugh-Veitch (K-V) mapping method, Combinational circuit design), Unit 5 - Servo-valves and Servo-mechanisms. Hydro-mechanical Servo-systems. Hydraulic power supplies and Control Circuits, Application of software in the design and simulation of hydraulic and pneumatic circuits . Fluid power circuits: Failure and troubleshooting.

3. Basics of Pneumatics Defn . The pneumatics may be defined as that branch of engineering science which deals with the study of the behavior and application of compressed air. Adv over Hydraulic sys 1. Lesser components, 2. Less frictional pressure and power losses, 3. Air exhausted to atm hence reduce special designs, 4. Cheaper, 5. Better operational advantage, 6. less weight and 7. leakage will not affect because continues supply of pressurized air. Disadvantages: Due to the high compressibility of air, pneumatic systems cannot provide precise actuator control and precise positioning control. Due to compressor design limitations, pneumatic systems can be applied only to low-pressure(less than 17 bars) application; whereas hydraulic systems can be applied to high-pressure ( upto 700 bars) applications.

4. Applications: 1. Stamping, 2. Drilling, 3. Hoisting, 4. Punching, 5. Assembling, 6. Clamping, 7. Riveting, 8. Materials handling, 9. Logic controlling, and 10. Hammering. Selection: If the application requires a very high pressure or an extremely accurate feed, then an oil hydraulic system can be used. If the application requires speed, a medium amount of pressure, and only a fairly accurate feed, then an air pneumatic system can be used. If the application requires only a medium amount of pressure and a feed of greater accuracy, then a combination of air and hydraulic systems can be used.

5. Properties of Air Composition of Air: 78% Nitrogen, 21% Oxygen, 1% Other gases (argon and carbon dioxide) 2. Pressure relationship: Atmospheric Pressure, Gauge Pressure and Absolute Pressure. 3. Perfect Gas Laws: Boyle’s law, Charles’ Law and Gay-Lussac’s Law. 4. Other Properties: Density, Specific volume, Compressibility, viscosity and bulk modulus etc.

6. Basic Pneumatic System Components of Pneumatic System:

7. Construction and Operation

8. Air Compressors and Fluid Conditioner Compressor: Types: ( i ) Positive Displacement (ii) Dynamic type

9. Piston-type Reciprocating Compressor Construction and Operation

10. Two Stage Compressor

11. Parts of Reciprocating Air Compressor

12. Screw Compressor Screw compressors are used in many applications where medium pressures (<10 bar) and medium volumes of air ( upto 5000 m 3 / hr ) are required.

13. Rotary Compressor

14. Advantages: Rotary vane compressors are pulse free and therefore can be used without a receiver if needed, They are smaller in size and lighter in weight, They can work at high speed. Ranges: The rotary vane type compressors are available with capacities upto 3000 m 3 / hr and pressures of 3 to 10 bars Specification of Compressors: Air compressors are generally specified/rated by the following: Outlet pressure of air that can be delivered by the compressor, Capacity or volume of air that can be delivered by the compressor, and Compressor configuration and cylinder geometry.

15. Fluid Conditioner Atmosphere air is not clean, so, conditioner are used to condition the compressed air before leaving into various pneumatic components. Elements of fluid conditioners: 1. Filters, 2. Regulators, 3. Lubricators, 4. Mufflers, and 5. Air dryers. FRL: Filer-Regulator-Lubricator unit or service unit Air Filter: Fine mesh wire cloth only strains out heavier foreign particles Synthetic material remove very small particles Selection of Filter: Size of particles to be filtered from the system Capacity of the filter Accessibility and maintainability Life of the filter Ability to drain the condensate Construction

16. Air Pressure Regulator Regulate the pressure of the incoming compressed air Ensure the constant supply pressure Acts as pressure guards Types: 1. Diaphram -type regulatr , and 2. Piston-type regulator Construction

17. Air Lubricator

18. FRL Unit

19. Mufflers

20. Air Dryers

21. Pneumatic Actuators Pressure energy convert into mechanical energy to perform useful work Types: 1. Linear actuator (pneumatic cylinder) 2. Rotary actuator (air motor) Pneumatic linear Actuators (Pneumatic cylinders) Types:

22. Name any two type of rotary pump. What is the use of intercooler in two stage air compressor. Draw the P-v diagram for the compressor with the thermodynamic processes. What is FRL unit. Draw the symbolic representation for Shuttle valve