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Boiler Controls & Instrumentation
K KarthikeyanManager
Controls & InstrumentationBHEL, Tiruchirappalli
Email : [email protected]
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
INTRODUCTION
PART I - BOILER
PART 2 - INSTRUMENTATION
PART 3 - CONTROLS
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Boiler C&I -Functions
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Control systems engineering• Instrumentation engineering• Electrical systems engineering • New product development
Boiler Controls & Instrumentation
Broad engineering activities
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Proposal Engineering• Contract Engineering• Product Engineering• Quality Assurance & Control• Field Engineering• Research & Development
Boiler Controls & Instrumentation
Functions
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Proposal Engineering
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Scope of Work• Project Estimate• Offer submission• Offer evaluation by
customer• Award of contract
Proposal EngineeringBoiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• In summary, the purpose is to draw-up
- Scope of Work- Project Estimate
of the project.
Deliverables : - Estimable quantity(BOM)- main and spares- Datasheets- Descriptive offers of packages & - Preliminary design sketches(P&IDs, GA).
Boiler Controls & Instrumentation
Proposal Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Arrived based on a broad specification prepared by the customer/consultant.
• Individual system scope identified gets recompiled into a project scope of work .
• Project scope document includes scope of work , terminal points & exclusions
Scope of Work
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• The typical scope covered in Boiler C&I discipline include– Furnace safeguard Supervisory system– Secondary Air Damper control system– Soot blower control system– Boiler area field instruments – Associated cable & accessories.– Electricals(MCC, elevator etc.)
Scope of Work
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Offer evaluation
• The offers get evaluated at the customer end.
• Customer awards the contract on a technically qualified bid with the lowest price.
• The award of contract is indicated by a ‘Letter of Intent’ received from the customer.
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Award of contract
• The offers get evaluated at the customer end.
• Customer awards the contract on a technically qualified bid with the lowest price.
• The award of contract is indicated by a ‘Letter of Intent’ received from the customer.
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Contract Engineering
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Packages• SG integral C&I(Trichy)• Station C&I(PEM or customer)- in case of BTG
or Turnkey• SG integral electricals(Trichy)• Station Electricals(PEM or customer)- in case
of BTG or Turnkey
Contract Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Contract Engineering
The role involves system level contract coordination for the boiler C&I area.
• Applicable PGMA List• Sub Delivery check list.• Boiler Contract Regular activity(BCR) schedule• ‘00’ PG list(erection documents).• Applicable O&M documents.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
System Engg. Documents involved :• Piping&Instrumentation Diagrams(P&IDs)• Measurement & control recommendations• Automatic control schemes• Interlock & protection schemes
Contract Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
P & I Diagram- Air & flue gas (portion)
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Instrument schedule steam & water (sample)
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Product Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Product Engineering
Detailed design of Boiler C&I products & systems
• Digital controls• Analog controls• Electrical systems & cables• Field instruments• Special instruments• Actuators
• Digital ControlsBurner management system.Soot Blower control system
• Analog Controls Secondary air damper control system.Auxiliary PRDS control system.
Product Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Electrical systemsControl supply panels
LT Motor control centresPower distribution panels
• Field instrumentsSwitches & gauges for Pressure,Level & temperatureThermocouplesFlow elements
Product Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Flame scanner system• Acoustic steam leak detection system.• Electronic water level indicator.• Closed circuit television system.• Vibration monitoring system.• Flue gas analysers.• Steam and water analysers.
