Introduction to Pneumatic System 2024 Student Notes PDF

1.0 Introduction to Pneumatic System CLO 1 : 2 Hours 1.0 INTRODUCTION TO PNEUMATIC SYSTEM 2 Hours Learning Outcomes : ⦁ Explain Pneumatic System ⦁ Explain the usage of pneumatic control in the industry. ⦁ Discuss the advantages and disadvantages of pneumati...

1.0 Introduction to Pneumatic System CLO 1 : 2 Hours 1.0 INTRODUCTION TO PNEUMATIC SYSTEM 2 Hours Learning Outcomes : ⦁ Explain Pneumatic System ⦁ Explain the usage of pneumatic control in the industry. ⦁ Discuss the advantages and disadvantages of pneumatic system. ⦁ Explain the diagram of structural block and pneumatic system signal flow. 1.1 Pneumatic System Definition Pneuma = breath (Greek) The use of compressed air in drive and control engineering Principle The basic components of a pneumatic circuit or system are the following: The compressor is in charge of compressing the air to the required working pressure. Compressed air tank. Where pressurized air is stored at a certain temperature. The pressurized air circulation circuit and the control and distribution valves for the compressed air. Working mechanism, cylinders, rod, bearings, etc. to do the concrete job. Pneumatic tool or specific system to which it is applied (pneumatic gun, drills, hammers, elevators, etc.) 1.1.1 The usage of pneumatic control in the industry. Pneumatic technology, one of the most effective means, with high efficiency, safety and longevity, low cost, easy maintenance, anti-overload, etc., Get more and more widely used in many areas of the industrial sector. Machine tool industry to the machinery industry to provide 'working machine’, is the basis of the machinery industry. The main application of pneumatic products: Printing machinery Food machinery Packaging machinery Semiconductor welding machine, chip grinding Mechanical arm CNC machine tools Auto industry Water treatment industry Industries that use Pneumatics Systems: Aerospace Automotive Chemical Manufacturing Electronics Food and Beverage General Manufacturing Glass Manufacturing Hospitals/Medical Mining Pharmaceuticals Plastics Power Generation Wood Products and many more  1.1.2 The advantages and disadvantages of pneumatic system. Advantages Infinite availability of the source Air is the most important thing in the pneumatic system, and as we all know, air is available in the world around us in unlimited quantities at all times and places. Easy channeled Air is a substance that is easily passed or move from one place to another through a small pipe, the long and winding. Temperature is flexible Air can be used flexibly at various temperatures are required, through equipment designed for specific circumstances, even in quite extreme conditions, the air was still able to work. Safe The air can be loaded more safely than it is not flammable and does not short circuit occurs or explode, so protection against both of these things pretty easily, unlike the electrical system that could lead to fires. Clean The air around us are tend to clean without chemicals that are harmful, and also, it can be minimized or cleaned with some processes, so it is safe to use pneumatic systems to the pharmaceutical industry, food and beverages and textiles. The transfer of power and the speed is very easy to set up Air could move at speeds that can be adjusted from low to high or vice versa. When using a pneumatic cylinder actuator, the piston speed can reach 3 m / s. For pneumatic motors can spins at 30,000 rpm, while the turbine engine systems can reach 450,000 rpm. Can be stored The air can be stored through the seat tube fed excess air pressure. Moreover, it can be installed so that the pressure boundary or the safety of the system to be safe. Easy utilized Easy air either directly utilized to clean surfaces such as metal and machinery, or indirectly, ie through pneumatic equipment to produce certain movements.  1.1.2 The advantages and disadvantages of pneumatic system. Disadvantages: Requires installation of air-producing equipment. Compressed air should be well prepared to meet the requirements. Meet certain criteria, such as dry, clean, and contain the necessary lubricant for pneumatic equipment. Therefore, require installation of pneumatic systems are relatively expensive equipment, such as compressors, air filter, lube tube, dryer, regulators, etc. Easy to leak One of the properties of pressurized air is like to always occupy the empty space and the air pressure is maintained in hard work. Therefore, we need a seal so that air does not leak. Seal leakage can cause energy loss. Pneumatic equipment should be equipped with airtight equipment that compressed air leaks in the system can be minimized. Potential noise Pneumatic using open system, meaning that the air that has been used will be thrown out of the system, the air comes out pretty loud and noisy so will cause noise, especially on the exhaust tract. The fix is ​to put a silencer on each dump line. Easy condenses Pressurized air is easily condensed, so before entering the system must be processed first in order to meet certain requirements, such as dry, have enough pressure, and contains a small amount of lubricant to reduce friction in the valves and actuators.  