15.3.0 Programmable Logic Based Control System :
15.3.1 PLC Processor : The processor unit shall be capable of executing the following functions :-
a Receiving binary and analog signals from the field and operator initiated commands from OWS/ control panel.
b Implementing all logic functions for control, protection and annunciation of the equipment and systems.
c Implementing modulating control function for certain application as specified elsewhere in the specification.
d Issuing control commands.
e Providing supervisory information for alarm, various types of displays, status information, trending, historical storage of data etc.
f Performing self-monitoring and diagnostic functions.
15.3.1.1 The controller shall provide all basic functions for binary gating operations, modulating controls, storage, counting, timing, logging, transfer operations and comparison functions. The Contractor in his bid shall submit full details regarding various functions along with expansion capability.
15.3.1.2 The programmable system shall be delivered completely programmed for the complete and reliable operation of the plant.
15.3.1.3 Each PLC unit shall be provided with two processors (Main processing unit and memories) one for normal operation and one as hot standby. In case of failure of working processor, there shall be an appropriate alarm and simultaneously the hot standby processor shall take over the complete plant operation automatically. The transfer from main processor to standby processor shall be totally bumpless and shall not cause any plant disturbance whatsoever. In the event of both processors failing, the system shall revert to fail safe mode. It shall be possible to keep any of the processors as master and other as standby. The standby processor shall be updated in line with the changes made in working processor.
15.3.1.4 The memory shall be field expandable. The memory capacity shall be sufficient for the complete system operation and have a capability for at least 20% expansion in future. Programmed operating sequences and criteria shall be stored in non volatile semi conductor memories like EPROM. All dynamic memories shall be provided with buffer battery back up which shall be for at least 360 hours. The batteries shall be lithium or Ni-Cd type.
15.3.1.5 The PLC system shall be provided with necessary interface hardware and software for dual fibre optic connectivity & interconnection with station wide LAN ( In Purchaser’s Scope)for two – way transfer of signals for the purpose of information sharing. The plant information shall be made available through an OPC compliant Ethernet link following TCP/IP standard. The exact data structure shall be as decided during detailed engg. All required plant data shall be transferred to/from through this ensuring complete security. The exact number of points to be transferred through the above communication link and the format of the data shall be finalised during detailed engineering.
15.3.1.6 Two (2) nos latest version of PC based Operator Work Stations each with 19” color CRT’s and key boards shall be provided for control & monitoring and programming function. One no. number heavy duty A3 size color inkjet printer shall be provided along with operator work station.
PC based OWS (Operator Work Station, Spec. as provided at the end of this chapter) shall perform control, monitoring and operation of all auxiliaries/ drives interacting with PLC based control system. It shall be possible to use the same as programming station of the PLC. It shall basically perform the following functions. In case the PC based OWS can not be used as programming station of the PLC, then a separate PC based programming station shall be provided.
A Operator interface for PLC based control system. Operator functions shall as minimum include local/ remote selection, A/M selection, open/ close operation, sequence auto, start/ stop selection, ON/OFF, bypassing criteria etc.
b Supervisory functions like:-
Mimic displays, which shall depict the process in graphical form and shall cover all the process areas being monitored.
Alarm monitoring/reporting, generation of logs, calculations, printing of logs & reports etc.
c Suitable Interface with stations wide LAN ( In Purchaser’s Scope) for two-way transfer of data.
15.3.1.7 Programming station shall have access to the processor of the control system for programming. Programming shall not require special computer skills. On the programming console, it shall be possible to do the programming, self-diagnostics, testing of sequence, simulation and any sequence modification.
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Programming shall be possible in any of the following formats : |
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a)
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Flow-chart or block logic representing the instructions graphically. |
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b) |
Ladder diagrams. |
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A forcing facility shall be provided for changing the states of inputs and outputs, timers and flags to facilitate fault finding and other testing requirements. It shall be possible to display the signal flow during operation of the program. Programming shall be possible OFF line. |
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A NORMAL / TEST / PROGRAM / OFF lockable selector switch shall be provided. In case of test mode of operation, all outputs should be blocked. |
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15.3.1.8 Provision shall be made for erasing and duplicating the user program and longterm storage facilities shall be provided with the help of mag. tape cartridge or EPROM.