Product Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Special instruments
• Electrical and C & I engineering design• Release of indents for C & I sub-delivery items.• Evaluation of technical offers for bought-out items• Technical Delivery Conditions (TDC)
Product Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Quality Control & Assurance
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
The role involves preparation/review of following activity w.r.t C&I products & systems
• Prepare Standard Quality Plans (SQP)• Prepare Contract Quality Plans (CQP)• Review/Approve Vendor Quality Plans (VQP)• Issue Reference Quality Plans (RQP)• Prepare Inspection Check Lists (ICL)
Quality Control & Assurance
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Performing inspection at vendor works for CI products & systems - bought-out items
• Review & dispose Site Action Requests on CI products & systems
Quality Control & Assurance
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Field Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
The role involves • Providing technical support / trouble shooting of C&I
products / system during - Erection & commissioning stage of project
- Operation after handing over to customer• Review & dispose Commissioning action requests• Review & dispose Contract closing pending issues• Visiting sites to ensure smooth progress of C&I site
activity
Field Engineering
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Research & Development
Boiler Controls & Instrumentation
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Microprocessor based Gravimetric coal feeder controls - BHELFEED
• Microcontroller based Flame moniotirng system - BHELSCAN
• Acoustic steam leak detection system – BHELSONIC
• Electronic water level Indicator system- BHELVISION
Research & Development
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
In-house developed C&I systems & products
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Boiler Basics
BOILER CLASSIFICATION
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
BHEL BOILERS
• Power Boilers Up to 600 MW rating(Coal, oil and gas fired - Subcritical)Up to 800 MW - Supercritical
• Nuclear steam generators Up to 235 MW rating
• Industrial boilers Up to 450 Tonnes/hour rating Fertilisers, Petrochemical, Steel & Paper industries Wide range of fuels- Oil, Gas, BFG, Bagasse, Black liquor.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Schematic of a boiler
• Furnace & Circulation system• Superheaters• Reheaters• Economiser• Airheaters• Fans• Pulverisers• Raw coal feeders• Fuel firing system• Sootblowers
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
UTILITY BOILERS - ESSENTIAL COMPONENTS
• Natural circulation• Controlled circulation • Once through
Circulation ratio : Mass rate of water fed to the steam generating tubes to the mass
rate of steam generated.
Natural circulation 6 Controlled circ 4Once through 1
CIRCULATION SYSTEMS
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
BOILER CIRCULATION SYSTEMS
Bharat Heavy Electricals Limited - Tiruchirappalli
1. Axial – Impulse type - IGV Control.
– Reaction type - Blade pitch Control.
2. RadialInlet damper control, Variable speed control; Variable speed control by two speed motor, Hydraulic coupling or Variable frequency drive.
Fans
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Radial FanBharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Axial Reaction
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
- Flow proportional to Speed - Flow proportional to (Impeller Dia) 3
- Head proportional to (Speed) 2
- Head proportional to (Impeller Dia) 2
Hence Variation in speed alters the performance
Bharat Heavy Electricals Limited - Tiruchirappalli
RADIAL FANS - SPEED CONTROL
Boiler C&I
FANS IN BOILER - SCOPE
• Primary air fans - Dries & transports Pulverised coal
• Forced draft fans - Supplies Combustion air
• Induced draft fans - Sucks Flue gas out of furnace
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
MILL - GRINDS COAL
• Slow speed mills (Tube mills - 15 to 25 RPM)
• Medium speed mills (Bowl mill, Ball and race mill
etc.- 50 to 100 RPM)
• High speed mills (hammer mills directly coupled to
motor - 750 to 1000 RPM)
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
RAW COAL FEEDERS
• Volumetric - Rotary and drag link,
• Gravimetric – Endless belt type
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Scope : CONVEY RAW COAL TO MILL
Types :
AIRHEATER
Heat recovery equipmentExtract heat from Flue gas to heat primary & secy. Air
• Regenerative type ( Rotating drive )
• Tubular type
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Types :
SOOTBLOWERS
Remove ash & slag from pressure part tubes
Types
• Long retractable sootblowers - traverse & rotary motors• Half retractable sootblowers- traverse & rotary motors• Rotary blowers - rotary motor• Wall blowers - traverse & rotary motors• Furnace temperature probe - Used during boiler start up
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Fuels : Coal Oil Gas
H/C ratio • Natural gas 0.3 Fuel oil 0.1 Coal 0.07
Calorific value (kcal/kg )• Gas 10000 Oil 8000 • Bituminous coal 3000-3500 Lignite 2500
Coal burning methods• "On grate" “In suspension" Fluidised bed
Three 'T's of combustion – Time – Temperature and – Turbulence.
