Introduction of Fluid Power
● After learning fluid mechanics and machinery in the fourth semester, students of mechanical engineering are able to know the use of fluids for power generation using turbines like pelton wheel, Francis, Kaplan turbines, etc.
● It means fluid possesses energy and we can utilize the energies of fluids for various applications.
● In this course, fluid power can be used to operate various industrial machines and equipments, which is termed as "Industrial hydraulics and pneumatics."
● After various technical developments, from 1920 oil hydraulic emerged to operate industrial machines tools,material handling equipments, mining equipments, etc.
● In industrial sector, the various machines, equipments were operated by using the power source of mechanical transmission, electrical transmission, fluid transmission systems,
e.g screw jack is mechanical operated device to lift the load. Electrical motor is used to operate various machines using electrical power.
Fluid Power System :
● It is the technology which deals with transmission energy by means of enclosed pressurized fluids.
● This technology is highly versatile power transmission system which utilize the energy of fluid (Oil, air, gas) to perform the required work or task.
e.g. Lifting of very huge vehicles by using hydraulic crane, hydraulic press machine, etc.
Definition of fluid power system: It is the technology in which we transmit and control forces and velocities by transmitting and controlling pressure and flow of fluids.
Applications
● It has wide range of applications in various fields like automotive, agricultural uses, aircraft manufacturing, etc.
Types of Fluid Power System :
According to the nature or type of fluid used, it is divided into two categories.
1) Oil hydraulic system :
When the branch of fluid power system which uses incompressible oil for energy transmission to do useful work it is known as oil hydraulic system.
e.g. 1) Lifting of tractor trolley using hydraulic system.
2) JCB machine arm movement.
2) Pneumatic system :
When the branch of fluid power system, which uses compressed air for energy transmission to do useful work, it is known as pneumatic system.
e.g. 1) Pneumatic hand tools like pneumatic drill.
2) Pneumatic clamping system.
The two branches are quite different in behavior and performance and therefore separately treated with their names.
Oil Hydraulic System :
General Layout of Oil Hydraulic System
Definition: It is defined as fluid power system in which hydraulic oil is used as a working medium with required high pressure to transmit force/motion for useful work.
e.g. Hydraulic crane system
● Oil hydraulic system uses pressurized oil which is circulated through various components of the hydraulic system to perform the given task/application.
● When we observe any oil hydraulic system, it consists of various components which are arranged in a systematic manner to transmit energy. It is mainly divided into three main elements as given in the block diagram.
Meaning of General layout:
● The hydraulic system consists of various components which are mounted or placed in a logical sequence as per their function and connected with the help of pipelines and fittings. It is known as general layout of hydraulic system.
● The layout may vary or changes as per the application or task to be performed.
Components of Hydraulic System :
It is mainly consists of
Components of Hydraulic System
1) Reservoir Tank
2) Filter
3) Hydraulic Pump
4) Control Valves
5) Actuator
6) Pipelines and fittings
7) Accessories
1) Reservoir/Tank :
● It is used to store adequate quantity of hydraulic oil required for the system.
● It is either circular or rectangular in shape with capacity in liters.
● It is provided with oil level indicator to observe oil level in the tank.
● The oil is circulated through various elements with the help of pipelines and returns back to the tank.
● It is provided with oil heaters and coolers for operating under low temperature or high temperature applications.
2) Filter:
● It is the device which removes or separate out contaminants or impurities from the oil.
● It will help to supply clean and pure oil to the system.
3) Hydraulic Pump:
● It is the device which increases pressure of oil to the required value. It will supply oil with pressure in required flow rate to the hydraulic system. It is driven with the help of prime mover like electric motor, I.C. engine etc.
● Hydraulic system may use gear pump, vane pump,screw pump, piston pump, etc.
● The system will not able to work without pump hence it is heart of any hydraulic system.
4) Control Valves :
● As name indicates, valves are provided to control pressure of oil, Direction of flow of oil and flow of oil.
● Control valves are listed at particular position as per their function in the hydraulic system,.
● According to function, there are three types of control valves.
a) Pressure control valve: It is provided to control pressure of oil in the hydraulic system.
e.g. Pressure relief valve.
b) Direction control valve : It is provided to change or alter the direction of oil to operate hydraulic actuators.
e.g. 3/2 D.C. valve used for single acting hydraulic actuator.
c) Flow control valve : It is provided to control flow of oil supplied to the actuator to achieve slow/fast movement.
e.g. Needle type flow control valve.
5) Actuator :
● It is the device which utilises the energy of oil and convert it in mechanical energy in the form of motion/force.
● It has two types as per mechanical energy produced :
a) Linear actuator : It gives lincar motion in horizontal/vertical inclination using hydraulic cylinders.
eg. Single acting cylinder, Double acting cylinder.
