Introduction - Time Delay Systems

Typical application – Leo Laboratories

• Practical understanding of process control. • Process control - industrial applications

Reference: GPG354 Good Practice Guide, http://www.carbontrust.co.uk

• Everyone has a good background for this course.1

Integration of instruments, actuators and controllers2

Structure of discussion

1. Housekeeping

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• Office - B4B; Phone - 4024875; e-mail – [email protected] • 12 week course (September-December); 4 hours contact/week: nominally, 2 hours lectures, 2 hours practical work. • Exam: 70% of subject; do 4 out of 5 questions, 2.5 hours. Exam takes place at the end of January. • Practical Work: 30% of subject. Continuously assessed by means of - PowerPoint presentation on an engineering topic (15%) - Formal laboratory work (5%) - Mini-project work (10%) • The module builds on the following completed modules: - Control and Automation (Year 3, Sem. 1) - Instrumentation and Measurement (Year 3, Sem. 1).

Housekeeping Process organisation and layout Control systems philosophy Documentation – control and instrumentation A note on career learning

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2. Process Organisation and Layout

Housekeeping This year, for the first time, WebCT will be used to store lecture notes. New lectures will be placed on WebCT the week before the topic is covered in lectures. WebCT is available at http://webct.dit.ie/webct/public/home.pl Placing the lecture notes on WebCT is to allow you access to the original notes to supplement your learning; these notes have extra features such as colour diagrams. They are not a replacement for attending and participating in lectures; many lectures will involve design and problem solving, skills which are more difficult to learn on your own. Student login to WebCT (from web address above): ID is student number in the format C08123456 (i.e. capital C or D, followed by eight digits usually starting with zero). Default password is your date of birth in eight-digit format (i.e. if your birth-date is 1 January 1989, it becomes 01011989): you will 5 change this on your first login.

Plants are divided into process areas Areas are defined based on equipment or process grouping e.g. tank farm, boiler house. Plant operators are responsible for the operation of one or more process areas. Multiple units of similar equipment may be located in one process area e.g. the boiler house area may consist of one or more boilers. 7

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In cooler climates or to meet special processing conditions, the process equipment may be contained in buildings. The equipment associated with larger processes may be located in the open. Processes are sometimes also called ‘plants’.

Reference: Process Control Special Short Course 2006 - Fisher-Rosemount Systems 6

Labs and instrument shops may be distributed throughout the entire site • Lab tests are often required, since some parameters of the process cannot be measured on-line. • Instrument technicians are responsible for calibrating and maintaining field devices, and may also be responsible for the maintenance of the control system.

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3. Control Systems Philosophy … if every instrument could accomplish its own work, obeying and anticipating the will of others … if the shuttle would weave and the pick touch the lyre without a hand to guide them, chief workmen would not need servants, nor masters slaves. Aristotle, Politics, Book 1, Chapter 3

Control system The measurement and control system is the ‘central nervous system’ of an industrial process plant (Figure 1). •Basic closed loop control systems look after plant operations – work automatically •Higher levels define process conditions, ensuring efficient operation. Reference: GPG346 Good Practice Guide, http://www.carbontrust.co.uk

(as quoted by Bennett, S. (1979). A History of Control Engineering, 1800-1930. Publisher: Peter Peregrinus Ltd, London).

A well designed and maintained control system is energy efficient, maintains safe conditions, ensures waste and effluent streams are controlled properly, reduces variation in product quality and reduces manufacturing costs.

Aristotle, 384-322 B.C. 9 Reference: http://www.iep.utm.edu/a/aristotl.htm

The control loop

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Example control loop

• Plant control system typically has hundreds/thousands of control loops • Task: hold process variable at its setpoint or command signal (set by higher levels in the control hierarchy). • Changes in setpoint must be implemented quickly and efficiently. • A (closed loop) control system has 4 components: measurement device, controller, regulator and process. 11

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Structure of course

Closed loop control block diagram

The course is divided into two main sections • Basic process control • Advanced process control

Compare setpoint to measured value to give the error controller output (manipulated variable)

command value (desired value or setpoint) +

Controller

Actuator

Process

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controlled or measured variable

Negative feedback

After completing these technical sections of the course, we will consider how to improve the effectiveness of closed loop control systems. This will be a project management and business oriented discussion.

Measuring Instrument

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Basic process control

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Advanced Process Control • Statistical Process Control • Performance of feedback control systems • Feedforward and ratio control • Cascade control • Split range and selective control • Control of MIMO processes • Single variable and multivariable model predictive control • Time delay compensators

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Controllers Processes Measurement devices Actuators Integration issues Empirical model building • PID controller tuning

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4. Documentation – Control and Instrumentation

Process Flow Diagram example

Typical documentation • Plot Plan – physical layout of the plant • Process Flow Diagram – major pieces of equipment in a process area • P&ID – shows the piping and instrumentation that will be installed • Loop Sheet – details field wiring and instrumentation details. Reference: Process Control Special Short Course 2006 - Fisher-Rosemount Systems17

P&ID example

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Loop Sheet example

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How to read Piping and Instrumentation Diagrams (P&ID) Instrumentation detail varies with the degree of design complexity. For example, simplified or conceptual designs, process flow diagrams, provide less detail than fully developed piping and instrumentation diagrams (P&IDs). Being able to understand instrumentation symbols appearing on diagrams means understanding ANSI/ISA's S5.1-1984 (R 1992) Instrumentation symbols and identification standard, that defines how each symbol is constructed using graphical elements, alpha and numeric identification codes, abbreviations, function blocks, and connecting lines. Reference: Harrold, D. (2000). “How to read P&ID’s”, Control Engineering, 2000.