FUELS & COMBUSTION
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Short period of time• High temperature & • Very turbulent flame .
FUELS & COMBUSTION
Rapid combustion
•Less turbulence and longer burning produces fewer nitrous oxide.
•In some cases combustion is delayed or staged intentionally to obtain fewer nitrous oxide or to obtain desired flame characteristics.
Boiler C&I
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler Instruments
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Boiler measurements• Pressure• Differential pressure• Temperature• Differential
temperature(heat flux)• Flow • Level• Vibration (rotating
device)• Speed (rotating
device)• Position• Weight
• Flue gas analysis(O2, CO, SOx, NOx, Opacity)
• SWAS(Conductivity, pH, Silica, DissilvedO2, Hydazine)
• Image sensing(CCTV)• Sound(steam leak)• Viscosity (fuel oil)• Calorific value
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
First letter• P-Pressure• T-temperature• F- Flow• A- Analytical
Succeeding letters• A- Alarm• I- Indicate• R- Record• Q- Integrate• C- Control• S- Switch• T- tansmitter• E- Element• P- Pocket• W- Well
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Instrumentation representation- ISA
Boiler Controls
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Continuous control :
ObjectiveEnabling Automatic Operation. Optimising operating performance.
On-Off control :
ObjectiveSupervise process operation for safetyPrevent process from entering unsafe condition.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
BOILER CONTROLS
BOILER CONTROLS
• Auto control system
• Boiler Auxiliaries interlocks & protection system
• Furnace safeguard supervisory system (FSSS)
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Master demand
• Combustion and draft control
• Feed-water control
• Steam-temperature control
Auto control system.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&IMaster demand
• 'Master demand' controls the boiler operation.
• Set from unit load demand or main steam header pressure control
• ‘Master demand’ sets burners firing at a rate required for steam
production and corresponding air flow demand
Objective :
Fuel is consumed at a rate that exactly matches the Steam demand.
Fuel is consumed safely, so that the energy is released without risk to plant, personnel or environment
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I Combustion control
• Fuel flow control
• Air Flow Control
• Coal mill control
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I Combustion control Air Fuel/Cross Limiting
AIR CONTROL
FT PT FT
A
A TP I
A TP I
A TP I
f(x)
f(x)
Fuel FLOWSTEAMHEADER PRESSURE AIR FLOW
SP SP
LO SELECT HI SELECTFuel CONTROL
Fuel FeedAIR DAMPER
Air Feed
67
Mill uses primary air -
• For transporting coal from mill to furnace.
• To "dry" coal.
• Air flow to mill and mill outlet temperature are regulated using Hot air damper and cold air damper respectively
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Mill air flow and temperature control
Feedwater control
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Objective :
To supply enough water to the boiler to match the evaporation rate.
Water level in the drum indicates amount of water in boiler
Actual Steam Flow - Used to determine required feedwater during transient conditions when level may not be accurate.
Difference between Actual steam flow and Actual Feedwater Flow is added to the level error to form the ‘Feedwater demand’.
Feedwater demand drives the feed control station to adjust feedwater sa as to maintain the drum level to normal value.
Feedwater control
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
P R E S S U R EC OMP E N S AT IO N
f(x)
A
X
P T F T T E
f(x) f(x)
X
LT P T
f(x)
X
F T T E
f(x)
K
K
D
D
T A
FINA LC O NT R O LD E VIC E
M/A C O NT R O LS TATION
S E T P OINT
P R E S S U R E ANDT EMP E R AT U R EC OMP E N S ATION
S T E AM
T EMP E R ATU R EF L OWP R E S S U R E
Typical single-drive control system. For simplicity, redundanttransmitters have not been shown on this typical control drawing.S ee Figure 4A for AN S I/IS A- S 5.1-1984 format.