1.1.3 The diagram of structural block and pneumatic system signal flow. The compressor compresses the air coming from the surroundings and pressurizes it for its use. The reservoir tank is used to store and stabilized the air pressure that is compressed. The Dryer remove water vapor from the compressed air. Air service unit is to deliver clean air, at a fixed pressure, and lubricated to ensure proper pneumatic component operation. The valves have to control the flow, pressure and direction of compressed air. Actuators are devices that convert the energy of compressed air or gas into a mechanical motion Pneumatic system structure Pneumatic system signal flow. 1.2 :Air Generation System and Air Distribution System CLO 1 : 1.5 Hours 1.0 INTRODUCTION TO PNEUMATIC SYSTEM :Air Generation System and Air Distribution System 1.5 Hours Learning Outcomes : 1.2 Distinguish Air Generation System and Air Distribution System 1.2.1 State and compare the types of air compressor: a. Reciprocating compressors: i. Single stage piston compressor ii. Double stage piston compressor b. Rotary compressors: i. Screw compressor ii. Slide ram compressor 1.2.2 Explain Air Dehydration: a. After Cooler i. Water cooled after cooler ii. Air cooled after cooler b. Air Dryer i. Absorbance drying ii. Adsorption drying iii. Low temperature drying 1.2.3 Explain the function and principle of: a. Compressed Air Filter b. Pressure Regulating Valve c. Compressed Air Lubricator AIRCOMPRESSOR A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible, so the main action of a pump is to pressurize and transport liquids. COMPRESSED AIR PLANT A typical instrument air skid package contains multiple compressors with dryers and filtration systems that provide high-quality, dry air for a range of applications from pneumatic controls and actuation of critical valves,to buffer sealing gas. Compressed air is one of the Key utilities across various industrial sectors. Compressed air is used in thousands of applications, like manufacturing/ assembly, pharmaceuticals, Power Generation units, Processing units, to perform painting activities, pneumatic pressure testing, Oil and Gas ,etc. ▪ It can power rotary equipment. ▪ It drives reciprocating equipment. ▪ It can impact, and convey. ▪ It can atomize, spray, sand blast, agitate, and cool. ▪ It can operate controls. ▪ The applications are endless…. Equipment of compressed air plant 1.Intake Air Filters: 3. After Coolers: Prevent dust from The objective is to remove the moisture entering compressor; in the air by reducing the temperature in Dust causes sticking a water-cooled heat exchanger valves, scoured cylinders, excessive 4. Air Receiver/Tank: wear etc. Air receivers are provided as storage and smoothening pulsating air output - reducing pressure variations from the 2. Compressor: compressor The compressor produces compressed 5. Air-Dryers: air at the required The remaining traces of moisture after pressure. after-cooler are removed using air dryers, as air for instrument and 6. Moisture Drain Traps: pneumatic equipment has to be Moisture drain traps are relatively free of any moisture. The used for removal of moisture is removed by using moisture in the adsorbents like silica gel /activated compressed air. carbon, or refrigerant dryers, or heat of These traps resemble compression dryers. steam traps. Various types of traps used are manual drain cocks, 7. Piping System: timer based / automatic The piping system will be designed for a maximum allowable pressure drop of 5% from the compressor to the most drain valves etc. distinct point of use. The piping system should be arranged in a closed loop to allow more uniform pressure distribution. Air Distribution System 1.2.1 State and compare the types of air compressor Types of compressors. Compressors are broadly classified as: Positive displacement compressor and Dynamic compressor. Positive displacement compressors increase the pressure of the gas by reducing the volume. Positive displacement compressors are further classified as reciprocating and rotary compressors. Dynamic compressors increase the air velocity, which is then converted to increased pressure at the outlet. Dynamic compressors are basically centrifugal compressors and are further classified as radial and axial flow types. The flow and pressure requirements of a given application determine the suitability of a particulars type of compressor. a. Reciprocating compressors Single stage a. Reciprocating compressors i. Single stage piston compressor ii. Double stage piston compressor b. Rotary compressors i. Screw compressor Rotary screw compressors use two