N3 Mechanotechnology Module 10 Pneumatics

MECHANOTECNOLOGY N3 MALUTI TVET COLLEGE LECTURER: MT MPHAGO Downloaded from hlayiso.com ITEMOHELENG CAMPUS

MODULE 10 PNEUMATICS LO : Explain pressure, flow rate and area as factor to consider in a pneumatic system, and describe the functions of basic components in a pneumatic system and design a basic pneumatic circuit. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

INTRODUCTION  Pneumatic power is used to drive tools and machines requiring rotary motion such as drills and reciprocation motion such as hammers  Pneumatic tools are driven by air motors which are powered by compressed air.  Pneumatic cylinders, rotary actuators and air motors provide force and movement of most pneumatic systems, to hold, move, form and process material.  To operate and control these actuators other pneumatic components are required. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

BASIC PNEUMATIC SYSTEM  Basic pneumatic system consists of air production and distribution system, and air consumption system. See the diagram below Downloaded from hlayiso.com ITEMOHELENG CAMPUS

FUNCTIONS OF THE COMPONENTS ON THE AIR PRODUCTION SIDE SYSTEM Compressor  Air is taken in at atmospheric pressure via an air filter and compressed.  The is air compressed and delivered to a reservoir or tank where it is stored for use.  The compressor converts mechanical energy and motion into pneumatic energy or fluid power. Electric Motor  Supplies mechanical power to the compressor.  It transform electrical energy into mechanical energy. Pressure switch  Controls the electric motor by sensing the pressure the tank.  It stops the motor when maximum pressure is reached and restart it when the pressure drops to minimum. Check Valve  Allows compressed air from the compressor into the tank and prevent it from leaking back Downloaded from hlayiso.com when the compressor is stopped. ITEMOHELENG CAMPUS

FUNCTIONS OF THE COMPONENTS ON THE AIR PRODUCTION SIDE SYSTEM Air receiver or Tank  Is a pressure vessel in which compressed air is stored for use.  The size or the receiver or tank is determined by the capacity of the compressor.  Air receiver or tank absorb the pulsations , that is the noise and vibration in the discharge line from the compressor.  Smooths the flow of air to the service line and compressor controls.  Serves as a reservoir for momentary demand s in excess of the compressor output. Pressure gauge  Indicates the pressure inside the air receiver.  It shows blockage or damage in the system.  The gauge verifies a safe and satisfactory air pressure. Auto drain  Drains all the water condensing in the tank automatically. Pressure reducing valve or Safety Valve  Allows compressed air to escape into the atmosphere if the pressure in the tank rise above Downloaded from hlayiso.com the allowed safe pressure.  It is a device which limits the maximum system pressure ITEMOHELENG CAMPUS

FUNCTIONS OF THE COMPONENTS ON THE AIR PRODUCTION SIDE SYSTEM Refrigerated air dryer  The dryer cools the compressed air to a few degrees above the freezing point.  It means that most of the water vapour in the air will condense.  It is a device which reduces the water vapour content of compressed air.  It prevent water from contaminating the downstream system. Line filter  Is the main pipe and must have minimal pressure drop and the capability of oil mist removal.  It helps to keep the line free from dust ,water and oil. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

FUNCTIONS OF THE COMPONENTS ON THE AIR CONSUMING SIDE SYSTEM Air take - off  Air required by the consumer is taken off from the top of main pipe.  A water take off situated at a low point from beneath , the pipe will allow the water into an automatic drain. Auto drain  Every descending tube should have a drain at its low end.  The efficient way is to have auto drain which prevents water from remaining in the tube even when manual drain is neglected. Air service unit  This also known as conditioning unit.  It consists of a filter to prevent dust, pressure regulator with gauge to reduce the line pressure and maintain constant pressure , and a lubricator to introduce oil droplet.  The service unit prepares air for use in the system  The gauge verifies a safe and satisfactory air pressure. Directional control valve  Pressurises and exhausts the two cylinders connections alternately, to control the direction of the movement. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

FUNCTIONS OF THE COMPONENTS ON THE AIR CONSUMING SIDE OF SYSTEM Actuator  Transforms the potential energy of the compressed air into mechanical work.  It can also be a rotary or an air tool depending on the working situation and other factors . Speed controllers  Allow easy speed adjustment of the actuator movement. Pipes  Pipes manufactured from steel, copper, stainless steel and aluminium are suitable for conveying compressed air.  These pipes the system act as air conductors. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