L E V E L P R E S S U R E
D R UM
T EMP E R AT U R EC OND E N S ATIO N
F L OW T EMP E R AT U R E
F E E DWAT E R
Objective: To maintain a constant steam temperature at turbine inlet despite large load swings .
Basic methods :
DESUPERHEATING (ATTEMPERATION)
Fine spray of comparatively cool water droplets into the vapour to reduce steam temperature.
BURNER TILT POSITIONING
Raise/Lower the Fireball in the furnace by tilting burners upwards or downwards.
Steam temperature control
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Steam temperature control
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Secondary Air Damper Control
Maintains proper windbox air flow distribution
0 to 30 % unit load, all auxiliary dampers modulated to maintain windbox to furnace differential pressure
Above 30% unit load, BMS “closes” elevations of auxiliary dampers that are not required for elevations of fuel currently in service
Fuel air dampers are positioned on an elevation basis as a function of thecorresponding coal feeder speed
High windbox to furnace differential pressure opens all the secondary air dampers
Two types of dampers – Fuel air dampers & Auxiliary air dampers
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
• Cascade control used for Spray de-superheating loop
• MS temperature error establishes the set point for SH DESH outlet temp.
• SH DESH outlet temp. error positions the spray control valve such as to regulate the MS temperature within allowable limits.
• Burner tilt responds to the lower of SH or RH outlet temp.
• Spray control responds to the higher of SH or RH outlet temp.
Steam temperature control
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
BOILER AUXILIARIES INTERLOCKS AND PROTECTION SYSTEM
Scope : Sequence control of starting and protection & interlocking of boiler auxiliaries…
– FD fans – ID fans– PA fans – Airheaters– Dampers– Valves
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FURNACE SAFEGUARD SUPERVISORY SYSTEM ( FSSS )
This system takes care of interlocks required for starting, supervising the operating and safe shut down of the equipments connected with fuel firing system.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Tangential Windbox
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FURNACE PLAN CORNER DESIGNATION
FRONT WATER WALL
SEC
ON
DA
RY A
IR
2
C
E
RN
O
R -
SEC
ON
DA
RY A
IR
1
C
E
RNO
R-
4
C
E
RN
O
R-
3
C
E
RNO
R-
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Fireball –Tangential Firing
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
CAUSES OF FURNACE EXPLOSIONS– An interruption of
• Fuel or • Air supply or • Ignition energy
to the burners, sufficient to result in momentary loss of flames, followed by restoration and delayed re-ignition of an accumulation.
– Fuel leakage into an idle furnace and the ignition of the accumulation by a spark or other source of ignition.
– Repeated unsuccessful attempts to light-off without appropriate purging, resulting in the accumulation of an explosive mixture.
– The accumulation of an explosive mixture of fuel and air as a result of loss of flame or incomplete combustion at one or more burners in the presence of other burners operating normally or during lighting of additional burners.
– The accumulation of an explosive mixture of fuel and air as a result of a complete furnace flameout and the ignition of the accumulation by a spark or other ignition source, such as could occur where attempting to light a burner(s).
– Purging with an airflow that is too high, which stirs up combustibles smoldering in hoppers.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
CAUSES OF FURNACE IMPLOSIONS
– A mal-operation of the equipment regulating the boiler gas flow, including air supply and flue gas removal, resulting in furnace exposure to excessive induced draft fan head assembly.
– The rapid decay of furnace gas temperatures and pressure resulting from either a rapid reduction in fuel input or a master fuel trip.