meshed rotating positive- displacement helical screws to force the air into a smaller space These are usually used for continuous operation in commercial and industrial applications and may be either stationary or portable. Because of simple design and few wearing parts, rotary screw air compressors are easy to install, operate, and maintain. ROTARYSCREWAIR COMPRESSOR Thisis the most widely used compressor type in the industry for Instrument air where large volumes of high-pressure air are needed, unlike reciprocating type. Rotary screw compressors are available in oil-free (Dry) and oil-flooded (oil injected) construction. Oil Flooded or Oil Injected Screw Compressors In an oil-injected rotary-screw compressor, oil is injected into the compression cavities to aid sealing and provide cooling sink for the gas charge. The oil is separated from the discharge stream, then cooled, filtered and recycled. Oil Free or DryScrew Compressors Oil-free compressors are used in applications where entrained oil carry-over is Not acceptable, such as medical research and semiconductor manufacturing. ii. Slide ram( Vane) compressor One of the oldest compressor technologies, rotary vane compressors consist of a rotor with a number of blades inserted in radial slots in the rotor. The rotor is mounted offset in a larger housing that is either circular or a more complex shape. As the rotor turns, blades slide in and out of the slots keeping contact with the outer wall of the housing. Thus, a series of decreasing volumes is created by the rotating blades They can be either stationary or portable, can be single or multistage, and can be driven by electric motors or internal combustion engines. They are well suited to electric motor drive and is significantly quieter in operation than the equivalent piston compressor. They can have mechanical efficiencies of about 90% Free Air Delivery (FAD). It is the volume of compressed air delivered by a compressor at the specified discharge pressure and is stated in terms of the actual atmospheric inlet conditions. It is expressed in terms of lpm (fad) or cfm (fad). Not include in the syllabus Air Dehydration Why Do You Need to Dry Compressed Air? By convention, the higher the temperature of environmental air, the higher its water vapor content. Compressing this air raises its temperature further (heat of compression) thus increasing its water saturation. Compressed air with a high content of vaporized water is not ideal for most industrial processes as they mostly require dried air. Apart from their non-suitability for industrial manufacturing, compressed air with high levels of moisture will damage compressor components by causing corrosion and channel blockages. To avoid an accumulation of damaging moisture, compressed air coolers are incorporated into compressor systems to rid the air excess water. WHAT IS AN AFTERCOOLER Every air compression process generates some amount of heat referred to as the heat-of-compression and the temperature values vary differ between compressor types. An air compressor aftercooler device is a device that acts as a heat exchanger removing the heat of compression from a stream of compressed air. The intent in this action is to reduce the temperature of the air stream. Taking the system temperature below the dew point temperature of compressed air allows suspended water vapor to condense and be eliminated. This results in a drier, high-quality air more suitable to your industrial applications. Air-Cooled Aftercooler An air to air aftercooler uses environmental air to achieve its compressed air cooling effect. The typical setup is a series of coiled tubes through which the heated compressed air is channeled. Ambient air is pulled from the external environment by motor-driven fans and forced over the coils to cool the air within the aftercooler’s tubing. Once the compressed air has cooled sufficiently the suspended moisture condenses and can be collected by a dedicated basin while dry compressed air is channeled to a separate outlet. Water-Cooled Aftercooler Different variants of water-cooled aftercoolers are available for compressed air drying processes. A common water-cooled aftercooler is the shell and tube version. This heat exchanger type is composed of a network of coiled tubes within a shell casing. While heated compressed air is passed through the tubes in one direction, cool water is channeled through the surrounding shell eliminating the heat from the process. As cooling is achieved, suspended water is precipitated into the aftercooler coils and is removed by an attached moisture separation unit. b. Air Dryer All compressed air treatment components should be installed to dry and clean the air. Dryers typically grouped into two major categories: 1. Desiccant 2. Refrigerant Desiccant dryer, Desiccant dryer, water vapor is removed through absorption and adsorption processes. In the event compressed air lines are exposed to temperatures below 32˚F (or 0˚C), the use of a desiccant dryer is required to eliminate the hazard of a compressed air line freezing. i. Absorption processes Absorption drying is a chemical process in which water vapor is bound to absorption material. The absorption material can either be a solid or liquid. Sodium chloride and sulfuric acid are frequently used, which means that the possibility of corrosion must be taken into consideration. This method is unusual and involves high consumption of absorbent materials. The dew point is only lowered to a limited extent.  