LONG TERM PLANNING AND OVERHAULING PRACTICES IN NTPC
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LONG TERM PLANNINGAND
OVERHAULING
PRACTICES IN NTPC
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WHY OVERHAULING IS
REQUIRED ?
• Performance
• Reliability
• Availability
• Safety• Environment
• Cost
•Statutory Requirement
PRASECS
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PERFORMANCE
• Generation
• Heat Rate
• Parameters• Specific oil consumption
• Auxiliary power consumption
– Motor current – Capacity deterioration
– Utilising stand by eqpt.
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RELIABILITY
• Routine and repetitive maint.
• Poor performance of eqpt.
• Unplanned Breakdowns – High vibration of eqpt.
– Abnormal noise
–High Temperature
– Leakages
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AVAILABILITY
• ABT
• Availability of stand by eqpt.
•Availability of complete stream
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SAFETY
• Safety of the equipment
• Safety valves
•Poor condition of internals
• Safety of electrical eqpt.
• Condition of flow path
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ENVIRONMENT
• Flue gas emissions
– Air control act
•
Noise• Ash water
• Effluents
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COST
• Cost of generation
• Coal input
•Water consumption
• Oil consumption
• Auxiliary power consumption
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Statutory requirement
• Boiler certificate renewal
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WHEN TO DO OVERHAULING ?
• Summary of PRASECS• Grid condition
• Customer requirement• CERC Clearance
• Condition of other units of thestation
• MOU Target
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LONG TERM PLANNING
• Life cycle plan for 25 – 30 years
• Regional Eight years rolling plan
•Station Eight years rolling plan
• Engineering declaration
• Annual location plan
• Spares procurement plan
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LIFE CYCLE PLAN
• Likely trend of replacement of theequipment/parts which are likely to failbefore the life expectancy
• Factors for replacement
– Coal quality – Creep life of various components
– Equipment duty conditions
– Wear rate – Behavioural trend of plant/ equipment & its
past history
– RLA Reports
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MAJOR EQUIPMENT TO BE
COVERED IN LIFE CYCLE PLAN
• Gear Reducers
• Slurry pumps
•Coal crushers
• Conveyor Drives in CHP
• Chemical piping
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Cont’d
Boiler Pr.Parts• Super heaters
• Re-heaters
• High Pr. Valves
• Safety valves
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Cont’d
• Turbine & Aux.
– Turbine rotor blades
– Turbine bolts
– Boiler feed pump rotor
– H.P. Heater coil
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Cont’d
• Electrical
– H.T.Motor
– Transformer
– Switch gears
– Cables
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Regional Eight years rolling plan
• Minimum number of units at a time
• Regional electricity boards
•Regional grid demand
• Capital investment and revenue budget
• Unit/station merit rating based on
efficiency and economics of generation
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Define region into station/plant & areas
Consider plant life & potentialProblems In each station/unit
Formulate repair plans with cost data
Evaluate
Interim plan
Region/station rolling plan
Station location plan
Engg input
From similarplants
Maint. EngnrInput
Statutoryrequirement
PlantBetterment
plans
ResourceSpares
& materials
ResourceSkill and
T&P
Managementinput
Eight year rolling planFlow chart
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Station Eight year rolling plan
• Detail plan for first three years
• Diagnostic inspection and majorreplacements in subsequent years
• Modest updating each year
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Station annual location plan
• Detailed account of operation and maint. Of thecurrent year and plans for the next year.
• The plan should consist Unit merit rating basedon its performance in the last one year.
• Justification of heavy expenditure forimprovement and modifications
• Resource availability analysis
• Fuel cost
• Generation cost
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ENGINEERING DECLARATION
• Brief review of the past performance of the unit
• Objectives of the proposed overhaul
• Scope of work
• Resource plan
• Returns in terms of gain in reliability andefficiency
• Engg declaration to be issued 24 months aheadand reviewed periodically (six monthly)
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Format of Engg. Declaration
• Unit no
• Boiler license no
• Boiler license validity
• Overhaul history• Unit mile stones/ Major event
• Unit performance history
• Root cause analysis on Boiler tube leakagesand action plan
• Root cause analysis on trip and action plan
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Cont’d
• Major eqpt. Failure history
• Parameters assessment
•Work module
• Financial justification
• Techno economic evaluation
• Bar chart• Exception of condition monitoring reports
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Planning process of unit outage
• Pre shut down planning activities
• Shut down activities
•Post shut down activities
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activities
• Plan to start from the time unit issynchronised.
• Engg declaration
• Spares and materials schedules• Quality plans
• Recommissioning Schedules
• Defect work orders pending• PRE SHUT DOWN SURVEY
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Resources
• Spares & consumables
• Manpower
• Contracts
• Special T&P
• Material handling equipment like cranes,lifts and transport
• Availability of manufacturing facilities• Communication facilities
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Cont’d
• Testing facilities like radiography, hydrotest etc.
• Temporary store & office cubicles
• Dispensary & ambulance at site
• General amenities for additional workforce
• Input from other departments
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PRE SHUTDOWN SURVEY
• Equipment general condition
• Condition of bearings, filters and coolers
•Condition of APH – Pressure differential
– Heat pick up across APH
– Parameters of primary ,secondary air & fluegas
– Oxygen in flue gas
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Cont’d • ESP
– Ash evacuation capacity
– Heating system
– Flue gas emission
– Leakages through manholes – ESP inlet & outlet Temperatures.
