DCS Handbook

8/12/2019 DCS Handbook

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DCS Handbook

DCS HANDBOOK


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DCS Handbook

CUSTOMER:

OBJECT: Distributed Control System Engineering

SUPPLIER:

ENGINEERED BY: FAST Automation S.p.A.

REVISION HISTORY:

Issue No Date Revision History

Issue 1.0 January 2000 First Issue

DATE : 10 Jan 2000

COMPILED BY : P. Capelli

CHECKED BY :

APPROVED BY :

DESTINATION : E1


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CONTENTS

0 INTRODUCTION

1 CONFIGURATION OF THE CONTROL SYSTEM

1.1 Introduction 11.2 Devices and Communication Net 1

2 GRAPHIC PAGES

2.1 Introduction 3

2.2 Tag denomination rules 32.3 Tag dynamic representation 62.4 Synoptic graphic page list 102.5 Moving among graphic pages 112.6 Interlock pages 112.7 Soft keys 12

3 ALARMS, MESSAGE AND SECURITY

3.1 Alarms 133.2 Message 133.3 Security 14

4 HISTORICAL TRENDS AND REPORTS

4.1 Introduction 154.2 Historical trends 154.3 Reports 16

5 FCS ENGINEERING CONCEPTS

5.1 Introduction 175.2 Analogue variables 185.3 Motors and On/Off valves 195.4 Alarm switches 205.5 Calculation 205.6 Interlock and sequences 205.7 Other blocks 21


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1. INTRODUCTION

This operator guide is to be a handy quick help for the first approach to the

supervision system.

All supervision instruments, programming tools and features available with the

Centum CS3000 Distributed Control System are already described in Yokogawa

Manuals.

Once the operator has got a basic knowledge by these manuals, this guide will

introduce him how the system has been configured, how all CS3000 features

(controllers and operator stations, I/O instruments, graphic pages, alarms etc.) have

been configured, programmed and combined to provide the supervision and the

monitoring of the plant.

Nevertheless all information that the operator will find on the screen is supposed to

be enough to perform all operations, this guide will be necessary just to take a little

of getting used.


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CHAPTER 1

CONFIGURATION OF THE CONTROL SYSTEM

1.1 Introduction

This section briefly describes the Distributed Control System (DCS) Configuration as engineered

for a polyester production plant.

The DCS provides integrated process control, supervision and management facilities, within the

unified architecture and open environment offered by Yokogawa CENTUM CS3000 control system.

1.2 Devices and Communication Net

The control system is basically composed by the following components :

. 1 Engineering Station (HIS)

. 3 Operator Stations (HIS)

. 1 redundant Controller (FCS)

. 1 redundant Control Network (V-NET)

1.2.1 Engineering Station

The Engineering Station is a PC with Pentium II processor, standard keyboard, mouse and operator

keyboard. It is equipped with the Yokogawa engineering software, that provides the tools

necessary to configure the control and supervision system of the plant (graphic pages, control

strategies, historical trends and so on); it also provides the operator with the process interaction

via a graphical user interface (see next paragraph : Operator Stations).

The Engineering Station is located in the Control Room.

1.2.2 Operator Stations

The Operator Stations are PCs with the same hardware platform as the Engineering Station; they

provide the man-machine interface, i.e. all operations done toward the plant (like setting a

variable, bypassing an interlock condition, start a motor, etc.), and the whole process and control

system monitoring, the alarm management, the event and alarm historization etc. are performed in

a CS3000 system through the Operator Stations.

Each Operator Station can be dedicated to supervise the whole plant areas (thus realizing the full

redundancy of the supervision functions), or only some plant areas.

The Operator Stations are also located in the Control Room.

The supervision system is also equipped with laserjet printers, for alarm logging, self-

documentation and report generation.


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1.2.3 Controllers

The process control (discrete and continuous data acquisition, algorithms for the regulation of

continuous variables, complex calculations, sequence and interlocks, etc.) is carried out by the

Field Control Station (FCS).

The FCS, also located in the Control Room, consists of the following elements :

. 1 Field Control Unit (FCU), that is the intelligent part of FCS and is dedicated to

algorithm computation, control strategies, etc.; it is equipped with redundant Power Supply,

redundant CPU and redundant V-NET board;

. 5 Nodes, each one made up of a NIU (Node Interface Unit), and a number of I/O modules

and/or communication modules that provide the interface functions to the field; the I/O

interface modules and the RS-232 Communication Modules are installed in dedicated nests;

. redundant RIO Bus(Remote Input Output bus) which connects FCU and Nodes together.

