The Aspects of Pneumatic Controls - Coursework Example

Pneumatic Controls Student’s Name Institutional Affiliation Table of Contents Pneumatic Controls 1 Table of Contents 2 Abstract 3 Pneumatic Controls 4 Introduction 4 Advantages of Pneumatic Control 4 Components of Pneumatic Control 6 Push Button Switches 7 Limit Switches 8 Pressure Switches 9 Solenoids 10 Relays 11 Reed Proximity Switches 12 Conclusion 14 References 15 Abstract The following paper aims at aspects surrounding pneumatic control systems. This is specifically in term of why it is used over competing technologies, components used in pneumatic control and how they function. It focuses on the electro pneumatic control systems using diagrams to illustrate the components and their functionality. Pneumatic control systems are efficient, safe, and clean illustrating their wide use in the automation industry. Keywords: pneumatic control, air, contacts. Pneumatic Controls Introduction In the engineering field the term ‘Pneuma’ refers to breath of air. Pneumatic control refers to the use of compressed air in the automation industry. The control system applies compressed air as the working medium usually at a pressure between 6 bar and 8 bar (NPTEL, n.d). When applying this system, the pneumatic control can generate a maximum for of up to 50 kN. Pneumatic control systems can be actuated manually, through pneumatic actuation or electrical actuation. In the automation industry, electrical or electro pneumatics enjoy increased application in the automation industry. Moreover, they are used extensively in assembly, production, chemical, packaging, and assembly systems (NPTEL, n.d). In the automation industry, there is a substantial change in control systems where relays are being substituted with programmable logic switches to satisfy the rising demand for flexibility in automation. The following paper aims at discussing significant technical issues of pneumatic control specifically electrical pneumatic control. Advantages of Pneumatic Control Electric pneumatic control comprises of electro control systems that operate pneumatic power structures. This requires the use of solenoid valves as an interface between the pneumatic and electrical system (Springer, n.d). Devices such as proximity sensors and limit proximity are uses for feedback. The electrical pneumatic control incorporates electrical and pneumatic technologies. It utilizes an electrical signal through either DC or AC sources while the working medium is compressed air. Currently, operating voltages range between 12Volts and 220Volts (NPTEL, n.d). In the final valve, a solenoid actuation is used for activation. The valve is rest using either double solenoid valves or a simpering single solenoid. Electrical pneumatic control are operated or controlled using both contractors and relays or through programmable logic controllers (PLC) (NPTEL, n.d). The relay is applied to convert a signal input from switches and sensors to matching output signals. Signal processing is simply attained through the combination and contractors and relays. Moreover, a PLC can be appropriately applied to gain outputs as per the desired time delay, sequential operation, and logic. The output signals are then transmitted to the solenoids triggering the final control valves that control movement of numerous cylinders (Springer, n.d). This develops one the dominant advantages of electro pneumatics over other technologies as it can integrate with numerous types of PLCs and electrical proximity sensors achieve effective control. Furthermore, the signal speed of an electrical signal is much greater, meaning the cycle time can be decreased and signals can be transmitted over long distances (NPTEL, n.d). Based on this description, it is easy to understand why pneumatic control is widely used or better than other controls. With air as the main working medium, its supply is infinite because air is unlimited in all places and time (Sawain, 2009). Moreover, air is easily transmittable as it has low friction compared to other alternatives such as fluids. Air temperature is also controlled easily with its simple cooling or heating elements (Sawain, 2009). Even in high temperature cool water can still be used. The pneumatic control is also safer than other alternatives. Air is not flammable and cannot conduct electricity or cause short circuits. This is especially in electrical pneumatic control where electricity can come into contact with alternative working mediums such as fluids to short circuits. Furthermore, pneumatic control is cleaner than other alternatives. Air is generally clean and contains none harmful elements or has lesser toxic materials that may affect control systems (Sawain, 2009). Lastly, air is fast and can transfer power easily and effectively over other controls. Components of Pneumatic Control Figure 1 Structure and Components of a Pneumatic Control (NPTEL, n.d) As seen in Fig 1, the typical pneumatic control contains the illustrated elements including drive elements, final control elements, signal processing elements, signal input elements, and energy elements. The same elements apply to electro pneumatic control, but signal processing is transmitted through contractors and relays or through PLC. Again, the control valves are solenoid actuated for electro pneumatic control systems. The report will cover the electro pneumatic components and their numerous uses. Push Button Switches The push button switches are applied to open or close an electrical control unit. Basically, they start and stop the functioning of machinery or a system. Moreover, the offer manual overrides in case of an emergence. The switches are actuated after the actuator is pushed into the cylinder, which triggers a set of contacts to close or open (NPTEL, n.d). Push buttons can be categorized in monetary and maintained contact buttons. Monetary buttons retrieve their original position before actuation after releasing. Dependent or maintained buttons have a latching system for holding it in the desired position. The contact of these bush buttons is identified based on their functions. They include the normally open type (NO), normally closed type (NC), and change over type (CO) (NPTEL, n.d). The cross sector of numerous push buttons in their regular and actuated points as well as their symbols are illustrated in Figure 2. The NO type buttons have open contacts in their normal position, which inhibits energy flow through the opening. However, in the actuated point, contacts become closed allowing energy to stream through. The NC type buttons have closed contacts in their regular positions, allowing energy to pass along while in the actuated position, the contacts are closed allowing energy to pass (Springer, n.d). The NC type buttons have closed contacts in the regular position, which allows energy flow while in the actuated position the contacts are open permitting air energy flow. Inn a changeover contact, the NO type contacts and NC type contacts are combined together (Springer, n.d). Figure 2 Push Button (Springer, n.d) Limit Switches A limit switch is button that is actuated based on the position of a liquid power element (normally a hydraulic motor shaft, piston rod, or point of load) (Springer, n.d). Its actuation produces and electrical signal