Instr 12418 Distributed Control Systems

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----------Distributed Control Systems
Moduíe 12418
Instrument Trainee Task Module 12418
DISTRIBUTED CONTROL SYSTEMS-
Ob|ectíves
Upon completion of this module, the Trainee will be able to:
1. Defíne a Dístríbuted Controí System (DCS).
2. Identífy generaí components or parts of a DCS.
3. Descríbe uses for DCS.
Prerequísítes
Successfuí compíetíon of the foííowíng Task Moduíes ís requíred before
begínníng study of thís task moduíe: NCCER Task Moduíe 12401 through
12417.
Requíred Student Materíaí
1. Student Moduíe
2. Requíred Safety Equípment
Instrument Traínee Task Moduíe 12418 2
Course Map Informatíon
Thís course map shows aíí of the Wheels of Learning task moduíes ín the
fourth íeveí of the Instrument currícuía. The suggested traíníng order
begíns at the bottom and proceeds up. Skííí íeveís íncrease as a traínee
advances on the course map. The traíníng order may be ad|usted by the
íocaí Traíníng Program Sponsor.
Dístríbuted Controí Systems - Moduíe 12418 3
LEVEL 4 COMPLETE
TABLE OF CONTENTS
Section Topic ………………………………………………………………….
Page
1.0.0 Introductíon
.............................. 6
2.0.0 Basíc Dístríbuted Controí System ...................
Instrument Traínee Task Moduíe 12418 4
6
2.1.0 Communícatíons
............................ 7
2.1.1 Monítoríng and Recordíng
...................... 9
2.1.2 Controí
................................ 9
2.2.0 Hardware
............................... 10
2.2.1 Stand Aíone Controííer
........................ 10
2.2.2 Buíít ín Programmabíe Logíc Controííer (PLC) ............
11
3.0.0 Network 90 System Overvíew
..................... 11
3.1.0 The Process Controí Unít
...................... 12
3.2.0 The Operator Interface Unít .....................
12
3.2.1 Dísk Dríves
.............................. 13
3.2.2 CRT
.................................. 13
3.2.3 Keyboard
............................... 14
3.3.0 The Computer Interface Unít
.................... 15
3.4.0 The Management Command System .................
15
3.5.0 Supportíng Equípment
........................ 16
3.5.1 Píant Communícatíon Loop
..................... 16
3.6.0 Input Output Moduíes
......................... 16
3.6.1 Muítí-Functíon Controííer
...................... 17
3.6.2 Anaíog Master Moduíe
........................ 17
3.6.3 Síave Moduíes
............................. 17
3.7.0 Power Suppíy
............................ 17
4.0.0 DCS Operatíon
............................ 18
4.1.0 OIU Operatíng Theory
........................ 18
4.2.0 Process Monítoríng and Controí Actíon ...............
20
4.3.0 Aíarm Handííng
........................... 21
Dístríbuted Controí Systems - Moduíe 12418 5
Trade Terms Introduced In Thís Moduíe
ACK: Aíarm Acknowíedge: refers to acknowíedgíng aíarm state or message
usíng a' pushbutton key on the OIU fíxed keyboard.
Block: Specífíc numeríc address of the memory area ín a PCU moduíe
contaíníng a Network 90 functíon code.
Boolean: Mnemoníc: descríptíve word vaíue showíng íogíc states (1 and
0) for certaín OIU poínts, or tags. (OFF/ON, OPEN/CLOSED, etc.)
CIU: Computer Interface Unít: contaíns the necessary hardware and
software to províde a íínk between the píant communícatíons íoop (PCL)
and a computer.
CO: Controí Output: Statíon controí output vaíue.
Function Block: A user-confígurabíe bíock ín a PCU moduíe contaíníng a
functíon code.
Function Code: A Network 90 aígoríthm contaíníng specífícatíon data for
performíng a specífíc functíon.
Host: Locaí computer ínterfacíng through the CIU provídíng operatíng
controí for the Network 90 system.
Maste Module: Any one of a seríes of master controííer moduíes that
dírect fíeíd processes through síave output moduíes.
MCS: Management Command System unít: Integrated data acquísítíon
system contaíníng ; the necessary hardware and software to províde
híghíy fíexíbíe controí capabííítíes. (Símííar ín functíon to the OIU, but
havíng enhanced capabííítíes)
Mode: Statíon: descríbes methods of statíon operatíon. (Aíso Dígítaí
Controí Statíon.)
Instrument Traínee Task Moduíe 12418 6
!ode: Any |unctíon on the PCL through whích ínformatíon sígnaís pass.
(Commoníy refers to Process Controí Uníts, OIUs, CIUs, and PPG.) Such
sígnaís can pass ín and out of any node.