The Communication Modules are interfaces used to provide serial communication with the third

party PLCs and power center instruments.

The FCS is dual-redundant type. The processor card on board is fitted with two CPUs. If transient

error occurs, this is detected by comparing the calculation of the two CPUs; an error in the active

processor causes control to transfer to the standby processor. As the standby processor card carries

out the same control calculation as the active processor, continuity of control is mantained when

switching to the standby processor.

1.2.4 Control Network

The Engineering station, Operator stations and Controller are connected each others via redundant V-

net (Real-time control network), that provides the full communication between the various

component of the CS3000 system.

Furthermore the HISs are also connected each others via an RJ45 Ethernet network, by a 10Mb/s

HUB.


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03ISH-R01 Area 03, fault indication of agitator R01

32_1HC-P08C Area 32 part 1, Loc/Rem status indication of Pump 08C

2.2.5 On /Off Valves

Plant Area Code First two digits (i.e. 01,02,03,,...)

Subarea Code _ followed by one digit (i.e. _1, _2)

text CV

Instrument P&I No two or three digits and eventually one letter

Examples:

03CV02A Area 03, Valve 02A

10CV08 Area 10, Valve 08

2.2.6 On /Off Valve signals

Plant Area Code First two digits (i.e. 01,02,03,...)

Subarea Code _ followed by one digit (i.e. _1, _2)

Signal Tipe terxt ZSH : open proximity

ZSL : close dproximity

CV : command

Instrument P&I No - followed two or three digits and eventually by one letter

Examples:

03ZSH-02A Area 03, open proximity of Valve 02A10CV-08 Area 10, command to Valve 08

2.2.7 Other signals

Tag name of signals coming from local board (example : cutter board, TPA feeder board, etc.)

doesn t follow the above mentioned rules. As far as these name are concerned, please refer to

related I/O lists.


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2.3 Tag dynamic representation

2.3.1 Analogue Instruments

The analogue variables are divided in two main categories : not regulated and regulated variables.

A not regulated input variable is a variable whose value is acquired from the field. For example it

could be a temperature of an oil flow (input variable).

These variables are displayed in graphic pages as in the following :

01LRA-11 (tag name)

000.0 % (process value, eng. unit)

A regulated variable is a variable that takes part on the process outputting a regulating variable.

The value of the regulating output variable is modulated in order to keep the process variable as

close as possible to the set point value (entered by the operator).These variables are displayed in graphic panels as in the following :

04_1PRC-23 MAN (tag name, mode)

000.0 Bar (process value, eng. unit)

000.0 (set point)

000.0 % (regulating (or output) eng. unit)

The colour of the numeric field of process value of regulated and not regulated variables changes

according the following :

Colour Meaning

cyan no alarm (normal status)

flashing red not aknowledged alarm

steady red aknowledged alarm

flashing cyan not in alarm, but last alarm not acknowledged

All setting and displaying operations concerning the various parameters (thresholds, PID

parameters, set point, alarm state, etc.) might be done in any moment calling the faceplate and the

detail display of the point in two different ways:

- clicking on its relevant representation on the graphic pages

- clicking on the button NAME of the supervision upper menu and typing its tag name.

A not regulated output variable is a variable whose value is sent to the field. For example it could

be a set point to an inverter.

These variables are displayed in graphic panels as in the following:

set speed 000.0 %

Clicking on the button, the operator can easily set a value that is immediately sent to the related

physical device.


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2.3.2 Alarm Switches

Alarm switches are all the digital input signals that turn active when a specific alarm situation

occurs on the plant; they could be low level switches, high pressure switches, tank cover switches,

and so on.

Their representation in synoptic graphic pages is made by a character string (the tag name) that isplaced in the point where the alarm situation can arise; the dynamic graphic proprieties of alarm

switches follow this simple scheme :

Colour Meaning

dark grey no alarm

flashing red not aknowledged alarm


flashing dark grey not in alarm, but last alarm not acknowledged

The access to the faceplate of these instruments is possible by clicking on the button NAME of

the supervision upper menu and typing their tag name

2.3.3 Motors and On/Off Valves

Motors and on/off valves have been configured using the Switch Instruments Blocks (SIO).