● In JCB arm Double acting cylinder is used for movement.
b) Rotary actuator : It gives rotary motion in clockwise/counter clockwise direction where rotary motion is needed to perform the task/application.
e.g. Hydraulic motor to rotate heavy mixers.
6) Pipelines and fittings:
● They are known as fluid conducting elements. The oil with pressure is circulated to various components using pipelines and connections using pipe fittings.
● Rigid pipes, hose pipes and various fittings like connectors, couplings, reducers etc are needed for plumbing layout of oil hydraulic system.
7) Accessories:
● They are required to improve performance of hydraulic system by smooth functioning of various components of the system.
● The various accessories are:
a) Pressure gauges: To measure pressure of oil at various points in the hydraulic system e.g. After discharge of the pump..
b) Seals and Gaskets : They are provided for leak proof joints. It prevents leakage of oil.
c) Accumulator : It stores hydraulic energy of pressurised oil. It is energy storage device.
d) Heat Exchanger : They are provided for heating of oil in extreme cold condition and cooling of oil in hot working condition.
e) Flow meter : It is provided to measure flow or discharge of oil in the hydraulic system.
f) Intensifier or Pressure booster : It is provided to intensify or boost the pressure of oil whenever required
g) Temperature sensor/gauge : It will measure temperature of hydraulic oil.
Pneumatic System :
Definition: It is defined as fluid power system in which compressed air or gas is used as working medium for transmission and control of motion and forces.
e.g :Pneumatic clamping system, Pneumatic hand grinder,etc.
● Pneumatic system is designed to handle compressed air/gas through various components and is used for performing certain designated task.
As medium used is compressed air, it will differ from hydraulic system.
Applications :
● Pneumatic system finds applications in various fields which are listed below:
1. Spray painting of automobile body in paint shop.
2. Pneumatic grinders are used for grinding outer layer of casting components.
3. Dentist uses portable pneumatic motor with tooth cleaning tools for dental work. Pneumatic hand tools also used during assembly work.
Characteristics of Compressed Air :
1) Air is freely available anytime from the atmosphere.
2) There is no need to store as a input medium.
3) Easy transported using pipelines, hoses and air vessels.
4) Air is a safe medium as it is fire proof.
5) No need to recirculation. No return lines required for compressed air.
6) It is safe and can be directly exhausted to atmosphere safely without any pollution.
7) It can be easily stored in air receiver at high pressure.
8) Easy control of parameters like pressure, flow, etc.
Important Features of Pneumatic system:
1) It has less operating pressure in the range of 10 bar.
2) There is no need of return lines (piping) as air is directly exhausted to atmosphere.
3) It has high speed of response or movement of actuator is faster compared to hydraulic system.
4) High speed of rotation about 20000 RPM is possible.
5) As air/gas is compressible in nature, hence it is not suitable for precision/highly accurate movements.
6) Simple in construction and easy to operate compared to hydraulic/electrical system.
7) It produces heavy noise during its operation hence noise reducer/silencers/mufflers are required to reduce noise.
General layout of Pneumatic system :
● When we observe any pneumatic system, it consists of various components diagram shows main elements of pneumatic system.
Components of Pneumatic system
1) Compressor
2) Air cooler
3) Air Receiver
4) Moisture separator
5) FRL unit
6) Control valves
7) Air actuators
8) Pipeline and fittings
9) Accessories
1) Compressor:
● It is the main element of pneumatic system. It sucks air from atmosphere and compress it to the desired pressure by suitable mechanism.
● It will supply compressed air needed for pneumatic system. It includes reciprocating compressor, screw compressor, vane compressor, lobe type compressor,etc.
● Centralised compressor unit is provided with high capacity to store compressed air to operate number of pneumatic machines.
● It is driven by using prime mover like electric motor, diesel/petrol engines, gas turbines, etc.
2) Air cooler :
● It is provided to cool the compressed air which was get heated during compression.
3) Air Receiver:
● It is cylindrical vessel to store compressed air supplied by compressor. It is provided with pressure gauge to check the air pressure.
● It has capacity in cm and horizontally/ vertically mounted.
● The air from air receiver is utilised to supply compressed air to the pneumatic system
4) Moisture separator :
● The compressed air may contain moisture (water particles) and it is necessary to separate out moisture with the help of moisture separator.
● The water particles may cause corrosion of metallic components and therefore moisture is separated by mechanical or chemical type moisture separators.
5) FRL unit:
● It is also known as service unit. It consists of three components arranged in a series combination.
a) Filter : It will help to remove impurities/dust particles from compressed air.
b) Regulator :It will help to regulate pressure of compressed air.
c) Lubricator :It will help to add or mix Lubricating oil particles in compressed air for lubrication of moving parts of valves and actuators.