– A combination of the two conditions indicated in a, b above has resulted in the most severe furnace implosion incidents.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FUNCTIONS OF FSSS
1. FURNACE PURGE SUPERVISION2. SECONDARY AIR DAMPER MODULATION AND ON-OFF
CONTROL AND SUPERVISION3. IGNITOR ON-OFF CONTROL AND SUPERVISION4. LIGHT OIL ON-OFF CONTROL AND SUPERVISION 5. HEAVY OIL ON-OFF CONTROL AND SUPERVISION6. PULVERIZER AND FEEDER ON-OFF CONTROL AND
SUPERVISION7. FLAME SCANNER INTELLIGENCE AND CHECKING8. BOILER TRIP PROTECTION.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
F S S S
F - FURNACES - SAFEGUARDS - SUPERVISORYS - -SYSTEM
FSSS ENSURES SAFE FURNACE OPERATING CONDITIONS DURING
START UP LOW LOAD OPERATION SHUT DOWN.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
SOME OF THE PRECAUTIONARY MEASURES TO ACHIEVE SAFE AND RELIABLE OPERATION
FURNACE SHOULD BE PURGED BEFORE LIGHT UP ADEQUATE IGNITION ENERGY TO EACH BURNER ADEQUATE AIR SUPPLY TO EACH BURNER TO AVOID
FLAME OUT OPTIMUM FURNACE PRESSURE CORRECT AIR TO FUEL RATIO
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
FUNCTIONAL DIVISION OF LOGICS
UNIT LOGIC
ELEVATION LOGIC
CORNER LOGIC
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
TYPICAL CONDITIONS FOR FURNACE PURGE:
- Heavy fuel oil trip valve closed.- Heavy fuel oil nozzle valves closed.- Light fuel oil trip valve closed.- Light fuel oil nozzle valves closed.- Flame scanners on each elevation indicate no flame.- Air flow greater than 30% and less than 40%
- All pulverisers off. - All feeders off.- Pulveriser outlet gates closed.- All hot air gates closed. - All cold air dampers not greater than 5° open.- Both PA fans off.- No boiler trip existing.– All auxiliary air dampers modulating.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
BOILER TRIP COMMAND IS INITIATED BY
LOW OR HIGH DRUM WATER LEVEL BOTH I.D OR F.D ARE OFF LOW OR HIGH FURNACE PRESSURE REHEATER PROTECTION TRIP TURBINE LOSS OF ALL FUEL TRIP LOSS OF UNIT D.C POWER LESS THAN FIRE BALL AND LOSS OF AC AT
ANY ELEVATION MANUAL TRIP UNIT FLAME FAILURE TRIP INSUFFICIENT PRIMARY AIR
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
BOILER TRIP COMMAND RESULTS IN
STOPPAGE OF ALL FUEL INPUTS BY TRIPPING
1. ALL PULVERIZERS2. ALL FEEDERS3. ALL OIL GUNS4. ALL IGNITORS
IT CLOSES1. IGNITOR2. LIGHT OIL TRIP VALVES3. HEAVY OIL TRIP VALVES
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
Scanner Fan logic
• “Scanner duct to furnace DP” when low initiates a Scanner air fan -A “run” command
• If DP value remains “low” for more than five seconds, scanner air fan -B “run” command is issued.
• If DP condition is low even after 10 seconds “Loss Of Scanner Cooling Air” alarm is generated
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Seal Air Fan Control
• When either Primary Air Fan is on, seal air fan “A” is automatically placed in service.
• If either Primary Air Fan is on & Seal Air Header/Cold Air Duct DP is low, the seal air fan is auto started.