A SIO can read discrete input data (answerbacks) and transmit discrete output data. When a

command is sent by an operator or a sequence, the outputs are driven to the specified values and

the inputs are evaluated in order to understand if the current status matches the command; if the

inputs do not match within the pre-set transition time, the SIO goes in alarm status.

The simplest way to send commands to on/off valves and motors from the Operator Station is

obtained by clicking on the graphic representation of the device in the synoptic, thus calling the

relevant faceplate. At this point it is possible to issue the desired command and/or read the status.

The access to the faceplate of the instruments it is also possible by clicking on the NAME icon

and typing the tag name.

Motors and on/off valves are displayed in synoptic graphic pages according to the following colour

code :

Motors

Colour Meaningwhite not running

green running

flashing red not aknowledged alarm (thermic or answerback

fault)


flashing white or green not in alarm, but last alarm not acknowledged

Valves

Colour Meaning

white closed

green open

flashing red not aknowledged alarm (answerback fault)



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flashing white or green not in alarm, but last alarm not acknowledged

Furthermore a red text IHS appears near each motor when the relevantd thermical fault goes

active.

Finally, motors can be operated either locally (from the field) or remotely (from the DCS). Local

or remote status indication is shown next to motors, by a LOC/ REM yellow text.

2.3.4 Buttons

Buttons are graphic points that provide the operator the capability to set continuous values (i.e.

setting an additive concentration in the dosing system), and discrete commands (i.e.

enabling/disabling an interlock).

The button representation and the operations to be made to issue the command are similar to the

ones for not regulating output variables; over each button the operator find a string with its

meaning.

2.3.5 Modulating valves

Modulating valves (or control valves) have been considered static objects. Their colour correspond

to the colour of the process pipes where they are located.

In order to know how much the valves are open (or closed), it is necessary to read the output value

of the related loops.

2.3.6 Material flows and pipe colours

The plant piping represents the most important static information, as it allows to follow process

flows. The main pipes are drawned according to the following categories:

Pipe Colour Meaning

Red TPA and Product flow

Blue Glycol flow

Grey Steam flow anf Vacuum

Green Water flow

Light blue Air flowOrange Oil flow

Yellow Nitrogen

Magenta Additive flows

2.3.7 Texts

Various text labels have been used in the synoptic graphic panels near the objects (instruments,

equipment), in order to show their real name; furthermore, text labels close to flow pipes give an

indication about the flow pipe destination in the plant. All these labels are displayed in whitecolour.


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Labels showing an interlock number (i.e. Int.22) have been placed near the instruments that are

handled by interlocks or sequences. These labels are normally displayed in dark grey colour; when

the relevant interlocks go active (it means that at least interlock condition turns on), they change to

red colour, thus giving the operator the information on locked situation.

2.3.8 Bargraphs

Bargraphs are present near objects everywhere an analogue level value is measured.


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2.4 Synoptic graphic page list

The following table shows the list of synoptic graphic panels :

Area Panel Name

01 EG-STORAGE

02 PTA

03 PASTE-MIXER

ESTERIFICATOR

HEATING

04 1REACTOR

1HEATING2REACTOR

2HEATING

04-B-02

VACUUM

05 EXTRUSION

06 CHIPS

08 ADDITIVES

TIO2

10 EG-RECOVERY

18 TEG-STORAGE

TEG-RECOVERY

19 TEG-FILTER

32 BOILER

STEAMDIPHYL

CUTTING

33 COMPRESSOR

35 UTILITIES-DEMI

60/61 SCRUBBER

POWER CENTER POWER


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2.5 Moving among graphic pages

TheMain Overviewis a display that can be easily called by clicking on the dedicated icon in the

upper main menu or typing the dedicated function key in the operator keyboard; the Main

Overview page has been configured in order to give the operator the capability to immediately call

each synoptic graphic page. It means that whatever supervision display is operating, (graphicpanel, trend, faceplate, alarm display), it is possible to quickly jump to a desired synoptic simply

passing through the Main Overview page and clicking on the relevant box.

Furthermore, from each page it is possible to call all the logically connected synoptic pages

(logical connection is referred to physical process); this operation can be easily done clicking on

the arrows placed at the end of the flow pipe.

The operator keyboard provides another direct access to synoptics, thanks to the fact thet most of

its function keys have been configured to call them.

Finally a synoptic graphic page can be accessed directly from the faceplate of each point included

in the panel, clicking on the dedicated icon in upper menu.

2.6 Interlock pages

The interlock pages are graphic pages used to display the status of interlocks and sequences

(enabled or disabled) and provide access to related control groups.