ii. Adsorption processes Adsorption drying is a chemical process in which water vapor is bound to adsorption material that can either be a solid or liquid. The general working principle of adsorption dryers is simple: moist air flows over hygroscopic material — typically silica gel, molecular sieves or activated alumina — and is then dried. The exchange of water vapor from the moist compressed air into the hygroscopic material or desiccant causes the desiccant to gradually become saturated with adsorbed water. Therefore, adsorption dryers are typically built with two drying vessels to regularly regenerate the desiccant so it regains its drying capacity. The first tower dries the incoming compressed air while the second tower is being regenerated. Each tower switches tasks when the other tower is completely regenerated. These dryers are suitable for providing very, dry air for more critical applications since a typical pressure dew point of -40°F can be achieved. DESSICCANT AIR DRYER iii. Refrigerant Dryer Refrigerant type air dryers are the most economical compressed air dryers Within a refrigerant air dryer, compressed air is cooled, water vapor is condensed into liquid water where it is mechanically separated and drained from the compressed air system. Refrigerant air dryers are supplied with automatic condensate drains. 1.2.3 FRL Unit: Filter, Regulator, & Lubricator Filter, regulator, and lubricator (FRL) compressed air systems are used to deliver clean air, at a fixed pressure, and lubricated (if needed) to ensure proper pneumatic component operation and increase their operation lifetime. The air supplied by compressors is often times contaminated, over pressurized, and non-lubricated meaning that an FRL unit is required to prevent damage to equipment. Filters, regulators, and lubricators can be bought individually or as a package FRL a. Compressed Air Filter Filters remove water, dirt and other harmful debris from an air system The type and size of contaminants present in the system and the air requirements for components will ultimately affect what micron size and bowl material is needed for the filter. Common applications generally only require a filter rated between 5-40 microns. Filters will accumulate debris and must be cleaned and the media replaced on a regular basis. The service life of the media is generally based on no more than a 5 psig pressure drop across the device. b. Pressure Regulator Regulators, also called pressure reducing valves, adjust and control the air pressure of the system to ensure that down-line components do not exceed their maximum operating pressures c. Compressor Lubricator Pneumatic systems requiring heavy lubrication, such as a single air tool or a single cylinder, benefit from oil-fog delivery systems. However, in this high delivery system, the oil aerosol produced contains relatively large oil particles, which are affected by gravity, making this system unsuitable for lubricating a device at a higher level than itself or at a distance away. Water Separators Compressors turn water vapor in the intake air into free water inside the compressor. Compressors also increase the amount of water vapor in the compressed air in the tank. Both free water and water vapor laden air. Water Is Generated Right Away enter your air line and through it to your air tools. Water separator is installed on the air pressure line to remove water drops from compressed air. Not include in the syllabus 1.3 Symbols and Standards in Pneumatics. CLO 1 : 3 Hours 1.0 INTRODUCTION TO PNEUMATIC SYSTEM :Symbols and Standards in Pneumatics. 3 Hours Learning Outcomes : 1.3 Explain the Symbols and Standards in Pneumatics. 