Burner Management System Presentation

Burner Management System

General

guidelines Interlock and Protection Hardware architecture

What shall we look into, in today’s session? 

NFPA guidelines

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BMS requirements

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BMS applications dealing with 

Boiler purge control

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Fuel safety control (MFT)

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Pre light-up control

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Individual burner control  

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Oil burner Coal burner

BMS architecture

What is NFPA? NFPA is an abbreviation for National Fire Protection Association 

Established in 1896, NFPA an international nonprofit membership organisation serves as the world's leading advocate of fire prevention and is an authoritative source on public safety

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It is the authority on fire, electrical, and building safety.

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It‟s mission is to reduce the worldwide burden of fire and other hazards on the quality of life by providing and advocating consensus codes and standards, research, training, and education.

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NFPA's 300 codes and standards influence 

   

building, process, service, design, and installation

NFPA Applicable standards for Boilers and Furnaces NFPA 85: Boiler and Combustion Systems Hazards Code, 2007 Edition. PURPOSE  The standard provides minimum requirements for the design, installation, operation, and maintenance of large commercial and industrial boilers, heat recovery steam generators, and related combustion systems. These requirements help prevent fires, explosions, and implosions, and contribute to overall safety. SCOPE  The standard covers structural design, purging systems, and fuel-burning systems, including fuel supplies , the main burner, combustion control systems, burner management systems, furnace pressure control systems, and other system and function requirements. Procedures for normal and emergency start-up and shut-down, fuel transfer, and firing of more than one fuel are also covered. Some requirements are specific to certain equipment applications.

NFPA Applicable standards for Boilers and Furnaces NFPA      

85 is a compilation of six earlier standards:

NFPA 8501, Single-Burner Boiler Operation; NFPA 8502, Prevention of Furnace Explosions/ Implosions in MultipleBurner Boilers; NFPA 8503, Pulverized Fuel Systems, NFPA 8504, Atmospheric Fluidized-Bed Boiler Operation; NFPA 8505, Stoker Operation; and NFPA 8506, Heat-- Recovery Steam Generator Systems.

An excerpt from the above standard “the basic cause of a furnace explosion is the ignition of an accumulated combustible mixture within the confined space of the furnace or the associated boiler passes, ducts, and fans that convey the gases of combustion to the stack. “

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Situations Causing Explosive conditions? Numerous situations can arise in connection with the operation of a boiler furnace that will produce explosive conditions. 

Interruption of Fuel or air supply or ignition energy to the burners.

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Fuel Leakage into an idle furnace and the ignition of the accumulation

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Repeated Unsuccessful attempts to light up without appropriate purging

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The Accumulation of an explosive mixture of fuel and air as a result of a complete furnace flameout

Requirement Multiple burner boilers require two independent control systems. 

One to control steam production i.e. Boiler Control System and



One to control the fuel burning equipment i.e. Burner Management System

NFPA definition NFPA defines 



a Boiler Control System as “The group of control systems that regulates the boiler process, including the combustion control system but not the burner management system.” and A Combustion Control System is “The control system that regulates the furnace fuel and air inputs to maintain the air-fuel ratio within the limits that are required for continuous combustion and stable flame throughout the operating range of the boiler in accordance with demand .”

NFPA definition NFPA defines 

a Burner Management System as “The control system that is dedicated to combustion safety and operator assistance in the starting and stopping of fuel preparation and burning equipment and for preventing mal-operation of and damage to fuel preparation and burning equipment.”

BMS – What must it do? The Burner Management System 

must be designed to ensure a safe, orderly operating sequence in the startup and shutdown of fuel firing equipment and to reduce possible errors by following the operating procedure.



is intended to protect against malfunction of fuel firing equipment and associated systems.

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In some phases of operation, the BMS shall provide permissive interlocks only to ensure safe startup of equipment. Once the equipment is in service, the operator must follow acceptable safe operating practices.

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all parts of the BMS shall remain in good working order and in service whenever the burner is in service if the system is to provide the protection for which it is designed.

BMS - What are the basic Functions? The BMS shall be designed to perform the following functions: 

Prevent firing unless a satisfactory furnace purge has first been completed.

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Prohibit start-up of the equipment unless certain permissive interlocks have first been completed.

