text:
Are you sure?
This action might not be possible to undo. Are you sure you want to continue?
Process Control Fundamentals
Table of Contents
Introduction..................................................................................................................................................... 1 Performance Objective ............................................................................................................................. 1 The Importance of Process Control ............................................................................................................... 1 Learning Objectives.................................................................................................................................. 1 The Importance of Process Control................................................................................................................. 2 Process...................................................................................................................................................... 2 Process Control ........................................................................................................................................ 2 Reduce Variability ............................................................................................................................. 2 Increase Efficiency ............................................................................................................................ 3 Ensure Safety ..................................................................................................................................... 3 Control Theory Basics .................................................................................................................................... 4 Learning Objectives.................................................................................................................................. 4 The Control Loop............................................................................................................................................. 5 Three Tasks...............................................................................................................................................5 Process Control Terms ....................................................................................................................................6 Process Variable.......................................................................................................................................6 Setpoint .....................................................................................................................................................6 Measured Variables, Process Variables, and Manipulated Variables.....................................................7 Error .........................................................................................................................................................7 Offset.........................................................................................................................................................8 Load Disturbance .....................................................................................................................................8 Control Algorithm.....................................................................................................................................8 Manual and Automatic Control ................................................................................................................9 Closed and Open Control Loops ..............................................................................................................10 Components of Control Loops and ISA Symbology ...................................................................................... 11 Learning Objectives.................................................................................................................................. 11 Control Loop Equipment and Technology....................................................................................................... 12 Primary Elements/Sensors........................................................................................................................ 12 Transducers and Converters..................................................................................................................... 13 Transmitters.............................................................................................................................................. 13 Signals ...................................................................................................................................................... 14 Pneumatic Signals ............................................................................................................................. 14 Analog Signals................................................................................................................................... 14 Digital Signals ................................................................................................................................... 15 Indicators.................................................................................................................................................. 15 Recorders.................................................................................................................................................. 16 Controllers................................................................................................................................................ 16 Correcting Elements/Final Control Elements .......................................................................................... 18 Actuators................................................................................................................................................... 18
Fundamentals of Control
© 2006 PAControl.com
Table of Contents
ISA Symbology ................................................................................................................................................. 9 1 Symbols ................................................................................................................................................... 20 Pumps .............................................................................................................................................. 21 Piping and Connections .................................................................................................................. 22 Identification Letters............................................................................................................................... 23 Tag Numbers........................................................................................................................................... 23 ISA Symbology Review ........................................................................................................................... 26 Controller Algorithms and Tuning ...............................................................................................................27 Learning Objectives.................................................................................................................................27 Controller Algorithms.....................................................................................................................................28 Discrete Controllers ................................................................................................................................28 Multistep Controllers................................................................................................................................29 Continuous Controllers ............................................................................................................................29 Why controllers need tuning?...........................................................................................................................31 Gain ..........................................................................................................................................................31 Proportional Mode ..........................................................................................................................................33 Proportional Gain ....................................................................................................................................33 Proportional Band ....................................................................................................................................33 Limits of Proportional action ...................................................................................................................34 Determining the Controller Output..........................................................................................................34 Proportional Action- Closed Loop........................................................................................................... 35 . Integral Mode ................................................................................................................................................. 37 Integral Action ........................................................................................................................................ 37 Open Loop Analysis................................................................................................................................ 37 Closed Loop Analysis ............................................................................................................................. 38 Reset Windup .......................................................................................................................................... 39 Summary ................................................................................................................................................. 40 Derivative Mode .............................................................................................................................................. 41 Derivative Action .................................................................................................................................... 41 Rate Summary......................................................................................................................................... 44
Process Control Loops.....................................................................................................................................46 Learning Objectives..................................................................................................................................46 Single Control Loops .......................................................................................................................................47 Feedback Control .....................................................................................................................................47 Examples Of Single Control Loops..................................................................................................................48 Pressure Control Loops............................................................................................................................49 Flow Control Loops..................................................................................................................................49 Level Control Loops .................................................................................................................................50 Temperature Control Loops .....................................................................................................................51
Fundamentals of Control
© 2006 PAControl.com
.............PAControl............................................................................................................................................................ 57 Fundamentals of Control © 2006 PAControl.............52 Multivariable Loops .........................................................................................................................................................................................................................Table of Contents Multi-Variable / Advanced Control Loops ........com ...........................................................................53 Feedforward plus Feedback ....................................................... 56 Ratio Control ................................................................................................................... 57 Fuzzy Control ..........................com iv www...........................................................................................................................................................................................................................................................................................54 Cascade Control ................... 56 Selective Control...................52 Feedforward Control ...................................................................................................................................... 55 Batch Control .........................
go to the workbook to complete the designated exercise before moving on in the module. Workbook exercises help you measure your progress toward meeting each section's learning objectives. note the application boxes (double-bordered boxes) located throughout the module. The following five sections are included in this module: The importance of process control Control theory basics Components of control loops and ISA symbology Controller algorithms and tuning Process control systems As you proceed through the module. Precise control of level. PERFORMANCE OBJECTIVE After completing this module. answer the questions in the activities column on the right side of each page. Also. When you see the workbook exercise graphic at the bottom of a page. and identifies different ways in which precise control is ensured. Fundamentals of Control © 2006 PAControl. explains why control is important.PAControl. temperature.com . pressure and flow is important in many process applications. Application boxes provide key information about how you may use your baseline knowledge in the field. This module introduces you to control in process industries.Introduction Control in process industries refers to the regulation of all aspects of the process. you will be able to determine needed control loop components in specific process control applications.com v www.
flow. combining. handling. and many other factors must be carefully and consistently controlled to produce the desired end product with a minimum of raw materials and energy. Variations in proportions. Fundamentals of Control © 2006 PAControl. Process control technology is the tool that enables manufacturers to keep their operations running within specified limits and to set more precise limits to maximize profitability.com 1 www. efficiency. and safety Note: To answer the activity questions the Hand Tool (H) should be activated. demanding. and potentially hazardous process.PAControl. you will be able to: Define process Define process control Describe the importance of process control in terms of variability. and otherwise manipulating fluids to profitably produce end products can be a precise. ensure quality and safety. turbulence. LEARNING OBJECTIVES After completing this section. Small changes in a process can have a large impact on the end result.com . temperature.The Importance of Process Control Refining.
Manufacturers control the production process for three reasons: Reduce variability Increase efficiency Ensure safety Reduce Variability Process control can reduce variability in the end product. and the power industry. heated or cooled. Process industries include the chemical industry. filtered. as many as 12 or more different components may be blended to make a specific grade of gasoline. the water treatment industry. refers to the methods of changing or refining raw materials to create end products. Process is defined as the changing or refining of raw materials that pass through or remain in a liquid. The opposite situation would be customers receiving a lower grade at a higher price.PAControl. measured. and the refinery would lose money. 1 2 3 4 5 Pharmaceutical Satellite Oil and Gas Cement Power 2 Fundamentals of Control © 2006 PAControl. Manufacturers can also save money by reducing variability. the pharmaceutical industry. or slurry (a mix of solids and liquids) state during the process. or handled in some other way to produce the end product. PROCESS CONTROL Process control refers to the methods that are used to control process variables when manufacturing a product. Which of these industries are examples of the process industry? Select all options that apply.com. how well the ingredients are mixed. the gasoline may get too much of the high-octane components. the food and beverage industry. factors such as the proportion of one ingredient to another. For example. 1. mixed. www. The raw materials. customers would receive a higher grade and more expensive gasoline than they paid for. gaseous. the oil and gas industry.The Importance of Process Control The Importance of Process Control Activities PROCESS Process as used in the terms process control and process industry. For example. As a result. and the pressure under which the materials are held can significantly impact the quality of an end product. If the refinery does not have precise control over the flow of the separate components. which either pass through or remain in a liquid. the temperature of the materials. are transferred. stored. in a gasoline blending process. or slurry state to to create end products. 2. gaseous. which ensures a consistently high-quality product.com .
With accurate.e.PAControl. COMPLETE WORKBOOK EXERCISE . such as an out-of-control nuclear or chemical reaction. maintaining proper boiler pressure by controlling the inflow of air used in combustion and the outflow of exhaust gases is crucial in preventing boiler implosions that can clearly threaten the safety of workers. which adds to the cost.THE IMPORTANCE OF PROCESS CONTROL Fundamentals of Control © 2006 PAControl. When there is variability in the end product (i. when process control is poor). 1 2 3 4 PV limit to ensure quality PV Setpoint 5 Reduce variability Ensure safety Reduce costs Increase efficiency Increase productivity Low Variability PV Setpoint High Variability Increase Efficiency Some processes need to be maintained at a specific point to maximize efficiency. Padding refers to the process of making a product of higher-quality than it needs to be to meet specifications. What are the main reasons for manufacturers to control a process? Select all options that apply.com . dependable process control. For example. a control point might be the temperature at which a chemical reaction takes place.The Importance of Process Control product padding to meet required product specifications. may result if manufacturers do not maintain precise control of all of the processg variables. The consequences of a run-away process can be catastrophic. PV limit to ensure quality The Importance of Process Control Reducing variability can also save money by reducing the need for Activities 3. Precise process control may also be required to ensure safety. manufacturers are forced to pad the product to ensure that specifications are met. Ensure Safety A run-away process. For example.com 3 www. Accurate control of temperature ensures process efficiency. Manufacturers save money by minimizing the resources required to produce the end product. the setpoint (desired or optimal point) can be moved closer to the actual product specification and thus save the manufacturer money..