15.3.1.9 Priority of different commands shall be as follows :
15.3.1.10 Manual intervention shall be possible at any stage of operation. Protection commands shall have priority over manual commands and manual commands shall prevail over auto commands.
15.3.1.11 In PLC controller, memory should exist as to where the sequence was aborted due to power supply failure so that further operation from that point can restart after power supply restoration. This restart after recovery of the power supply shall be through operator intervention so as to enable verification of readiness of other related equipments.
15.3.1.12 All necessary software required for implementation of control logic, operator station displays / logs, storage & retrieval and other functional requirement shall be provided. The programs shall include high level languages as far as possible. The contractor shall provide sufficient documentation and program listing so that it is possible for the Purchaser to carry out modification at a later date.
15.3.1.13 The Contractor shall provide all software required by the system for meeting the intent and functional/parametric requirements of the specification.
a. Industry standard operating system like UNIX/WINDOWS NT etc. to ensure openness and connectivity with other system in industry standard protocols (TCP-IP/ OPC etc.) shall be provided. The system shall have user oriented programming language & graphic user interface.
b. All system related software including Real Time Operating System, File management software, screen editor, database management software. On line diagnostics/debug software, peripheral drivers software and latest versions of standard PC-based software and latest WINDOWS based packages etc. and any other standard language offered shall be furnished as a minimum.
c. All application software for PLC system functioning like input scanning, acquisition, conditioning processing, control and communication and software for operator interface of monitors, displays, trends, curves, bar charts etc. Historical storage and retrieval utility, and alarm functions shall be provided.
d. The Contractor shall provide software locks and passwords to Purchaser’s engineers at site for all operating & application software so that Purchaser’s engineers can take backup of these software and are able to do modifications at site.
15.3.2 Input/Output Modules :
15.3.2.1 The PLC system should be designed according to the location of the input/output cabinets as specified
15.3.2.2 Input Output modules, as required in the Control System for all type of field input signals ( 4-20 mA, RTD, Thermocouple, non change over/change over type of contact inputs etc.) and outputs from the control system (non change over/change over type of contact, 24/48 VDC output signals for energising interface relays,4-20 mA output etc.) are to be provided by the Contractor.
15.3.2.3 Electrical isolation of 1.5KV with optical couplers between the plant input/output and controller shall be provided on the I/O cards. The isolation shall ensure that any inadvertent voltage or voltage spikes (as may be encountered in a plant of this nature) shall not damage or mal-operate the internal processing equipment.
15.3.2.4 The Input/output system shall facilitate modular expansion in fixed stages. The individual input/output cards shall incorporate indications on the module front panels for displaying individual signal status.
15.3.2.5 Individually fused output circuits with the blower fuse indicator shall be provided. All input/output points shall be provided with status indicator. Input circuits shall be provided with fuses preferably for each input, alternatively suitable combination of inputs shall be done and provided with fuses such that for any fault, fuse failure shall affect the particular drive system only without affecting other systems.
15.3.2.6 All input/output cards shall have quick disconnect terminations allowing for card replacement without disconnection of external wiring and without switching of power supply.
15.3.2.7 The Contractor shall provide the following monitoring features:
a Power supply monitoring.
b Contact bounce filtering.
c Optical isolation between input and output signals with the internal circuits
d In case of power supply failure or hardware fault, the critical outputs shall be automatically switched to the fail-safe mode. The fail-safe mode shall be intimated to the successful Contractor during detailed engineering.
15.3.2.8 Further, keying-in of individual wire connectors shall be provided to ensure that only the correct card is plugged on the I/O module. It shall be possible to remove I/O module without disconnecting wiring from field inputs or outputs. There shall be atleast 20% spare capacity available on input, output and memory modules, over and above the system requirement.