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Monitor and control the correct component sequencing during start-up and shutdown of the equipment.

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Provide component condition feedback to the operator and, if so equipped, to the plant control systems and/or data loggers.

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Provide automatic supervision when the equipment is in service and provide means to make a Master Fuel Trip (MFT) should certain unacceptable firing conditions occur.

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Execute a MFT upon certain adverse unit operating conditions.

How do we categorize the different controls A Boiler Control System shall have the following applications   

Combustion control Excess air control Steam drum level control

A Burner Management System shall have the following applications    

Boiler purge control Fuel safety control Pre-light up control Individual burner control

Boiler Purge Control Why: For removing all combustibles from the boiler furnace and replacing them with air to prevent any explosive mixture from remaining in the furnace prior to light up. When: After a Master Fuel Trip has occurred How: A.

Ensuring that a predetermined set of fuel and air related permissive conditions are satisfied which shall include



All fuel valves (Shut-off valves, oil valves) closed Either of one FD Fan & ID Fan running All Mills and Feeders stopped and Mill discharge valves closed All PA Fans stopped and PA to Mill inlet dampers closed All scanners sense no flame Air flow is not less than 25% - 35 % (multiple burner boilers) of full load air flow 4 out of 6 secondary air dampers at Purge position No MFT conditions present MFT relay tripped

      



Now the Boiler is Ready for Purge

Boiler Purge Control B.

Initiate Boiler Purge

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Dampers are initiated to move to Purge position (air flow 30 to 80 T/hr) 5 minute purge timer triggers Boiler purge in progress is indicated After 5 minutes has elapsed the Purge process is complete and the boiler is ready for firing If any of the condition mentioned in „A‟ fails during purging process, purging is interrupted and the timer resets.

 

Fuel Safety Control Why: To prevent any explosive condition in the furnace What: Withdraws fuel feed to the Furnace When: If any of the predetermined trip conditions has occurred. Classification Depending on the fuels involved the fuel safety control can be made up of the following:  Master fuel trip  Oil fuel trip

Master Fuel Trip If any of the predetermined master fuel trip condition occurs a master fuel trip is initiated. The first out cause of trip indication is displayed and alarmed. Conditions of a master fuel trip are:          

All FD Fans off All ID Fans off Boiler air flow low for 3 secs Loss of all fuel Loss of all flame Furnace pressure very high/Low Drum level very high/low Critical Flameout Delayed light-up Re-heater protection operated

Master Fuel Trip Some more Conditions of a master fuel trip (continued) : Loss of HT power  Loss of UPS power  Loss of 220V DC power  Condenser vacuum low  MFT hard relay tripped  2 out of 3 main processors failed  Both emergency trip push buttons operated Any of the above occasions will result in a MFT 

MFT can be reset when 

 

None of the above trip conditions exist Boiler purge is complete Reset MFT is initiated NEXT

MFT – all FD fans off 

All FD fans Off Source :

Breaker off signal from both fans

Implication: Will result in in-sufficient air for the combustion process and the fuel cannot burn Action: MFT MFT conditions

MFT – all ID fans off 

All ID fans Off Source : Breaker off signal from all 3 fans Implication: Will result in an uncontrolled furnace pressurization. Action: MFT

MFT conditions

MFT – Air flow less than 25% 

Boiler air flow less than < 25% for 3 secs Source : Flow transmitters at FD suction Implication: Will result in in-sufficient air for the combustion process and the fuel cannot burn completely Action: MFT

MFT conditions

MFT – Loss of all fuel 

Loss of all fuel Source : Any oil burner in operation (MFT trip resets) and closure of all burner valves and all Mills „off‟ and no mill in shutdown mode. Implication: As no fuel is being fed into the furnace generation of heat for sustenance of combustion and subsequent production of steam cannot take place

Action: MFT MFT conditions

MFT – Loss of all flame 

Loss of all flame Source : Any oil burner in operation and no scanners see flame. Implication: Will proactively safeguard all adverse effect due to non burning of fuel (detected from the intensity of flame) being injected into the furnace

Action: MFT MFT conditions

MFT – Furnace pressure very high/low 

Furnace pressure very high /low Source : Pressure switch and transmitter.