Control Theory Basics This section presents some of the basic concepts of control and provides a foundation from which to understand more complex control processes and algorithms later described in this module. Common terms and concepts relating to process control are defined in this section. differentiate the following types of control: • Manual versus automatic feedback control • Closed-loop versus open-loop control Note: To answer the activity questions the Hand Tool (H) should be activated.com 4 www. you will be able to: Define control loop Describe the three tasks necessary for process control to occur: • Measure • Compare • Adjust Define the following terms: • Process variable • Setpoint • Manipulated variable • Measured variable • Error • Offset • Load disturbance • Control algorithm List at least five process variables that are commonly controlled in process measurement industries At a high level.PAControl.com . Fundamentals of Control © 2006 PAControl. LEARNING OBJECTIVES After completing this section.
The valve opens to let some liquid out of the tank.com. comparison. pumps). so you throw another log on the fire. Is this statement true or false? THREE TASKS Control loops in the process control industry work in the same way. You feel uncomfortably cold. sensors. a variable (temperature) fell below the setpoint (your comfort level). transmitters. but the three tasks of measurement. and you took action to bring the process back into the desired condition by adding fuel to the fire.g. The control loop will now remain static until the temperature again rises above or falls below your comfort level. and adjustment. www.PAControl.com . LIC Maximum level LT A Simple Control Loop 5 Fundamentals of Control © 2006 PAControl. The three tasks associated with any control loop are measurement. in this case. controllers.. requiring three tasks to occur: Measurement Comparison Adjustment In Figure 7. comparison. Activities 1.Control Theory Basics The Control Loop Imagine you are sitting in a cabin in front of a small fire on a cold winter evening.1. and finds that the values are equal. Many different instruments and devices may or may not be used in control loops (e. valves. a level transmitter (LT) measures the level in the tank and transmits a signal associated with the level reading to a controller (LIC). and adjustment are always present. In the control loop. Thisis an example of a control loop. the maximum tank level established by the plant operator. The controller compares the reading to a predetermined value. The controller then sends a signal to the device that can bring the tank level back to a lower level—a valve at the bottom of the tank.
For example. If the temperature reading is 110 °C. and a contoller compares the temperature reading from the sensor to the setpoint.PAControl.1. For example. 3. The sensor is inserted into the process. In the example of you sitting by the fire. so you throw another log into the fire. PROCESS VARIABLE A process variable is a condition of the process fluid (a liquid or gas) that can change the manufacturing process in some way.Control Theory Basics Process Control Terms As in any field. In the example of the tank in Figure 7. the process variable was temperature. A temperature sensor can be used to help maintain the temperature at setpoint. Common process variables include: Pressure Flow Level Temperature Density Ph (acidity or alkalinity) Liquid interface (the relative amounts of different liquids that are combined in a vessel) Mass Conductivity SETPOINT The setpoint is a value for a process variable that is desired to be maintained. In this scenario. what is the liquid's setpoint? 1 2 3 4 45 ft 55 ft 5 ft 50 ft Fundamentals of Control © 2006 PAControl. You feel uncomfortably cold. Imagine you are in a cabin in front of a small fire on a cold winter evening. Set points can also be maximum or minimum values. If the level of a liquid in a tank must be maintained within 5 ft of 50 ft.com . A process variable is a condition that can change the process in some way. Is this true or false? 4. Activities 2. then the setpoint is 100 °C.com 6 www. process control has its own set of common terms that you should be familiar with and that you will use when talking about control technology. level in tank cannot exceed 20 feet. if a process temperature needs to kept within 5 °C of 100 °C. then the controller determines that the process is above setpoint and signals the fuel valve of the burner to close slightly until the process cools to 100 °C. the process variable is temperature. the process variable is level.
The factor that is changed to keep the measured variable at setpoint is called the manipulated variable. The objective of any control scheme is to minimize or eliminate error. 6.com www. Sometimes the measured variable is not the same as the process variable. The magnitude of error at any point in time compared to the previous error provides the basis for determining the change in error. Setpoint Process variable or measured variable Activities 5. The measured variable is the condition of the process fluid that must be kept at the designated setpoint.Control Theory Basics Process Control Terms MEASURED VARIABLES. the measured variable is also the process variable. 7 Fundamentals of Control © 2006 PAControl. which must be held close to 100 °C. In the example described. AND MANIPULATED VARIABLES In the temperature control loop example. and the process fluid level is the process variable. flow is the measured variable. the error is +10 °C.com .PAControl. In the temperature control loop example.2). a manufacturer may measure flow into and out of a storage tank to determine tank level. Therefore. it is imperative that error be well understood. Any error can be seen as having three major components. The change in error is also an important value. the error is the difference between the 110 °C measured variable and the 100 °C setpoint—that is. For example. These three components are shown in the figure on the folowing page Magnitude The magnitude of the error is simply the deviation between the values of the setpoint and the process variable. Is this statement true or false? Controller Manipulated variable Variables ERROR Error is the difference between the measured variable and the setpoint and can be either positive or negative. In this example and in most instances. PROCESS VARIABLES. In this scenario. the manipulated variable would also be flow (Figure 7. A load disturbance is an undesired change in one of the factors that can affect the setpoint. ____________________ is a sustained deviation of the process variable from the setpoint. the measured variable is temperature.
In the temperature control loop example. adding cold process fluid to the vessel would be a load disturbance because it would lower the temperature of the process fluid.5 °C consistently.PAControl. Rate Of Change The rate of change is shown by the slope of the error plot. if the control system held the process fluid at 100. and e is the error. then an offset of 0.Control Theory Basics Process Control Terms Duration Duration refers to the length of time that an error condition has existed. CONTROL ALGORITHM A control algorithm is a mathematical expression of a control function.com 8 www. even though the setpoint is 100 °C.5 °C exists. V in the equation below is the fuel valve position.com . Activities Rate of Change of Error (Slope of Error Plot) PV Magnitude of Error Duration SP Components of Error OFFSET Offset is a sustained deviation of the process variable from the setpoint. Using the temperature control loop example. In the temperature control loop example. The relationship in a control algorithm can be expressed as: Fundamentals of Control © 2006 PAControl. LOAD DISTURBANCE A load disturbance is an undesired change in one of the factors that can affect the process variable.
Conversely. rather than machines. are called automatic control systems. people. For example.com . Is this statement true or false? The fuel valve position (V) is a function (f) of the sign (positive or negative) of the error (Figure 7. Control operations that involve human action to make an adjustment are called manual control systems. control operations in which no human intervention is required. .PAControl. Summing block Process variable Error Manipulated variable f(e) Valve position Feedback Algorithm Example Control algorithms can be used to calculate the requirements of much more complex control loops than the one described here. 9 Fundamentals of Control © 2006 PAControl. such as an automatic valve actuator that responds to a level controller. questions such as "How far should the valve be opened or closed in response to a given change in setpoint?" and "How long should the valve be held in the new position after the process variable moves back toward setpoint?" need to be answered. performed many of the process control tasks.Control Theory Basics Process Control Terms V = f ( ± e) Activities 7.com www. a human operator might have watched a level gauge and closed a valve when the level reached the setpoint. Automatic control systems are control operations that involve human action to make adjustment.3). In more complex control loops. MANUAL AND AUTOMATIC CONTROL Before process automation.
a water valve may be opened to add cooling water to a process to prevent the process fluid from getting too hot. regardless of the actual temperature of the process fluid.com .PAControl. For example.CONTROL THEORY BASICS 10 Fundamentals of Control ©2006 PAControl.com www. Under what circumstances does an open control loop exist? Select all options that apply.Control Theory Basics Process Control Terms CLOSED AND OPEN CONTROL LOOPS A closed control loop exists where a process variable is measured. but is instead taken without regard to process variable conditions. Activities 8. and action is taken to correct any deviation from setpoint. 1 2 3 4 5 Process variable is not measured Process variable is not compared Process variable is measured and compared to a setpoint Action is taken without regard to process variable conditions Action is taken with regard to process variable conditions COMPLETE WORKBOOK EXERCISE . compared to a setpoint. An open control loop exists where the process variable is not compared. and action is taken not in response to feedback on the condition of the process variable. based on a pre-set time interval.
Components of Control Loops and ISA Symbology This section describes the instruments..g. where appropriate. correctly label the: • Instrument symbols (e. transmitters) • Location symbols (e. control valves.com .g. the basic method of operation for the following control loop components: • Primary element/sensor • Transducer • Converter • Transmitter • Signal • Indicator • Recorder • Controller • Correcting element/final control element • Actuator List examples of each type of control loop component listed above State the advantages of 4–20 mA current signals when compared with other types of signals List at least three types of final control elements. local. this section describes how process control equipment is represented in technical drawings of control loops.. technologies. pneumatic. you will be able to: Describe the basic function of and..com 11 www.g. In addition. electrical) Accurately interpret instrument letter designations used on P&IDs Fundamentals of Control © 2006 PAControl. and for each one: • Provide a brief explanation of its method of operation • Describe its impact on the control loop • List common applications in which it is used Given a piping and instrumentation drawing (P&ID). and equipment used to develop and maintain process control loops. pumps. LEARNING OBJECTIVES After completing this section. panel-front) • Signal type symbols (e.PAControl.