• When both seal air fans are on and the Seal Air Header/Cold Air Duct DP is not low,either seal air fan can be stopped manually.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
PULVERIZER STARTING PROCEDURE
START< “PULVERIZER ON” FEEDBACK OPEN HOT AIR GATE< WAIT TILL PULVERIZER COMES TO TEMPERATURE
( 140°F ) START FEEDER ( AT MINIMUM FEEDER SPEED )< COAL FLOW INDICATOR OR PULVERIZER AMPERE (
( WITH IN 5 SECONDS )< FIFTY SECONDS FEEDER SPEED RELEASED TO AUTOMATIC CONTROL FUEL AIR DAMPER OPENED
FUEL AIR DAMPER MODULATED TO AUTOMATIC CONTROL.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
PULVERIZER START REQUIREMENTS
A IGNITION ENERGY AVAILABLE
B. ADEQUATE PRIMARY AIR
C. D.C POWER AVAILABLE
D. LOCAL PULVERIZER CONDITION SATISFACTORY
E. IF NO OTHER FEEDER IS WORKING FUEL AND AIR NOZZLE TILTS PLACED IN HORIZONDAL CONDITION.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
CONDITIONS ( LOCAL ) TO BE SATISFIED TO START RESPECTIVE PULVERIZER
A. DISCHARGE VALVE OPEN
B. SEAL AIR VALVE OPEN
C. COLD AIR DAMPER OPEN
D. PULVERIZER DAMPER OUTLET LESS THAN 200°F
E. FEEDER INLET GATE OPEN
F. TRAMP IRON HOPPER VALVE OPEN.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
PULVERIZER IGNITION ENERGY AVAILABLE
A MINIMUM OF 3 OF THE 4 LIGHT OIL OR HEAVY OIL NOZZLE VALVE OF THE ELEVATION JUST ABOVE OR BELOW, ARE OPEN
OR
BOILER LOADING IS GREATER THAN 30% AND PULVERIZER JUST ABOVE OR BELOW IS IN SERVICE AT GREATER THAN 50% LOADING.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
MILL OUTLET TEMPERATURE CONTROL
HIGH PULVERIZER OUTLET TEMPERATURE (ABOVE 200°F )
WILL
OPEN COLD AIR DAMPER
AND
CLOSE HOT AIR GATE.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
FEEDER CONTROL
A. FEEDER RUNS AT MINIMUM SPEED UNTIL INITIATING CONDITION IS CORRECTED, AT WHICH TIME THE FEEDER WILL BE RETURNED TO CONTROL.
A. PULVERIZER BOWL DIFFERENTIAL HIGH.B. PULVERIZER AMPS. ABOVE MAXIMUM SET POINT.
B. LOSS OF COAL FLOW AND LOW PULVERIZER CURRENT WILL TRIP THE FEEDER, OPEN COLD AIR DAMPER AND CLOSE HOT AIR GATE.AFTER CORRECTIVE ACTION THE HOT AIR GATE IS OPENED AND FEEDER IS RESTARTED.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
CONDITIONS FOR A PULVERIZER TRIP
PULVERIZER DISCHARGE VALVE NOT OPEN
LOSS OF UNIT DC POWER (FOR MORE THAN 2 SECONDS)
PULVERIZER IGNITION PERMIT NOT SATISFIED AND SUPPORT IGNITION IS REQUIRED.
BOILER TRIP
PRIMARY AIR FAN TRIP
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
PULVERIZER SHUT DOWN SEQUENCE
START ASSOCIATED OIL ELEVATION REDUCE FEEDER SPEED TO MINIMUM CLOSE HOT AIR GATE< PULVERIZER OUTLET TEMPERATURE IS 120°F STOP FEEDER< WAIT FOR 2 MINUTES STOP PULVERIZER< FURNACE STABILIZES ASSOCIATED OIL LEVEL SHUT DOWN.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
PULVERIZER SHUT DOWN
START ASSOCIATED OIL ELEVATION REDUCE FEEDER SPEED TO MINIMUM CLOSE HOT AIR GATE< PULVERIZER TEMPERATURE IS 120°F STOP FEEDER< TWO MINUTES STOP PULVERIZER< FURNACE STABILIZES SHUT OFF ASSOCIATED OIL ELEVATION.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
ARRANGEMENT OF SYSTEM
FSSS - MAJOR PARTS
LOGIC CABINET CONSOLE INSERT SECONDARY AIR DAMPER PANEL MILL PANEL FIELD EQUIPMENTS CUSTOMER SUPPLIED INTERFACE
EQUIPMENT.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
FSSS
Oil gun start sequence
• HEA Advances• Atomising valve opens• Corner oil valve opens• HEA sparks• Flame scanner picks up flame• HEA retracts • Corner valve closes if flame is not sensed.
Bharat Heavy Electricals Limited - Tiruchirappalli
Boiler C&I
Boiler C&I
FSSS – Oil gun start up timing sequence
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