Implication: Will result in explosion or implosion of the furnace resulting in mechanical deformity Action: MFT

MFT conditions

MFT – Drum level very high/low 

Drum level very high / low Source : Hydrastep and drum level transmitter Implication: High: Will result in Flooding of superheaters causing a. carryover of dissolved solids and hence deposition downstream effecting heat transfer b. fall of steam temperature and quenching of Turbine Low: Will result in starvation of water in the furnace tubes which will lead to tube metal overheating as no cooling medium is present Action: MFT MFT conditions

MFT – Critical flameout 

Critical Flameout Source : Furnace flame scanners detect 2 out of 3 zones no flame

Implication: Is a consequence of improper combustion in pre-identified zones within the furnace resulting in flame instability which may give rise to improper heat distribution Action: MFT MFT conditions

MFT – Delayed light-up 

Delayed light up Source : MFT reset , LDO shut off valves open and no oil gun in operation (or in other words put into service) within 10 mins of opening of LDO shut-off valves. Implication: Repeated unsuccessful attempts to light up the boiler with oil gun has resulted in accumulation of un-burnt fuel (oil) in the furnace and hence the furnace requires purging.

Action: MFT MFT conditions

MFT – Re-heater protection 

Re-heater protection Source : All governor valves closed, HP bypass valve < 2% open with a. at least one feeder running from remote or b. More than 8 out of 12 oil guns in operation Implication: Damage to tubes that can result from firing in excess of safe limit which will cause overheating of re-heater tubes due to absence of a steam flow through it. Action: MFT

MFT conditions

MFT – Condenser Vacuum Low 

Condenser Vacuum Low Source : Pressure switch installed at condenser (500 mmHg abs) Implication: Under turbine tripped condition and bypass in operation steam dumping continues at condenser which can result in pressurization. Under such poor vacuum conditions the condenser is not capable of dissipating the heat load with existing CW flow and with effect the temperature rises. Action: MFT

MFT conditions

EFFECTS OF MFT 

MFT RELAY OPERATED

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LDOT

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HFOT

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TRIP SEAL AIR FANS

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TRIP ALL MILLS

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TRIP ALL FEEDERS

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CLOSE ALL ATTEMPERATION BLOCK VALVES

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TRIP TURBINE

Oil Fuel Trip If any of the predetermined oil fuel trip conditions is exceeded the oil fuel trip is initiated. The first out cause of trip indication is displayed and alarmed. All oil fuel is removed from the boiler and all oil burners are shutdown. Depending on other conditions a master fuel trip may be generated. Conditions of an oil fuel trip are:       

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LDO trip valves close command LDO trip valves not closed and LDOT condition is present LDOT relay fail to trip and LDOT condition is present LDO pressure very low for 3 secs and any LDO burner valves not closed Atomising air pressure very low for 3 secs and any LDO burner valves not closed LDO trip valve not open within 10 secs of LDOT reset Any burner valve fail to close despite boiler load being > 50% LDOT hard relay tripped

LDOT can be reset when  None of the above trip conditions exist  MFT relay is reset  Trip valve open is initiated  All LDO burner valves are closed

Pre Light-up Control Why : To ensure all predetermined boiler LIGHT-UP conditions are satisfied prior to introducing any fuel in service. When : Once the boiler purge has been completed and the master fuel trip has been reset. How : It ensures that individual fuel and air conditions for pre lightup are satisfactory for igniter and burner operation, which shall include following checks and hence provide permission to light LDO,    

LDO trip valves open LDOT reset LDO pressure healthy Atomizing air pressure healthy

Individual Burner Control Classification of burners 

Burner for gas firing – nozzle type

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Burner for oil firing – sprayer plate type

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Burner for coal firing – gravity fed down shot fired, corner fired, front fired

Individual Burner Control - Oil Why : To ensure on light up a healthy flame is detected at the oil burner else burner is to be taken out of service ensuring no remnants of fuel in the burner When : Once the permission to light LDO is given

How : It ensures that individual burner shall operate in 4 modes   



Oil burner start permissives Oil burner light-up Oil burner shutdown Oil burner scavenging

Oil burner start permissives The following permissives are to be satisfied in order to proceed towards light-up     

Permission to light LDO is present Burner LDO valve is closed No flame is detected at burner Burner shutdown condition is not initiated Burner spark ignitor power healthy

