1. Instrumentation I - Session 5 Session 5 - Agenda ActivityEst. Time 1. Agenda 2. Introduction to Primary Sensors, Transmitters and Transducers (Chapter 9) 3. Component Purpose and Operation, Transmitter Signals and Scaling Transducers and Signals, Pneumatic and Electrical Signals (Chapter 9) 4. Introduction to Controllers/Terms (Chapter 10) 5. Controller Switching, Types of Controllers, Final Control Element Overview (Chapter 10) BREAK 6. Class activity and HWAs

2. Instrumentation I - Session 5 Learning Objectives 1. Describe the relationship between the measuring instruments (pressure, temperature, level, and flow) and their role in the overall control loop process. 2. Describe the purpose and operation of the transmitter (D/P Cell) in a control loop. 3. Discuss differential pressure in relation to the process input to the transmitter. 4. Compare and contrast the transmitter input and output signals. 5. Describe the function of a current to pneumatic transducer (signal converter). 6. Describe the relationship between a 3 psig to 15 psig air signal and a 4 ma to 20 ma electric signal. 7. Given a process control scheme, explain how a control loop functions.

3. Instrumentation I - Session 5 Sensors  Sensors can be mechanical or electronic. A thermocouple is an example of an electronic sensor that can be directly connected to a controller.  Thermocouples and RTDs are examples of discrete temperature sensors that are usually installed in a thermowell extending into the process.

4. Instrumentation I - Session 5 Primary Sensors, Transmitters and Transducers  The transmitter produces an output signal that carries the measurement information to the next instrument in the loop.  The sensor detects the process variable and the transducer converts one energy form into another.

5. Instrumentation I - Session 5 Transmitters  After being sensed and measured, the process variable measurement is transduced (converted) by the transmitter circuit into a standard instrument signal.  The standard instrument signals are 4-20 mA (electronic), 3-15 psig (pneumatic), or digital.

6. Instrumentation I - Session 5 Differential Pressure and the Transmitter  The differential pressure transmitter is a commonly used transmitter in the processing industry.  Differential pressure transmitters can measure pressure and differential pressure as well as infer level, flow rate, and even density.

7. Instrumentation I - Session 5 Transmitter Signals The output of the transmitter is typically converted into one of the common standard instrument signals. In an analog electronic control loop, a thermocouple with a millivolt input to the transmitter has a 4-20 mA output. Pressure inputs, as well as analytical measurements applied to transmitters, also have a corresponding 4- 20 mA output signal.

8. Instrumentation I - Session 5 Scaling n Scaling is the act of equating the numerical value of one scale to its mathematically proportional value on another scale. n For example, the measurement applied to a standard analog electronic pressure transmitter is represented on an appropriate pressure scale while the output signal is represented on a milliampere scale. (pages 143,144) n To better understand the relationship between the input of a transmitter and its output, calculating the input of a transmitter by observing its output is useful. (table 9-1)

9. Instrumentation I - Session 5 Scaling Terms n Upper Range Value (URV) – The number at the top of the scale. Expressed as one number. n Lower Range Value (LRV) – The number at the bottom of the scale. Expressed as one number. n Range – Range defines the set of values that exist between the LRV of a scale and the URV of a scale. It is expressed as two numbers. (Example 50 psig to 150 psig) n Span – Span is the algebraic difference between the upper range value of a scale minus the lower range value value of a scale expressed as one number. (Example: If URV=150 psig and LRV=50 psig, then Span=100psig)

10. Instrumentation I - Session 5 Calculating the Output of a Transmitter Page 144

11. Instrumentation I - Session 5 Transducers Transducer is a device that converts one energy form to another. Transducers can convert quantities such as temperature and pressure Into an electronic form.

12. Instrumentation I - Session 5 Transducer Signals A common instrument signal transducer converts an analog electronic signal (4-20 mA) into a pneumatic signal (3-15 psig). This device is called an I/P(current to pneumatic) transducer.

13. Instrumentation I - Session 5 Chapter 10 – Objectives (Page 1) 1. Define terms associated with controllers: n auto/manual switch n local/remote switch n setpoint n tuning n direct acting n reverse acting n proportional band/gain n integral/reset n derivative/rate 2. Define “bumpless” transfer of auto to manual/manual to auto control. 3. Describe the process for switching from auto control to manual control on a local controller.

14. Instrumentation I - Session 5 Chapter 10 – Objectives (Page 2) 4. Describe the process for switching from manual control to automatic control on a local pneumatic controller without bumping the process. 5. Demonstrate various control skills, such as: n make setpoint adjustments on a local controller n operate a local controller in manual mode n make setpoint adjustments on a remote pneumatic controller n switch from manual to automatic control on a remote pneumatic controller without bumping the process. 6. Given a drawing or actual local pneumatic controller, read the chart and state the high and low range values. 7. Given a simulator or actual device, identify if a control loop is in control or out of control and identify the information used to make the decision.

15. Instrumentation I - Session 5 Chapter 10 – Objectives (Page 3) 8. Given a drawing or actual device, identify and describe the operation of the following: n local controller n remote controller n split range controller n cascade/remote setpoint (RSP) controller n ratio controller 9. Provide an application requiring the following devices: n local controller n remote controller n split range controller n cascade/remote setpoint (RSP) controller n ratio controller 10. Describe the role of the final control element as it relates to the process and the control loop.

