CN&DCS unit 4 1

OPERATOR INTERFACES

CN&DCS unit 4 2

• Require well engineered human interface system for error free interaction

• Instrumentation and control engineers: setting up and maintaining control system

• Plant operator : monitoring, supervising and running the process during startup, operation and shutdown condition

CN&DCS unit 4 3

• Low level human interface : to local control unit (LCU) or data input output unit (DI/DO) via dedicated line

• High level human interface : to LCU or DI/DO via shared communication facility

CN&DCS unit 4 4

CN&DCS unit 4 5

CN&DCS unit 4 6

ADVANTAGESReduction in control room size (no panel board instrumentation)Reduction in wiring cost (LCU near process)

CN&DCS unit 4 7

• Interface equipment must be designed to meet– Large as well as small systems– Centralized and distributed equipment

configuration– CRT only operation or panelboard instrumentation

CN&DCS unit 4 8

Requirements

1. Process monitoring– Current values of all process variables in system– Identified by tag rather than address (descriptor

for that tag associated)– Display of PV in engineering units with values– Variables (functions of basic PV) available all

time in format

CN&DCS unit 4 9

• Alarming– Alarm status identified by control and computing devices

for each variable in DCS reported in clear manner– Also for computed variables– Display alarm along with PV or accessible to the operator– Alert and acknowledge from the operator– Multiple alarm in short time, informed with priority– Multivariable alarm (abnormal depend on several

variables) – appropriate mechanism to report the sameTrend in time

Fast access to recent history of selected PV known as trended variable(TV)

Requirements in trending• group related TV• Trend graph in engineering units• Able to obtain precise recent and trend variable• Also show auxiliary information; to evaluate status

CN&DCS unit 4 10

2. Process controlo Rapid access to all continuous and logic sequenceso Continuous control loop: changing control modes, set

points and monitor resultso Logic: starting and stopping pumps, opening and closing

of valveso Batch process: observe current status, and interact to

initiate new steps or halt sequenceo Both cases: access to and be able to manipulate (if any

single point failure)

CN&DCS unit 4 11

3. Process diagnosticsAbnormal conditions caused by equipment or I&C system, identify, correct•Ongoing tests and reasonable checks on sensors

•Ongoing self-tests on components and module

Automatic diagnostics functions1.First-out alarming function

2.Priority alarming functions

3.Advanced diagnostic function (failed process equipment and mode of failure)

CN&DCS unit 4 12

4. Process record keepingPeriodically note and record the current values

Record keeping requirements1. Recording of short-term trending information

2. Manual input of process data

3. Recording of alarms(with tag name, time, return to normal, operator acknowledgement)

4. Periodic records of process variable information

5. Long-term storage and retrieval of information

6. Recording of operator control actions

CN&DCS unit 4 13

5. Guidelines for human factors design– Convenience of equipment vendor or architect-engineer

– Later operator - Fewer operator errors

» Less operator fatigue

» Efficient use of personnel

Guidelines

1.Full range of expected operator population (male, female, large, small)

2.Minor disabilities (color blindness, near sightedness)

3.For operators not computer programmers

4.Rapid access to all necessary controls and displays

5.Arrange (equipment, displays) based on operational point of view, cluster

6.Use colors, symbols, labels to minimize operator confusion

7.Do not flood parallel information, give prioritized, arranged and meaningful

8.Aid with operator guides, menus, prompts or interactive sequences

9.Detect and filter erroneous operator input, tell operator what to do next

10.Control room equipment is consistent with proper selection and design of equipments

CN&DCS unit 4 14

low-level Operator Interface

Motivations to use LLOI

• Provides interface that is familiar to trained operator (resemble type of instrumentation)

• Less expensive than HLOI

• It can provide manual backup incase automatic or HLOI fails

LLOI includes– Control stations, indicator station, alarm annunciators and trend

recorders

CN&DCS unit 4 15

Control station - continuous

CN&DCS unit 4 16

Control station -logic

CN&DCS unit 4 17

High level operator interface• LLOI uses panel board instrumentation

• HLOI uses CRT, video display units

• Uses keyboard instead of switches

Microprocessor based digital technology

Advantages 1. Control space reduced significantly

2. Flexible (no panel board instrumentation)

3. Microprocessor cost effective implementation of functions

Consists ofOperator displays, keyboard or input devices, main processor and

memory, interface to shared facility and hard copy devices

CN&DCS unit 4 18

Disadvantages •All in one basket, vulnerable to single point failure•Single-processor, single-memory-less loops, datas•Not scalable, expensive for small systems