1. may perform more than one of the basic control functions. temperature is determined. compare. as the temperature of a process fluid surrounding the RTD rises or falls. In some cases. The primary element (magnetic flow tube) outputs a voltage that can be measured and used to calculate the fluid's flow rate. a single process control instrument. For example. comparison. the fluid generates a voltage that is directly proportional to the velocity of the process fluid. Primary elements will not make direct contact with the process fluid.com www. In practice. and adjust.Components of Control Loops and ISA Symbology Control Loop Equipment and Technology The previous section described the basic elements of control as Activities measurement. when a conductive fluid passes through the magnetic field in a magnetic flow tube. such as a modern pressure transmitter. With an RTD. they are also called primary elements. Resistance Temperature Detectors Thermocouples Control Valve Converter Pitot tubes 2.PAControl. strain gauges. Some of the greatest ingenuity in the process control field is apparent in sensing devices. and adjustment. Is this statement true or false? 12 Fundamentals of Control © 2006 PAControl. Examples of primary elements include: Pressure sensing diaphragms. and from this measurement. the electrical resistance of the RTD increases or decreases a proportional amount. Other technologies have been developed so that communication can occur among the components that measure. The resistance is measured. Identify three examples of a primary element/sensors in process control? Select all options that apply. capacitance cells Resistance temperature detectors (RTDs) Thermocouples Orifice plates Pitot tubes Venturi tubes Magnetic flow tubes Coriolis flow tubes Radar emitters and receivers Ultrasonic emitters and receivers Annubar flow elements Vortex sheddar Primary elements are devices that cause some change in their property with changes in process fluid conditions that can then be measured. Because sensing devices are the first element in the control loop to measure the process variable.com . 1 2 3 4 5 PRIMARY ELEMENTS/SENSORS In all cases. some kind of instrument is measuring changes in the process and reporting a process variable measurement. there are instruments and strategies to accomplish each of these essential tasks.
For example.com .com 13 www. TRANSMITTERS A transmitter is a device that converts a reading from a sensor or transducer into a standard signal and transmits that signal to a monitor or controller. a converter may convert current into voltage or an analog signal into a digital signal. a transducer converts changes in pressure into a proportional change in capacitance. Transmitter types include: Pressure transmitters Flow transmitters Temperature transmitters Level transmitters Analytic (O2 [oxygen]. Is this statement true or false? Fundamentals of Control © 2006 PAControl.PAControl. In process control. A converter is a device that converts one type of signal into another type of signal. and pH) transmitters 4.Components of Control Loops and ISA Symbology Control Loop Equipment and Technology TRANSDUCERS AND CONVERTERS A transducer is a device that translates a mechanical signal into an electrical signal. A ____________ is a device that translates a mechanical signal into an electrical signal. Activities 3. A transmitter is a device that converts a reading from a transducer into a standard signal and transmits that signal to a monitor or controller. For example. a converter used to convert a 4–20 mA current signal into a 3–15 psig pneumatic signal (commonly used by valve actuators) is called a current-to-pressure converter. inside a capacitance pressure device. CO [carbon monoxide].
Components of Control Loops and ISA Symbology Control Loop Equipment and Technology SIGNALS Activities There are three kinds of signals that exist for the process industry to transmit the process variable measurement from the instrument to a centralized control system. Analog signal 3.com . For example. 1 2 3 4 5 Hydraulic signals Digital signals Analog signals Pneumatic signals Electro-magnetic signals 14 Fundamentals of Control www. This signal can be converted to a temperature reading or an input to a control device. and the transmitter is set to produce a 4 mA signal when the process temperature is at 95 °C and a 20 mA signal when the process temperature is at 105 °C. such as a burner fuel valve.PAControl. Pneumatic signalling is still common. The common industry standard pneumatic signal range is 3–15 psig. Analog Signals The most common standard electrical signal is the 4–20 mA current signal. or zero. As the sensor's resistance property changes in response to changes in temperature. a transmitter sends a small current through a set of wires. Pneumatic signal 2. and 20 mA represents the highest possible measurement. the transmitter outputs a 4–20 mA signal that is proportionate to the temperature changes. Other common standard electrical signals include the 1–5 V (volts) signal and the pulse output. 5. 1. The current signal is a kind of gauge in which 4 mA represents the lowest possible measurement. The 3 corresponds to the lower range value (LRV) and the 15 corresponds to the upper range value (URV). since the advent of electronic instruments in the 1960s. Digital signal Pneumatic Signals Pneumatic signals are signals produced by changing the air pressure in a signal pipe in proportion to the measured change in a process variable. imagine a process that must be maintained at 100 °C. The transmitter will transmit a 12 mA signal when the temperature is at the 100 °C setpoint. An RTD temperature sensor and transmitter are installed in the process vessel. With this signal. Identify the signal types that are used in the process control industry? Select all options that apply. the lower costs involved in running electrical signal wire through a plant as opposed to running pressurized air tubes has made pneumatic signal technology less attractive. However.
Some indicators simply display the measured variable. Which of the following are examples of a digital signal? Select all options that apply. operators sometimes need to check a measurement on the factory floor at the measurement point. such as a digital read-out device.com www. An indictor makes this reading possible. INDICATORS While most instruments are connected to a control system.PAControl.) 6. The ___________ is a human-readable device that displays information about the process or the instrument it is connected to. Proprietary protocols are owned by specific companies and may be used only with their permission. An indicator is a human-readable device that displays information about the process. such as diagnostic information. while others have control buttons that enable operators to change settings in the field. (See Module 8: Communication Technologies for more information on digital communication protocols. The methodology used to combine the digital signals is referred to as protocol. Open protocols are those that anyone who is developing a control device can use. DeviceNet. Open digital protocols include the HART® (highway addressable remote transducer) protocol.20 mA 1-5v Fieldbus 3 .Components of Control Loops and ISA Symbology Control Loop Equipment and Technology Digital Signals Activities Digital signals are the most recent addition to process control signal technology. Digital signals are discrete levels or values that are combined in specific ways to represent process variables and also carry other information. FOUNDATION™ Fieldbus. Manufacturers may use either an open or a proprietary digital protocol.15 psig 15 Fundamentals of Control © 2006 PAControl. Profibus.com . 7. 1 2 3 4 5 Profibus 4 . Indicators may be as simple as a pressure or temperature gauge or more complex. and the Modbus® protocol.
or programmable local controller Transmitter Single-loop controller Valve Power supply Controller (CPU) I/O card Controllers 16 Fundamentals of Control © 2006 PAControl. Different recorders display the data they collect differently. electronic. Contollers also commonly reside in a digital control system.Components of Control Loops and ISA Symbology Control Loop Equipment and Technology RECORDERS Activities A recorder is a device that records the output of a measurement devices. electronic or programmable. Many process manufacturers are required by law to provide a process history to regulatory agencies. if necessary.PAControl. By recording the readings of critical measurement points and comparing those readings over time with the results of the process.com www. the process can be improved. and. others create a chart or graph of the readings. A recorder is a device that records the ________________ of a measurement or control device. manufacturers often use recorders to gather data for trend analyses. and manufacturers use recorders to help meet these regulatory requirements. Some recorders list a set of readings and the times the readings were taken. Recorders that create charts or graphs are called chart recorders. compares that data to a programmed setpoint. Computer-based central controller DCS Pneumatic. signals a control element to take corrective action. In addition. CONTROLLERS A controller is a device that receives data from a measurement instrument. Local controllers are usually one of the three types: pneumatic.com . 8.
maintain databases and advanced man-machine-interface. provide readings of the status of the process.PAControl. 9. and produce an output signal? 1 2 3 4 Actuators Transmitters Transducers Controllers Setpoint P I D Analog Rack Mount Controller (Electronic) 10. to perform a mathematical function with the input. The computers are programmed to respond to inputs by sending outputs to maintain all processes at setpoint.Components of Control Loops and ISA Symbology Control Loop Equipment and Technology Controllers may perform complex mathematical functions to compare Activities a set of data to setpoint or they may perform simple addition or subtraction functions to make comparisons. and to produce an output signal. to perform a mathematical function with the input. Distributed control systems (DCSs)—DCSs are controllers that.com . Which of the following have the ability to receive input. Which of the following is the most common final control element in process control industries? Pipestand Controller (Pneumatic or Electronic) 1 2 3 4 Agitator Pump motor Valve Louver Single Loop Digital Converter (Electronic) Distributed Control System (Electronic) Types of Process Controllers Fundamentals of Control © 2006 PAControl.com 17 www. Controllers always have an ability to receive input. Common examples of controllers include: Programmable logic controllers (PLCs)—PLCs are usually computers connected to a set of input/output (I/O) devices. in addition to performing control functions.
hydraulically. springs. the flow of a catalyst into a reactor to control a chemical reaction. solenoids. Diaphragms. hydraulic pilot valves. In most cases. The most common example of an actuator is a valve actuator. 18 Fundamentals of Control © 2006 PAControl. Final control elements are typically used to increase or decrease fluid flow. the speed with which a final control element reacts to correct a variable that is out of setpoint is very important. ACTUATORS An actuator is the part of a final control device that causes a physical change in the final control device when signalled to do so.Components of Control Loops and ISA Symbology Control Loop Equipment and Technology Activities 11. which opens or closes a valve in response to control signals from a controller. or electric motors are often parts of an actuator system. or the flow of air into a boiler to control boiler combustion.PAControl.com www. bellows. louvers (typically used to regulate air flow). a final control element may regulate the flow of fuel to a burner to control temperature. Actuators are often powered pneumatically. and other devices can also be final control elements. gears. the final control element is a valve used to restrict or cut off fluid flow.com . or electrically. but pump motors. _______________ is a part final control device that causes a physical change in the final control device when signaled to do so. pistons. Many of the technological improvements in final control elements are related to improving their response time. For example. In any control loop. Smart Transmitter Digital Valve Controller (Smart Positioner) Smart Transmitter (Provides PID Output) Types of Process Controllers CORRECTING ELEMENTS/FINAL CONTROL ELEMENTS The correcting or final control element is the part of the control system that acts to physically change the manipulated variable.
