Burner Management System Presentation

(1)

Burner Management System



General guidelines



Interlock and Protection

(2)

What shall we look into, in today’s

session?

 NFPA guidelines  BMS requirements

 BMS applications dealing with

 Boiler purge control

 Fuel safety control (MFT)  Pre light-up control

 Individual burner control

 Oil burner  Coal burner

(3)

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

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

 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.

 NFPA's 300 codes and standards influence

 building,  process,  service,  design, and  installation

(4)

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.

(5)

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. “

(6)

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.



Fuel Leakage into an idle furnace and the ignition of the

accumulation



Repeated Unsuccessful attempts to light up without appropriate

purging



The Accumulation of an explosive mixture of fuel and air as a

(7)

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.

(8)

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 .”

(9)

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.”

(10)

BMS – What must it do?

The

Burner Management System

 must be designed to ensure a safe, orderly operating sequence in the start-up 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.

 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.

 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.

(11)

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.

 Prohibit start-up of the equipment unless certain permissive interlocks have first

been completed.

 Monitor and control the correct component sequencing during start-up and

shut-down of the equipment.

 Provide component condition feedback to the operator and, if so equipped, to

the plant control systems and/or data loggers.

 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.

(12)

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

(13)

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

(14)

Boiler Purge Control

B. Initiate Boiler Purge

 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.

(15)

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

(16)

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

(17)

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

(18)

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

(19)

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

(20)

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

(21)

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

(22)

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

(23)

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

(24)

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

(25)

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

(26)

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

(27)

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

(28)

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

(29)

EFFECTS OF MFT

 MFT RELAY OPERATED

 LDOT

 HFOT

 TRIP SEAL AIR FANS

 TRIP ALL MILLS

 TRIP ALL FEEDERS

 CLOSE ALL ATTEMPERATION BLOCK VALVES

(30)

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:

 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

(31)

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

(32)

Individual Burner Control

Classification of burners



Burner for gas firing – nozzle type



Burner for oil firing – sprayer plate type



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

(33)

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

(34)

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

(35)

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

(36)

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:

Secondary air dampers are in oil position or Feeder is running from remote

 Oil gun insertion initiated

Step 3:

Oil gun inserted

(37)

Oil Burner Light-up

Sequence of

operation

Step 4:

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

(38)

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

(39)

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

(40)

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

(41)

Oil Burner Scavenging

Burner oil gun scavenge is blocked when

 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

(42)

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

(43)

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

(44)

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

(45)

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

(46)

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 % or coal flame not detected signifying low coal and no ignition source

 Feeder running from remote and coal and oil flame neither detected assuming

flame monitoring system is healthy signifying loss of coal flame without ignition source

 Loading gas pressure very low

 Lub oil pressure very low signifying no lubrication to Mill gear box and bearings  Both PA fans stopped

 Mill running from remote for >30 secs and PA flow below minimum  Mill running from remote for >30 secs and Secondary air flow < 45%  Seal air pressure very low

(47)

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

(48)

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

(49)

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

(50)

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

(51)

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

(52)

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

(53)

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

(54)

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

(55)

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

(56)

Hardware - PLC

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

 CONTAINS SAFETY GUIDELINES PROGRAMMED INSIDE FOR

– TAKING PREVENTIVE MEASURES

– 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.

Transferring control to Fault

Tolerant pair and running

self diagnostics

Running self

diagnostics and

monitoring

Chassis

with

Processor

and I/O

cards

(57)

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 FOR HOUSING THE WHOLE PLC

SYSTEM.

2. POWER SUPPLY FOR SUPPLYING POWER TO THE

PLC SYSTEM.

3. MAIN PROCESSOR THE BRAIN OF THE SYSTEM

4. I/O CARDS INTERFACING UNITS BETWEEN

SYSTEM & FIELD

5. SPECIAL MODULES COMMUNICATION WITH OTHER

SYSTEMS, ETC.

6. SPECIAL FUNCTIONS HIGH SPEED COUNTER,

(58)

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

(59)

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

(60)

Output Leg A Output Leg B Output Leg C _Loopback Input Leg B Input Leg C Main Processor B Main Processor A Main Processor C Output Leg A Output Leg B Output Leg C Loopback C B A +V A B Input Leg A