CN&DCS unit 4 19

CN&DCS unit 4 20

First available standard

CN&DCS unit 4 21

CN&DCS unit 4 22

CN&DCS unit 4 23

CN&DCS unit 4 24

CN&DCS unit 4 25

OPERATOR DISPLAYS

CN&DCS unit 4 26

CN&DCS unit 4 27

Big picture of current plant condition

CN&DCS unit 4 28

Situation in a selected plant area

CN&DCS unit 4 29

Alarm and operational status of process variables in the plant,but to control, require display similar to panel board instrumentation

CN&DCS unit 4 30

Group graphics display Includes piping and instrumentation diagram

CN&DCS unit 4 31

CN&DCS unit 4 32

Single loop or data points for control and analysis purpose

CN&DCS unit 4 33

Use to both operator and instrumentation engineer

CN&DCS unit 4 34

• Design consideration for displays– Not cluttered, simple as simple– Not flashy and proper background for display– Top few lines display common information– Proper color conventions of industry– For color blind use underline or blinking

CN&DCS unit 4 35

• Design consideration for operator input– Display-select commands– Cursor-movement commands– Control-input commands– Data inputs

CN&DCS unit 4 36

CN&DCS unit 4 37

CN&DCS unit 4 38

Engineering interface

CN&DCS unit 4 39

• Human interface - to monitor and control

• Engineer – to put DCS onto field

– Design for engineer to monitor, control, procure, arrange, wiring, testing

– Select device for operator, mount in panelboard, wire, test

– documentation

– Error detected – new module, wiring, documentation update

CN&DCS unit 4 40

• Dedicated inter module wiring replaced by shared communication

• CRT based instead of huge panel board

Engineering made simple

Special hardware (part of DCS) to make this painless – Engineering interface

CN&DCS unit 4 41

• Low-level engineer interface– Min. function devices

– Inexpensive

– Small

• High-level engineer interface– Full function devices

– Powerful (expensive)

– Medium and large

CN&DCS unit 4 42

Functions • System configuration

– Define H/W configuration, interconnection, algorithms

• Operator interface configuration– Define equipment, relate this to DCS

• System documentation– System and interface for quick changes

• System failure diagnostics– Determine existence of failure, quick and efficient

CN&DCS unit 4 43

Requirements • Access security:

– control logic and tuning parameter, unauthorized not allowed

• Ergonomic design: – not for programmers,

– many devices- interface between them

• Data reasonable and consistency: – check with previous entered value, prompt to correct,

– enter not more than once,

– many control for one- pick, keep track,

– for several related H/W, system should provide check

• User convenience– Easy storage when not in use

– No need to shut down to connect or disconnect devices (convenient)

• Cost effectiveness

CN&DCS unit 4 44

System configuration requirement• Manual work

– determining control system requirement

– Selecting and procuring H/W

– Physically assembling

– Connecting wires between transmitter and terminating point in control room

1. Define address of I/P, O/P points in system

2. Define tag name and descriptor, relate these to tags

3. Signal conditioning (if required) of I/P• Linearization, zero or span shifting, conversion (O/P too)

4. Select, configure and tune control and computational algorithm• Define auxiliary function- trending, logging

5. Requires transmission, define link from element to other• System to check, so preloaded, duplicate in mass storage

CN&DCS unit 4 45

Operator interface configuration requirement

• Implement panel board or video display unit

Functions

• To select and define devices and mechanism for operator– Control station, indicators, recorders

• Relate operator interface or display to control &instrumentation H/W in field– Labelling devices, display with tag

CN&DCS unit 4 46

Documentation requirement

• Bulk of configuration through engineering interface and stores in mass storage– Include hard copy to support documentation

– Support tabular and graphical data format

– Keep track of field changes• EI must handle these changes, as well as original design

– Automatic with less human effort

CN&DCS unit 4 47

Diagnostics of system requirement• Self diagnostics (intelligent individual device)