1.3.1 Explain the symbols and descriptions of components a. Symbols for the power supply section b. Directional control valves i. Ports and switching positions ii. Port designation iii. Types of actuation c. Non-return, flow control and pressure control valves d. Combination valves e. Symbols of the principal working elements 1.3 The Symbols and Standards in Pneumatics. Components of pneumatic systems Pneumatic circuits DIRECT ACTUACTION OF CYLINDERS 1.3.1 The symbols and descriptions of components Example of the symbols used in pneumatic circuit a. SYMBOLS FOR THE POWER SUPPLY SECTION A pneumatic control system requires a supply of clean, dry, compressed air. The air source must be continuous because many pneumatic sensors, controllers, relays, and other devices bleed air. A typical air supply system includes a compressor, an air dryer, an air filter, a pressure reducing valve, and air tubing to the control system a. SYMBOLS FOR THE POWER SUPPLY SECTION b. SYMBOL FOR DIRECTIONAL CONTROL VALVES Directional control valves are used in pneumatic systems to direct or stop the flow of compressed air or oil to their appliances. They are probably the most used elements in pneumatic systems and can be used for example to actuate a cylinder, a larger industrial valve, or air tools. i. SYMBOLS FOR DIRECTIONAL CONTROL VALVES : PORTS AND SWITCHING POSITIONS ii. SYMBOLS FOR DIRECTIONAL CONTROL VALVES : PORTS DESIGNATIONS iii. SYMBOLS FOR DIRECTIONAL CONTROL VALVES : TYPE OF ACTUACTION c. SYMBOLS FOR NON-RETURN Non-return valves allow compressed air to flow in one direction and prevent it from flowing in the other. Fitted upstream of the circuit to be protected, they provide total protection. c. SYMBOLS FOR FLOW CONTROL VALVE Flow Control Valves are used to reduce the rate of flow in a section of a pneumatic circuit, resulting in a slower actuator speed. c. SYMBOLS FOR LOGIC VALVE The signal processing in the pneumatics takes place within the control circuit via logic valves. In this case, any complex logic function can be installed using the three basic logic functions "- OR - AND - NOT". Each air logic valve is built differently but is made to produce the same function, which is to provide the ability to insert logic into a control system. c. SYMBOLS FOR QUICK EXHAUST VALVE Quick exhaust valves are installed at the rod or blind end of a pneumatic cylinder to provide a quick extension and retraction of the equipment. Quick exhaust valves operate by increasing the speed of the pneumatic cylinder's rod in order to expel the exhaust air at the port of the cylinder directly. c. SYMBOLS FOR PRESSURE VALVES (cont.) The pressure control valve (also known as relief valves) are used to restrict the pressure downstream of a unit. They are utilized mainly to prevent the pneumatic system from overpressure and to ensure safety. d. SYMBOLS FOR Combination valves d. SYMBOLS FOR Combination valves e. SYMBOLS FOR THE PRINCILPE WORKING ELEMENTS Pneumatic actuators are devices that convert the energy of compressed air or gas into a mechanical motion that regulates one or more final control elements. SYMBOLS FOR LINEAR ACTUACTORS A linear actuator creates motion in a straight line. SYMBOLS FOR LINEAR ACTUACTORS SYMBOLS FOR ROTARY ACTUACTORS A rotary actuator is an actuator that produces a rotary motion or torque. SYMBOLS FOR ROTARY ACTUACTORS SYMBOLS FOR COMPONENTS DESIGNATION SYMBOLS FOR MULTI ACTUACT0R PNEUMATIC CIRCUIT DESIGN INPUT/OUTPUT SIGNAL FLOW CIRCUIT DESIGN POSITIONAL DIAGRAM EXAMPLE OF SYMNOLS APPLICATION IN MULTI ACTUACT0R PNEUMATIC CIRCUIT DESIGN STEP 1: INPUT/OUTPUT SIGNAL FLOW STEP 4 : CIRCUIT DESIGN STEP 2 : TIME MOTION DIAGRAM POSITIONAL DIAGRAM STEP 3 : LIST OF COMPONENTS Label Component A Cylinder A B Cylinder B STEP 5 : CIRCUIT OPERATION V1 5/2 Way Double Air Piloted Valve INITIAL POSITION : V2 5/2 Way Double Air Piloted Valve P → PB(1), → V1(1 →2) → A- → V1(4→5), → B1(1), →A1(1), → V2(1→2) → B- → V2(4→5), →A0(1 → 2) A0 3/2 Way Roller Limit Switch A+ : Cylinder A Extend P → PB(1→2) → B0(1→2) → V1,14(1→4) → A+ → V1(2→3) A1 3/2 Way Roller Limit Switch B+ : Cylinder B Extend B0 3/2 Way Roller Limit Switch P → A1(1→2) → V2,14(1→4) → B+ → V2(2→3) A- : Cylinder A Retard B1 3/2 Way Roller Limit Switch P → B1(1→2) → V1,12(1→2) → A- → V1(4→5) PB Push Button B- : Cylinder B Retard P → A0(1→2) → V2,12(1→2) → B- → V2(4→5) P Power Supply 1.4 Types of Actuator CLO 1 : 1 Hour 1.0 INTRODUCTION TO PNEUMATIC SYSTEM : Types of Actuator 1 Hours Learning Outcomes : 1.4 Classify the Types of Actuator 1.4.1 Explain the functions of linear actuator by sketching: a. Single acting cylinder b. Double acting cylinder 1.4.2 Explain the functions of rotary actuator: a. Air motor b. Rotary cylinder c. Swivel drive 1.4.3 Determine the size of cylinder 1.4.4 Clarify cushioned double acting cylinder e. SYMBOLS FOR THE PRINCILPE WORKING ELEMENTS Pneumatic actuators are devices that convert the energy of compressed air or gas into a mechanical motion that regulates one or more final control elements. 