PRESSURE, FLOW RATE AND AREA Pressure  When you inflate a tyre , you are squeezing in air more than the tyre would like to hold. The air inside the tyre resists this squeezing by pushing outward on the casing of the tyre. The outward push of the air is pressure.  Pressure is responsible for pushing or exerting a force or torque  Pressure is defined as force per unit of area and is measured by Pascal (Pa) . Flow rate  Is responsible for causing something move, causing motion.  Flow is the quantity of the compressed air passing through a given cross section during a specific unit of time.  Flow is measured in liters per second (l/s) or in cubic meter per second ( M3/s).  1 cubic meter = 1 000 litres Area  If the air flows through pipes of varying diameters, at any particular time the same volume flows at all points. It means that the velocity of the air flow or flow rate will increase at a narrow point.  Velocity of air in a pneumatic line is inversely proportional to the cross –sectional area or to the diameter squared.  The flow velocity in 100mm diameter line will be one quarter as fast as the same flow rate in a 50 mm diameter line.  Area is measured in metres squared and unit is 𝑚𝑚2 . Downloaded from hlayiso.com ITEMOHELENG CAMPUS

SYMBOLS USED FOR BASIC PNEUMATIC SYSTEMS  In order to draw a pneumatic circuit diagrams we need to have a standardised symbols.  These symbols are laid down at international level by the ISO standards organisation.  Most commonly used symbols are listed below : Downloaded from hlayiso.com ITEMOHELENG CAMPUS

DIAGRAM OF BASIC PNEUMATIC CIRCUITS  A pneumatic circuit is essential to the designer, people building and repairing machines.  It show the order in which components must be connected, what each component should do and where the air should go.  A pneumatic circuit showing the compressor filling the air receiver with air.  Excess pressure being bled off through the pressure relief valve.  The compressor fills the air receiver with air.  The air travels through the service unit for purification before it enters the pneumatic tool or device. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

DIAGRAMS OF BASIC PNEUMATIC CIRCUITS  A linear actuator operated be a 4 –port, 2 – directional control valve, is shown by this pneumatic circuit .  Air is directed through the valve to the right hand side of the cylinder in order to push the piston to the left.  Air in the left side of the cylinder flows back through the valve and is exhausted.  When the air is moved into the opposite direction “ crossed” flow path is in valve symbol is used.  As indicated by arrows the, supply air is directed to the left hand side of the cylinder.  The piston is now pushed over to the right and air inside the right hand side of the cylinder is exhausted through the valve as indicated. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

DIFFERENCE BETWEEN A HYDRUALIC AND A PNEUAMATIC SYSTEM  The working medium is pressurized air for pneumatic cylinder and pressurized liquid for hydraulic cylinders.  A pneumatic cylinder open in an open-ended circuit with compressed air exhausting to the atmosphere, normal hydraulic circuit operate in a re-circulating or closed circuit.  Supply of compressed air can be done by tapping, and supply of pressurized hydraulic fluid requires a driven motor.  Pneumatic is faster than hydraulics.  Pneumatics is suitable for applications under high temperatures and hydraulics oil working temperature is limited to 93 degree Celsius.  Pneumatic is cheap in operating costs compared to hydraulics.  Hydraulic system are self lubricating and pneumatic system require introduction of lubrication. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

SUMMARY • Basic pneumatic system • Functions of the components on the production side system. • Functions of the components on the air consuming side system. • Pressure, Flow rate and area. • Symbols used for basic pneumatic system. • Diagram of basic pneumatic system circuit. • Difference between a hydraulic and a pneumatic system. Downloaded from hlayiso.com ITEMOHELENG CAMPUS

ASSESSMENT • Assessment on pages 224 and 225 of the textbook supplied by the college, “ Mechanotechnology N3 second edition by FM GOUWS”. • Number 1 to 5. YOU CAN TO CONTACT ME ON WHATTSHAP FOR ANY QUESTIONS THAT YOU MAY HAVE. MY WHATTSHAP NUMBER IS 073 215 7689 THANK YOU ALL Downloaded from hlayiso.com ITEMOHELENG CAMPUS