that triggers a suitable system response. The limit switch achieves the same roles as that of a push button switches. Nonetheless, limit switches are automatically actuated while push buttons are physically actuated. The limit switches are classified in two types based on the technique of actuating their contacts. These include the spring load and lever actuated contacts. Operation of lever limit switches is relatively slow while in the spring limit switches, operation is rapid. Figure 3 illustrates a basic cross sectional design of a limit switch plus its symbol. Figure 3 Limit Switch (Springer, n.d) Pressure Switches The pressure switch converts pneumatic signals to electrical signals (Springer, n.d). It is applied in sensing changes in pressure where it automatically closes or opens an electrical switch after a scheduled pressure level is achieved. Pressure switches use the diaphragm or the bellow to sense changes in pressure. The bellows are used to contract or expand in reaction to rise or fall in pressure (see Figure 4). After pressure is released at the inlet and the predetermined level is achieved, the bellow inflates pushing the spring loaded nozzle to break or make contact. Figure 4 Cross sectional design of the pressure switch (Springer, n.d) Solenoids An electro pneumatic control is composed of two parts that are interfaced by electrically actuated reversing control valves. The main function of the electrically actuated reversing control valves is switch air supply on and off as well as retraction and extension of cylinder discs. The valves are switched through the support of solenoids (NPTEL, n.d). These valves can be classified into two types including the double solenoid and spring return. The spring return group consists of valves that only stay in the actuated position when current is flowing across the solenoid. The double solenoid groups consist of valves that keep the last actuated position regardless of current flowing across the solenoid. In the normal, electronically actuated turning control valve solenoids have no energy, thus remain inactive. Nonetheless, the double control valve has no definite normal position because it has no return spring. Figure 5 Design of single selonoid valve (NPTEL, n.d) The initial and actuated positions of the single solenoid valve are illustrated in Figure 5. In the regular position, the first port is obstructed while the second port is linked to the third port though the back opening. When the appropriate voltage is connected to the coil, the frame is drawn towards the core of the coil triggering the frame to lift away from the bottom of the valve (NPTEL, n.d). Compressed air can now flow from the first port to the second port while the third port is obstructed or closed. When the voltage seizes to be applied to the coil the control valve retreats to the regular position. Relays A relay is a switch that is actuated through an electromagnetic system. The relay is a simple electrical tool applied for processing signals. It is designed to endure severe environmental conditions and high power surges. When voltage released to the solenoid coil, it generates an electromagnetic field. This triggers the frame to be attracted towards the center of the solenoid coil. The return spring then retreats the frame back to its regular position after voltage is disconnected. Figure 6 illustrates a basic relay. Figure 6 Basic relay (NPTEL, n.d) Numerous control contacts can be integrated into the relay compared to the push buttons that can handle less numbers of contacts. The relays are normally designed under specifications of K1, K2, and K3 and so on (NPTEL, n.d). Furthermore, relays have the capability to interlock, which is a significant safety factor in control circuits. The interlocking capability there is no synchronized switching of specific coils. Reed Proximity Switches Reed switches are comparable to relays, only that they use a permanent magnet rather than a coil. They are also magnetically actuated as in the case of relays. Figure 1 illustrates the schematic view of a reed switch. Reed switches consist of two ferromagnetic stems located with a gap in the middle and hermetically wrapped in a tube made of glass. The tube is packed with passive gas to inhibit the triggering of contacts. Iridium or rhodium is used to coat the surfaces of the reed contacts (NPTEL, n.d). The whole using is compressed with epoxy mastic to avoid mechanical harm to the switch (NPTEL, n.d). Furthermore, the switches are designed with an LED indicator to illustrate their switching status. The switch remains open when the magnet is pulled away. Nonetheless, when the magnet returns close to the switch it closes. Reed switches are operated through magnetic fields from a permanent magnet or an energized coil that consists of both south and north poles on the stems or reeds. The contacts are closed through the magnetic field force as they attract towards the magnet or magnetic field. As the magnet force or field is detached, the stem elasticity triggers the contacts to expose the circuit. Normally, the transfer nature stem is on based on mechanical bias from common lead that is located in the middle of the normally open and normally closed contacts of the reed. If an outward magnetic field is applied, the normally closed contact is not activated as it is non-magnetic while the common lead is attracted pulled by the normally open contact to trigger movement (NPTEL, n.d). If the magnetic field is detached, the common lead repeats the movement back to the normally closed led through mechanical motion. The features of reed switch are illustrated in Figure 7. Figure 7 Reed Switch (NPTEL, n.d) Conclusion In conclusion, the report has discussed the main advantages of pneumatic control and its components as well as their functionality. Pneumatic control is among the widely used control systems for the automation industry. It uses air as the main working medium, which enable increased flexibility and effectiveness when it comes to control systems in automation. Pneumatic control can integrated with an electrical system to increase its flexibility in automation. The use of both air and electricity in the pneumatic control ensures increased advantages over other alternatives such hydraulic control systems. One of the main advantages of pneumatic control is the controllability. The speed and force generated by compressed air allows for effective controlling of components. Moreover, the supply of air is unlimited meaning it is cheaper and reliable as air cannot run out and can be found almost everywhere at any time. Air is also easily transmitted because it has reduced friction unlike fluids. Additionally, air is also clean, and safer in terms of toxic materials and causing hazards. Pneumatic control systems present an effective, safe, and clean way of achieving flexibility and control in the automation industry. References National Program on Technology Enhanced Learning (NPTEL) (n.d). Electro-Pneumatic Control. Retrieved from http://nptel.ac.in/courses/112106175/Module%204/Lecture%2041.pdf Sawain, R.E. (2009). Pneumatic Control System. Retrieved from http://www.kohlerandlewis.com/pdf/pneutech.pdf Springer (n.d). Pneumatic Control Devices. Retrieved from http://www.springer.com/978-0-387-30521-9 Read More

