human interface
TRANSCRIPT
-
8/3/2019 Human Interface
1/20
HUMAN INTERFACE
To promote error free operation Safe and effective control functions
Group of interacting plant personals
Instrumentation and control system engineers Initial setting Regular monitoring Plant operators Monitoring Supervising Running the process in different stages (startup, operation, and shutdown)
Classification
Low-Level Human Interface (LLHI) High-Level Human Interface (HLHI)
Low-Level Human Interface
Panel board Instruments (indicators, recorders) Located close to LCU or DI/OU(100-200 feet)
-
8/3/2019 Human Interface
2/20
High-Level Human Interface
High level display devices (CRT, Printers and magnetic storage devices) Located anywhere in the plant
Configurations
Stand-alone Control Configuration Geographically centralized configuration Geographically distributed configuration
Stand-alone Control Configuration
Small and simple Applicable to a small process/digital control system with conventional controllers.
Geographically centralized configuration
Functionally distributed however geographically centralized Low-level as backup of High-level interfaces.
Advantage
Monitoring without disturbing plant operation
-
8/3/2019 Human Interface
3/20
Geographically distributed configuration
LLHI- plant area
HLHI- control roomAdvantages
Reduction in control room size Reduction in field wiring cost
Operator Interface Requirements
Process Monitoring Process control Process Diagnostics Process record keeping
Process Monitoring
-
8/3/2019 Human Interface
4/20
Normal Functions
Instantaneous value of process variables Continuous (flow, temp and pressure) Discrete variables (pump and switch positions) Status of any sensors
Tag should be included Process variables with Engg units Derived variables
Abnormal status
Alarm status of individual variable Display alarm limit Distinct alarm condition for different status Multiple alarm condition with priority status Combination of several variables at abnormal condition.
Trended Variables
Group of trended variables With engg units, time increments, and absolute time of day. With additional informations set point, allowed range and allowed rate etc.
Process control
Rapid access to continues control loop and logic sequences Facility to change
Control modes Set point Result of changes
Operator to perform logical operations with interlocking signal monitoring Information about new step initiation and halting any operations in order to perform new
logical sequences.
-
8/3/2019 Human Interface
5/20
Facility to manipulate control outputs to avoid single point failure.
Process Diagnosis
Information about hazardous condition
Test sensor and analyzers of process variables Test components and modules, controllers, communication elements, computing devices
and human interface itself.
Automatic detection of process faults
First-out alarm function Priority alarming functions More advanced diagnosis based on combination of alarming functions, mode of failure
Process Record Keeping
Record of short-term trending information Manual input of process data Recording of alarms : tag name of PV, time of alarm, type of alarm Periodic records of PV information Long-term storage and retrieval of information Recording of operator control actions
LLOI
Connected directly to LCU Controlling and monitoring LCU Dedicated to single LCU
Applications
conjunction with HLOI In place of HLOI Only during emergency and failure conditions
-
8/3/2019 Human Interface
6/20
Advantages
Suitable for operators trained to use panel-board instruments Less expensive for small applications Manual backup HLOI and control equipment
Typical LLOI instruments are
Control station Indicator station Alarm annunciators Trend recorders Smart instrumentation
Smart Continuous control station
Bar graph- Sp and PV Control output as % Digital display with units High and Low alarms Mode of operation
(slow and fast mode)
Ramp button for SP and PV Operational status alarm
-
8/3/2019 Human Interface
7/20
Manual Loader station
Low cost alternative of Continuous control station Back up purpose
Indicator station
To monitor process variables not associated with control loop Similar to control station with no control
push button
Optional alarming facilityLogic (sequential) station
push button and indicating lights Used for turn on/offpumps, start
automatic sequence, feed i/ps to logic
systems
Simple and low cost LLOI
Smart announciators
Alarm prioritization Annunciation and acknowledgement mode options
-
8/3/2019 Human Interface
8/20
First-out annunciation Alarm cutout
Chart recorders
Analog and Digital recorders Round chart , bar chart. P based recorders
Display with memory Impact or heat mechanism for plotting Axis with scale plain papers can be used Automatic labeling, range selection using alpha-numeric key Distinguish plots with colors and symbolsSmart announciators
Alarm prioritization Annunciation and acknowledgement mode options First-out annunciation Alarm cutout
Chart recorders
Analog and Digital recorders Round chart , bar chart. P based recorders
Display with memory Impact or heat mechanism for plotting Axis with scale plain papers can be used Automatic labeling, range selection using alpha-numeric key Distinguish plots with colors and symbols
-
8/3/2019 Human Interface
9/20
LLOI requirements
Display and push buttons sealed against the atmosphere Display with high visibility in the expected ambient light condition Push button with tactile feedback to the operatorsHLOI
Shared interface not dedicated to any LCU Control over any or all LCUs CRT and advanced display techniques (VDUs) Information shared thro shared communication facilitiesAdvantages
Saving floor space and equipment expensesArchitecture configurations
Centralized HLOI Decentralized HLOI
Overlap type Fixed HLOI Modular HLOI
Single central processing unit CRT can access to any of the control loop More no of CRT can be used as backups Peripherals are shared not dedicated
to any CRT.