OIU: Operator Interface Unít: work statíon that provídes maín controí
access to any poínt ín the Network 90 System. (Operatíons, engíneeríng,
and maíntenance personneí use the OIU. )
PCU: Process Controí Unít: a cabínet contaíníng controí, síave, and/or
termínatíon moduíes connected to user process. Can aíso refer to certaín
moduíes mounted ín the cabínet ítseíf.
PC": Píant Communícatíon Loop: The physícaí píant transmíssíon medía.
Communícatíon system connectíng aíí nodes on the píant network.
Trade Terms (contínued)
PP#: Píant-Loop-to-Píant-Loop Gateway: Network 90 moduíe that can
eíther ínterface any two píant íoops to a síngíe íocaí píant íoop. Thís
ínterface process íets exceptíon reports, controí, tuníng, and confíguratíon
commands pass from one píant íoop to another, or from remote íoops to a
íocaí íoop over the PCL.
P$: Process Varíabíe: changeabíe process vaíue.
%CM: Remote Controí Memory: Network 90 functíon code enabííng íogíc
ínformatíon reportíng and tag status changíng.
%&A": Anaíog: certaín tags ín OIU expressed as fíoatíng decímaí poínt
numeríc vaíues.
%I: Ratío Index: anaíog vaíue set by user ín a statíon bíock compared to
CO duríng system operatíon.
%MSC: Remote Manuaí Set Constant: Network 90 functíon code provídíng
ad|ustabíe reaí vaíue (constant) entry ínto controí scheme. Any functíon
bíock receívíng thís command generates an exceptíon report showíng tag
vaíue change as ít occurs.
SP: Setpoínt: statíon vaíue set by user compared to PV duríng system
operatíon.
SP&CS: Specífícatíon data contaíned ín specífíc Network 90 functíon
codes. The spec data ís requíred for settíng up (confíguríng) user-
confígurabíe functíon íocks ín the varíous moduíes used. Specs are aíso
known as parameters.
Station: A functíon code íocated at a specífíc bíock (address) ín a Network
90 moduíe. The functíon code íncíudes parameters determíníng íts
executíon duríng system operatíon.
1.0.0 INTRODUCTION-
Dístríbuted Controí Systems - Moduíe 12418 7
Thís moduíe wííí íntroduce the traínee to the use and appíícatíon of
Dístríbuted Controí System (DCS). Whííe the DCS ís a compíex devíce,
basíc understandíng of how the system works ís the goaí of thís moduíe.
We have seíected the Baííey Net 90 as our typícaí system.
2.0.0 BASIC DISTRIBUTED CONTROL SYSTEM-
The Baííey Network 90 ís a mícroprocessor-based moduíar controí system
capabíe of dístríbuted process controí and programmabíe controí.
The next íogícaí questíon that shouíd be asked ís "what ís dístríbuted
controí?" Dístríbuted Controí ís the remote controí and management of
functíons that are automated and connected to the DCS. These controíííng
devíces are not concentrated ín a computer. Sínce the need for controí
and management ís dístríbuted, ít ís desírabíe to dístríbute the hardware
and the capabííítíes of accompííshíng thís controí and management.
Dístríbuted controí ís feasíbíe due to the íow cost of modern dígítaí
equípment and mícroprocessors. The graphícaí representatíon of a typícaí
dístríbuted controí system ís províded ín Figure 1.
Fígure 1. Dístríbuted Controí
In dístríbuted controí, the índívíduaí feedback controííers for each process
íoop are removed from the controí room íocatíon and píaced cíoser to the
fíeíd sensors and/or actuators.
2.1.0 Communícatíons
The dístríbuted system requíres a faíríy compíex communícatíon íínk. e.g.,
a dígítaí bus or data híghway that connects índívíduaí controííers wíth
operators, computers, consoíes, and díspíays. In addítíon, there ís the
Instrument Traínee Task Moduíe 12418 8
obvíous necessíty for sophístícated software to coordínate the many
communícatíon functíons.
Dístríbuted controí systems can be ímpíemented wíth eíther anaíog or
dígítaí controííers and even the pneumatíc controííers; but, to date, the
mostíy dígítaí hardware approach prevaíís and wííí contínue to do so ín the
future. By, usíng dígítaí controííers the operator ín the centraí controí room
has access to aíí controííer data such as setpoínts, process varíabíe
measurements, controííer output sígnaí íeveís, etc. Sophístícated díspíays
are aíso avaííabíe and the supervísory or management functíon wíth aíí of
the potentíaí for advanced management ínformatíon, optímízatíon, and
supervísíon - are easííy ímpíemented wíthín the controí room ítseíf.
Essentíaííy, the devíces ín thís archítecture are grouped ínto three
categoríes: those that ínterface dírectíy to the process to be controííed or
monítored, those that perform hígh-íeveí human ínterfacíng and
computíng functíons, and those that províde the means of communícatíon
between the other devíces. A bríef defínítíon of each devíce ís gíven beíow:
• Locaí Controí Unít (LCU) - The smaííest coííectíon of hardware ín the
system that can do cíosed-íoop controí. The LCU ínterfaces dírectíy
to the process.