This gives the Burner permission to start

Oil Burner Light-up : Notes Note 1:  

Burner Permission to start is present Burner start PB operated

This puts the burner in lighting mode Note 2 :    

Atomising air valve open LDO valve open Oil gun inserted Oil flame detected

These conditions indicate burner in operation

Oil Burner Light-up Sequence of operation Step 1:

Burner is in lighting mode Burner is not in operation Feeder is not running from remote  Secondary air dampers are initiated to move to oil position ( air flow 30 to 120 T/hr) Step 2:

Burner is in lighting mode Secondary air dampers are in oil position or Feeder is running from remote  Oil gun insertion initiated Step 3:

Burner is in lighting mode Oil gun inserted  Atomising air valve open initiated

Oil Burner Light-up Sequence of operation Step 4: Burner is in lighting mode Oil gun inserted Atomising air valve open Scavenge valve closed Spark ignitor insertion initiated (and 15 secs timer triggered)

Step 5a:

Burner is in lighting mode Oil gun inserted Atomising air valve open Scavenge valve closed Spark ignitor inserted  Energise spark ignitor

Oil Burner Light-up Sequence of operation Step 5b: Burner is in lighting mode Oil gun inserted Atomising air valve open Scavenge valve closed Spark ignitor inserted LDO selected  LDO valve open initiated Oil flame is detected After 15 secs of ignitor insertion, command is withdrawn and hence ignitor retracts 

Burner Light up done

Oil Burner shutdown If any of the predetermined conditions occurs a burner shutdown is initiated. – It denies permission to start and resets lighting mode and as a result it closes atomising air valve and LDO valve, but oil gun remains inserted  

       

Burner in lighting mode for 60 secs and oil gun not inserted Burner in lighting mode for 60 secs and LDO valve closed Burner in lighting mode for 60 secs and atomising air valve not full open LDO valve not closed and oil gun not inserted LDO valve neither full close for 15 secs nor full open LDO valve not closed for 10 secs and oil flame not detected LDO valve not closed and scavenge valve not closed LDOT MFT Air flow < 10 %

Oil Burner Scavenging A condition which sees LDO valve close from open condition generates Burner oil gun scavenge required (resets when oil gun is retracted or LDO valve is not closed)

Sequence of operation Step 1:

Burner oil scavenge required persists Oil gun scavenge not blocked Indicates burner oil gun in scavenge mode Step 2:

Oil gun in scavenge mode Oil gun inserted Atomising pressure healthy Spark ignitor insertion initiated and 2 min timer triggered to start countdown of scavenge process Step 3a:

Spark ignitor inserted Energise spark ignitor

Oil Burner Scavenging Burner oil gun scavenge is blocked when   



  

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MFT LDOT Either scavenge valve or atomising valve not full open when burner is in scavenge mode, oil gun is inserted, atomizing air pressure is healthy, ignitor is inserted and sparking Either ignitor power is not available or ignitor not inserted when burner is in scavenge mode, oil gun is inserted, atomizing air pressure is healthy, Oil gun scavenge required persists and Atomizing air pressure not healthy Oil gun scavenge required persists and Oil gun not inserted Oil Burner stop command

The above conditions block scavenge mode

Oil Burner Scavenging Sequence of operation Step 3b: Oil gun in scavenge mode Oil gun inserted Atomising pressure healthy Spark ignitor inserted Spark ignitor power available Scavenge

valve open initiated

Step 4: Scavenge valve open Step 3b condition satisfied Atomising air selected Atomizing

air valve open initiated

Oil Burner Scavenging Sequence of operation Step 5: Atomizing air valve open Scavenge valve open Spark ignitor inserted Spark ignitor power available 2 mins has not elapsed since starting of scavenge process Indicates

Burner oil gun purge/scavenge in progress

Step 6: Step 5 all conditions remaining except that 2 mins has elapsed since starting of scavenge process Oil

gun retract initiated

Oil Burner Scavenging Sequence of operation Step 7: Oil gun retracted 

Initiates     

scavenge valve to close, atomising air valve to close, de-energise spark ignitor, retract spark ignitor and simultaneously “scavenge required” message will disappear

Back to “Individual Burner Control”

Individual Burner Control - Coal Why : To transfer the firing from oil to coal and attain a stable flame in the furnace at high loads

