Series 270: Process Instrumentation
Course 271: Introduction to Process Control
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.
Lesson 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.
Lesson 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.
Lesson 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.
Lesson 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.
Lesson 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.
Lesson 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.
