Main Report DCS

8/12/2019 Main Report DCS

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DISTRIBUTED CONTROL SYSTEM

In process control technologies we have had numerousadvancements over the years. The following shows the modifications

that have taken place in chronological order:

Analog Control SystemsThese systems used operational amplifiers for their control

operations.

Digital Control SystemsThese systems use microprocessors and micro controllers for

their monitoring and control operations. They can be further

classified into:

Centralized Control System (CCS)This method employs the idea of centralized

monitoring and centralized control. In other words, there is only one processor which

performs both monitoring and controlling

operations of the plant.

Distributed Control Systems (DCS)This method employs the idea of centralized

monitoring but distributed control.

In other words, different units of the plant arecontrolled by different processors even though the

whole plant is monitored by one single master

station.


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BASIC STRUCURE OF A CENTRALISED CONTROL SYSTEM (CCS)

INPUT SIGNALS FROM FIELD OUTPUT SIGNALS TO FIELD

SET VALUES

CENTRAL PROCESSING

UNIT


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BASIC DCS LOOP

COMMUNICATION BUS

OUTPUTS TO FIELD

SET VALUES

OUTPUTS TO FIELD

SET VALUES

OUTPUTS TO FIELD

SET VALUES

INPUTS FROM FIELD

OPS1

FCS2

FCS3

FCS1

OPS2


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BASIC COMPONENTS OF DCS

The basic components of a DCS are listed below:

Field Control Station/ Central Processing Unit

Human Interface Station Operating Console Station Engineering Station

Communication Bus

Field Control Station

This unit all the controlling and monitoring operations of theplant.

All the instruments and interlocks created by software residein the memory of the FCS.

All the field instruments (inclusive of the Final ControlElements) like transmitters and control valves are wired to the

FCS.

Operating Console Station

This is a part of the Human Interface System (HIS). It is meant solely for monitoring and operating purposes. A continuous real time picture of the plant including the

process variables and high resolution graphics appear on the

screen of the OPS.

Any changes in values of process variables, detection of faultsby alarms are enabled in the OPS.


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Engineering Station

The Engineering Station constitutes the most important partof the HIS.

It features the engineering software (Standard BuilderFunction) which enables the system to perform the plantgeneration and maintenance operations.

Creation of new control loops, modification of existing loops,and introduction of new alarms, instruments, and graphics

are possible in this unit only, not in the OPS.

It has all the features of a general OPS as described earlier. This station differs from the general OPS because it is

endowed with the extra packages for setup and cancellationof FCS and HISwherever necessary.

Communication Bus

These are used as a medium to facilitate communicationbetween the various plant units and their respective control

stations as well with the other control stations and sub

stations.


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CENTUM CS-3000

Yokogawa was the worlds first organization to develop a real

time operating DCS. Its subsequent modifications in chronological

order are as follows:

CENTUM/ CENTUM V (first DCS ever) CENTUM-XL CENTUM CS CENTUM CS 3000 R3 CENTUM VP

We shall limit our discussion to the CENTUM CS 3000 R3

version only.

SYSTEM SPECIFICATIONS

Maximum number of stations per domain: 64 Maximum number of HIS per domain: 16 Maximum number of FCS per domain: 48 Station number for HIS: 49, 50, 51,., 62, 63, 64 Station number for FCS: 1, 2, 3, 4, 5,,, 46, 47, 48 Maximum number of domains per system: 16 Numbering of Domains: 1, 2, 3,, 62, 63, 64 Maximum number of stations per system: 256


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HIS SPECIFICATIONS

Maximum number of tags that can be monitored fromHIS : 100,000 (expansible up to 1,000,000 tags)

Maximum number of windows that can be created perHIS : 4000

Maximum number of Trend Recording Points per HIS :3328.

Engineering Station is used to do the engineeringbuilder for all the stations like HIS, FCS, CGW, BCV

etc.

ENG station is a PC loaded with engineering software(Standard builder function).

It is mainly used to perform CS3000 system generationand Maintenance Management.

The HIS can be loaded with engineering software, sothat it can be used as HIS as well as engineering

station.

Basic O/S Software: WINDOWS NT with Service Pack6A / WINDOWS 2000 with Service Pack 4A/WINDOWS

XP with Service Pack 2. Software: CS3000 R3 Packages with necessary

software licenses.


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CS-3000 COMMUNICATION NETWORKS

V-Net Communication NetworkThis network is used solely for the purpose of data

communication.