Four interlock pages have been configured :

. Interlock page Area 03

. Interlock page Area 04

. Interlock page Area 10-18-19

. Interlock page Area 08-32-33

They are accessible by Main Overview Page, by dedicated function keys in the operator keyboard

and, finally, by dedicated soft keys from synoptic pages.

For each interlock or sequence the following information is displayed :

.Number

. Brief functional description

. Status (enabled/disabled)

. Control Group (that can be accessed clicking on the relevant button)

The Control Group is generally a graphic page that includes more instrument faceplates; speakingabout interlocks, control groups have been realised to give an immediate view about the current

interlock situation.

The set of interlock pages and control groups allows a complete monitoring and management of

interlock and sequences. Nevertheless, some information about interlocks and sequences is also

shown in the synoptics, in fact close to each involved equipment (motor or valve), a red text

appears if at least one related interlock condition goes active.


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2.7 Soft Keys

Soft keys are functional buttons placed in the bottom of synoptic graphic panels; they can be

configured to give the operator the capability to run specified functions directly from the page they

are included in.

In the developed supervision system the soft keys have been configured to realise the following

tasks:

. calling the Main Overview page;

. calling the interlock pages (This rule is only for synoptic pages that include at least one device

managed by an interlock or a sequence);

.calling the historical trends of the points included in the synoptic page;

. calling dedicated pages (i.e. pages for setting the dosing values, or pages showing the signal

detail of devices such as cutter).


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CHAPTER 3

ALARMS, MESSAGES AND SECURITY

3.1 Alarms

HIS grouping configuration is the function that assigns plant area to HIS; it means that a single

Operator Station can manage the whole plant or only some plant areas according to its grouping

configuration.

These considerations are obviously valid also for alarm management; in other words, from an

Operator Station the operator can handle the alarms (silencing the horn, acknowledge the alarms,

etc.) for only those points allocated in the HIS by grouping assignment.

(Buttons to silent the horn and acknowledge alarms are placed both in the operator keyboard and

in the upper menu of the supervision pages).

Process alarm acknowledgement can be indifferently done from the instrument faceplate (single

acknowledgement), from the synoptic page (acknowledgement of all the alarms active on that

page) or from the process alarm display (acknowledgement of all the active alarms).

In order to have a summary of the process and system alarms, the process alarm and the system

alarm displays can be called clicking on the dedicated icons on the main upper menu. This pages

let available all the information regarding alarms belonging to assigned area: date and time,

acknowledgement status, type of alarm, description, etc.; furthermore the colour of the associated

mark gives an immediate information about alarm priority.

From the point of view of priority, alarms can be configured according the following :

. High priority

. Medium priority

. Low priority

. Logging

This scheme implies different actions regarding horn sounds, output on printer and display,

locking after acknowledgement and so on.

3.2 Messages

Other than default messages (process and system alarms),two kinds of message have beenconfigured using the tools of CS3000 engineering software, with the aim to provide the operator

with a further information about some conditions that are potential for critical situations :

.Alarm Annunciators

. Operator Guide messages

Alarm Annunciators advise the operator with a horn sound and a message regarding an alarm

situation or an interlock intervention, i.e. 32-B-01 HIGH LEVEL , INTERLOCK 63 ACTIVE,

etc.


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The message appears in the dedicated row in the upper part of each supervisor display and is

collected in the process alarm display.

Operator Guides output further messages about interlock actions and sequence situation, i.e.

POLYMER PUMP STOPPED BECAUSE PRESSURE IS TOO HIGH (INT.37) and, in somecases, give operators suggestion about action to be taken, i.e. SEQ.64 - INSERT LOAD TIME

AND ERROR TIME .

When a new Operator Guide message goes active, the horn sounds and the dedicated button

(placed on the operator keyboard) and icon (in the upper main menu) start to blink. Typing the

button or clicking on the icon the message appears.

3.3 Security

Usually two kinds of personnel interact with the control system during the life of the plant :

. Engineers, that have in charge the development of software necessary to control and

supervise the plant.

.Operators, that have in charge the running of the plant.

Two hierarchical level of system users have been defined in order to practically realise this task

partition :Administrator and Users.

People that can be logged as Administrator have the access to CS3000 engineering tools; it means

they can add, change or delete instruments, interlocks and sequences, synoptic pages, trend panels

and so on.