• Low-Leveí Human Interface (LLHI) - A devíce that aííows the traínee
or ínstrument engíneer to ínteract wíth the íocaí controí unít, thís
aííows the operator to change set poínts, controí modes, controí
confíguratíons, or tuníng parameters by usíng a dírect connectíon.
LLHIs can aíso ínterface dírectíy to the process.
• Data Input/Output Unít (DI/OU) - A devíce that ínterfaces to the
process soíeíy for the purpose of acquíríng or outputtíng data. It
performs no controí functíons.
• Hígh-Leveí Human Interface (HLHI) - A coííectíon of hardware that
performs functíons símííar to the LLHI but wíth íncreased capabíííty
and user fríendííness. It ínterfaces to other devíces oníy over the
shared communícatíon facííítíes.
• Hígh-Leveí Computíng Devíce (HLCD) - A coííectíon of
mícroprocessor-based hardware that performs by a píant
computer. It ínterfaces to other devíces oníy over the shared
communícatíon facííítíes.
• Computer Interface Devíce (CID) - A coííectíon of hardware that
aííows an externaí generaí-purpose computer to ínteract wíth other
devíces ín the dístríbuted controí system usíng the shared
communícatíon facííítíes.
• Shared Communícatíon Facííítíes - One or more íeveís of
communícatíon hardware and assocíated software that aííows the
sharíng of data among aíí devíces ín the dístríbuted system.
Shared communícatíon facííítíes do not íncíude dedícated
communícatíon channeís between specífíc devíces or between
hardware eíements wíthín a devíce.
Not íncíuded ín the archítecture of Figure 2, but of vítaí ímportance, are
Dístríbuted Controí Systems - Moduíe 12418
the packagíng and eíectrícaí power systems. These varíous
communícatíon devíces descríbed above are shown ín Figure 2. Figure 2
provídes a schematíc representatíon of how the varíous devíces are
connected for communícatíon purpose.
Fígure 2. Basíc Arrangement
2.1.1 Monítoríng and Recordíng
These varíous ínterfaces that aííow ínput from the reaí woríd ínto the DCS
woríd aíso provídes for the DCS to províde output to the reaí woríd. The
reaí woríd ís everythíng that ís outsíde of the CPU and íts support system.
In other words, we exíst ín the reaí woríd and the DCS exíst ín the chíp's
woríd. The output that the DCS can províde us aííows us to monítor and
record the progress of the process.
2.1.2 Controí
One of the ma|or advantages of a DCS ís that ít provídes controí of a totaí
system as weíí as provídes for the ad|ustment of setpoínts and controí
parameters. Thís ís a sígnífícant change from síngíe íoop or stand aíone
controííers. Let us say that a for stage process ís beíng controííed by
"stand aíone" controííer or PLC sequencer. As shown ín Fígure 3.
Instrument Traínee Task Moduíe 12418 1!
Fígure 3. A Four Stage Process
If stand aíone controííers or íocaí controí uníts are used, a change ín one
of the process outputs wouíd be feít throughout the remaínder of the
system. Let us say that the output temperature of process "A" ríses by
50°F. The remaíníng processes wííí be effected. The whoíe system may be
abíe to correct for thís temperature change, however, the output of each
process wííí have a deíayíng effect on the next process reactíon thus
effectíng overaíí system's process. Wíth a DCS, the entíre system ís
ad|usted causíng a more stabíe output.
2.2.0 Hardware
Hardware ís the components that wííí make up the DCS. We wííí address:
• a stand aíone controííer
• a buíít ín PLC
• harddríve
• redundancy
2.2.1 Stand Aíone Controííer
A stand aíone controííer ís a íoop command controííer that ís not ínterfaced
wíth any other component of a DCS. The Loop Command Controííer
deveíoped by Baííey Controís ís a mícroprocessor based ínstrument made
to controí smaíí processes. It has the capabíííty to handíe símpíe
proportíonaí íntegraí derívatíve functíons aíí the way up to very compíex
muítííoop controí aígoríthms. The controííers can be used as "stand aíone"
controííers or assocíated wíth DCS Systems.
9
Four versíons of the Loop Command Controííer are avaííabíe from the
manufacturer. They are the basíc moduíes, CLC01 and CLC03, and the
enhanced moduíes, the CLC02 and CLC04. The CLC02 has aíí the features
of the CLC01 modeí, íncíudíng the same Input/Output structure, but ít
provídes advanced mathematícaí functíon capabíííty. The CLC03 and the
CLC04 modeís are updated versíons of the CLC01 and CLC02 modeís
Dístríbuted Controí Systems - Moduíe 12418 11
respectíveíy and can be íooked upon as second generatíon ínstruments.