They employ BUS TOPOLOGY.Transmission Speed: 10Mbps.Transmission Distance: 500m to 20Kms. Medium of Transmission: Coaxial cable (V-Net, VL-

Net)/Optical Fiber.

Bus Coupler:

V-Net Cables are compatible to the FCS, while the VL-NetCables are compatible to the HIS.

V-Net Cables are suited for communication between an FCSand an HIS.

VL-Net Cables are suited for communication between twoFCS.

A device called BUS COUPLER is used in order to facilitatecommunication in the system between the HIS and FCS.

An adjoined diagram shows the schematic of such anetwork.

It basically performs level conversion of a data signaloutgoing from the data bus/ control bus.

A T connector is used wherever there is 1 FCS linked tomore than 1HIS.

A 50 ohm resistance is used as a terminator whereverthere is only one HIS connected to an FCS.


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THE BASIC V-NET SYSTEM

COMMUNICATION BUS (ETHERNET CABLES)

BUS 1 BUS COUPLERS

BUS 2

HIS1

HIS HIS3

HIS4

FCS

1

FCS

2

FCS

3

FCS

4


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V-Net/IP or Ethernet Communication NetworkThis network is employed for the purpose of data sharing

between a number of general purpose computers, printouts,

etc. It is enabled by a Local Area Network (LAN). It employs a STAR/ TREE topology.Transmission Speed: 1Gbps (Hardware), 100Mbps (general

communication) Medium of Communication: CAT5E, CAT6E, Fiber Optic

Cables.

Layer 2 Switch

It is a device that facilitates communication between theFCS and HIS in a V-Net/IP domain.

The maximum number of L-2 switches that can beconnected in a domain is 7.

The max. allowable distance between an L-2 switch and astation is 100m.

The maximum allowable distance between two L-2 switchesis 5km (when optical fibers are used).


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THE BASIC VNET/IP SYSTEM

BUS 1

BUS 2 BUS 2

BUS1

FCS

1

HIS

2

HIS

1

LAY 2

SWITCH

2

FCS

2

LAY 2

SWITCH

1


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The Domain Concept

A group of certain number of Field Control Stations (FCS)and Human Interface Stations (HIS) connected together is

called a domain. A maximum number of 64 stations can be connected perdomain.

Out of these 64, there will be a maximum of 48 FCS and 16HIS.

Multiple Domainsare used wherever:There are more than 64 stations to be connected. When there are multiple sections in the plant.To reduce the load on the system.

Layer 3 Switch

It is a device used to connect two domains in a V-Net/IPsystem.

It incorporates in itself all the features of an L-2 Switch too.

Bus Converter (BCV)

It is a device that links the domain of one system to thedomain of another system.

For example, it can connect the V net system bus of onesystem to another CENTUM CS 3000 domain or to anexisting CENTUM or XL(micro XL) system.

Different types of Bus Convertors are: V net to V net Bus Convertor: this is used to

connect CS3000 or Centum CS to CS3000 system. HF Bus to V net Convertor: this is used to connect

Centum V or Centum-XL toCS3000 system or CentumCS to CS3000 system. RL Bus to V net Convertor: This is used to connect

Micro-XL to CS3000 system.


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Communication Gateway Network (CGW)This feature links the V-Net communication bus to the

Ethernet bus.

CGW wide area communication function is used to link twoCENTUM CS 3000 V nets in different places using adedicated telephone line.


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Software Installation

Available Accessories:

1 Centum CS3000 software CD. 1 Floppy Disk for the key code/ license

1 key code is valid for 1 and only 1 HIS. It is an alphanumeric code.The network will reject the key code if it is used in more

than 1 HIS. 1 Instruction Manual CD

Installation of CS-3000 in VNet technology

Insert the installation disc into the CD slot. Insert the floppy disc into the floppy disk drive. A folder named COMDRV will appear on the disc along

with many other supporting system files. We select the COMDRV SETUP file and install it.

We restart the system now.The Network Adapterfile is now installed. We copy the license code from the floppy disc and paste it in

the field where it is asked for. However while pasting the key code onto the required field

the floppy disk should be inside the system drive, otherwisethe installation procedure will be aborted.

The processor card VF701 (dip switch set) is keptconnected to the HIS in the PCI (processor card interface)slot.

Enter the IP addresses in the Network Adapter field. Change the computer name. Restart the system. Remove the firewall (includes the control panel and

windows firewall). PING HIS and FCS.


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Software settings are required only for the HIS beforeinstallation.

The FCS will automatically download it from the HIS.The system is restarted once again and now ready for use.

