Fluid power Pneumatics and Hydraulic System-FITTER ONLINE NOTE
Fluid power
1- The term "fluid power" relates to the employment of fluid media under controlled conditions to perform some useful work.
2- Fluid power in industry has been important in the development of automatic machinery and equipment for use in industrial plants.
3- There are two main branches of fluid power i - Pneumatics, ii- Hydraulics
i- Fluid power Pneumatics system
1- A Fluid power pneumatic system carries power by employing compressed gas, generally air, as a fluid for transmitting energy from an energy generating source to an energy using point to accomplish useful work.
2- Figure shows a simple circuit of a pneumatic system with basic components.
3- The functions of various components shown in figure are as follows:
4- The pneumatic actuator converts the fluid power into mechanical power to perform useful work.
5- The compressor is used to compress the fresh air drawn from the atmosphere.
6- The storage reservoir is used to store a given volume of compressed air.
7- The valves are used to control the direction, flow rate. And pressure of compressed air.
8- External power supply (motor) is used to drive the compressor.
9- The piping system carries the pressurized air from one location to another.
ii- Fluid power Hydraulic system
1- A Fluid power Hydraulics is a means of transmitting power by pushing on a confined liquid.
2- The input component of the system is called a pump and the output is called an actuator.
3- The working of a hydraulic system is very simple.
4- The basic fluid used in this system is oil.
5- A hydraulic machine has two or more cylinders that are connected to a single pipe containing the oil and the pistons that helps in pushing the fluids in the cylinders.
6- Even the car brakes are based on the hydraulic system.
7- When you apply your car brakes, your brake pedal makes the piston to act and apply force on the master cylinder.
8- The main pipe is connected to four slave pistons that activate the brake pads of your car to the brake rotor, which in turn makes the car come to a stop.
Comparison between both Fluid power hydraulic and pneumatic systems .
Hydraulic System
1- It employs a pressurized liquid as fluid.
2- An oil hydraulic system operates at pressures up to 700 bar .
3- Generally designed as closed system.
4- The system slows down when leakage Occurs .
5- Valve operations are difficult.
6- Heavier in weight
7- Pumps are used to provide pressurized liquids.
8- The system is unsafe to fire hazards .
9- Automatic lubrication is provided.
Pneumatic System
1- It employs a compressed gas, usually air, as a fluid .
2- A pneumatic system usually operates at 5-10 bar .
3- Usually designed as open system
4- Leakage does not affect the system much.
5- Valve operations are easy .
6- Lighter in weight used to provide compressed gases.
7- The system is free from fire hazards .
8- Special arrangements for lubrication are needed.
Overview of a pneumatic system
1- Air is drawn from the atmosphere through an air filter and raised to required pressure by an air compressor.
2- As the pressure rises, the temperature also rises; hence, an air cooler is provided to cool the air with some preliminary treatment to remove the moisture.
3- The treated pressurized air then needs to get stored to maintain the pressure.
4- With the storage reservoir, a pressure switch is fitted to start and stop the electric motor when pressure falls and reaches the required level, respectively.
5- The three-position change over the valve delivering air to the cylinder operates in a way similar to its hydraulic circuit.
Boyle's law concept of pneumatic system
2- Boyle's law states that, at constant temperature, the volume (V) occupied by a gas is inversely proportional to the pressure (P).
3- As the pressure goes up, the volume of the gas goes down and vice versa.
P∝1/V (or) PV = constant .
4- A plot of pressure verses volume for Boyle's law is a rectangular hyperbola.
5- In Boyle's law,
P1V1 = P2V2 and
V1/V2= P2/P1
Where
P1 and V1 are initial pressure and volume.
P2 and V2 are final pressure and volume.
Overview of an industrial hydraulic system
1- Hydraulics is used in many machines that we see in our daily lives. Some of its uses are:
2- Hydraulics is used in heavy equipment's like log splitters.
3- You can find the simplest hydraulics system in log splitters as it consists of most of the components of a basic hydraulic system such as the hydraulic pump, an engine, the hydraulic cylinder, the various valves and the hydraulic pistons.
4- The heavy-duty machines make use of the hydraulic system that is often seen at construction sites and other excavations.
5- A large machines such as excavator may weighing about two tones without any difficulty.
6- An excavator has a motor for each of its tracks and a motor for swinging its huge arm that all runs on the system of hydraulics.
7- Other construction vehicles making use of hydraulics system include the loading machine also known as the skid.
8- This machine makes use of 3 pairs of hydraulic pistons and also hydraulic motors on each of its four wheels.
9-Another vehicle that we often see in our daily routine is a garbage dump truck. It makes use of the all hydraulic components.
10- The only exception in its case is the use of telescopic cylinders that help them to attain the feat of positioning the dump bucket to an almost vertical stance to allow the garbage fall over.
11- Hydraulics is also used in mechanical wheel chairs to push the wheel chair forward.
12- It is also used for aircraft landing gears to push the wheels out when landing the plane.
Pascal's law concept of hydraulic system
1- Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container.
2- Otherwise, It states that the pressure or intensity of pressure at a point in static fluid is equal in all directions.
3- Let us consider a container, contains a fluid and three pressure gauge is fixed at three point P1, P2 and P3 as shown below.
4- Consider that pressure at point P1, P2 and P3 as 1, 3 and 5 unit pressure respectively.
5- This pressure different is due to the potential head (datum).
6- When external pressure applied to the fluid, this.additional pressure will added in all points.
7- If 5 units of external presure is added to fluid, then the pressure at Pr, P2 and P3 also increases to 1+5 = 6, 3+5 = 8 and 5+5=10 unit pressure respectively.
Applications of Hydraulic, pneumatic system and Boyle's law and Pascal's law
Hydraulic applications
1- Automobile power steering,
2- Brakes,
3- Aircraft landing gear,
4- Lift trucks,
5- Front end loaders
Pneumatic applications
1- Packaging machinery,
2- Bottle filling Industry,
3- Artificial heart,
4- Logic control systems .
5- And robotic materials handling devices.
Applications of Boyle's law
1- Spray paint
2- The syringe .
3- The soda can
4- The bends
Applications of Pascal's law
1- Hydraulic lift
2- Hydraulic brake
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