When : Once oil flame is detected, mill discharge valves are closed and PA to Mill inlet damper is closed

How : It ensures that individual burner shall operate in 6 modes      

Mill start permissive and Mill starting Operation of Mill discharge valves Feeder starting Feeder normal shutdown Mill normal shutdown Preferential Mill tripping

Mill Trip Conditions The following conditions shall cause a Mill to trip  



   

  

LOS or emergency stop pressed Mill and feeder running from remote, oil flame not detected with either feeder speed 30 secs and PA flow below minimum Mill running from remote for >30 secs and Secondary air flow < 45% Seal air pressure very low MFT or Mill hard relay

Mill trip reset conditions The following conditions if satisfied will reset the Mill Trip Relay 

Oil flame is detected



Mill discharge valves are closed



PA to Mill inlet damper is closed

Note: Mill running from remote for 10 secs moves the secondary air dampers to PF position

Mill Start Permissive The following conditions shall be satisfied prior to starting a Mill  

       

No mill trip condition present and Trip relay reset Either both PA fans running OR one PA fan running with less than 3 mills running Selector switch in remote and breaker in service Seal air pressure healthy Mill outlet temperature > 60°C but < 110°C Oil flame detected Mill discharge valve open Mill lub oil pressure healthy Mill loading gas pressure healthy PA to mill inlet damper closed

The above conditions gives the permissive to start a Mill and when Mill start is initiated from remote……….. MILL STARTS provided Mill is not in shutdown mode

Mill discharge valve open and close The following conditions need to be true prior to opening a Mill Discharge Valve    

Mill Trip relay reset Oil flame detected MDV not open Seal air pressure healthy

The above conditions gives the permissive to open Mill discharge valve and when Open is initiated ……….. MDV opens The following conditions need to be true prior to closing a Mill Discharge Valve   

Feeder stopped Mill stopped MDV open

The above conditions gives the permissive to close Mill discharge valve and when Close is initiated or MFT or Mill hard relay trip occurs……….. MDV closes

Feeder Starting The following conditions generates a start permissive for a Feeder         

Mill Trip relay reset Oil flame detected Feeder selected to remote Seal air pressure healthy Mill running from remote Feeder selected in remote Mill secondary air dampers in PF position ( air flow 80 to 140 t/hr) Mill PA flow not below minimum (not less than 45 T/hr) Feeder trip condition not present and not running from remote

The above conditions gives the permissive to start a Feeder from remote

and when start is initiated ……….. Feeder starts provided Feeder is not in shutdown mode

Certain points to note The following conditions generates a permission to shutdown oil burners   

Coal flame has been detected Coal flame is healthy Feeder is running from remote for more than 10 mins

The oil burners are now taken out of service For providing support ignition the following conditions need to be true   

Coal flame has been detected Coal flame is not healthy Feeder is running from remote

This generates an alarm Mill support ignition required and accordingly oil burners are to be put in service

Feeder Normal Shutdown The following conditions generates a permission to stop a Feeder   

Oil flame detected LDO valve open for both oil burners Feeder running and speed at minimum

Either of the following conditions generates a trip condition for a Feeder and indicates Feeder in shutdown mode    

Permission to stop Feeder persists, Feeder selected to remote, Stop feeder initiated MFT Mill Trip relay Feeder motor protection operated

Mill Normal Shutdown The following conditions generates a permission to stop a Mill 



Mill running from remote Mill differential pressure low

OR    

Mill running from remote Oil flame detected LDO valve open Feeder stopped

The above condition need to persist for more than 5 mins to initiate a permission to stop a Mill . It signifies Mill is empty. Either of the following conditions below de-energize Mill hard relay and indicates Mill in shutdown mode   

Mill is empty, Mill selected to remote, Stop Mill initiated…. Inhibits oil burner shutdown until Mill outlet temperature is < 60°C and mill is stopped MFT Mill Trip relay

Mill Seal Air valve Open / Close Either of the following conditions will result in opening of Mill Seal Air Valve   

Mill Trip relay reset PA to Mill inlet damper not closed Open Seal air valve initiated

Provided no Seal air valve close signal persists Either of the following conditions will result in closing a Mill Seal Air Valve 