PAControl. You should be familiar with ISA symbology so that you can demonstrate possible process control loop solutions on paper to your customer. SP Activities 12.com 19 www. Drawings of this kind are known as piping and instrumentation drawings (P&ID). Systems.com . The ISA has developed a set of symbols for use in engineering drawings and designs of control loops (ISA S5.5 shows a control loop using ISA symbology. and Automation Society (ISA) is one of the leading process control trade and standards organizations. Intergral and Derivative control TY 123 YIC 123 TT 123 FT 123 Piping and Instrumentation Drawing (P&ID) Fundamentals of Control © 2006 PAControl.1 instrumentation symbol specification). What does the acronym P&ID stand for? 1 2 3 FIC 123 TIC 123 4 Piping and Instrument Designing Piping and Instrumentation Drawing Process Control and Installation Drawing Proportional. Figure 7.Components of Control Loops and ISA Symbology ISA Symbology The Instrumentation.
com www.Components of Control Loops and ISA Symbology ISA Symbology SYMBOLS In a P&ID. Which of the following is a symbol of a field-mounted control/display element? Control Room Field Not Accessible Flow/ Square Root Shared Control/Display Elements 1 A hexagon represents computer functions. and detectors (Figure 7. a circle represents individual measurement instruments. The absence of a line indicates that the function is field mounted.g. A double line indicates that the function is in an auxiliary location (e. Which of the following is a symbol of a transmitter in an auxiliary location? 1 Control Room Auxiliary Field Not Accessible Figure 7. an instrument rack). located behind a panel board).. LOCATION Activities 13. such as transmitters... a control room).g. and a dotted line indicates that the function or instrument is inaccessible (e.PAControl. DISPLAY AND CONTROL TYPES 2 3 4 14.g. A square with a circle inside represents instruments that both display measurement readings and perform some control function (Figure 7.8).7).6). such as those carried out by a controller (Figure 7. sensors.6: Discrete Instruments A single horizontal line running across the center of the shape indicates that the instrument or function is located in a primary location (e. Many modern transmitters are equipped with microprocessors that perform control calculations and send control output signals to final control elements.com . Control Types 2 3 4 Control Room Auxiliary Field Not Accessible Computer Functions (Controllers) 20 Fundamentals of Control © 2006 PAControl.
Components of Control Loops and ISA Symbology
ISA Symbology
15. Which of the following is a symbol of a controller located behind a panel?
Fundamentals of Control
© 2006 PAControl.com
Components of Control Loops and ISA Symbology
ISA Symbology
A square with a diamond inside represents PLCs (Figure 7.9).
PLC Types
16. The symbol displayed below denotes a PLC in a primary location. Is this statement true or false?
Control Room
Not accessible
Two triangles with their apexes contacting each other (a "bow tie" shape) represent a valve in the piping. An actuator is always drawn above the valve (Figure 7.10).
Pneumatic valve Manual valve Electric valve
17. Which of the following is a symbol of a pneumatic valve?
Pumps Directional arrows showing the flow direction represent a pump (Figure 7.11).
Fundamentals of Control
© 2006 PAControl.com
Components of Control Loops and ISA Symbology
ISA Symbology
Piping and Connections Piping and connections are represented with several different symbols (Figure 7.12): A heavy solid line represents piping A thin solid line represents process connections to instruments (e.g., impulse piping) A dashed line represents electrical signals (e.g., 4–20 mA connections) A slashed line represents pneumatic signal tubes A line with circles on it represents data links Other connection symbols include capillary tubing for filled systems (e.g., remote diaphragm seals), hydraulic signal lines, and guided electromagnetic or sonic signals.
18. The symbols displayed below represent a data link and a process connection. Is this statement true or false?
Process connection
Electrical signal
Pneumatic signal
Data link
Capillary tubing for filled systems
Hydraulic signal line
Guided electromagnetic or sonic signal
Piping and Connection Symbols
Fundamentals of Control
© 2006 PAControl.com
g.. Often these numbers are associated with a particular control loop (e.com .. Activities 19.13. TT for temperature transmitter) indicate: The variable being measured (e. "PT" represents a pressure transmitter. temperature) The device's function (e.g. switch.g.org. readout.isa.. The initial letter on an ISA symbol indicates the measured variable.PAControl. transmitter. multifunction) Table 7.1 on page 26 shows the ISA identification letter designations. valve. The third letter usually indicates either a device function or a modifier. See Figure 7. indicator) Some modifiers (e. or device function.. Is this statement true or false? 20. pressure.g.com 24 www.g. For example. low.Components of Control Loops and ISA Symbology ISA Symbology IDENTIFICATION LETTERS Identification letters on the ISA symbols (e. flow. high. The second letter indicates a modifier. What does the third letter on an ISA symbol indicate? TAG NUMBERS Numbers on P&ID symbols represent instrument tag numbers. Identification letters 1 2 3 4 Device function or a modifier Measured variable Readout Type of process fluid FIC 123 Tag number Identification Letters and Tag Number Fundamentals of Control © 2006 PAControl. sensor. You can find identification letter symbology information on the ISA Web site at http://www. The initial letter indicates the measured variable.. flow transmitter 123). "FIC" on an instrument tag represents a flow indicating controller.
viewing device H Hand High I Electrical Current Indication J Power Scan K Time.PAControl. force Well X Unclassified X axis Unclassified Unclassified Unclassified Y Event. louver W Weight. time schedule Time rate of change Control station L Level Light Low M User's choice Momentary Middle. actuator ISA Identification Letters 25 Fundamentals of Control © 2006 PAControl. vacuum Point. test connection Q Quantity Integrate. convert Z Position. state. or presence Y axis Relay. intermediate N User's choice User's choice User's choice User's choice O User's choice Orifice.Components of Control Loops and ISA Symbology ISA Symbology Measured Variable Modifier Readout Device Function Modifier Activities A Analysis Alarm B Burner.com www. damper. restriction P Pressure. combustion User's choice User's choice User's choice C User's choice Control D User's choice Differential E Voltage Sensor (primary element) F Flow rate Ration (fraction) G User's choice Glass. dimension Z axis Driver. compute. frequency Safety Switch T Temperature Transmit U Multivariable Multifunction Multifunction Multifunction V Vibration.com . mechanical analysis Valve. totalizer R Radiation Record S Speed.
com .COMPONENTS OF CONTROL LOOPS AND ISA SYMBOLOGY Fundamentals of Control © 2006 PAControl. signal is transmitted out from the temperature transmitter? FIC 123 SP Data link Electrical signal 1 2 3 TIC 123 PLC 4 Data link Mechanical signal Electrical signal Pneumatic signal Flow transmitter Temperature computer TY 123 YIC 123 Pneumatic line FT 123 Impulse Tubing Pipe TT 123 Temperature transmitter Pneumatically actuated valve Electrically actuated valve P&ID with ISA Symbology COMPLETE WORKBOOK EXERCISE . what kind of .14. Flow indicating controller that performs a square root flow calculation (primary location) Activities Temperature indicating controller (field mounted) 21. In Figure 7.com 26 www.Components of Control Loops and ISA Symbology ISA Symbology ISA SYMBOLOGY REVIEW Figure 7.14 shows the elements of ISA symbology used in a P&ID.PAControl.
Controller Algorithms and Tuning The previous sections of this module described the purpose of control. LEARNING OBJECTIVES After completing this section. Describe the basic mechanism. The strategies used to hold a process at setpoint are not always simple. you will be introduced to some of the strategies and methods used in complex process control loops. multistep. and the interaction of numerous setpoints in an overall process control plan can be subtle and complex. Identify the basic implementation of P. and demonstrated the symbology used to represent those elements in an engineering drawing.com . and continuous controllers Describe the general goal of controller tuning. defined individual elements within control loops.com 27 www. you will be able to: Differentiate between discrete. advantages and disadvantages of the following mode of controller action: • Proportional action • Intergral action • Derivative action Give examples of typical applications or situations in which each mode of controller action would be used. Fundamentals of Control © 2006 PAControl.PAControl. PI and PID control in the following types of loops: • Pressure loop • Flow loop • Level loop • Temperature loop Note: To answer the activity questions the Hand Tool (H) should be activated. control loops can be fairly complex. In this section. The examples of control loops used thus far have been very basic. In practice.
Refrigerator Electric iron Air conditioner Rice cooker Dead zone Process variable action Control action Discrete Control 28 Fundamentals of Control © 2006 PAControl. A common example of a discrete controller is a home hot water heater.15). Grouped by control mechanism function. 1 2 3 4 DISCRETE CONTROLLERS Discrete controllers are controllers that have only two modes or positions: on and off. This type of control doesn't actually hold the variable at setpoint.com www. the burner turns on.Controller Algorithms and Tuning Controller Algorithms The actions of controllers can be divided into groups based upon the functions of their control mechanism.com .PAControl. the three types of controllers are: Discrete controllers Multistep controllers Continuous controllers Activities 1. the burner turns off. it is only a matter of time before the cycle begins again. Each type of contoller has advantages and disadvantages and will meet the needs of different applications. Because the water starts cooling again when the burner turns off. When the water in the tank reaches setpoint. Which one of the following is an everyday example of a discrete controller? Select the options that apply. but keeps the variable within proximity of setpoint in what is known as a dead zone (Figure 7. When the temperature of the water in the tank falls below setpoint.
