1. Instrumentation 1 – Session 10 Session 10 - Agenda ActivityEstimated Time 1. Agenda – Class Roster -Survey 2. Chapter 20 - PLC Learning Objectives Ladder logic diagrams, the purpose of PLCs Define terms associated with PLCs 3. Chapter 14 – Switches, Relays, and Annunciators Learning objectives Define the function, terms, and the purpose of using these devices 4. Chapter 15 – signal transmission and conversion The purpose and operation of transmitters, type of common transmissions BREAK 9. HWAs - Class Activity – Midterm grades

2. Instrumentation 1 – Session 10 Chapter 20- Objectives Define terms associated with programmable logic control (PLC) Ladder logic diagram Explain the purpose of PLCs: sequential control on/off emergency shut down (ESD) systems integral to distributed control systems (DCS) Stand-alone capability Explain how ladder logic applies to programmable logic control

3. Instrumentation 1 – Session 10 PLC Programming Slide 6

4. Instrumentation 1 – Session 10 Programmable Logic Controllers Slide 3

5. Instrumentation 1 – Session 10 History Modern Electronic PLCs were first introduced during the 1970s. Today PLCs represent the first and most widespread application of computers in process control, mainly because of the numerous advantages they offer over previous hardwired systems.

6. Advantages Those advantages include the following: - cost effectiveness (a relatively inexpensive way to control complex systems) - more sophisticated control (computational abilities increase sophistication) - flexibility(modular construction allows easy replacement and addition of units) - improved troubleshooting( programming is easier and downtime is reduced) - reliability (components tend to be more reliable and don’t fail as frequently Instrumentation 1 – Session 10

7. Background n In the pre-computer PLC era, logic was accomplished by hard wired relays, switches, rotary contactors, or contacts, housed in relay control cabinets. n These relay control cabinets were then connected to electric motor control circuits contained in motor control centers(MCCs) or to electric solenoid valves for on/off control of control valves. n These MCCs, controlled the starting, stopping, and sequencing of motors and other devices. n Computer – based PLCs now perform these functions faster and with greater reliability. Instrumentation 1 – Session 10

8. Motor Control Center

9. Instrumentation 1 – Session 10 Ladder Logic Diagram Slide 7

10. Ladder Logic Diagrams n Diagrams that guide electricians in the fabrication process. n They derive their name from the ladder –like graphical symbolism used to illustrate PLC logic. n The vertical lines, indicate power to an electrical system. n The horizontal lines, which look like the rungs of a ladder, illustrate the availability of power to a device or through a device. n Gates in the horizontal lines indicate whether current is actually flowing through a particular device. Instrumentation 1 – Session 10

11. Ladder Logic Diagrams n Ladder logic diagrams are read from left to right and from top to bottom, just like a page of text would be read. n Generally devices are arranged in order of decreasing impact. n Contacts, relays, and other devices are shown in their shelf position. n Figures 20-2 shows a sample ladder diagram. n In figure 20-2, A is a normally open switch that keeps the circuit path broken and don’t let the current to flow in the circuit and energize device X n In figure 20-3, B is a normally closed valve (has a diagonal line in it). Instrumentation 1 – Session 10

12. Practical Tips n Instrument and electrical (I&E) technicians are good with PLC and instrumentation, but they may lack the knowledge of process. So they should work with process technicians. n A by pass or jumper should be removed right after the completion of work. n Before issuing a maintenance work permit, plan the job thoroughly Instrumentation 1 – Session 10

13. PlCs Today n Modern PLCs allow logic changes to be easily programmed using PCs. n These PLCs allow changes to ladder diagrams to be automatically recorded during the programming process, thus saving considerable amounts of time and money. n PLCs can be stand alone units controlling only a single operation or also be integrated into a broader control scheme such as DCSs Instrumentation 1 – Session 10

14. Logic in PLCs n PLCs gained their name from the ability to program logic into these controls for example: Programming and/or, if/then, or true/fulse functions like figure 20-5 Instrumentation 1 – Session 10

15. Controller Logic

16. PLC functionality PLC functionality can be expressed as a three – part process: 1. Scan inputs from switches or transmitters. 2. Execute logic or control within the PLC. 3. Set outputs based upon results of logic. There are a number of ways that a PLC can be programmed : Fortran, C++, Java, or other computer languages. Instrumentation 1 – Session 10

17. Chapter 14 – Objectives for this class n Define the function of a switch n Describe three common uses for switches in process control n Given a drawing, picture, or actual device, identify and describe basic switch devices. n Given a PFD or P&ID and a legend, locate and identify switches used in process control n Explain how relays are used in the process industry n Explain the purpose of annunciator systems Instrumentation 1 – Session 10

18. Switches n A switch is a mechanical or electrical device that is used to operate, energize, or de-energize mechanical or electrical circuits for alarm, shutdown, or control purposes. n Switches maybe operated by hand, actuated by a mechanical signal, or actuated by a process or electrical signal. n Switches may be used to control P, T, L, or F n They can be purchased as normally open (N.O.) contacts, normally closed (N.C.) contacts or both. Instrumentation 1 – Session 10

19. Switches n The N.O. switch closes its contacts when powered, while an N.C. switch opens when powered n Figure 14-16 to 14-19 Instrumentation 1 – Session 10