• Identify failed devices– Sensors, power supply, communication devices

• Partial failure– Severity and nature, to identify

• Trouble shooting of control system– Initial, online

– Continuous, logic, batch

CN&DCS unit 4 48

Low-level engineering interface

• Micro-processor based

• Can be– hand held

– module that can be mounted

• Minimal input, output

• Plug and play-not needed throughout

• Use of code word, symbol – min I/O,O/P

CN&DCS unit 4 49

CN&DCS unit 4 50

System configuration

• H/W selected and configured manually

• Provide with guides or documentation

• LLEI to provide tool for configure algorithm– Enter control strategies, setting tuning parameters, alarm

limits, etc

• Storage available, W/O controller, only with power supply and controller limits– Upload from controller, or download to controller

• Not support high-level language

CN&DCS unit 4 51

Operator Interface Configuration

• Minimum devices – manually

– Assign tag names, labeling station

• Difficult, time consuming, prone to error

Documentation

• Manual – with standard forms

Diagnosis Of System Problems

• Not always connected

• Rely on Self test of equipment

CN&DCS unit 4 52

High-level Engineering Interface

• Cost-effective for medium and large system

• CRT console or VDU

• Similar to HLOI

• Modular- keyboard, printer added- flexibility

• Same elements of Operator interface used for Engineer interface

• Interact through Communication facility

CN&DCS unit 4 53

Dual – console function• Operator- display, mode selection, control operation

• Engineer- control logic configuration, modification, tuning, documentation

• Engineering interface not required always– Using switch can be changed to OI or EI

– Cost effective

– Switch also provides security for EI

CN&DCS unit 4 54

Special hardware required

• Operator interface- not much input/output, so simple keyboard

• Engineer interface- wider range of input, use of general purpose keyboard– Special characters- special purpose

– Printers or plotters for documentation

Portable Engineering interface• Compromise between full function and minimum

function

• Bulk memory, plug and play type, for single LCU or cabinet

CN&DCS unit 4 55

System configuration• HLEI – major role in automating process

• Control structures, computational algorithm stored in HLEI. Following information– Number, type and location of H/W in LCU

– Definition of any H/W selected on each module

– Define input point to H/W module

– Number, type and location of all operator and engineering consoles in the system

– Number, type and location of any other device that communicate using shared communication facility(special logging or computing device)

• Some manually others automatic using broadcast messages

Control and computational information Tags, descriptors, definitions, addresses Logic state descriptors for digital system Signal conditioning in DI/OUs Communication linkages High-level language computation algorithms in LCU

CN&DCS unit 4 56

• Control and computational logic configuration– Fill-in-the-blanks function; through sequence of prompts and

responses

– Graphics capability engineer draws using light pen, similar to CAD

– Enter debug and check high level language routines

• Storage of configuration– Use of mass memory to store configuration information

• Control logics without presence of target H/W

• Verify engineer input to LCU; comparison from mass storage

• Failed devices replaced with new one, configuration downloaded to it

• Upload configuration from device to interface

CN&DCS unit 4 57

Operator interface configuration

• Configure or change display structures– Number of areas in plant, identifying tags and descriptors

– Number of groups in each area

– Assignment of control loops and input points to group

– Types of display at each level (preformatted or custom)

– Linkages between displays

– Assignment of points in system for special function

• Layout of display– Graphic symbols

– Static background elements

– Dynamic graphics elements

– Dynamic alphanumeric elements

– Control stations

– Poke points- touch screen

CN&DCS unit 4 58

• Operator input mechanisms– Special function definition

– Graphics drawing and editing

– Symbol modifications

– Macro symbol operations

– Display transportability

– Expanded display definition

CN&DCS unit 4 59

Documentation• Following documentation automatically

– List of H/W modules and their location

– Control configuration and associated tuning parameters for each LCU

– Listing of tags, descriptors, H/W address of I/P or O/P modules

– Listing of special operator interface function with tag

– Operator display in system with drawing and display hierarchy

CN&DCS unit 4 60

Diagnosis of system problems

• Most of H/W devices is microprocessor based, intelligent to perform on-line self-diagnosis

CN&DCS unit 4 61

CN&DCS unit 4 62