● This combined unit is available in market with required specifications.
6) Control valves :
● They are provided for controlling direction of flow of compressed air, controlling flow of compressed air for controlling changing speed of actuators.
● They are known as D.C. valves and flow control valves as per their use.
● Special valves are also used like twin pressure valve, shuttle valve, Time delay valve, etc for special applications.
7) Air actuators:
● They are output elements converts air energy into mechanical motion It may be linear or rotary actuators depending upon their type. e.g. pneumatic single acting cylinder, Air motor used in pneumatic hand grinder,
8) Pipeline and fittings:
● It is also known as air conducting elements through which compressed air is allowed to flow at pressure through various components.
● Rigid pipes, hoses are used with minimum pressure drop to supply compressed air to the application points.
● Pipe fittings are used for joining and making connections in pipe layout of pneumatic system.
9) Accessories :
● They are provided for improving performance and smooth working of the system.
● It includes coolers, Air dryers, noise reducer (muffler), pressure gauges, seals and Gaskets, etc.
Factors considered for selection of components:
1) Compressor:
a) Requirement of Pressure for pneumatic system
b) Volume of Air
c) configuration of Compressor
2) Actuators:
a) Maximum pressure
b) Type of motion/application-Linear/Rotary
c) Shape and size of actuator
3) Air Receiver:
a) Air Storage capacity
b) Material of the tank
4) FRL unit:
a) According to working environment (cold/hot/Moist)
b) According to pressure required at hand tools
5) DCV :
a) According to maximum pressure of system.
b) According to actuator configuration
c) According to application-One hand Two hand.
d) According to actuation method suitable for application.
Applications, Advantages and Disadvantages of Oil Hydraulic and Pneumatic System
Applications of Oil Hydraulic System
Oil hydraulic system can able to operate at higher pressure ranges and suitable for various applications in the wide areas of industrial fields.
1) Agricultural Equipments :
● Modern farm equipments uses hydraulic system for raise and lowers equipments with hydraulic mechanism.
● Hydraulic operated tractors,harvesting equipments, spreaders, special planting, etc.
2) Material Handling system :
● It includes hydraulic lifts, cranes jacks for movement of heavy and large objects from one location to other.
e.g. forklift trucks, cranes, etc.
3) Machine Tools :
● It includes hydraulic press machines, hydraulic grinder, hydraulic shaper, Hydraulic power hacksaw, hydraulic shearing machine, pressure die casting machines, etc.
4) Construction Equipments :
● It includes various machines at construction sites like JCB, Hydraulic shovel, dumper. excavator, caterpillars, hydraulic lift, mixers, crushers etc.
5) Defense/Aerospace :
● Hydraulic control system in aeroplanes, use of JCB, shovels, power steering of land vehicles, rocket launchers, landing gear mechanism of aeroplanes, wing control system, etc.
6) Mining :
● They are used in open pit and underground operations. Mine drilling. crushing and material handling devices are hydraulically operated.
7) Earthmoving equipments :
● The large size hydraulic equipments used at mega projects like bridges, towers, road construction, Metro railway projects, etc. are known as earthmoving equipments.
● It includes bulldozers, excavator, back shoe loaders, heavy cranes, tractors, crawlers, etc
8) Other applications :
● It may include ship building. Adventure rides, robotics, injection moulding, etc.
Applications of Pneumatic System :
It operated at low pressure range upto 10 bar and suitable for various applications given below.
1) Industrial automation :
● It helps to reduce the manual handling of jobs/workpieces by automation for loading/unloading. It can be used to obtain sequence of movement of workpieces at faster rate by eliminating human involvement of pneumatic bending machine, pneumatic automatic packaging, pneumatic embossing machine
2) Automobile field:
● Pneumatic system is useful for air brake system for buses/trucks i.e. heavy automobiles.
● Vehicle tyres are filled with compressed air. Spray painting of automobile panels and body parts can be done by using pneumatic system.
3) Construction equipments :
● Pneumatic vibrators, rock drilling during construction work can be done using pneumatic system.
● Pneumatic hammers, concrete mixers, pneumatic pistol drills are also used at construction work.
4 Foundry shop :
● Pneumatic system can be used for operating joiting machines, cleaning of moulds and castings with the help of pneumatic power tools like hand grinders, etc.
5) Hand Tools:
● Various portable hand tools are most popular application of pneumatic system.
● Pneumatic hand tools includes pneumatic drills, pneumatic screwdrivers pneumatic riveters, etc.
● Pneumatic grinders are commonly used for finishing of welded joints, casted components etc.
● Assembly lines, service stations of automobiles are equipped with hand tools.
● Pneumatic press machines are used for sheet metal operations like punching, blanking, etc
6) Borewell drilling:
● Underground borewells are possible with the help of pneumatic drilling of borewells.