People that can be logged as Operator can access all the control and supervision objects realised by

engineers; it means they can supervise the plant (read process values and states, send commands,

manage alarms, display trends, and so on ), but they cannot work with engineering tools.

The level of access to the system is defined by the password typed when log-on.

Another level of security is realised at operator level, in order to give operators different privileges

according to their duties; the privilege practically defines the type of function the operator can

perform on the supervision system.

CS3000 defines 3 standard default privileges :

. ENG

. ON

. OFF

The privilege depends by the position of the security key in the operator keyboard or, in case that

the operator keyboard is not present, it depends by the password set with the dedicated icon in the

upper main menu.

The operator can act on the supervision objects (instrument faceplates, synoptic pages, etc.)

according to the current security key position (or password) and according to the security level

assigned to the objects during the configuration, i.e. an operator can start a motor or change an

alarm threshold only if the privilege scheme allows these operations.


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CHAPTER 4

HISTORICAL TRENDS AND REPORTS

4.1 Introduction

The CS3000 system performs historization of the process data by means of the configuration of

trend panels.

An interface with Microsoft Excel provides a way to obtain printing of plant reports, such as

consumption data, process data statistics and so on.

4.2 Historical trends

An historical trend is a graphic representation of the values of a process variable collected during a

pre-defined period in the life of the plant; at any moment the trend can be printed on the screen or

the printer, thus providing the personnel with a further powerful way for the plant management.

Historical trends are organised on page basis, where each page can show up to eight variables;

generally the trend pages have been configured with the aim to include variables that are logically

connected from the point of view of the process. At the end of this paragraph the complete list ofthe configured trend pages is shown.

The sample time and the time span are configurable data (please refer to Yokogawa manuals).

Actually in each trend page data are collected according the following rules :

. sample time = 1 minute

. time span = 2 days

It means that all the variables are registered on two days basis; because of the circular structure,

further acquired data overwrite the oldest values.

Historical trends can be accessed in three different ways :

. calling the instrument faceplate which trend is required and clicking on the dedicated

button of the upper main menu;. passing through the Trend Overview Page; it is a graphic page that provides the operator

the capability to immediately call every configured trend page;

. each synoptic page contains the soft keys that provide direct access to the trends of the

analogue variables included in that synoptic


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Trend page list

Area Panel Name Area Panel Name

01 EG-STORAGE 05 FILTER

CUTTER03 DOSING SYS

TPA FLOW 08 ADDITIVES

03K01 TiO2

03C01 (1)

03C01 (2) 10 10X01 (1)

03K01 HEAT 10X01(2)

03C01 HEAT 10B01

03C01 HEAT

18 18K01

04 04K01 18B05

04C01 18B01-02-06

04C01 HEAT

04C01 HEAT 20 AREA 20

04R01

SPEED-CURR 32 BOILER

04R01 HEAT STEAM

04B02 FLOW DIPHYL

04B02 TEMP AIR PROD

VACUUM 1

VACUUM 2 60-61 SCRUBER

4.3 Reports

The raw material consumption and PET production report has been realised in the Engineering

Station using Report Package, that is a dedicated package developed on Microsoft Excel platform.

The application program is scheduled on daily basis, that means every day, at a fixed time, the

system automatically prints the table containing the raw material consumption and PET production

data .The flows of all the materials consumed in the plant (glycol, additives and so on) are available as

analogue input; the PET flow is computed on the basis of pump speed and capacity.

Other than the Report Package, one further application is involved in the report management :

. the scheduler, which is a standard CS3000 engineering software tool, provides the System

Administrator the capability to print the report at a fixed time and frequency.


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CHAPTER 5

FCS ENGINEERING CONCEPTS

5.1 Introduction

The following chapter will briefly describe the basic concepts about the main software instruments

used to develop the FCS (Field Control System) application software, that is the heart of the whole

control system. FCS application software includes the field interface (field variable collection and

output setiings), control and regulation alghoritms, complex calculations development, interlock

and automatic sequences realization and so on.

The aim of the handbook is only to give the DCS users a general view about the functions

involved in the system they work with; for complete details about FCS software please refer toYokogawa manuals (IM 33S1B30-01E).


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5.2 Analogue variables

The Input Indication Block (PVI) is used to implement the Analogue Input module, i.e the

functional block that realise an analogue variable acquisition from the field.

ExampleIN

%%03TT-19 03TR-19

(PVI)

%%03TT-19 represents the physical connection of the field instrument to CS3000; it is realised by

its assignment in a a channal of an analogue input board.