20. Relays n Relays, in pneumatic devices, are analog instruments handling continuously variable signals. n In electrical devices are discrete, on/off devices. n In this chapter, it is defined as a device that boosts, maintains, or control the flow of a signal so it can be properly received. Instrumentation 1 – Session 10

21. Annunciator Systems n An annunciator is a type of instrument that provides audible and/or visual alarms in reference to some measured variables n They can be a stand alone panel board device or configured as the alarm package of a DCS. Instrumentation 1 – Session 10

22. Chapter 15 – Learning Objectives for this class n Recall the purpose and operation of transmitters n Recall types of common transmissions n Recall purpose and operation of signal converter equipment Instrumentation 1 – Session 10

23. Transmitters and conversion equipment n Transmitters and conversion equipment are integral parts of signal transmission. n They send process information or data in different signal formats to displays, controllers, or sometimes just to utilize this information to control a process or to convey information for human decision or verifications. n Transmitted information can be in either a mechanical, pneumatic, electrical (analog or digital), or optical format. n When sending information between two or more devices, it is sometimes necessary to convert the signals from one format to another.(signal converter) Instrumentation 1 – Session 10

24. Transducers n Transducers convert energy from one form to another, e.g. sound to electrical n Signal transmission is an important part of data transfer. n Common Types of transmissions: 1) Mechanical (levers, arms, torque tubes, cables, pulleys, etc.) 2) Pneumatic (compressed gas send the signal) 3) Electrical (Analog, Digital, Optical) Instrumentation 1 – Session 10

25. Analog Transmission n Analog signals have an infinite number of values and can vary both in magnitude or frequency depending on the mode. n Simple analog transmission in which the voltage or current amount is transmitted or conducted to a controller or receiver is the usual method for process control signals. n The method is reliable and inexpensive and uses simple electrical circuits. n The main disadvantage is the length of transmission typically 2500 feet and its weakness for noisy environments. n Standard 4-20 mA, 0-10 V, and 0-50 mV loops utilize this method of transmission. Instrumentation 1 – Session 10

26. Digital Transmission n Digital transmission consists of either retransmitting digital pulses that are already produced by the field sensor or by converting the analog signal containing the process control variable data or information into a digital representation (by an A/D converter) n There are standards for the various digital transmission methods, but compatibility between the transmitting field device and the controller, final control element, or receiver must be considered. Instrumentation 1 – Session 10

27. Optical Transmission n Fiber – optic transmission is becoming more and more common in process control because of cost reductions, noise immunity, and intrinsically safe operating characteristics. n Light transmitters (LEDs or laser diodes) and receivers used with fiber-optic cabling make up a complete circuit. n The transmitter is modulated with the process variable information that is conveyed over the optical cable to the receiver, which senses or detects the modulated signal contained in the light signal. n The process variable data may either be analog or digital but is typically digital. Instrumentation 1 – Session 10

28. Signal Conversion n The purpose of signal conversion is to change the form of one signal value into another signal value to ensure device or signal compatibility. n Transducers perform this kind of conversion. n The following are common signal conversions: I/P, P/I I/E, E/I E/P I/F, F/I E/F, F/E Instrumentation 1 – Session 10

29. True - False 1.PLC logic refers to computer instructions that produce on/off commands based on true/false assessments. A.True B.False Slide 8

30. Instrumentation 1 – Session 10 True - False 1.PLC logic refers to computer instructions that produce on/off commands based on true/false assessments. A.True B.False Slide 9

31. Instrumentation 1 – Session 10 True - False 3.One disadvantage of the transition to PLCs is that system documentation became more difficult. A.True B.False Slide 12

32. Instrumentation 1 – Session 10 True - False 3.One disadvantage of the transition to PLCs is that system documentation became more difficult. A.True B.False Slide 13

33. Instrumentation 1 – Session 10 Match From the List 4.PLCs now handle functions formerly performed by: A.instrumentation technicians B.mainframe computers C.distributed control systems D.motor control centers Slide 14

34. Instrumentation 1 – Session 10 Match From the List 4.PLCs now handle functions formerly performed by: A.instrumentation technicians B.mainframe computers C.distributed control systems D. motor control centers Slide 15

35. Instrumentation 1 – Session 10 Match From the List 5.Ladder logic diagrams generally show contacts and relays: A.in the closed position B.in their normal position C.in the open position D.without gates Slide 16

36. Instrumentation 1 – Session 10 Match From the List 5.Ladder logic diagrams generally show contacts and relays: A.in the closed position B.in their normal position C.in the open position D.without gates Slide 17

37. Class Activity – 11/07/2015 Please work in a group of 3, find a P&ID from the web for a process unit and describe it in the following format: 1. Identify and list all the instrumentation with their symbols and their related process variable 2. Define each symbol using directions in chapter 12 (you can use the internet to find some symbols that are not in the book) 3. Find control loops. 4. Describe them and mention the type of each control system (local, cascade, split, ratio,…) Instrumentation 1 – Session 10

38. Class Activity 5. Explain the whole process in a very clear and simple manner. 6. Type them and present it as a group in the class No HWAs for next week Instrumentation 1 – Session 10