Functíonaííy they remaín the same, aíthough ínternaí círcuítry
modífícatíons have been made to íncrease system reííabíííty.
2.2.2 Buíít ín Programmabíe Logíc Controííer (PLC)
Programmabíe íogíc controííers (PLC) can be used aíone or wíth a DCS. The
PLC provídes the user an "ínteííígent" controííer that ís abíe to perform
more compíícated sequences than those performed by the íocaí controííer.
Whííe thís may seem ííke a great advantage, ít ís oníy abíe to react to ínput
from íts sensíng devíces. |ust as díscussed earííer, we can remove some of
the íag tíme to ad|ust by íncreasíng the PLC ínput sensor, thís ís done vía
the DCS.
3.0.0 NETWORK 90 SYSTEM OVERVIEW-
The Network 90 System ís a dístríbuted process controí system. Usíng a
seríes of íntegrated controí nodes, the Network 90 System, shown ín Figure
4 íets you monítor and controí process varíabíes such as fíow rate,
temperature, and pressure accordíng to a controí confíguratíon that the
process (system) engíneer sets for your píant.
The ma|or controí Nodes of the Network 90 System are:
• the Process Controí Unít (PCU)
• the Operator Interface Unít (OIU)
• the Computer Interface Unít (CIU)
• the Management Command System (MCS)
• the Píant Loop to Píant Loop Gateway (PPG)
The Píant Communícatíon Loop (PCL) tíes the nodes together. The PCL
enabíes communícatíon among the nodes for:
• shared controí varíabíes among moduíes ín dífferent nodes
• monítoríng operatíon of controí schemes ín controí nodes
• takíng controí actíon at an OIU, than a CIU, or the MCS
• confíguríng and maíntaíníng PCU controí from an OIU, MCS, or CIU
• monítoríng the status of components from an OIU, MCS, or CIU
• monítoríng and ínterfacíng of PCUs by CIUs.
Instrument Traínee Task Moduíe 12418 12
Fígure 4. Network 90 Overvíew
3.1.0 The Process Controí Unít
The Process Controí Unít (PCU) ís the fundamentaí controí node of a
Network 90 System. A PCU can eíther refer to severaí Network 90 controí
moduíes, or to any cabínet contaíníng power paneís, confígurabíe controí
moduíes, or termínatíon uníts.
Network 90 moduíes comprísíng a PCU can perform data manípuíatíon and
specífíc controí functíons. Certaín moduíes contaín a compíete ííbrary of
aígoríthms supportíng system functíons, as weíí as nonvoíatííe memory
(EEROM) for storíng confígurabíe controí schemes.
A PCU, can be a stand-aíone controí system contaíníng paneíboard
statíons for system ínterfacíng and a Confíguratíon and Tuníng Moduíe
(CTM) for confíguríng controí schemes. A CTM enabíes íocaí buíídíng
modífyíng of controí schemes (confíguratíon) ínto PCU moduíes.
The PCU connects dírectíy to process fííed devíces. The PCL íínks aíí PCUs
together ín seríes. Thís enabíes other PCUs ín the píant to share controí
functíons and data from any PCU ín the system. It aíso íets OIUs, CIUs, and
MCS uníts communícate wíth any PCU. The poínt where the PCU connects
to PCL ís a Node.
3.2.0 The Operator Interface Unít
The overaíí píant operatíon can be monítored and controííed usíng the OIU,
as shown ín Figure 5. The number of OIUs ín a system varíes dependíng on
the overaíí controí pían and síze of a píant. An OIU can monítor and controí
an entíre píant process. There are many other operator devíces such as:
Dígítaí Controí statíon, Dígítaí Indícator Statíon, Dígítaí Logíc Statíon, for
exampíe, that the OIU aíso enhances.
Dístríbuted Controí Systems - Moduíe 12418 13
Fígure 5. Operator Interface Unít
A person can use the OIU to confígure and maíntaín controí schemes
throughout the píant system. The OIU reads any moduíe controí scheme ín
the system and díspíays ít. You can modífy any controí scheme, havíng the
OIU wríte ít back to the moduíe. You can aíso read moduíe confíguratíon
and save ít on a dískette or read a saved confíguratíon from dískette,
wrítíng ít back to the moduíe.
The OIU ís an íntegrated controí statíon contaíníng a dríver unít, a CRT
coíor graphíc díspíay, a fíxed and auxíííary keyboard, and one or more
optíonaí ííne prínters. The dríer unít connects the OIU to the PCL and
executes programs controíííng OIU operatíon. The dríver communícates
wíth the CRT, keyboard, and prínter, accessíng the entíre píant system
through user-fríendíy díspíays.
There are actuaííy three physícaííy dífferent versíons of the OIU: the
NOIU01(Desk to OIU wíth separate Dríver Unít), the NOIU02 (OIU havíng aíí
components ín same consoíe) and the NOIU03 ruggedízed versíon of the
NOIU02.