PAControl. Activities 2.com 29 www. A controller with three or more set positions is called a continuous controller. the multistep controller takes intermediate steps. If there is an error. Therefore. but as setpoint is approached. Fundamentals of Control © 2006 PAControl. Multistep controllers operate similarly to discrete controllers. the oscillation around setpoint can be less dramatic when multistep controllers are employed than when discrete controllers are used (Figure 7. Is this statement true or false? Process variable action Control action Figure 7.Controller Algorithms and Tuning Controller Algorithms MULTISTEP CONTROLLERS Multistep controllers are controllers that have at least one other possible position in addition to on and off. The tuning parameters essentially determine: How much correction should be made? The magnitude of the correction( change in controller output) is determined by the proportional mode of the controller.16: Multistep Control Profile CONTINUOUS CONTROLLERS Controllers automatically compare the value of the PV to the SP to determine if an error exists.16). How long should the correction be applied? The duration of the adjustment to the controller output is determined by the integral mode of the controller How fast should the correction be applied? The speed at which a correction is made is determined by the derivative mode of the controller.com . the controller adjusts its output according to the parameters that have been set in the controller.
com .Controller Algorithms and Tuning Controller Algorithms When there is an error.com 30 www.PAControl. It determines: How much? Proportional Mode How long? Integral Mode How fast? Derivative Mode Setpoint LIC I/P P I D SP PV Activities Controller LT PV SP Load Automatic Feedback Control Fundamentals of Control © 2006 PAControl. the controller makes a change in its output.
10% Change in Controller Output . cause sufficient change in valve position to eliminate error. transmitters.PAControl.com www. The change in the controller output divided by the change in the input to the controller is known as __________ . and signals in greater detail so you can understand the importance of electricity in process control. In particular. The next three sections in this module discuss electricity.20% Gain = 20% / 10% = 2 Change in Input to Controller . circuits. 31 Fundamentals of Control © 2006 PAControl.Controller Algorithms and Tuning Why Controllers Need Tuning? Controllers are tuned in an effort to match the characteristics of the control equipment to the process so that two goals are achieved: is the foundation of process control measurement in that electricity: The system responds quickly to errors.5 convey measurements and instructions to other instruments in a control loop to maintain the highest level of safety and efficiency.5% Gain = 5% / 10% = 0. 3. but not so great a change as to cause instability or cycling.com . The system remains stable (PV does not oscillate around the SP). Gain is defined simply as the change in output divided by the change in input. we are interested in adjusting the gain of the controller such that a change in controller input will result in a change in controller output that will.10% Change in Controller Output . in turn. Examples: Change in Input to Controller . Activities GAIN Controller tuning is performed to adjust the manner in which a control valve (or other final control element) responds to a change in error.
Is this statement true or false? Output % 50 Gain=0. LIC I/P LIC I/P LT LT Controllers May be Tuned to Help Match the Valve to the Process Fast Process May Require Less Gain To Achieve Stability Small volume liquid process Slow Process May Require Higher Gain To Achieve Responsiveness Large volume gas process Fast and Slow Processes May Require Different Controller Gain Settings 32 Fundamentals of Control © 2006 PAControl.com . Gain Kc =∆ Output % / ∆ Input % 100 Gain=2 Gain=1 Activities 4. Fast or slow processes have no impact on controller gain settings.5 0 0 50 100 Input % Graphical Representaion of Gain Concept Examples .PAControl.Controller Algorithms and Tuning Why Controllers Need Tuning? Gain Plot .The Figure below is simply another graphical way of representing the concept of gain.com www.The following examples help to illustrate the purpose of setting the controller gain to different values.
Controller Algorithms and Tuning Proportional Mode PROPORTIONAL ACTION The proportional mode is used to set the basic gain value of the controller.PAControl. (Kc) = ∆Output% / ∆Input % PB= ∆Input(%Span) For 100%∆Output 33 Fundamentals of Control © 2006 PAControl. Proportional Gain (Kc) answers the question: "What is the percentage change of the controller output relative to the percentage change in controller input?" Proportional Gain is expressed as: Gain. (Kc) = ∆Output% /∆Input % PROPORTIONAL BAND Proportional Band (PB) is another way of representing the same information and answers this question: "What percentage of change of the controller input span will cause a 100% change in controller output?" PB = ∆Input (% Span) For 100%∆Output Tends to leave an offset Reset Windup during shutdown Possible overshoot during startup Can cause cycling in fast process by amplifying noisy signals Converting Between PB and Gain A simple equation converts gain to proportional Band: added. Proportional Gain 2. PB = 100/Gain Also recall that: Gain = 100%/PB Proportional Gain.com www.com . Identify the major disadvantage of proportional action. Proportional Band Activities 5. The setting for the proportional mode may be expressed as either: 1. proportional action is typically expressed as proportional gain. 1 2 3 4 PROPORTIONAL GAIN In electronic controllers.
If proportional gain is 0. DETERMINING THE CONTROLLER OUTPUT Controller Output . the output will change as follows: Calculating Controller Output ∆Controller Output = ∆Input.5 / 5> % of its full range.com . however. % = (Error Change. Output % 50 0 0 50 100 150 200 Input % Relationship of Proportional Gain and Proportional Band LIMITS OF PROPORTIONAL ACTION Responds Only to a Change in error . Output Change.Proportional action will not return the PV to setpoint.PAControl.Proportional action responds only to a change in the magnitude of the error. Does Not Return the PV to Setpoint . the output is a function of the change in error and controller gain. so Gain = 100%/50% = 2 34 Fundamentals of Control © 2006 PAControl.com www. %) (Gain) Example: If the setpoint is suddenly changed 10% with a proportional band setting of 50%.5. % X Gain Gain = 100%/PB EXAMPLE ∆Input = 10% PB = 50%. return the PV to a value that is within a defined span (PB) around the PV.In a proportional only controller.Controller Algorithms and Tuning Proportional Mode Gain=2 100 PB= 50% Gain=1 PB=100% Gain=0. and a level reading is 5% above setpoint. It will. a proportional controller will signal the outflow control valve to open by <1 / 2.5 PB=200% Activities 6.
CLOSED LOOP Loop Gain .2)(12 psi span) = 2.2)(16 mA span) = 3.In the example.Controller Algorithms and Tuning Proportional Mode ∆Controller Output = ∆ Input X Gain ∆Controller Output = 10% X 2 = 20% Expressed in Units: Controller Output Change = (0. Low Gain Example . The loop is very stable.com www.PAControl.e. This critical frequency is determined by all of the loop components. This is the frequency at which cycling may exist. 10 9 8 7 % 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 PB= 200% Time IVP PV SP Proportional Control Closed Loop . the proportional band is small resulting in high gain. the PV will cycle around the SP.In the example below.com .2 mA Activities PROPORTIONAL ACTION .Every loop has a critical or natural frequency..4 psi OR (0. but an error remains between SP and PV. If the loop gain is too high at this frequency. 35 Fundamentals of Control © 2006 PAControl. i. Notice that the process variable is still not on set point.Low Gain Example High Gain Example . the process will become unstable. the proportional band is high (gain is low). which is causing instability.
High Gain example Proportional Summary . 36 Fundamentals of Control © 2006 PAControl. Proportional band is expressed in terms of the percentage change in error that will cause 100% change in controller output. Proportional gain is expressed as the percentage change in output divided by the percentage change in input.Simple Disadvantages .For the proportional mode. % / ∆Output. What will be the result if the proportional gain is set too high? Select all options that apply. 1 2 3 4 Large offset Minimized offset Possible cycling Stable loop Proportional Control Closed Loop .Controller Algorithms and Tuning Proportional Mode 10 9 8 7 SP 6 %5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 PB=10% TIME PV IVP Activities 7.com . % ) x 100 = 100/Gain Gain= ∆Input % / ∆Output % ∆ Controller Output = (Change in Error)(Gain) 1. Proportional mode alone will not return the PV to SP.Error Settings . controller output is a function of a change in error.PB settings have the following effects: Small PB (%) High Gain (%) Large PB (%) Low Gain Minimize Offset Possible cycling Large Offset Stable Loop Tuning . PB = (∆Input.reduce PB (increase gain) until the process cycles following a disturbance. Advantages .PAControl.com www. then double the PB (reduce gain by 50%). Proportional Mode Responds only to a change in error 2.
PAControl.The purpose of integral action is to return the PV to SP. or reset action. Minutes Per Repeat . 37 Fundamentals of Control © 2006 PAControl.com www. the integral or reset mode is always used with the proportional mode.Another component of error is the duration of the error.How many minutes are required for 1 repeat to occur.. INTEGRAL(RESET) OPEN LOOP ANALYSIS Purpose. This is accomplished by repeating the action of the proportional mode as long as an error exists. _____________ action is the type of control algorithm that eliminates offset. how long has the error existed? The controller output from the integral or reset mode is a function of the duration of the error.e. may be expressed in terms of: Repeats Per Minute . i.Integral.com .How many times the proportional action is repeated each minute. Setting .Controller Algorithms and Tuning Integral Mode INTEGRAL ACTION Duration of Error and Integral Mode . With the exception of some electronic controllers. 100 90 80 70 60 % 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 SP Duration PV Activities 8.
The faster the reset action. 100 90 80 70 60 50 % 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 IVP PB=80% Repeat=10 Repeats/min TIME 10 PV SP FAST RESET. 1 Repeats per setting Notice thatthe process variable does reach set point due to the reset 2 Repeats per minute action. Select all options that apply.PAControl. CLOSED LOOP 38 Fundamentals of Control © 2006 PAControl. 3 Repeats per loop 100 4 Minutes per repeat 90 80 70 60 % 40 50 PV SP 30 20 10 0 PB=80% Repeat=2. the greater terms of? the gain.com .In the example the rest is too fast and the PV is cycling around the SP.Controller Algorithms and Tuning Integral Mode CLOSED LOOP ANALYSIS Activities Closed Loop With Reset . CLOSED LOOP Fast Reset Example .In this example the loop is stable because the total loop gain is not too high at the loop critical frequency. Slow Reset Example . Which of the following are integral or reset actions expressed in gain component to the loop.0 Repeats/min TIME 0 1 2 3 4 5 6 7 8 9 10 IVP SLOW RESET.com www.Adding reset to the controller adds one more 9.