1.4 What is Pneumatic Actuators Pneumatic actuators are the devices used for converting pressure energy of compressed air into the mechanical energy to perform useful work. In other words, Actuators are used to perform the task of exerting the required force at the end of the stroke or used to create displacement by the movement of the piston. The pressurized air from the compressor is supplied to reservoir. The pressurized air from storage is supplied to pneumatic actuator to do work. THE BENEFITS OF ACTUATORS: Components – Another major advantage offered by pneumatic actuators is their simple design and operating components. They are not just easily available, but are also relatively inexpensive & low priced. Heavy loads – These actuators can easily tolerate heavy loads, and are thus, quite commonly used in a number of applications. High force & speed – When used in linear motion control applications, wherein high precision is not a much essential parameter, these actuators offer high force and speed, which is difficult to find in any other actuator, except the hydraulic ones. Easy accessibility of the source – For any pneumatic system to work, air is a major source. Easy availability of this source makes pneumatic actuators the preferred choice of many. Easy channeling – Apart from being easily available, air can also be channeled and routed from one place to another. Thus, using the pneumatic actuators becomes easy through easy channeling of the source. Safe to be used – Pneumatic actuators are safe to be used. Thanks to the use of air, they are not flammable and are not susceptible to short circuit, in contrast to the electric actuators. Storage functionality – It is great to understand the fact that as the pneumatic actuators contain just compressed gases, they can be stored even in the absence of electricity or power. Thus, the users get another benefit with their use. Clean technology – These types of actuators offer a clean technology to the users as they are less prone to contamination. Due to the use of air, which is free from harmful chemicals the pneumatic systems are quite well known in the food and pharmaceutical industries. No overheating issue – The pneumatic actuators do not overheat upon excessive use, and are thus favored by many users in applications that require longer use. Cost-effective substitute – A pneumatic actuator is said to be a cost effective tool for systems. With its easy installation and maintenance, it has become a great option to go for when you are looking for inexpensive actuators. High durability – Another benefit of having pneumatic actuators is that they offer a long term use, thanks to their high durability. It’s good to note that these actuators can easily sustain constant pressures, which is great when you compare them with the other types of actuators. 1.4 Types Of Pneumatic Actuators Pneumatic cylinders can be used to get linear, rotary and oscillatory motion. There are three types of pneumatic actuator: they are i) Linear Actuator or Pneumatic cylinders ii) Rotary Actuator or Air motors iii) Limited angle Actuators The different classification scheme of the pneumatic cylinders 5. Based on the cylinder action Based on cylinder action we can classify the cylinders as single acting and double acting. Single acting cylinders have single air inlet line. Double acting cylinders have two air inlet lines. Advantages of double acting cylinders over single acting cylinders are 1. In single acting cylinder, compressed air is fed only on one side. Hence this cylinder can produce work only in one direction. But the compressed air moves the piston in two directions in double acting cylinder, so they work in both directions 2. In a single acting cylinder, the stroke length is limited by the compressed length of the spring. But in principle , the stroke length is unlimited in a double acting cylinder 3. While the piston moves forward in a single acting cylinder, air has to overcome the pressure of the spring and hence some power is lost before the actual stroke of the piston starts. But this problem is not present in a double acting cylinder. a. Single-acting cylinders It consists of a piston inside a cylindrical housing called barrel. On one end of the piston there is a rod, which can reciprocate. At the opposite end, there is a port for the entrance and exit of oil. Single-acting cylinders produce force in one direction by pneumatic pressure acting on the piston. (Single-acting cylinders can exert a force in the extending direction only.) The return of the piston is not done pneumatically. In single-acting cylinders, retraction is done either by gravity or by a spring. b. Double-acting cylinders A double-acting pneumatic cylinder is one where the thrust, or output force, is developed in both extending and retracting A - cap-end port directions. B - tie rod Double-acting cylinders have a port at each end and move the C - rod-end port piston forward and back by alternating the port that receives D - piston the high-pressure air, necessary when a load must be moved E - barrel in both directions such as opening and closing a gate. F - piston rod 1.4.2 Rotary actuator: A pneumatic motor (air motor), or compressed air engine, is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air energy to mechanical work through either linear or rotary motion. Rotary motion is supplied by either a vane type air motor, piston air motor, air turbine or gear type motor. a. Air motor (Vane air motor) The vane-type rotary