3.2.1 Dísk Dríves
The dríver unít contaíns both a hard dísk and a fíoppy dísk, or dískette
dríve. The dískette dríve handíes removabíe dískettes that can save and
restore PCU and OIU confíguratíons, as weíí as íoad OIU software. The hard
dísk dríve provídes on-ííne storage for OIU operatíng software, hístorícaí
trend and OIU confíguratíon data.
3.2.2 CRT
The CRT díspíay provídes a coíor graphíc díspíay usíng a 19-ínch screen.
The screen ís the prímary ínformatíon devíce, usíng a varíety of díspíays to
perform aíí OIU functíons. There are two types of díspíays: Operatíon and
Confíguratíon. Operatíon díspíays show píant process or system
Instrument Traínee Task Moduíe 12418 14
ínformatíon. Confíguratíon díspíays íet the engíneer desígn the operatíonaí
díspíays for partícuíar píant processes. The operator can díspíay process
ínformatíon usíng a varíety of predefíned eíements.
3.2.3 Keyboard
The fíxed keyboard ís a fíat paneí devíce (covered by a myíar membrane)
íocated ín front of the CRT screen, havíng aíphabetíc, numeríc, and
specíaíízed functíon keys. The keyboard íets you access varíous díspíays
and then ínteract wíth them. You can díspíay and controí any process íoop
ín the Network 90 System.
The optíonaí auxíííary keyboard ís a typewríter-styíe keyboard used for
confíguratíon and graphíc edítíng.
Authorízed personneí can confígure or tune most PCU moduíes, as weíí as
troubíeshoot the system usíng the fíxed keyboard. The keyboard aíso has
two keyíock swítches protectíng confíguratíon and tuníng from accídentaí
change or íoss. The two keyswítches restríct confíguratíon and tuníng to
authorízed personneí. The swítches are at the upper íeft of the keyboard,
above the actuaí pushbuttons.
!OT&: The keyíock swítches are íabeíed as: tuníng (TUNE) and
confíguratíon (CONF). The oníy way to change the swítch posítíons ís to
ínsert a key ínto each and turn. After authorízed personneí change swítch
posítíon they remove the keys. Thís íocks the keyswítches ínto the proper
posítíon for operatíon. Operators do not change the keyswítch posítíon.
The optíonaí ííne prínter íogs aíarm occurrences ín the píant system,
príntíng íogs and copíes of the varíous OIU díspíays. The ííne prínter can
copy any current CRT screen díspíay usíng the same coíor scheme as the
díspíay ítseíf. Figure 6 ís an exampíe of a prínter produced CRT díspíay.
Dístríbuted Controí Systems - Moduíe 12418 15
Fígure 6. Prínted Hard Copy of CRT Díspíay
3.3.0 The Computer Interface Unít
The Computer Interface Unít (CIU), ís the host computer equívaíent to the
OIU. The CIU íínks a host computer the PCUs, OIUs, and MCS nodes
throughout the PCL. Usíng the CIU, the host computer gathers process
ínformatíon, makes process decísíons, and performs or recommends
process changes. The CIU does not dírectíy díspíay any ínformatíon.
The CIU ís an automatícaííy operatíng devíce for the host computer ín your
píant. The CIU íets the host perform process monítoríng and controíííng
based on ínternaí performance caícuíatíons. The CIU aíso serves as a data
acquísítíon poínt for the host computer.
The CIU ís programmabíe duríng confíguratíon but the operator does not
use ít to ínterface wíth the system. The CIU ínterfaces automatícaííy. The
CIU reínforces Network 90 data processíng capabíííty and enhances OIU
performance.
3.4.0 The Management Command System
The Management Command System (MCS) unít provídes totaí píant
controí, monítoríng, and appíícatíons programmíng from síngíe or muítípíe
consoíes. There can be more than one
MCS on a system dependíng on the user's need. The MCS acts símííaríy to
Instrument Traínee Task Moduíe 12418 16
the OIU but has enhanced functíons and capabííítíes íackíng ín the OIU.
The MCS enabíes management personneí to take píant controí from any
díspíay ín the system ííke operatíng personneí do usíng an OIU. The
manager can confígure specífíc díspíay eíements and use one-key access
for up to 32 dífferent díspíays, ínstead of usíng muítí-key access on the
OIU. The MCS aíso íets the manager prínt, archíve, and retríeve varíous
íogs ín a manner símííar to the OIU.
Usíng the MCS, the manager can aíso ííst tag detaíís, change varíous aíarm
íímíts, effect tuníng functíons, íockout píant controí by password, and
manípuíate fííes by varíous fííe management commands. The MCS has on-
ííne utííítíes, on-ííne documentatíon capabííítíes, and díagnostícs, as weíí.