The installation CD and the floppy disk can now be safelyremoved. For reinstallation we have to select the COMDRIVE

UNINSTALL file.The system is then restarted and the above procedure is

repeated.The general internet connectivity is provided by a separate

bus and supported by a Local Area Network (LAN).

Installation of CS-3000 in VNet-IPtechnology

Insert the installation disc into the CD slot. Insert the floppy disc into the floppy disk drive.Two folders named COMDRV and COMDRV OPN will

appear on the disc along with many other supportingsystem files.

We select the COMDRV SETUP file first and install it. We restart the system now.The Network Adapterfile is now installed. We copy the license code from the floppy disc and paste it in

the field where it is asked for. However while pasting the key code onto the required field

the floppy disk should be inside the system drive, otherwisethe installation procedure will be aborted.

The processor card VF701 (dip switch set) is keptconnected to the HIS in the PCI (processor card interface)slot.

Enter the IP addresses in the Network Adapter field. Change the computer name. Restart the system. Remove the firewall (includes the control panel and

windows firewall).


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PING HIS and FCS. Software settings are required only for the HIS before

installation.The FCS will automatically download it from the HIS.

We now select the COMDRV OPN SETUP file and installit.This extra file is required as the data communication as well

as the general internet communication (given by LAN) isboth supported by the same kind of buses.

We restart the system now.The system is restarted once again and now ready for use.The installation CD and the floppy disk can now be safely

removed. For reinstallation we have to select the COMDRIVE

UNINSTALL and COMDRV UNINSTALL files.The system is then restarted and the above procedure is

repeated.

POWER SUPPLY

The power supply delivered to an FCS is generally a 110VAC, 220V AC or 24V DC system.

The system is parallel and redundant. When the active source is in operation, another similar power

source runs parallel in standby mode.

Online Power Supply Replacement

Ensure that at least one switch is working properly. Turn OFF the replaceable power supply switch. Replace the switch. Turn ON the system again.


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DIP SWITCHES

These are certain adjustable miniature switches used forsetting the domain and station addresses of an FCS/HIS.

The Dip Switches are located on the Central Processing(CP) Card of the FCS.

Station addressing is discussed later in the report.

CENTRAL PROCESSORS

In any DCS, the central processors exist in the form ofredundant numbers so that failure of one processor doesnt

cause the whole network to trip.

To prevent tripping, we generally employ the concept of eitherActive Standby or Pair and Spare.

In the active standby mode, both the processors will beactive however only one of them shall be performing

controlling and monitoring actions, while the other will be

ready to take over whenever necessary.

Basic Scan Period:It is a fundamental property for any processor card and

is therefore an important criterion for measurement of

FCS performance.It has a maximum value of 1 second (slow but thorough

scan).It can however be adjusted to 500ms (Medium Scan) and

200ms (Quick Scan).


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Idle Time: It is the time given to a processor for free diagnosis after

completion of scan time.

It is done so as to ensure that the system doesnt sufferfrom loading errors, caused by low scan time.

Percentage Load on Processor: It is given by % Load= [{60-idle time}/60]*100

Online Processor Replacement Choose which processor to replace Ensure the presence of an anti static strip. Dip switches should be correctly set.

If the Standby Card is replaced:

Stop and remove the current standby processor card.

The active card is not disturbed. Replace the standby PCI slot with a new card.

If the Active Card is replaced:

Check if the Standby Card is working properly. Stop and remove the Current Active Processor Card.The Standby Card is not disturbed. Replace the Active PCI slot with a new card.


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STATION ADDRESSING

The figure adjoined in the next page, gives a brief description

on the addressing of a station (valid for both FCS and HIS). The

standard procedure is as follows:

Two dip switches are selected. One dip switch is for domain addressing The other dip switch is for station addressing. There are a number of ports on the Dip Switch which have to

be turned either ON/ OFF depending on the address to be

allocated to that respective station.

The number of switches turned ON should always be ofODD PARITY. If in any case the number of ON switches is even, we turn ON

the MSB to make the resultant number of ON switches as

odd.

The general prescribed format for denoting an FCS or HIS isFCS/DD/SS or HIS/DD/SS respectively.

Here, DD denotes domain number. Here, SS denotes station number.