15.3.2.9 Binary Output modules shall be rated to switch ON/OFF coupling relays of approx. 3 VA at 24 VDC. Analog ouput modules shall be able to drive an load impedance of 500 Ohms minimum.
15.3.2.10 Output module shall be capable of switching ON/OFF inductive loads like solenoid valves, auxiliary relays etc. without any extra hardware.
15.3.2.11 Only one changeover contact shall be provided in MCC for control and interlock requirement. Further multiplication, if required ,shall be done by the contractor in PLC system.
15.3.2.12 All input field interrogation voltage shall be 24V DC or 48 V DC.
15.3.2.13 In case of loss of I/O communication link with the main processing unit, the I/O shall be able to go to predetermined fail safe mode (to be decided during detailed engineering) with proper annunciation.
15.3.2.14 Contractor shall provide for 20% spare I/O modules in each system cabinet to take case of any further addition.
15.3.3 Printer
One number A3 size color inkjet printer per PLC shall be provided as a part of the supervisory system. It shall print out all alarm/trip conditions and event changes in plant status alongwith date and time of occurrence. The time least count for event recording shall not be more than 100 milliseconds.
15.3.4 Data Communication System (DCS)
The DCS shall include a redundant System Bus with hot back-up and other applicable bus systems like cubicle bus, local bus, I/O bus etc.
The DCS shall have the following minimum features :
a Redundant communication controllers shall be provided to handle the communication between I/O Modules (including remote I/O) and PLCs and between PLCs and operator work station.
b The design shall be such as to minimise interruption of signals. It shall ensure that a single failure anywhere in the media shall cause no more than a single message to be disrupted and that message shall automatically be retransmitted. Any failure or physical removal of any station/module connected to the system bus shall not result in loss of any communication function to and from any other station/module.
c If the system bus requires a master bus controller philosophy, it shall employ redundant master bus controller with automatic switchover facility.
d Built-in diagnostics shall be provided for easy fault detection. Communication error detection and correction facility (ECC) shall be provided at all levels of communication. Failure of one bus and changeover to the standby system bus shall be automatic and completely bumpless and the same shall be suitably alarmed/ logged.
e The design and installation of the system bus shall take care of the environmental conditions as applicable.
f Data transmitting speed shall be sufficient to meet the responses of the system in terms of displays, control etc. plus 25% spare capacity shall be available for future expansion.
g Passive coaxial cables or fibre optic cables shall be employed.
The Contractor shall furnish details regarding the communication system like communication protocol, bus utilisation calculations etc.
15.3.5 System Reaction Time
The reaction time of the programmable control system from input signals at the input cards to output of the associated signals or commands of the output card inclusive of programmed logic processing, comprising a mixture of logic gates, arithmetic operations and other internal operations shall be less than 100 milli seconds under the most arduous control system operating conditions.
15.3.6 Operator Interface Displays/Logs
Suitable displays and reports for control operation & monitoring shall be provided. The details shall be finalised during detailed Eng. stage.
15.3.7 Control & Power Supply Scheme
15.3.7.1 For PLC system, redundant 24 V DC power supply shall be provided by the contractor. Necessary redundant transformers and redundant chargers with 24 V DC battery back-up shall be provided by the Contractor to derive power supply from 415 V, 3-phase redundant incomers of 415V MCC. The Contractor shall, however, furnish all required hardware/ equipment/ cubicles for conversion and/or stabilisation of the power source to all other levels which may be necessary for meeting the individual requirements of equipments/ systems furnished by him within the Contractor’s quoted lumpsum price. For separately mounted I/O racks, separate power supplies shall be provided. Power supply module shall be of ample capacity to supply all modules. In addition 20% spare capacity for future shall be provided. All the drives shall be switched ON/OFF through 24V DC coupling relays to be provided in HT/LT SWGR panels. Complete power supply scheme above with power supply distribution cabinets shall be in the scope of Contractor. The exact power supply scheme shall be as approved by Purchaser during detailed Engineering stage.