16. Instrumentation I - Session 5 Chapter 10 – Objectives (Page 4) 11. Describe three types of final control elements and provide an application for each type: n control valve – manipulates a process flow (liquid/gas) in response to a control signal n damper/louver – manipulates an air flow to control draft setting or temperature setting n motor – starts or stops in response to a control signal. 12. Given a drawing or actual instrument, identify and describe the operation of the following: n louver/damper final control element n variable speed motor used as a final control element n instrument air regulator

17. Instrumentation I - Session 5 Controllers  The controller is a device in a control loop that operates automatically to regulate a process variable.  In a simple feedback control loop, the controller first compares the value of the measurement signal to a setpoint value. The result of this comparison produces another value called the error.  The error signal is then acted upon by one or more separate action components (control algorithms) to generate an appropriate output signal.

18. Instrumentation I - Session 5 Controller Front Panel  Auto/manual switch  Output adjustment in manual (thumb wheel)  Remote/local switch (RSP) is received from an external source(usually another controller)  Set point knob  Process value  Set pointer  Scale  Figure 10-2 (Page 152)

19. Instrumentation I - Session 5 Controller Side Panel  Direct/Reverse acting Direct acting: increasing input process variable goes to increasing output power, increasing temperature turns on the heater on controller Indirect acting: increasing input (measured variable) goes to decreasing output power, increasing temperature turns off the heater  Proportional band (Gain) (A proportional band of 100 percent means that it takes a full range or 100 percent change in input to drive the output of the controller through its full range. PB=(1/Gain)*100%

20. Instrumentation I - Session 5 Controller Side Panel  Gain is a proportioning factor describing how the magnitude of the input relates to the magnitude of the output.  Gain of 1 means the controller will respond to an input change of 10 percent by producing an output change of 10 percent. (Page 153-154)  Integral action (Reset) is designed in a controller to eliminate the offset (error) in feedback control loops.  Derivative action (Rate) Rate of a controller responds to the rate of change of the controlled variable. The faster the rate of change in the error signal, the greater the derivative response.

21. Instrumentation I - Session 5 Local Controller Physically mounted in the processing area near the other instruments in the loop.

22. Instrumentation I - Session 5 Remote Controller  It is not located in the processing area.  They are found mostly in panels located in control rooms.  Figure shows a pressure loop with the transmitter and control valve located in the processing area.  JB-100 and JB-200 are bundle tubes for connecting and distributing points. (Page 156)

23. Instrumentation I - Session 5 Split Range Controller  The output of a controller may be divided between two final control elements.  Modern digital controllers can have more than one output. So, they can be split range controllers.  For example, the signal from output 1 could be 4-11.4 mA (3-8.5 psig) to valve A, while output 2 could be 12.6-20 mA (9.5-15 psig) to valve B Both valves receive the full range output of the controller. (Page 156)

24. Instrumentation I - Session 5 Cascade/Remote Set Point (RSP) Controller  RSP controller is characterized by the output of one controller becoming the remote setpoint of another  The primary controller is responding to the temperature of the product while the secondary controller is operating to control steam flow.(page 157)(there is an error in the picture!!!!???)

25. Instrumentation I - Session 5 Ratio Controller  Ratio control loops are designed to ratio the rates of flow between two separate flows entering a mixing point.

26. Instrumentation I - Session 5 Final Control Elements  A final control element is the last active device in the instrument control loop.  They manipulate operation on the process that brings about a change in the controlled variable.  The most common are control valves, louvers, and variable speed drives.

27. Instrumentation I - Session 5 Control valves  They manipulate the flow rate of some component in a process that will in some way affect the measured value of the controlled variable.  An actuating device is mounted to the control valve. The actuator changes an instrument signal into a linear or rotary motion.

28. Instrumentation I - Session 5 Manipulated Stream=Controlled Stream n A simple feedback control loop controlling flow rate where the controlled variable is the same stream as the manipulated variable. n In this example, the controller adjusts the signal to the control valve, which manipulates the flow rate of the material moving through the process.

29. Instrumentation I - Session 5 Manipulated Stream=Controlled Stream n The transmitter then measures the resulting flow rate and feeds the new measurement value back to the controller where the control cycle continues.

30. Instrumentation I - Session 5 Manipulated Stream=Controlled Stream n A heat exchanger where the temperature transmitter (product side) is located on the outlet of the tube side and control valve is located on the inlet to the shell side. n In this example, the manipulated stream is not the same as the controlled stream.

31. Instrumentation I - Session 5 Louver/Damper n Louvers and dampers are devices similar in design to shutters or miniblinds used to control airflow. n They can be opened (positioned parallel to one another when fully opened) n Each louver in an industrial airflow system usually pivots on a shaft that runs parallel across its midsection.

32. Instrumentation I - Session 5 Electric Motors n If an electric motor is automatically turned on and off by a controller responding to a process variable, then the motor can be considered as a final control element or an actuator of the final control element. n Variable speed motors are used to control fluid pumping rates, conveyor belt speeds, and other final controlling devices.

33. Homework Assignments - HWAs Design 10 True/False questions From chapter 8 & 9 using the following format: Times New Roman, 12 pt. font size, according to the form distributed by Instructor. Handwriting will not be accepted Session 5 - Fall 201533

34. Homework Assignments - HWAs The answer key for this question and the address in the Book.(the edition, Page and line) Due date: Please email me these questions before coming Friday (October 2 nd ) at 8 AM. The following week you will ask your questions from the students and explain the answer to us. Your grade for this HWA will be for your extracting and presenting these questions and answers to the class. This HWA will have 5% of your total grade. Please send your questions before the due date otherwise you will lose the whole point. Session 5 - Fall 201534

35. Homework Assignments - HWAs 1.Example: 1.A curve upper surface of a column of a liquid material is called convex 2. A distance from a zero reference point to the surface is called Height 1.False 2.True Session 5 - Fall 201535