The MCS ís very símííar to the OIU ín appearance and functíon. The MCS
aíso uses a coíor graphíc CRT díspíay screen and standard overíay
pushbutton keyboard. But the MCS CRT uses more coíors than an OIU CRT
whííe the MCS keyboard has more controí bíocks for greater ínput/access
fíexíbíííty.
3.5.0 Supportíng Equípment
In order to operate properíy, the DSC needs to have equípment to support
ít. Thís equípment íncíudes communícatíon moduíes, power suppííes,
anaíog moduíes, and varíous other píeces of support equípment.
3.5.1 Píant Communícatíon Loop
The Píant Loop ís a redundant (optíon) twínax cabíe system for connectíng
aíí nodes on the Loop. The Loop carríes data from one node to another
node. A maxímum of 63 nodes wíth up to 2,000 meters between nodes ís
aííowed. Interfacíng each mode to the Loop ís the Loop Interface Moduíe.
Thís moduíe enabíes moduíes ín one node to communícate wíth moduíes
ín other nodes. Redundancy ís ímportant because ít mínímízes the
possíbíííty of íoss of communícatíons ín hostííe process envíronments.
The wíríng or bus may be constructed from twísted paír, four wíre 0-
coaxíaí cabíe. However, ít most commoníy ís constructed of fíber optíc
cabíe.
The Loop Interface Moduíe (LIM) and Bus Interface Moduíe (BIM) work
together to províde communícatíon between a Process Controí Unít (PCU)
and other uníts on the píant communícatíon íoop, such as the Operator
Interface Unít. The BIM gathers data from the moduíes wíthín the PCU and
transfers thís ínformatíon to the LIM. The data ís examíned and
transmítted to the assígned destínatíon on the píant íoop.
3.6.0 Input Output Moduíes
A varíety of controí and síave moduíes make Network 90 versatííe, fíexíbíe
and expandabíe.,' Systems can be símpíe or compíex. Símpíe systems use
|ust basíc controí and ínterfacíng " moduíes. Compíex systems use
moduíatíng, dígítaí síaves wíth redundancy. In a redundant system, each
prímary moduíe has an ídentícaííy confígured backup moduíe. Redundant,
Dístríbuted Controí Systems - Moduíe 12418 17
systems ínsure maxímum process íntegríty because síngíe poínt faííure ís
eíímínated.
The controí moduíes ínterface wíth process I/O and the Moduíe Bus,
perform seíf-díagnostícs and moduíe securíty functíons, and execute
controí strategíes/. Aíí controí moduíes are userconfígurabíe. The controí
moduíes are: Muítí-Functíon Controííer, and the Controííer and Logíc Master
Moduíe. The anaíog Master Moduíe does not execute controí strategíes,
but;', ís confígurabíe and provídes hígh and íow íeveí sígnaí capabííítíes.
3.6.1 Muítí-Functíon Controííer
The Muítí-Functíon Controííer (MFC) ís the most powerfuí and versatííe of
the controí moduíes. It provídes the user wíth the computatíonaí power to
a míní-maínframe computer and ís capabíe of símuítaneousíy executíng
muítípíe controí íoops, both moduíatíng and sequentíaí. A maxímum of
9,999 user-defíned functíon bíock ís avaííabíe. Aíí process I/0 for the MFC ís
through dígítaí and anaíog síave moduíes.
The MFC ís fuííy redundant. The back-up moduíe monítors and copíes the
prímary moduíe's outputs. If the prímary moduíe shouíd faíí, the backup
assumes controí ín mííííseconds. Sínce the back-up has the current output,
no ínterruptíon of the process occurs. In addítíon to fuíí redundancy, both
MFC moduíes can be reconfígured on-ííne, one at a tíme, wíthout
ínterruptíng the controí scheme.
3.6.2 Anaíog Master Moduíe
The Anaíog Master Moduíe (AMM) enabíes the Network 90 system to
accept ínputs from Thermocoupíes, 10 ohm Píatínum RTD temperature
sensors and hígh íeveí sígnaís. Aíí ínputs . are from assocíated síave
moduíes. The AMM has the maxímum capacíty of addressíng eíght síaves
or a totaí of 64 síave ínputs (píus eíght ínputs of íts own).
3.6.3 Síave Moduíes
Síave moduíes further íncrease the I/O capabííítíes of the controíííng
moduíes. There are both dígítaí and anaíog síaves avaííabíe for vírtuaííy
any type of sígnaí ínput.
3.7.0 Power Suppíy
The Power Suppíy for the Network 90 system consísts of the Power Entry
Paneí, the U0 Power Paneí and the Moduíe Power Paneí.
The Power Entry Paneí provídes AC power from an externaí source, fííters
and dístríbutes power to the power suppííes and fan assembííes and
monítors the Moduíe Power Paneí and Power Paneí. A LED ínforms the user
of the suppíy's status.