Mill trip relay tripped Mill stopped and close seal air valve command initiated

Provided PA to Mill inlet damper open does not persist

Preferential Mill Tripping Why : To take out certain running Mills out of service as per preference in order to reduce firing and compensate for the furnace conditions prevailing

When :   

On Turbine trip Load rejection >50 % Single FD or PA fan running

How : It ensures that extreme burners shall trip 

Under 4 mill condition    



if Mill D is not in service then Mill A trips If Mill A is not in service then Mill D trips If both Mill A and Mill D are in service, Mill A trips if Mill D is the single Mill in the rear OR Mill D trips if Mill A is the single Mill in the front If Mill A and Mill D both are not in service then Mill B trips

Under 5 mill condition   

Mill A and Mill D trips if they are both in service Mill A and Mill B trips if Mill D is not in service Mill B and Mill D trips if Mill A is not in service

Hardware - PLC  EFFECTIVE AND RELIABLE SYSTEM FOR OVERALL SUPERVISION OF BOILER SAFETY IN A POWER PLANT.

Transferring control to Fault Tolerant pair and running self diagnostics

 CONTAINS SAFETY GUIDELINES PROGRAMMED INSIDE FOR

– –

TAKING PREVENTIVE MEASURES

Chassis with Processor and I/O cards

IN EXTREME CASES TO TAKE THE WHOLE SYSTEM TO STEP-BY-STEP SHUTDOWN.

 IT FORESEES FUTURE ERROR AND GENERATE ALARMS.

 BMS IS THE SUPPORTIVE SYSTEM WITH THE DCS TO MANAGE THE PLANT IN SIMPLER WAY.

Running self diagnostics and monitoring

Hardware - PLC  THE BMS IS A PLC, PROGRAMMED ACCORDING TO USER NEED.  LIKE CONVENTIONAL PLC SYSTEMS THE BMS ALSO CONSISTS OF THE FOLLOWING PARTS:1. MOUNTING RACK 2. POWER SUPPLY

3. MAIN PROCESSOR 4. I/O CARDS 5. SPECIAL MODULES 6. SPECIAL FUNCTIONS

FOR HOUSING THE WHOLE PLC SYSTEM. FOR SUPPLYING POWER TO THE PLC SYSTEM. THE BRAIN OF THE SYSTEM INTERFACING UNITS BETWEEN SYSTEM & FIELD COMMUNICATION WITH OTHER SYSTEMS, ETC. HIGH SPEED COUNTER, THERMOCOUPLE SENSORS (NOT IN BBGS)

What is TMR architecture?

 





It means Triple Modular Redundant TMR architecture integrates three isolated parallel control systems ( as evident in diagram) Extensive diagnostics carried out in each Control System The system uses TWO-OUT-OF-THREE voting to provide high integrity, error free uninterrupted process operation with no single point failure

WHAT ARE THE KEY FEATURES?



The Tricon controller uses three identical channels to process single data from field



Each channel independently and parallely executes the application program which can remain in the form of Ladder Logic, Functional Block Diagram or Statement List in the processors



Specialised hardware / software voting mechanisms qualify and verify digital inputs / outputs from / to field



Analog inputs are subjected to a MEDIAN VALUE selection



Each channel is isolated from the others and no single point failure in any channel can pass to another channel

TMR Architecture Input Leg A

Input Leg B

Input Leg C

Main Processor A

Output Output Leg Leg A A Output Output Leg Leg B B

Main Processor B

Main Processor C

Output Output Leg Leg CC

A B

A

+V C

B

Loopback Loopback

Terminology and “buzz” words 



 

Fault Tolerant  The Ability of the System to Continue to Perform its Function in the Presence of Faults and Errors.  No Single Point of Failure will Shutdown the System Fail-Safe  If the System does Fail it will Fail to the Safe State or the state of the Equipment Under Control (EUC) when safety is achieved - de-energized for ESD Systems PFD - Probability-to-Fail On Demand Availability  The probability that the system will be operational at some instant of time

WHAT ARE THE KEY FEATURES?



Diagnostic Features •

•

•

Input card – checks for “stuck on” points Output card – checks for “output voter diagnostic” – 2OO3 voting Processor – checks for faults at input and output modules as well as itself and generates appropriate alarms for corrective action