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ADDRESS ASSIGNMENT TO A

FCS or HIS

OFF ON OFF ON

22 27 27

26 26

25 25

24 24

23 23

22 22

21 21

20 20

FOR DOMAIN-03 FOR STATION-03(DIP SWITCH) (DIP SWITCH)

MSB 1

1

1

1

1

1

1

1

MSB 1

1

1

1

1

1

1

1


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NETWORK ADDRESSING

For addressing a V-Net network: Card used: VF701. Driver software used: V-Net N/T adapter (for both data

buses)

IP address: 172.16:DD:SS Subnet Mask: 255.255.0.0

For addressing an V-Net/IP network: Card used: VI701 Driver software used:

V-Net N/T adapter: Data Bus (Bus 1) V-OPN adapter: Bus 2 (for General LAN/ Internet

connectivity with V-Net/IP).

For addressing general LAN/ Internet connectivity only: IP address: 192.168: (128+DD): (128+DD+SS) Subnet Mask: 255.255.255.0


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Creation of Project

The following is a standard procedure to create a project:

From the Start menu, we go to system view window. Create a Default Project. Creation of a default project includes the following:

Project name Project information Miscellaneous details

Create a new FCS and a new HIS.This is required as any project will consist of at least 1

FCS and 1 HIS.

Duplicate Next Card Tab When a new FCS is created, it is necessary to

assign it the address of FCS:01:01

By default, the redundant FCS is thenautomatically generated with address

FCS:01:02

Similar is the case when a new HIS is created. It is observed for both an FCS as well as HIS

that the initial slot is always an odd

number while the redundant slot is always

an even number.

Create Nodes using IOM (Input Output Modules) toenable conversion and transmission of signals from field

to control stations and vice versa.The IOM is a function that enables the creation of

nodes.

A maximum of four nodes can be created by an IOMin an FCS.


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The first node must always be a local node, whilethe other three may be local as well as remote

nodes.

Local Node A node that resides in the memory of the

FCS itself is called a local node.

This first node will always reside adjacentto the power supply port in processor

card.

Remote NodeThese nodes are located in the plant

cabinets and are composed of an

interface of ER BUS Interface and I/Omodules.

Next we design the individual I/O modules after takingthe various input and output processes under

consideration.

This is done using the IOM BUILDER DEFINITIONfunction.

Input and Output channels are configured for theirrespective roles by programming the FCS using this

user defined function.

Project Attribution:There are 3 kindsof projects as defined by

CENTUM CS 3000. They are:

Default Project(created when a system is runfor the first time)

Current Projecto When a default project is downloaded

onto an offline FCS it is called a current

project.


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o Online/ Real-time monitoring offunctions and operations is possible onto

that project then.

User Defined Project: A project copied fromeither a default or current project is called anuser defined project.

According to the previous definitions, we willattribute our project to one of these (as the case

may be).

Downloading to FCSThis option transfers the FCS execution data from

the HIS to FCS.

The execution data is a database containing theapplication logic to be copied onto the processor

card of the FCS.

There are 3 modes of downloading: Offline Download: This function downloads a

database generated by the application logic

developed in the HIS for the first time.

Online Download: This function downloadsonly those application logics created in the HIS

that were updated previously.

IOM Download: This function downloads onlythose application logics that are active as new

I/O modules (at present) having been

previously replaced.

After designing the logic, we update it and thenwe save the Control Diagram.


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This will initiate the downloading of data andinformation into the FCS.

Now, the project is created and is ready to be worked on.The various Control Loops required to meet the demands

of the process plant can now be created which isdiscussed in the next section.


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Creation of Closed Control Loops

This feature is enabled only in the Engineering Stationof a system.

A number of functional and user defined blocks areavailable for creation of simple and complex/ multiple

process control loops.

Let us use the PIO(Process Input/ Output block). We use a PID (Proportional Integral Derivative) block as a

controller.

Each block in the control drawing shall have to beendowed with the necessary operating instructions which

are given in the form of certain codes known as syntax. We are also required to fill up the Tag numbers of the

respective control blocks and they must match the

information filled in the syntax.

In the Control drawing we make the necessary wiringconnections and fill up the required information fields.

The Control drawing is now saved, after updating theindividual block details.

Upon applying an input to the PID controller we will nowget the visual display of an output change on a graphical

icon called the faceplate.

We can assign as well as remove alarmswherevernecessary.

We can further perform logic operations like AND, NAND,NOR, NOT, OR, X-OR, etc wherever necessary using

Logic Operation Blocks.

A special feature inside the logic blocks enables us tocreate time shifted responses.

The process controlling mode can also be programmed tochange.

The loop is now ready to receive inputs and give us thedesired outputs.

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Main Report DCS