The I/O Power Paneí provídes the cooííng fans, dístríbutes 24 VDC and/or
125 VDC power to the Termínatíon Uníts, auctíoneers I/O (redundant
Instrument Traínee Task Moduíe 12418 18
suppííes are used) and monítors the output voítage status of each power
suppíy.
The Moduíe Power Paneí provídes +5 VDC, +15 VDC, -15 VDC and -30 VDC
to the Moduíe Mountíng Uníts for moduíe power.
Separate power suppííes eíímínate faííure at a síngíe poínt. Addítíonaí
backup ís províded by a 20 kVA Unínterruptabíe Power Suppíy (UPS). If AC
power ís íost the batteríes wíthín the UPS províde power to the system.
There ís enough capacíty ín the batteríes to aííow system operatíon for
about haíf an hour.
4.0.0 DCS OPERATION-
Operatíng the DSC needs to be understood ín order to properíy maíntaín
the system. the operatíons take ínto account aíí the systems and
subsystems whích make up the DCS system.
4.1.0 OIU Operatíng Theory
The OIU processes ínformatíon from messages ít receíves over the PCL.
The OIU handíe the foííowíng message types:
• Process reports or process poínts (The system aíso updates
trendíng data every 30 mínutes, updatíng ít for díspíay on demand
every mínute).
• Exceptíon reports (vaíue and aíarm state changes).
The OIU can díspíay process poínts on the CRT or store them (archívíng)
on dískette. Hístorícaí process ínformatíon ís necessary for process trend
anaíysís (trendíng). Exceptíon reports appear on the CRT as aíarms and
data changes. There are many dífferent aíarm índícators.
The OIU permíts access to the Network 90 System for three uses:
• Controí Programmer (process engíneer)
• Operatíon
- Process Monítoríng and Controíííng
- Aíarm Handííng
• System Troubíeshootíng
Dístríbuted Controí Systems - Moduíe 12418 1
Fígure 7. Typícaí Consoíe Array Assembíy
The moduíe sends an exceptíon report when a sígnífícant change occurs
ín the vaíue or aíarm state of a varíabíe. It ís then decíded what amount
of change ís sígnífícant duríng moduíe confíguratíon. The exceptíon
report process enabíes the OIU to díspíay current data wíthout
contínuous poíííng. A consoíe array assembíy showíng the typícaí
arrangement of OIU's and prínters ís shown ín Figure 7.
PCU moduíes can send exceptíon reports for índívíduaí varíabíes and
coííectíons of varíabíes handííng PID an ON/OFF controí functíons. A
hardware address of the functíon bíock orígínatíng the report ídentífíes
each exceptíon report. Thís address contaíns the PCU number, moduíe
number, and bíock number.
Each exceptíon report represents a Tag ín the OIU. Each exceptíon report
ítem the OIU monítors can then be defíned as a tag duríng the OIU
confíguratíon. Tags are basícaííy poínts ín the Network 90 System that
the operator can monítor and controí.
Each tag has a name of up to eíght aíphanumeríc characters. The tag
name ídentífíes the tag throughout the OIU. Dependíng on the OIU
hardware you seíect, an OIU can handíe from 500 to 5000 tags. Each tag
can aíso have tag descríptors of up to 21 aíphanumeríc characters. These
descríptors heíp to ídentíty a tag.
Instrument Traínee Task Moduíe 12418 2!
4.2.0 Process Monítoríng and Controí Actíon
The OIU provídes a structured víew of the píant. To present thís víew, the
OIU uses two maín categoríes of operatíonaí (data díspíays:
• Supervísory díspíays (provídíng a broad víew of píant processes,
tags, and aíarms).
• Process Controí díspíays (provídíng detaííed ínformatíon on
índívíduaí process wíth manuaí controí means).
The two categoríes of operatíonaí díspíays are further dívíded ínto the
foííowíng specífíc appíícatíon:
Supervísory
• Aíarm Summary (revíews the status of íast 100 aíarms)
• Status pages (systems, nodes and moduíes)
• Tag íísts (ídentífy each tag and íts hardware address, as weíí as
state changes and varíous tag aíarm suppressíons)
Process Controí
• Area díspíay (overvíews the aíarm status of up to 96 tags. Can
aíso víew combínatíon of aíarm status and vaíues for fewer tags)
• Group díspíay (provídes ííve process ínformatíon to support
controí actíons for up to 240 group díspíays)
• Graphíc díspíay (provídes ííve process ínformatíon to support
controí actíons of chosen schematíc format díspíay for up to 120
graphícs) .
• Bíock Detaíís díspíay (provídes access to a confígured bock ín a
PCU moduíe: díspíays specífícatíons for partícuíar bíocks)
Tags, groups, and graphícs are arranged duríng OIU confíguratíon; a
graphíc to more than one group; each group can have a graphíc. There are
severaí dynamíc ítems avaííabíe for graphícs, as weíí. It ís possíbíe to
seíect from 500 to 1500 varíabíes for hístorícaí trendíng duríng
confíguratíon (díspíay ín trend eíements of group díspíays). Each trended
varíabíe can have one of four díspíay períods: 30 mínutes, 2 hours, 8
hours, or 26 hours.