03TR-19 is the PVI, i.e. the software block that provides the analogue input acquisition function.

When this diagram is loaded into FCS, a process variable with Tag name 03TR-19 is available to

the whole control system, and it can be referenced for all the control and supervision functions,such as graphic display and history collection.

The PID Controller Block (PID) provides the function that implements proportional-integral-

derivative control based on deviation between a process variable and a set point.

ExamplesIN OUT

%%03FT-08 03FRC-08 %%03FV-08

(PID)

IN

%%03TT-13 03TRC-13

(PID)

OUT

SETIN OUT

%%03FT-10 03FRC-10 %%03FV-10

(PID)

The examples show a simply PID block and two PID blocks that can operate in cascade mode.

%%03FT-08, %%03TT-13 and %%03FT-10 are the connection with the regulated variables

(inputs);

%%03FV-08 and 03FV-10 are the connections with the regulating variables (outputs);

03FRC-08, 03TRC-13 and 03FRC-10 are the blocks that implement the PID algorithm; their tag

names are referenced in the all the DCS application sofware to realize the control and supervision

functions. Furthermore the plant personnel can act on them to change PID parameters, operatingmode, set point, etc.


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The Manual Loader Block (MLD) provide the CS3000 operators the capability to manually force

analogue actuators such as the motor inverters, or set continuous values such as the additive

concentration.

Example

OUT

03SET-R01 %%03SV-R01

(MLD)

%%03SV-R01 is the connection with the physical actuator;

03SET-R01 is the software instrument by which the operators can set the inverter speed.

5.3 Motors and On/Off valves

Motors and On/Off valves are implemented by Switch Instrument Block (SIO), that is a software

instrument that can read discrete input data (answerbacks) and transmit discrete output data.

. SIO-11 : 1 input data - 1 output data

. SIO-21 : 2 input data - 1 output data

ExamplesIN OUT

Motor : 03ESI-P01S 03P01S 03ST-P01S

(SIO-11)

TSI

CPVIN

03HC-P01S 03P01S-REMOTE

(NOT)

IN OUTOn/Off valve : 03ZSH-06A 03CV06A 03CV-06A

(SIO-21)

03ESI-P01S and 03ZSH-06A are the discrete input data, respectively the status of the motor

(running/stop) and the open proximity of the valve;

03ST-P01S and 03CV-06A are the discrete commands, respectively the start/stop and the

open/close command;

03HC-P01S is the local/remote switch;

the discrete input and output data and the local/remote switch are defined by their assignment in

the channels of a digital board.03P01S and 03CV06A are the tag names that allow the reference for operators and other software

blocks, every time they have to be managed.


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03P01S-REMOTE is a NOT function block used to invert the local/remote switch.

5.4 Alarm switches

The physical connection of an Alarm Switch in the relevant input board simply performs its

implementation in the control system. Furthermore the software link with an Alarm Annunciatorprovides the alarm features.

5.5 Calculation

The arithmetic calculation and logical function can be implemented by the general purpose

calculation block (CALCU), using an expression description language.

General purpose calculation have been used in the application software every time a calculation

algorithms was required; an example is the development of the dosing system in the paste mixer.

Example

DEG-CALCU

(CALCU)

5.6 Interlock and sequences

Interlock and sequences are the procedures that carry out automatic action of some devices,

according to the behaviour of the process.

The word interlock define a procedure that has in charge the moving of one or more actuators as

answer to events that may be critical for the process or for the safety of the plant equipment (for

example stopping the dosing system because the paste mixer agitator is not running).

The word sequences instead define a procedure whose actions depend from events that are

considered to be normal in the process running (for example opening and closing an On/Off valve

to charge and discharge a tank).

The software blocks involved in these functions are the Sequence Tables (ST16) and theSequential Function Chart (_SFCSW).

Please note that both types of block can realise interlocks and sequences; their use only depends by

the specific application to be realised, that sometimes lets one type of block more suitable to easily

realise the required function.

Example

INT-29

(ST16)


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5.7 Other blocks

Please find in the following the list of other types of functional blocks used in the development of

application software :

TM : Timer Block, that measures the time in minutes or seconds thus providing periodic actions.

CTS : Counter Block, that counts the number of events.RL : Relational Expression Block, that provides the implementation of relationships between

two data, for example two process variable, or one process variable and one fixed value.

Documents

DCS Handbook