Moreover, a PLC can be appropriately applied to gain outputs as per the desired time delay, sequential operation, and logic. The output signals are then transmitted to the solenoids triggering the final control valves that control movement of numerous cylinders (Springer, n.d). This develops one the dominant advantages of electro pneumatics over other technologies as it can integrate with numerous types of PLCs and electrical proximity sensors achieve effective control. Furthermore, the signal speed of an electrical signal is much greater, meaning the cycle time can be decreased and signals can be transmitted over long distances (NPTEL, n.d). Based on this description, it is easy to understand why pneumatic control is widely used or better than other controls.

With air as the main working medium, its supply is infinite because air is unlimited in all places and time (Sawain, 2009). Moreover, air is easily transmittable as it has low friction compared to other alternatives such as fluids. Air temperature is also controlled easily with its simple cooling or heating elements (Sawain, 2009). Even in high temperature cool water can still be used. The pneumatic control is also safer than other alternatives. Air is not flammable and cannot conduct electricity or cause short circuits.

This is especially in electrical pneumatic control where electricity can come into contact with alternative working mediums such as fluids to short circuits. Furthermore, pneumatic control is cleaner than other alternatives. Air is generally clean and contains none harmful elements or has lesser toxic materials that may affect control systems (Sawain, 2009). Lastly, air is fast and can transfer power easily and effectively over other controls. Components of Pneumatic Control Figure 1 Structure and Components of a Pneumatic Control (NPTEL, n.d) As seen in Fig 1, the typical pneumatic control contains the illustrated elements including drive elements, final control elements, signal processing elements, signal input elements, and energy elements.

The same elements apply to electro pneumatic control, but signal processing is transmitted through contractors and relays or through PLC. Again, the control valves are solenoid actuated for electro pneumatic control systems. The report will cover the electro pneumatic components and their numerous uses. Push Button Switches The push button switches are applied to open or close an electrical control unit. Basically, they start and stop the functioning of machinery or a system. Moreover, the offer manual overrides in case of an emergence.

The switches are actuated after the actuator is pushed into the cylinder, which triggers a set of contacts to close or open (NPTEL, n.d). Push buttons can be categorized in monetary and maintained contact buttons. Monetary buttons retrieve their original position before actuation after releasing. Dependent or maintained buttons have a latching system for holding it in the desired position. The contact of these bush buttons is identified based on their functions. They include the normally open type (NO), normally closed type (NC), and change over type (CO) (NPTEL, n.d). The cross sector of numerous push buttons in their regular and actuated points as well as their symbols are illustrated in Figure 2.

The NO type buttons have open contacts in their normal position, which inhibits energy flow through the opening. However, in the actuated point, contacts become closed allowing energy to stream through. The NC type buttons have closed contacts in their regular positions, allowing energy to pass along while in the actuated position, the contacts are closed allowing energy to pass (Springer, n.d). The NC type buttons have closed contacts in the regular position, which allows energy flow while in the actuated position the contacts are open permitting air energy flow.

Inn a changeover contact, the NO type contacts and NC type contacts are combined together (Springer, n.d). Figure 2 Push Button (Springer, n.

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