Introduction to Process Control

Course Number: 771

Covers the function of basic devices for measuring and controlling different kinds of variables in process control. Introduces closed-loop control and PID functions. Introduces analog and digital devices and programmable logic controllers (PLCs). ISA and SAMA instrumentation symbols and interpretation and use of process diagrams are covered.

Recommended Contact Hours - 9

Chapter 1: The Nature of Process Control

Topics: Process variables; On-off control; Measuring data; Controlling variables, Error and feedback; Open- and closed-loop control

Learning Objectives:

• Define setpoint and error.
• Explain how measurement and control are related in industrial processes.
• Describe the four essential functions of an automatic control system.
• Discuss the functions of the CRT and PLC in control systems.
• Identify variables in industrial processes.
• Explain the importance of feedback in a closed-loop control system.

Chapter 2: Elements of Process Control

Topics: Analog and digital control signals; ASCII; Measuring pressure, level, and flow rate; Digital pulse control; System terminology; Controller action

Learning Objectives:

• Discuss the differences between modern automatic control systems and older ones.
• Identify the standard signals used in process control.
• Define the terms commonly used in control terminology.
• Explain the differences between open-loop control and closed-loop control.
• Describe on-off, proportional, integral, derivative, and PID controller action.

Chapter 3: Process Control Signals

Topics: Linear and nonlinear transducers; Signal operating values; Error; Controller output; Pneumatic and electrical signal transmission; Control loops

Learning Objectives:

• Discuss standard signals and linearity and explain how to calculate the value of a variable from an instrument's span and range.
• Describe five common sources of error in signal measurement.
• Discuss the basic principles governing pneumatic signal transmission and explain how a flapper-nozzle device works.
• Describe the function of the controller in a control loop.
• Discuss the basic principles governing electrical signal transmission, including Ohm's law, and list standard current and voltage signals.
• Explain the function of I/P devices in a typical control system and discuss the use of digital signals and optical signals.

Chapter 4: Process Control Diagrams

Topics: Symbol recognition; Piping and instrument drawing; Location and installation drawing; Loop and wiring diagram

Learning Objectives:

• Recognize standard symbols used in process control diagrams.
• Describe a process control system through the use of instrument symbols.
• Recognize and use four kinds of process control diagrams.
• Analyze a process control drawing for the elements, signal flow, and process flow.

Chapter 5: Using Symbols and Diagrams in Process Control

Topics: Sequence of operation; Flowchart; Switches; Relays; Electrical elementary diagram; Pump system schematic; PLC diagram; Symbols

Learning Objectives:

• Convert sequence-of-operation text to a flowchart.
• Read electrical and electronic control diagrams and drawings.
• Recognize symbols used on electrical and electronic diagrams, including those for PLCs and SAMA logic.
• Convert electrical diagrams to PLC diagrams.
• Discuss the role of computers in process control.

Chapter 6: Process Control Loop Operations

Topics: On-off and proportional control; Controller sensitivity; Typical control loops; Reset; Derivative; Cascade control; Tuning a control loop; Ratio control

Learning Objectives:

• Explain how to increase the sensitivity of a control system.
• Explain the advantage of proportional control over on-off control.
• Describe the advantage of a proportional-plus-reset controller over a proportional controller without reset.
• List the elements in a single-variable control loop.
• Describe how a cascade control system works and identify the primary and secondary loops in a diagram of a cascade control system.
• State the sequence of loop tuning in a cascade control system.
• Describe how a ratio control system works.