Deciphering symbols • ISA S5.1 defines four graphical elements-discrete instruments, shared control/display, computer function, and programmable logic controller-and groups them into three location categories (primary location, auxiliary location, and field mounted). • Adding a single horizontal bar across any of the four graphical elements indicates the function resides in the primary location category. A double line indicates an auxiliary location, and no line places the device or function in the field. Devices located behind a panel-board in some other inaccessible location are shown with a dashed horizontal line. • Discrete instruments are indicated by circular elements.

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• Shared control/display elements are circles surrounded by a square. • Computer functions are indicted by a hexagon • Programmable logic controller (PLC) functions are shown as a triangle inside a square. • Letter and number combinations appear inside each graphical element and letter combinations are defined by the ISA standard. • The first letter defines the measured or initiating variables such as Analysis (A), Flow (F), Temperature (T), etc. with succeeding letters defining readout, passive, or output functions such as Indicator (I), Record (R), Transmit (T), and so forth.

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FT 101 represents a field-mounted flow transmitter connected via electrical signals (dotted line) to flow indicating controller FIC 101 located in a shared control/display device. A square root extraction of the input signal is applied as part of FIC 101's functionality. The output of FIC 101 is an electrical signal to TY 101 located in an inaccessible or behind-the-panel-board location. The output signal from TY 101 is a pneumatic signal (line with double forward slash marks) making TY 101 an I/P (current to pneumatic transducer). TT 101 and TIC 101 are similar to FT 101 and FIC 101 but are measuring, indicating, and controlling temperature. TIC 101's output is connected via an internal software or data link (line with bubbles) to the setpoint (SP) of FIC 101.

Example P&ID

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Example P&ID - continued

Lifelong learning - documentation The ISA - Instrumentation, Systems, and Automation Society (www.isa.org) have standards and reference books that deal with this issue. As of June 2007: • Seven relevant standards are available on a new CD-ROM: ISA Documentation Standards and User Resources for Industrial Automation and Control Systems. • Two relevant books are available:

Typical YIC indicates an on/off valve is controlled by a solenoid valve and is fitted with limit switches to indicate open (ZSH) and closed (ZSL) positions. All inputs and outputs are wired to a PLC that's accessible to the operator (diamond in a square with a solid horizontal line). The letter 'Y' indicates an event, state, or presence. The letter 'I' depicts indication is provided, and the letter 'C' means control takes place in this device.

Control System Documentation: Applying Symbols and Identification, 2nd Edition, providing the symbols and identification commonly used throughout the process industries and reflecting changes in documentation and the evolution of control systems engineering and design work over the past decade. Instrumentation and Control Systems Documentation, helping the novice to read, understand, and apply the symbols and documents used to define a modern industrial instrumentation and control system and giving insights to the more experienced professionals into using the symbols and documents more effectively. 25

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Further reading: ISA S5.1 (1984). Instrument symbols and identification, www.isa.org

5. A note on career learning Process control, as a technical discipline, is constantly advancing. The present state of the art of process control (in technology issues) is well captured by the following books: • Seborg, D.E., Edgar, T.F. and Mellichamp, D.A. (2004). Process dynamics and Control, 2nd edition, Wiley • Marlin, T.E. (2000). Process Control: designing processes and control systems for dynamic performance, Mc-Graw-Hill, 2nd edition. • Chau, P.C. (2002). Process control: A first course with MATLAB, Cambridge University Press. The following professional bodies provide resources in the area: • ISA (Instrumentation, Systems, and Automation Society) – www.isa.org • InstMC (Institute of Measurement and Control) – www.instmc.org • IET (Institute of Engineering and Technology) – http://www.theiet.org/ • IChemE (Institute of Chemical Engineers) – http://www.icheme.org 27

Many of the professional bodies have their own technical journals in which recent research results are reported. An example is ISA Transactions. In addition, there are three electronic magazines which report implementation developments, as well as giving tutorials in measurement and control techniques. They are: • Control Engineering (http://www.controleng.com) • Intech (http://www.isa.org/InTechTemplate.cfm) • Control (http://www.controlglobal.com/issues/) Finally, there are many websites which deal with process control issues. Reference will be made to them when appropriate. One good website with many links is http://www.che.utexas.edu/cache/trc/t_process.html 1) Software/Simulation 2) Course Syllabi 3) Course notes 4) Process Systems Research Consortia 5) Optimization websites 6) Academic Research in Process Systems Engineering 7) Process Control TextBooks 8) Comment form

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