15.3.7.2 Each set of PC along with CRT shall be provided with smart type line interactive UPS with software & hardware for remote management along with features of surge suppression & AVR facility by the Contractor. The UPS shall be of sufficient capacity of at least 30 minute at machine load.
15.3.7.3 The battery shall be sealed maintenance free Ni-Cd type or Plante type Lead Acid batteries with long life and shall be able to provide a back-up for one hour at full load requirement of the complete control system.
15.3.8 Annunciation System
15.3.8.1 Contractor shall provide annunciation system as integral part of PLC system. Field contacts shall be acquired through PLC only. The annunciation sequence logics shall be implemented as a part of PLC controllers. The annunciation window lamps mounted on control panel shall be driven through contact output modules of PLC. It shall be preferable to have each window as mosaic compatible. The lamp box shall have removable impact polystyrene window shall be 50 mm x 50 mm or 48mm x 48mm with 5 mm size inscription in black lettering on white background. Each annunciation window shall be back lighted with two long life LED lamps The changing of lamps shall be conveniently done from the front by single removal of window. Redundant audible devices for alarms shall be cone type or metallic horn type and shall be driven by electronic tone generator of adjustable width and sound level. The trip alarm audible & ring back audible shall be differentiated from other alarms.
15.3.8.2 The annunciator sequence shall conform to ISA sequence ISA-2A. The number of annunciation facia windows and the provision for original input will be on as required basis. However, the minimum number of facia windows, signal input to the annunciation system shall be 50 nos.
15.3.9 Software Documentation and Software Listings
15.3.9.1 All technical manuals, reference manuals, user’s guide etc., in English required for modification/editing/addition/deletion of features in the software of the PLC System shall be furnished. The Contractor shall furnish a comprehensive list of all system/application software documentation after system finalisation for owner’s review and approval.
15.3.9.2 All The software listings including Source code for application software, All special-to-project data files etc. shall be submitted by the Contractor:
15.3.9.3 SOFTWARE LICENCES
The Contractor shall provide software license for all software being used in control system. The software licenses shall be provided for the project) and shall not be hardware/machine-specific. That is, if any hardware/machine is upgraded or changed, the same license shall hold good and it shall not be necessary for owner to seek a new license/renew license due to upgradation/change of hardware/machine at site. All licenses shall be valid for the continuous service life of the plant.
15.3.9.4 Software Upgrades
As a customer support, the Contractor shall periodically inform the designated officer of the owner about the software upgrades/new releases that would be taking place after the system is commissioned so that if required, same can be procured & implemented at site.
15.3.10 Specifications of PC
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The minimum requirement for PC shall be as below: |
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CPU |
Latest with adequate no. of Ethernet/ LAN connectivity port |
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Main memory |
256 MB SD RAM - expandable to 512 MB |
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Drives |
3 1/2″ floppy drive, 48 x CD ROM drive |
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Hard disk |
19 GB |
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Monitor |
19″ multi-sync colour monitor, 0.26 mm dot pitch, Resolution 1600 x 1280 non-interlaced, refresh rate min 85 Hz |
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Graphic accelerator |
8 MB |
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Communication port |
2 serial plus one parallel, 1 USB port |
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Expansion slots |
5 |
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Other Features |
101 Keys Keyboard and Mouse |
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Intelligent UPS(on-line) with remote monitoring |
1 no. with 30 mins. battery backup on full load(for PC & its printer) |
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Accessories |
Industrial grade furniture (computer table & chair) for PC & its printer, as approved during detailed engineering |
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Software |
a |
General MS Windows’ NT, MS office, VISUAL C ++ VISUAL BASIC, RDBMS, anti-virus, etc. |
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b |
Application specific – to suit specific requirement |
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