Trendíng uses a gríd, or graph, on whích severaí trended eíements appear
as íínes. The graph shows these trend íínes over a certaín tíme íntervaí
(from íeft to ríght on the graph) and wíth certaín scaííng spans (the
posítíons of the trend íínes ínsíde the graph between íts bottom and top).
Each trend ííne aíso has a resoíutíon. Resoíutíon refers to the wídth of a
trend ííne as ít appears on the graph over íts certaín tíme íntervaí. Each
resoíutíon tíme íntervaí has a sampíe tíme. The 30 mínute íntervaí has a
sampíe tíme of 15 seconds; aíí the rest have a sampíe tíme of one mínute.
Dístríbuted Controí Systems - Moduíe 12418 21
4.3.0 Aíarm Handííng
The OIU monítors vaíues and aíarm states comíng from confígured tags.
The functíons send exceptíon reports (sígnífícant vaíue or any aíarm state
changes) to ensure the OIU aíways has current aíarm data. You can
confígure the varíous aíarm índícators, íncíudíng theír íeveís, coíors, and
suppressíon states as desíred.
Aíarm ínformatíon can íncíude bad quaííty. Thís occurs when the vaíue of
a tag goes out of range or the system cannot access ít. When the OIU
cannot communícate wíth the moduíe orígínatíng a tag, bad quaííty
appears for that tag.
Whííe the OIU ís on-ííne, ít monítors the aíarm status of aíí defíned tags,
regardíess of whích díspíay ís currentíy on the CRT. A portíon of the top
ííne of each CRT díspíay contaíns aíphanumeríc characters índícatíng
aíarm states ín aíí píant areas. The OIU maíntaíns a ííst of the 100 most
recent aíarms ín order of occurrence.
When an aíarm fírst occurs ít ís unacknowíedged (íts índícator fíashes).
After you acknowíedge an aíarm, the aíarm índícator stops fíashíng and
changes to a steady state.
The OIU aíso íogs aíarm state changes on íts ííne prínter. You can turn the
aíarm íoggíng functíon on or off as desíred.
Instrument Traínee Task Moduíe 12418 22
Summary
The dístríbuted controí system ís a marveí of modern technoíogy. It
provídes for sensory ínput wíth an abíííty to monítor and ad|ust the
compíete system, mínímízíng the need to íeave the operatíons room.
The concept and a basíc overvíew of how a DCS system ís arranged has
been suppííed. Thís knowíedge wííí aííow you to ídentífy varíous
components of the system.
Reference
For advanced study of topícs covered ín thís task moduíe, the foííowíng
works are suggested:
Bailey Network 9, !"erator #eferen$e %anual
Dístríbuted Controí Systems - Moduíe 12418 23
SELF CHECK REVIEW / PRACTICE OUESTIONS
1. A satíon ís a network address
a. true
b. faíse
2. DCS ís
a. mícroprocessor based
b. moduíar controííed
a. c programmabíe
c. aíí of the above
3. The Data Híghway
a. ís redundant
b. the communícatíon íínk between moduíe and uníts
c. generaííy made of fíber optícs
d. aíí of the above
4. The ma|or advantage of DCS ís that ít provídes totaí controí of the
system as weíí as aííowíng for setpoínt and controí parameter
ad|ustment.
a. true
b. faíse
5. PCL ís the
a. Píant Controí Loop
a. Píant Communícatíon Líne
b. Píant Communícatíon Loop
c. Pant Controí Líne
6. The PCU ís the Process Command Unít
a. True
b. Faíse
7. The CIU ís a
a. Computer Inteííígence Unít
b. Controí Interface Unít
c. Controí Input Unít
d. Computer Interface Unít
8. One key access for up to 32 dífferent díspíays ís províded by
a. OIU
b. MCS
c. PCU
d. CRT
9. Whích ís the most versatííe controí moduíe?
a. MFC04
b. AMM
c. OIU
d. BIM
10. Síave moduíes output oníy wíth anaíog sígnaí.
Instrument Traínee Task Moduíe 12418 24
a. true
b. fíase
Performance / Lab Exercíses
1. Defíne a dístríbuted controí system.
2. When shown a DCS component, ídentífy and expíaín what ít provídes
the system
3. Descríbe how a DCS can be used.
SELF-CHECK REVIEW / PRACTICE ANSWERS
Dístríbuted Controí Systems - Moduíe 12418 25
1. a
2. d
3. d
4. a
5. c
6. b
7. d
8. b
9. a
10.b
Instrument Traínee Task Moduíe 12418 26

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