actuator is like the vane-type pneumatic motor, but its revolving angle is limited and its output is determined by the vane’s pressure-receiving area and working air pressure. As shown in Figure 1, the number of vanes determines whether an actuator is a single vane or double vane type. Tilting the angle decreases as the number of vanes increases, but the torque increases. The single vane type applies about 270-300 degrees of tilting angle, while the double vane type apples about 90-120 degrees. Also, the vane type rotary actuator is subject to a small amount of air leakage because it cannot be completely air-tightened. b. Rotary cylinder (Rack-and-pinion) A rack-and-pinion, as shown in Figure 2, consists of a circular gear (the pinion) engaged to a linear gear (the rack). When actuated, the piston which is attached to the rack moves linearly. Due to the gear connection to the pinion, it rotates it with the attached output shaft effectively turning the linear motion into rotational. Often two pistons and racks are installed on the opposite side of each other to double the amount of torque on the pinion as shown in Figure 3. In this double acting actuator, the two chambers on the sides are filled with pressurized air which push the pistons to the center. To return the pistons to the initial position, the Upon air supply, pistons move chamber in the center is in turn pressurized. horizontally, turning the shaft that is linked to the piston gear. b. Rotary cylinder (Scotch-yoke) In a Scotch Yoke mechanism, the shaft of the piston is engaged with a rotary shaft via a pin and a slot, as shown in Figure 5. The linear motion of the shaft causes the pin to rotate. Scotch yoke actuators can be spring return or double acting. These actuators can also be equipped with two opposing pistons to double the amount of torque on the output shaft as shown in Figure 5 on the right. Scotch yoke actuators are heavy duty actuators producing torques ranging from multiple thousands to hundreds of thousands of Nm Upon air supply, pistons move horizontally, turning the shaft by the arm connected to the pistons. c. Swivel drive Pneumatic swivel delivers a versatile rotating drive solution for difficult and larger loads. Ideal for manufacturing automation, the swivel drive eliminates the need for additional guidance or bearing system while seamlessly combining a precision heavy duty bearing with a high performance semi-rotary vane drive to conveniently rotate larger loads via adjustable angle up to 270 degrees. From a standard compressed air supply of 1.5 to 10 bar, pneumatic swivel module delivers significant torque output and accommodates higher moments of inertial and high radial and Rotate large or unwieldy products in axial forces. assembly, handling, and packaging This makes the swivel module suitable for use applications. in demanding applications with offset or large loads as well as in semi- or fully-automatic manufacturing handling and assembly automation that may require the application of Indexing in packaging and added force to its flange during the operation. assembly machines can be completed easily with pneumatic swivels. 1.4.3 Determine the size of cylinder Stroke length, force requirements, and operating environment are among the many considerations when specifying pneumatic cylinders. In retract mode, air pressure can act only part of the piston, because the rod blocks the center portion of the piston How to choose a cylinder of the correct size, based on an application.. Example - Double Acting Piston The force exerted from a single acting pneumatic cylinder with 1 bar (105 N/m2), full bore diameter of 100 mm (0.1 m) and rod diameter 10 mm (0.01 m) can be calculated as F = p π (d12 - d22) / 4 = (105 N/m2) π [(0.1 m)2 - (0.01 m)2] / 4 = 778 N = 0.78 kN instroke capacity is reduced compared to outstroke capacity - due to the rod and reduced active pressurized areal 1.4.3 Determine the size of cylinder 1.4.4 Clarify cushioned double acting cylinder A tube in which a piston operates under the action of fluid pressure is referred to as cylinder housing. Cylinder cushioning is an arrangement intended to regulate the speed of the piston as it ends the stroke. Cushioning is needed to lower the speed of the cylinder before it reaches the end cap. Lowering the speed of the piston helps reduce stress on the components within the cylinder. It also lessens vibration conveyed to the other parts of the machine. A needle valve in the head provides a parallel path for the air to exit. Clippard's needle design has a high flow gain, allowing the user to fine-tune the cushion's effectiveness anywhere from little effect to actually stopping the cylinder. Cushioned cylinders are not designed to decelerate machine members or to take the place of shock absorbers in applications with high kinetic energy. Cushions cannot be added to existing cylinders (requires additional components and machining).