Select all options that apply. 1 2 3 4 Output% IVP ARW Tends to leave an offset Reset windup during shutdown Possible overshoot during start up Can cause cycling in fast process by amplifying noisy signals 0 INPUT(ERROR) Reset Windup .Shutdown and Startup Startup .Ant-Reset Windup Shutdown .Reset windup is common on shut down because the process variable may go to zero but the set point has not changed. Identify the major disadvantages of integral action.At start up. 100 SP Input % PV ARW 0 Shutdown Input(Error) Startup Reset Windup . 100 Activities 10.PAControl.Reset windup is described as a situation where the controller output is driven from a desired output level because of a large difference between the set point and the process variable. Anti Reset Windup .com www. therefore this large error will drive the output to one extreme.Controllers can be modified with an anti-reset 39 Fundamentals of Control © 2006 PAControl.com .Controller Algorithms and Tuning Integral Mode RESET WINDUP Defined . large process variable overshoot may occur because the reset speed prevents the output from reaching its desired value fast enough.
Stable Loop Trailing and Error Tuning .Small Min. then slow the reset action to a value that is 1/3 of the initial setting../Repeat) 2.Fast Return To Setpoint 3.Increase repeats per minute until the PV cycles following a disturbance. Activities SUMMARY Integral (Reset) Summary .com www./Repeats) 2. The purpose of an anti-reset option is to allow the output to reach its desired value quicker. Advantages .Reset windup and possible overshoot Fast Reset 1.com . 40 Fundamentals of Control © 2006 PAControl..Eliminates error Disadvantages . The units are in terms of repeats per minute or minutes per repeat.PAControl.Large Min.Slow Return To Setpoint 3.Low Gain (Small Repeats/Min.Controller Algorithms and Tuning Integral Mode windup (ARW) device.High Gain (Large Repeats/Min.Output is a repeat of the proportional action as long as error exists.Possible Cycling Slow Reset 1. therefore minimizing the overshoot.
In oper ation. Activities 11. 1 Repeats per minute 100 Hours 2 90 Seconds 3 80 Slope= Rate of Error Change(Y/X) Minutes 4 70 5 Milliseconds 60 50 % 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 TIME Y X PV SP Derivative Action is based on the rate of change in Error (Y/X) 41 Fundamentals of Control © 2006 PAControl.com www. Which of the following are derivative or etermines what its output would be at a future point in time rate actions expressed in terms of? (the future point in time is determined by the value of the derivative setting. The magnitude of the derivative action is determined by the setting of the derivative . a large initial change in controller output may be applied.Controller Algorithms and Tuning Derivative Mode DERIVATIVE ACTION Derivative Mode Basics . To improve response. The mode of a PID controller and the rate of change of the PV. the controller 12. The derivative action is initiated whenever there is a change in the rate of change of the error (the slope of the PV).com . the the controller first compares the current PV with the last value of the PV. For example. If there is a change in the slope of the PV. The Derivative setting is expressed in terms of minutes. in minutes).PAControl. The derivative mode immediately increases the output by that amount. ___________ action is a control algorithm that is tied to the rate of change in the error. a large liquid level process or a large thermal process (a heat exchanger) may react very slowly to a small change in controller output. This action is the role of the derivative mode.Some large and/or slow process do not respond well to small changes in controller output.
which in a step is nearly infinite.Let's start a closed loop example by looking at a temperature control system.To illustrate the effect of rate action. The output spike is the result of rate action. the PV never becomes equal to the SP because there is no reset. Recall that the change in output due to rate action is a function of the speed (rate) of change of error.Controller Algorithms and Tuning Derivative Mode Example . There is no reset at this time. Is this statement true or false? 100 IVP 90 80 70 PV 60 50 40 30 20 10 0 0 100 200 300 400 PB=50% Reset=0 Rate=1 min TIME PV SP No Rate.com www.com . Small Rate examples. Rate Effect . in this example. IN this example. Closed Loop 42 Fundamentals of Control © 2006 PAControl. The addition of derivative or rate alone to a close loop control can cause the process variable to match the set point. Assume a proportional band settingof 50%. 100 90 80 70 60 50 40 30 20 10 0 0 100 200 300 400 PB=50% Reset=0 Rate=0 TIME PV SP IVP Activities 13.PAControl. The proportional gain of 2 acting on a 10% change in set pint results in a change in controller output of 20%. we will add the are mode with a setting of 1 minute. the time scale has been lengthened to help illustrate controller actions in a slow process. Because temperature is a slow process the setting time after a change in error is quite long. The addition of rate alone will not cause the process variable to match the set point. Notice the very large controller output at time 0. And.
It is now clear that reset must be added to bring process variable back to set point. especially digital types. are designed to respond to changes in the PV only. As a result.com www. 100 90 80 70 60 50 40 30 20 10 0 PB= 50% Reset=0 Rate= 10 min 0 100 200 300 400 PV SP IVP Activities TIME P+D. 43 Fundamentals of Control © 2006 PAControl.PAControl. both the IVP (controller output) and the PV are cycling.Many controllers. This feature eliminates a major upset upset that would occur following a change in the setpoint. the output will be very erratic if rate is used on fast process or one with noisy signals.Let's now increase the rate setting to 10 minutes. Controller Option to Ignore Change in SP . The point here is that increasing the rate setting will not cause the PV to settle at the SP. will have the greatest change when the input changes rapidly. and to ignore changes in SP. The controller gain is now much higher. The controller output.com .Controller Algorithms and Tuning Derivative Mode Effect of Fast Rate .Because this component of the controller output is dependent on the speed of change of the input or error. Applications . Closed Loop Analysis Need for Reset Action . High Rate Setting. as a result of rate.
Rate action is a function of the speed of change of the error. The units are minutes.Rapid output reduces the time that is required to return PV to SP in slow process.Controller Algorithms and Tuning Derivative Mode SUMMARY Derivative (Rate) Sumary . Settings Large (Minutes) 1.Large Output Change 3.PAControl.com .Low Gain 2. Advantages .Stable Loop Activities Small (Minutes) Trial-and-Error Tuning Increase the rate setting until the process cycles following a disturbance.Dramatically amplifies noisy signals. The action is to apply an immediate response that is equal to the proportional plus reset action that would have occurred some number of minutes I the future.High Gain 2. Disadvantage .com www. then reduce the rate setting to one-third of the initial value. can cause cycling in fast processes.Possible Cycling 1.Small Output Change 3. 44 Fundamentals of Control © 2006 PAControl.
Controlled Variable Activities 14. process operators can: Achieve rapid response to major disturbances with derivative control Hold the process near setpoint without major fluctuations with proportional control Eliminate offset with integral control Not every process requires a full PID control strategy. PI.com . What type of control is used in an application where noise is present.Controller Algorithms and Tuning Controller Algorithms Proportional.PAControl. Table 7.2 shows common types of control loops and which types of control algorithms are typically used. PI control is used where no offset can be tolerated. and PID Control By using all three control algorithms together.2: Control Loops and Control Algorithms COMPLETE WORKBOOK EXERCISE . and where dead time is an issue.com 45 www. and where excessive dead time (time after a disturbance before control action takes place) is not a problem. then proportional control alone may be sufficient.CONTROLLER ALGORITHMS AND TUNING Fundamentals of Control © 2006 PAControl. customers can use full PID control. where noise (temporary error readings that do not reflect the true process variable condition) may be present. In processes where no offset can be tolerated. no noise is present. but where no offset can be tolerated? 1 2 3 4 P only PD PI PID Proportional Control PI Control PID Control Flow Yes Yes No Level Yes Yes Rare Temperature Yes Yes Yes Pressure Yes Yes Rare Analytical Yes Yes Rare Table 7. If a small offset has no impact on the process.
noise) • Identify typical equipment requirements • Diagram the loop using ISA symbology Explain the basic implementation process.PAControl. and temperature): • State the type of control typically used and explain why it is used • Identify and describe considerations for equipment selection (e.g. benefits. LEARNING OBJECTIVES After completing this section. and each variable can have an impact on the entire system. for each of the following types of control: • Cascade control • Batch control • Ratio control • Selective control • Fuzzy control Describe benefits and limitations of each type of control listed above Give examples of process applications in which each type of control described in this section might be used Note: To answer the activity questions the Hand Tool (H) should be activated. pressure. and limitations Perform the following functions for each type of standard process control loop (i. including a description of equipment requirements and considerations.com 46 www. design. level.. you will be able to: Explain how a multivariable loop is different from a single loop.e. Fundamentals of Control © 2006 PAControl. control systems must be designed to respond to disturbances at any point in the system and to mitigate the effect of those disturbances throughout the system. Because in some processes many variables must be controlled. Differentiate feedback and feedforward control loops in terms of their operation. speed. flow. you will learn about how control components and control algorithms are integrated to create a process control system.Process Control Loops In this section.com ..
What type of control loop takes action in response to measured deviation from setpoint? FEEDBACK CONTROL A feedback loop measures a process variable and sends the measurement to a controller for comparison to setpoint.com . the speed drops below setpoint and the controller adjusts the throttle to return the car's speed to setpoint.18 illustrates a feedback loop in which a transmitter measures the temperature of a fluid and. Activities 1. if necessary. 1 2 3 4 Discrete control loop Multi-step control loop Open loop Feedback control loop Controller Process fluid Steam valve Transmitter Feedback Loop An everyday example of a feedback loop is the cruise control system in an automobile. Feedback loops are commonly used in the process control industry.PAControl.com. A setpoint is established for speed. If the process variable is not at setpoint. When the car begins to climb a hill. 47 Fundamentals of Control © 2006 PAControl. opens or closes a hot steam valve to adjust the fluid's temperature. www. Figure 7. control action is taken to return the process variable to setpoint.Process Control Loops Single Control Loops Control loops can be divided into two categories: Single variable loops and multi-variable loops. The disadvantage to feedback loops is that the process variable must leave setpoint for action to be taken. The advantage of a feedback loop is that it directly controls the desired process variable.