7) Packaging :
● It includes food, pharmaceutical industries, agricultural goods packaging, etc.
8) Other applications : Textiles automatic looms,pneumatic conveyors, pneumatic dental instruments,etc.
Merits (Advantages) of Oil Hydraulic System:
● When oil hydraulic system was compared with mechanical, electrical and pneumatic system, it has many advantages and disadvantages which are discussed below.
● The various merits of oil hydraulic system are listed and as given below.
1) No need of lubrication :
● As hydraulic oil is working medium. It is "self lubricated system and there is no need of any additional lubrication system.
2) Less weight to power ratio :
● Compared to electro mechanical system, hydraulic system has less weight required to transmit same power. It is nearly 1/10 of electromechanical system.
3) Accuracy in motion :
● It provides highly accurate and precise motions, hence suitable for movement of tools in CNC/VMC machines, servo controlled mechanisms,etc.
4) High hydraulic advantages :
● It generates high output force with use of small input effort, thus provides high advantage to generate more output forces.
e.g. lifting of heavy vehicle at service station.
5) Versatile system :
● This system is suitable for various fields like construction, machine tools, material handling equipments, Aerospace, etc.
6) Smooth working :
● When compared to mechanical and pneumatic system, it is smooth working with minimum noise, friction, vibration during its operation/working.
7) Easy power distribution:
● Using pipe lines and fittings. it is easy to distribute power to the various subsystems easily.
8) High pressure operating range :
● Hydraulic system can able to operate at higher range of oil pressure upto 700 bar.
● Heavy earth moving equipments are operated only by hydraulic system to handle heavy and massive workloads.
● There is no any other system can able to work to handle Much heavy loads efficiently.
Limitations/Demerits of oil hydraulic system:
1) Oil leakage problem :
● Oil leakage may occur at joints if seals are broken, womout. It will reduce the pressure of oil and efficiency of the hydraulic system.
2) Dirty work environment:
● Oil leakage causes collection of dirt and causes slippery, messy work environment around hydraulic equipment.
3) Fire hazards :
● As oil is flammable and may cause fire hazards if flash/fire point occurs due to high operating temperature of the system.
4) Oil disposal issue :
● The oil after use requires special handling and disposal procedures to avoid pollution as per strict rules of environmental control.
● We cannot drain/throw away the oil to the soil, water,etc.
5) Initial high investment :
● It requires high investment to purchase hydraulic equipments considering initial investment.
6) Precision components :
● Hydraulic system components are machined to high degree of accuracy for perfect assembly hence cost of manufacturing is very high.
7) High maintenance cost :
● The cost of maintenance of hydraulic components is high compared to mechanical/pneumatic system.
Merits (Advantages) of Pneumatic System.
● Pneumatic system has following advantages explained below
1) Freely available air:
● The working medium is atmosphere air which is freely available 24 hours in unlimited large quantity naturally.
2) Clean system :
● It will not create dirty climate or nearby work area which is major problem of oil hydraulic system.
This system is neat, clean do not create any dirt.
3) Fire proof :
● Air is having fire proof characteristics. It can be used in high temperature zones easily.
4) Simple and easy system :
● lt is easy to make connections and operate pneumatic system
5) No need of return lines :
● The air after use is exhausted directly to the atmosphere and no need to store/recirculate. Hence no need to provide return lines. It will reduce the cost of retum pipelines.
6) Simplified maintenance:
● The maintenance of compressor, FRL unit, valves and actuators is easy compared to hydraulic system.
7) Easy distribution :
● Compressed air is easily stored and distributed by using pipelines. Centralised compressor can be used to operate multiple machines.
Limitations of Pneumatic System:
● Pneumatic system has some demerits which are listed below.
1) High cost of compression : The cost of compressing and conditioning of air is high in pneumatic system.
2) Less accuracy: Because of compressible nature of air,it may causes errors due to change in pressure and reduces accuracy of movement.
Therefore it is not suitable for precise and accurate control of movements.
3) Noisy operation : Air when flows through pipes, small openings of valves, actuators, will produce noise. The level of noise is high at exhaust and silencers or noise reducers (mufflers) are provided to reduce this problem.
4) High operating cost : Though air is free from atmosphere, cost of compression, distribution, conditioning of air is more. Therefore increases cos of operating the system.
5) Low pressure applications : It is suitable to work in the range of 10 bar pressure of compressed air. This low pressure can able to perform applications like punching press, etc.
It cannot able to handle heavy loads compared to oil hydraulic system.
6) Additional lubrication needed : Pneumatic system requires additional lubricator to mix oil particles in the compressed air.
It will help to reduce the friction or smooth movement of actuators, sliding components, etc.