Disadvantages
Complex peripheral switching andMemory-sharing implementation
Limited to less number of loops and
-
8/3/2019 Human Interface
10/20
Data points
More display response time Too expensive for small ones
Sharing of data among HLOI The loss of any single HLOI does not affect the system. More expensive method No extra back up units necessary
-
8/3/2019 Human Interface
11/20
Fixed HLOI configuration
Optional additional hardware
Secondary CRTS Keyboards Printers Mass Storage units Trend recorders voice alarm system Interface port to special communication systems Backups for all important units
Advantages
Flexibility in configuration
Modular HLOI configuration
-
8/3/2019 Human Interface
12/20
Modular HLOI configuration in detail
Elements used as HLOI
Microprocessor and memory components
Winchester disk magnetic disk Read/write optical disk
Removable mass memory
Floppy disk Magnetic tape Read only optical disks
Printers and plotters
Black and white dot matrix printer Pen plotter ink-jet printer Thermal transfer printers
Modular packaging Approach
Additional units
CRT module Alarm panel module
-
8/3/2019 Human Interface
13/20
Panel board instrumentationmodule
Work space moduleDesired characteristics on modules
Good anthropometic design Elimination of glare Easy accessibility of peripherals Simple interconnection of modules
Operator Display
Plant level Display : Information about entire unit, single are many Area level display : portion of plant (related to each other) information. Group level Display : single process information Loop level : individual control loop information
-
8/3/2019 Human Interface
14/20
Plant level display
Plant level information summary
Area- level display
Selected plant area displayTypes
Deviation overview display Absolute value display Panel board type display
Deviation overview display
Bar graph of deviation in process variable from set point Normalized deviation to total span Clustered plot representing no of groups in each area Exceed predetermined level deviation alarm initiated graph colour changes (green-band
concept).
-
8/3/2019 Human Interface
15/20
Absolute value display
Absolute PV indication Additional information: set
Value and high/low alarm limit
Panel board type display
Tag number of loops and PV PV is not in alarm low-key colour PV in alarm statuschanges color
With flashing
Underlining also possible colourblind operator
Addition to tag no, absolute valuealso displayed
-
8/3/2019 Human Interface
16/20
Other area level display
Area graphic display piping and Instrumentation diagram Alarm summary display list of current alarm, outstanding alarm, tag number, description of
alarm, alarm time, type of alarm, alarm status (returned to normal, acknowledgement etc)
-
8/3/2019 Human Interface
17/20
Group level display
Mimics panel board display: SP, control output, PV, manual, automatic, cascade mode, highlow alarm level,
Logical station, trend records
Advantages
Without additional hardware, additional stations and recorders can be added. Duplications of stations and recorders are also possible.
Other types of Display (as area display)
Batch control displays :Permits to start, top, continue, diagnose
problems in logic sequence.
Operator guides :Information about problem diagnosed by
Automatic system, emergency alternatives
-
8/3/2019 Human Interface
18/20
Loop-level displays : single loop information
One PV as a function of another PV Tuning display - with following facilities
Fast trend plotting manual,/auto station List of tuning parameters
-
8/3/2019 Human Interface
19/20
Graphic display features
Static fields background of dynamic display, includes labels, symbols and other necessaryitems
Data fields PV numerical values with units Dynamic display elements size , color , shape flexibility Zooming facility
Design considerations for displays
Simple with necessary information , freedom to change include more information Over flashy and light-colored back-ground not suitable Top 2 lines common information, bottom two line communication between operator and
HLOI
Color consistency Addition to color change during alarm state blinking , underlining should be provided.
Engineering Interface
LLEI- low level, minimum functional devices
inexpensive
HLEI full-function devices, more powerful, expensive.
Functions
System configuration : define hardware configuration, interconnections, control logic andcomputational algorithm
Operator interface configuration : define operator interacting system System documentation System failure diagnosis
Requirements
General requirements
Access security : security mech to protect unauthorized user Erconomic design : prompt-and response sequence facility, data formats understandable to
process instrumentation Engg, interconnection between engineering interfaces
-
8/3/2019 Human Interface
20/20
Data reasonableness and consistency : self checking of data entered by the engineers forconsistency and reasonableness.
User convenience: easy to interface EI without shutdown of the system Cost effectiveness
Requirements
System configuration requirements
Define the address of input output points based on their location in the sharedcommunication in an informative way.
Provision to define tag names and associated descriptions Define signal conditioning need to perform (such as linearization, zero and span adjustment,
unit conversion)
Provision to select ,configure and tune the control algorithms Define the communication among various units included in the control function (shared
communication address)