. How does a high-volume pressure control loop react as compared to a small-volume pressure control loop? 1 2 3 4 Same rate Quicker Slower Extremely fast Relief valve Pressure transmitter Process fluid Fluid pump A Pressure Loop Fundamentals of Control © 2006 PAControl. The speed required in a pressure control loop may be dictated by the volume of the process fluid. level.21). large natural gas storage facilities) tend to change more slowly than low-volume systems (Figure 7.com .com 48 www. PRESSURE CONTROL LOOPS Pressure control loops vary in speed—that is. flow. some general Activities statements can be made about pressure.PAControl. and temperature loops. they can respond to changes in load or to control action slowly or quickly. Pneumatic controller 2. High-volume systems (e.g.Process Control Loops Examples of Single Control Loops While each application has its own characteristics.
www. flow control equipment must have fast sampling and response times. filters are added between the transmitter and the control system. Sometimes. many flow transmitters have a damping function that filters out noise. Flow control loops are generally considered to be slow responding loops.22).com . a transmitter. flow control loops are regarded as fast loops that respond to changes quickly.Process Control Loops Examples of Single Control Loops FLOW CONTROL LOOPS Activities Generally. Pneumatic controller 3. temperature measurements are often taken with flow measurements and compensation for temperature is accounted for in the flow calculation. Is this statement true or false? Flow transmitter Valve Process fluid Fluid pump A Flow Loop 49 Fundamentals of Control © 2006 PAControl.com. Therefore. Because flow transmitters tend to be rather sensitive devices. they can produce rapid fluctuations or noise in the control signal. and a valve or pump are used in flow control loops (Figure 7. To compensate for noise. Typically.PAControl. a controller. Because the temperature of the process fluid affects its density. a flow sensor.
Manufacturers may use one of many different measurement technologies to determine level. ultrasonic. and pressure measurement.g. Redundant control systems are sometimes used in level applications because preventing tank overflow is often critically important. float gauge. redundant level control systems are sometimes employed.com . larger vessels take longer to fill than smaller ones) and the flow rate of the input and outflow pipes.com 50 www.23). Converter Level controller 4.PAControl. including radar.. The final control element in a level control loop is usually a valve on the input and/or outflow connections to the tank (Figure 7. Because it is often critical to avoid tank overflow.Process Control Loops Examples of Single Control Loops Activities LEVEL CONTROL LOOPS The speed of changes in a level control loop largely depends on the size and shape of the process vessel (e. Is this statement true or false? Differential pressure transmitter A Level Loop Fundamentals of Control © 2006 PAControl.
cool process fluid is added to the mix to maintain temperature (Figure 7. Temperature transmitters and controllers are used. although it is not uncommon to see temperature sensors wired directly to the input interface of a controller. temperature loops tend to be relatively slow. Controller 5.com www. RTDs or thermocouples are typical temperature sensors.24). Sometimes. The final control element for a temperature loop is usually the fuel valve to a burner or a valve to some kind of heat exchanger. Feedforward control strategies are often used to increase the speed of the temperature loop response. What type of control strategy is often used to increase the speed of a temperature control loop? 1 2 3 4 Feedforward control Feedback control Cascade control Ratio control Process fluid Valve Temperature transmitter A Temperature Loop 51 Fundamentals of Control © 2006 PAControl.Process Control Loops Examples of Single Control Loops TEMPERATURE CONTROL LOOPS Activities Because of the time required to change the temperature of a process fluid.com .PAControl.
PAControl. 6. 52 Fundamentals of Control © 2006 PAControl. For example.Process Control Loops Multi-Variable / Advanced Control Loops MULTIVARIABLE LOOPS Activities Multivariable loops are control loops in which a primary controller controls one process variable by sending signals to a controller of a different loop that impacts the process variable of the primary loop. Tuning the primary loop will not impact the secondary loop tuning.17). the primary (master) controller signals the secondary (slave) controller that is controlling steam pressure. The primary controller will manipulate the setpoint of the secondary controller to maintain the setpoint temperature of the primary process variable (Figure 7. To control the primary variable (temperature).com www. it is important to take into account the presence of multivariable loops. the primary process variable may be the temperature of the fluid in a tank that is heated by a steam jacket (a pressurized steam chamber surrounding the tank). . A multivariable control loop contains a primary and secondary controller assigned to different process variables? Is this statement true or false? Primary controller Transmitter SP Transmitter Secondary controller Valve Multivariable Loop When tuning a control loop. The standard procedure is to tune the secondary loop before tuning the primary loop because adjustments to the secondary loop impact the primary loop.com .
feedforward systems should be used in cases where the controlled variable has the potential of being a major load disturbance on the process variable ultimately being controlled. it is difficult to account for all possible load disturbances in a system through feedforward control. However.com . rather than corrected.com 53 www.19 shows a feedforward loop in which a flow transmitter opens or closes a hot steam valve based on how much cold fluid passes through the flow sensor. Figure 7. In general.PAControl. the user must have a mathematical understanding of how the manipulated variables will impact the process variable. consistency of raw materials. Flow transmitter 7. and moisture content can all become load disturbances and cannot always be effectively accounted for in a feedforward system. buildup in pipes. For feedforward control to work. What type of control loop anticipates and controls load disturbances before they can impact the process variable? 1 2 3 4 Controller Feedback control loop Feedforward control loop Ratio control loop Single variable loop Cold process fluid Steam valve Feedforward Control An advantage of feedforward control is that error is prevented. Fundamentals of Control © 2006 PAControl. Factors such as outside temperature. The added complexity and expense of feedforward control may not be equal to the benefits of increased control in the case of a variable that causes only a small load disturbance. humidity.Process Control Loops Multi-Variable / Advanced Control Loops Activities FEEDFORWARD CONTROL Feedforward control is a control system that anticipates load disturbances and controls them before they can impact the process variable.
and send a unified signal to the final control element. This is how a single control signal is sent to the final control element in a feedforward plus feedback system. Controllers with summing functions are used in these combined systems to total the input from both the feedforward loop and the feedback loop. Figure 7.com. A controller with a summing function totals the input from both the feedforward loop and the feedback loop and sends a unified signal to the final control element. Feedforward controller 8. www.com .PAControl. feedforward systems are often combined with feedback systems. Is this statement true or false? Summing controller Feedback controller Flow transmitter Process fluid Steam valve Temperature transmitter Feedforward Plus Feedback Control System 54 Fundamentals of Control © 2006 PAControl.20 shows a feedforward-plus-feedback loop in which both a flow transmitter and a temperature transmitter provide information for controlling a hot steam valve.Process Control Loops Multi-Variable / Advanced Control Loops FEEDFORWARD PLUS FEEDBACK Activities Because of the difficulty of accounting for every possible load disturbance in a feedforward system.
what Activities components are used in them. flow. Is this statement true or false? CASCADE CONTROL Cascade control is a control system in which a secondary (slave) control loop is set up to control a variable that is a major source of load disturbance for another primary (master) control loop.PAControl. This section will acquaint you with some of the methods of control currently being used in process industries. temperature) they are applied to. 9.com . Ratio control is the term used to describe a system in which the controller of the primary loop determines the setpoint of a secondary loop. pressure.25). many independent and interconnected loops are combined to control the workings of a typical plant. Secondary controller Primary controller Process fluid Temperature transmitter Flow transmitter Valve Cascade Control Fundamentals of Control © 2006 PAControl. however.g.Process Control Loops Multi-Variable / Advanced Control Loops This module has discussed specific types of control loops. The controller of the primary loop determines the setpoint of the summing contoller in the secondary loop (Figure 7. In practice..com 55 www. and some of the applications (e.
pressure. it is not practical to have a continuous process running. control instruments may need to be recalibrated.26).PAControl. For example. For these reasons. typically. 10. The controller performs a ratio calculation and signals the appropriate setpoint to another controller that sets the flow of the second fluid so that the proper proportion of the second fluid can be added. Ratio control is used in many applications and involves a contoller that receives input from a flow measurement device on the unregulated (wild) flow. If a tank has an acid supply on one side of a mixing vessel and a water supply on the other. flow. A disadvantage of batch control is that the process must be frequently restarted. a limited amount of one flavor (e.g.g. Another disadvantage is that as recipes change. even though the water supply itself may not be controlled..Process Control Loops Multi-Variable / Advanced Control Loops BATCH CONTROL Activities Batch processes are those processes that are taken from start to finish in batches. Ratio control might be used where a continuous process is going on and an additive is being put into the flow (e. a control system could be developed to control the ratio of acid to water. mixing the ingredients for a juice drinks is often a batch process. all measurements in the system are below setpoint at start-up. Level. chlorination of water). and often mass measurements are used at various stages of batch processes. temperature. This type of control system is called ratio control (Figure 7.com . Which term describes a control system in which controlled flow is added proportionately to an uncontrolled flow? 1 2 3 4 Selective control Cascade control Ratio control Fuzzy control RATIO CONTROL Imagine a process in which an acid must be diluted with water in the proportion two parts water to one part acid.com www. orange drink or apple drink) is mixed at a time. Start-up presents control problems because. Batch processes often involve getting the correct proportion of ingredients into the batch. Typically. Water flow Acid flow Ratio Control 56 Fundamentals of Control © 2006 PAControl..
com . then uncombusted fuel can build up in the boiler and cause an explosion. 11. but none of the responsibility.Process Control Loops Multi-Variable / Advanced Control Loops Activities SELECTIVE CONTROL Selective control refers to a control system in which the more important of two variables will be maintained. Selective control is used to allow for an air-rich mixture. Fuzzy control is a relatively new technology. For example. but never a fuel-rich mixture. COMPLETE WORKBOOK EXERCISE . adjust the process. fuzzy control removes from operators some of the ability. to control a process. Fuzzy control Cascade control Ratio control Selective control 12. Fuzzy logic is a form of computer logic where whether something is or is not included in a set is based on a grading scale in which multiple factors are accounted for and rated by the computer. formulate a theory of how to make improvements. and learn from the result. if fuel flow outpaces air flow.PROCESS CONTROL LOOPS Fundamentals of Control © 2006 PAControl. Selective control is most often used when equipment must be protected or safety maintained. The essential idea of fuzzy control is to create a kind of artificial intelligence that will account for numerous variables.com 57 www. ___________ control is the term used to describe a control system in which the controller uses computer logic to make decisions about adjusting the process. even at the cost of not maintaining an optimal process variable setpoint.PAControl. In which type of control system will the more important of two variables be maintained? 1 2 3 4 FUZZY CONTROL Fuzzy control is a form of adaptive control in which the controller uses fuzzy logic to make decisions about adjusting the process. in a boiler control system. Because a machine makes process control changes without consulting humans.
Helps ensure increase in efficiency of the process. Which of the following are advantages of reducing variability in a process application? (1) (2) (3) (4) Helps ensure a consistently high-quality end product. Is this statement true or false? (1) (2) True False 3. Helps ensure an increase in the reaction rate of the process.Module 7: Workbook Exercises EXERCISE 7.com www. Process is defined as the method of changing or refining raw materials to create end products. Helps ensure safety Page 58 Workbook Exercises © 2006 PAControl.1— THE IMPORTANCE OF PROCESS CONTROL 1.PAControl. Which of the following options best represents the reasons to control a process? (Select three options that apply) (1) (2) (3) (4) (5) Reduce variability Increase productivity Increase efficiency Reduce cost Ensure safety 2.com .
Which of the following variables are commonly measured or monitored in process control applications? (Select three options that apply) (1) (2) (3) (4) (5) Pressure Viscosity Nitrogen content Flow rate Temperature 3.Module 7: Workbook Exercises EXERCISE 7. A pressure transmitter monitors the liquid's level using a pressure reading and sends the result to a controller. The controller compares the level reading to the set point and opens or closes an inflow or outflow pipe depending on the liquid level. Which of the following tasks is associated with process control? (Select three options that apply) (1) (2) (3) (4) (5) Measurement Comparison Quality Analysis Adjustment Calculation 2.2 — CONTROL THEORY BASICS 1.com . A process liquid level needs to be held within 5 ft of 150 ft in a large tank. Keeping in mind the given scenario. (1) (2) (3) (4) Inferred process variable Manipulated variable Measured variable Set point (A) (B) (C) (D) 150 ft Pressure Flow of liquid to the tank Level Workbook Exercises © 2006 PAControl.PAControl. match the terms in Column A with their values in Column B.com Page 59 www.
A temperature sensor measures process temperature. automatic control _____ _____ _____ An operator turns off the heater coil when the temperature transmitter outputs a certain reading. (1) (2) (3) Load disturbance Offset Pressure Page 60 Workbook Exercises © 2006 PAControl. An undesired change in a factor that can affect the process variable. automatic control Closed-loop. A mathematical expression of a control function 5. __________ is a continuing error due to the inability of a control system to keep the measured variable at set point. A controller turns off the heater coil at set intervals. (1) (2) (3) Error Offset Rate of change 7.com . A value or range of values for a process variable that must be maintained to keep the process running properly. __________ is a deviation from set point due to load disturbance.PAControl. (1) (2) (3) (4) (5) (A) (B) (C) (D) (E) Load disturbance Control algorithm Manual control Manipulated variable Set point The factor that is changed to keep a measured variable at set point. A control operation that directly involves human action. Match each term to its correct definition. sends the result to a controller to compare to the setpoint. (1) (2) (3) (A) (B) (C) Closed-loop. 6. manual control Open-loop. Match each term to its correct description. and the controller turns off the heater coil. regardless of the process temperature.Module 7: Workbook Exercises 4.com www.
com . 4–20 mA is the most common standard analog signal used in the process control industry today. A customer would use __________to read the temperature of a process fluid on a display. (1) (2) (3) (4) Recorder Controller Final control element Actuator _____ _____ _____ _____ 6. The basic function of a __________ is to convert a reading from a transducer into a standard signal and transmit that signal to a controller or computer monitor. A pump motor is the most commonly used final control element. Match each control loop equipment to its correct description.3 — COMPONENTS OF CONTROL LOOPS AND ISA SYMBOLOGY 1.com Page 61 www. Profibus and Modbus 4-20 mA and 1 – 5 V 4.Module 7: Workbook Exercises EXERCISE 7. (1) (2) (3) Analog signal Pneumatic signal Digital signal (A) (B) (C) 3 –15 psig Fieldbus. Is this statement true or false? (1) (2) True False Workbook Exercises © 2006 PAControl. Match the signal type in Column A with its example/application in Column B. Is this statement true or false? (1) (2) True False 3. (1) (2) (3) recorder transmitter converter 2.PAControl. (1) (2) (3) an indicator a volt-meter an actuator 5.
com .PAControl. (1) (A) Programmable logic control (2) (B) Temperature transmitter (3) (C) Pneumatically actuated valve (4) (D) Electrically actuated valve Page 62 Workbook Exercises © 2006 PAControl.Module 7: Workbook Exercises 7. Match the ISA symbols in Column A with its respective description in Column B.com www.
com . Derivative gain (Dgain) is typically set to zero in flow applications since flow applications are usually noisy and derivative control will react to readings that are in fact noise. (1) (2) (3) (4) (5) (A) (B) (C) (D) (E) Proportional band Proportional/integral (PI) control Proportional control Derivative control Integral control A type of control that corrects error and eliminates offset. Match each term to its correct definitions.com Page 63 www.PAControl.4 — CONTROL ALGORITHMS AND TUNING 1. A type of control that produce erratic output in noisy applications. thus preventing the process from holding set point. A type of control that is prone to leaving an offset. The percent change in error that will cause a 100% change in controller output. Identify the two effects on a process variable if the proportional gain (Pgain) is set too high? (Select all that apply) (1) (2) (3) (4) Minimize offset Large offset Stable loop Possible cycling 3. A type of control that repeats the action of the proportional mode as long as an error exists. Is this statement true or false? (1) (2) True False Workbook Exercises © 2006 PAControl. 2.Module 7: Workbook Exercises EXERCISE 7.
If R1 = 60 .5 — PROCESS CONTROL LOOPS 1.PAControl. R2 = 100 the circuit? (1) (2) (3) slow fast variable speed . (1) Flow transmitter (A) (2) Temperature transmitter (B) (3) Flow controller (C) (4) Valve (D) 3. Which control system anticipates load disturbances and controls them before they can impact the process variable? (1) (2) (3) (4) Selective control Fuzzy control Feed forward control Cascade control 2. www. Match the component label in Column A to its ISA symbol representation in Column B.com. and R3 = 100 .Module 7: Workbook Exercises EXERCISE 7. what is the equivalent resistance (Req) in Page 64 Workbook Exercises © 2006 PAControl.com .
2. A. 7. B. 2. 3. B. 3. C C. 5 1 1 Exercise 7. A. 5.com Page 65 www.3 – Components of Control Loops and ISA Symbology 1. 3. E. C. 4. D. 4.PAControl. E 1.2 – Control Theory Basics 1.5 – Process Control Loops 1. 7. 2. 4 1. 2. A 1 Workbook Exercises © 2006 PAControl. D. 5 D. C. 3 B. A. D.com . A Exercise 7. 5.Answers Exercise 7. 6.Module 7: Workbook Exercises . 4. C. A. 2 1 C. 1. 3. C. 6.1 – The Importance of Process Control 1. D. 3. 2. D. A B. 3. B 1 2 Exercise 7.4 – Control Algorithms and Tuning 1. 2. 1. A 2 B. B. 4 1 Exercise 7. B 1 C.
7. True 1.com www. 9. 4. 10. 16. 1. 13.2. 3.PAControl. True True True 4 3 False False 2.4 2 4 3 1 2 1 2 3 True 4 True True 1 3 Page 66 Activity Answers © 2006 PAControl.4 Control Theory Basics 1.com . 19. 2. 3.2.5 1.3. 11. 15.4 Components of Control Loops and ISA Symbology 1. 2. 3. 8. 8. 5. 2. 5. 6. 20.4 1 1.3.5 False 3 True 2. 4.Module 7: Activity Answers The Importance of Process Control 1. 7. 21. 17. 14. 12. 18. 6.
5 2.4 False 2 False 1 2.4 2. 3. 6. 2.2. 12.PAControl.com Page 67 www. 7. 4. 8.com .3 2 4 False 3 Process Control Loops 1. 5. 9. 7. 10. 14. 13.3. 4. 9.3 3 2. 12. 6. 11. 10. 8. 1. 2. 4 3 False True 1 True 2 True False 3 4 1 Activity Answers © 2006 PAControl.Module 7: Activity Answers Controller Algorithms and Tuning 1. 3. 5. 11.
www.PAControl.com .