•Coal mills – Reject rate
– Coal fineness
– Leakages
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Cont’d •
Boiler – Boiler expansion
– Leakages through manholes, peep holes
– Coal leakages
– Burner tilt mechanism
– Soot blower status
• Valves & Fittings
– Steam leakages – Steam passing
– Local/remote operation
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Cont’d
• Ducts & Dampers
– Hot air leakages
– Air suction in the gas path
– Ash leakages
– Leakages at expansion joints
– Dampers operation from local & remote
– Dampers isolation
– Duct insolation
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Cont’d
• Turbo Generators
– Bearing condition
– Vibration & Temp
– Oil leakage
– Analysis of lub oil
– Operation of control valves
– Leakage of hydrogen
– Stator water DP
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Cont’d
• Motors
– Bearing vibration
– Lubrication & Temp. rise
• Transformers
– General condition of oil
– Dielectric strength
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Execution
• Unit shut down• Issue of PTWs• Daily overhaul review meeting• Follow up of the bar chart• Filling the quality check sheets• Return of PTWs• Recommissioning activities
• Boiler hydro test• Unit light up• Unit synchronisation
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Post overhaul review
• Deviation from the planning if any
• Performance of contracting agencies
•Plant parameters review
• Overhaul report
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SCOPE OF WORK
PRESSURE PARTS
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PRESSURE PARTS
WATER WALL ‘S’-Panel: All corners & L&R walls inspn. & repairs
Burner transition & corner tubes inspn. & repairs,TT survey in erosion prone areas, HP Jet cleaning,
DPT of scallop bar, support & ww tubes in deadchamber, Bottom ring header inspn.
WW screen & hanger tubes inspn.
LTSH Coils lifting (condition based), Inspection of Bifurcationbends, Cassette baffles & Terminal tubes inspectionDPT of hanger tubes & TT survey
PLATEN SH /FINAL SH
Spacer tube healthiness checking & TT survey
DPT of Lugs to tube welding
DIVISIONALSH
Scissor tubes sleeves, lugs inspn. & repairs and DPT ofLugs to tube welding, TT survey
STEAMCOOLED
WALL
TT survey in Screen tubes, tubes near manholes, Gapbetween LTSH coil & steam cooled wall, Eco coil& SCW,mechanical rubbing due to cassette baffles, stubs ofSHH-4A &4B
PRESSURE PARTS
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PRESSURE PARTS CONTD..
REHEATER Spacer tube healthiness checks & lugs inspn.ORIFICE FIXING ? & TT survey
ECONOMISER Coils lifting (Condition based)DPT of root joints of stubs of Inlet headerCassette baffles & hanger tubes inspection & TTsurvey
DRUM Drum inspection
Drum ‘J’-bolts inspn. & DPT
HANGERS Pre O/H & Post O/H readings comparisionSurvey of Cold readings & Adjustment, if any
SAFETY V/Vs& ERVs
Defective Safety valves & ERVs (Condition based)overhauling/Servicing
SOOT BLWRS Soot blowers overhauling & LRSBs servicing
PENT HOUSE Inspection of supports, headers, vents, DPT of roots,attachment weld joints& all header joints
PRESSURE PARTS
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PRESSURE PARTS CONTD…
BURNERS 36 NO.S of Coal nozzles replacementAir/oil nozzles in-situ repair (condition based)
SADC/BURNER TILT CHECKSNMEJs Repair & Rectification of defective portion of joints
after pre-overhaul survey
QUICK ERECTSCAFFOLDING
Erection of QES and Thorough inspection & cleaningof Water walls, Divisional panel
WIND BOX Cleaning, Inspection & repairs
BOILER
EXPANSIONS
Expansion indicators checking for any foulingproblems
HP VALVES CC pump- discharge v/v bonnet leakage, CBD v/vs,MS, Spray v/vs, root valves gland packingreplacement
BOILER
SUPPORT SYST
Boiler support systems checks as per LMI
ROTATING MACHINES
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ROTATING MACHINESMILLS 2 No.of Mills Overhaul , Lub station servicing
FEEDERS 8 no.of RC feeders overhauling
DAMPERS &GATES
Dampers & gates overhauling & Passing problemsrectification
FANS All fans servicing, Blade pitch control servicing,
silencer cleaning, Visual inspection of shaft, welds &NDT. Lub station servicing.
AIR PREHEATERS
Damaged baskets replacement, if anyRadial / Axial seals inspn, repairs & replacementAll bearings/ gear boxes inspectionOverrunning clutches problems attending.SCAPH heat transfer areas inspn , cleaning & repair
DUCTS &
DAMPERS
Air & Gas duct inspection & repairsRepair of defective dampers & servicing of diversiondampers
ASH HANDLING SYSTEM
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ASH HANDLING SYSTEMBOTTOM ASHSYSTEM
Repair of refractory, Seal trough & viewglasses inspection & cleaning, Clinker
grinders rollers (2 sets) replacement, SSpipes replacement, Feed gate seal & barrelreplacement & attending to passingproblems, Bottom ash nozzles inspectionBA discharge new lines connection
FLY ASHSYSTEM
Fly ash slurry line rotation/ replacement,Collector tanks & Air washers inspection,Vacuum line valves servicing, All vacuumlines washing, Vacuum pumps servicing,
Collector seal boxes repairs.
ESP Emptying of all hoppersAll ESP internals cleaning,inspection/ repairs
TURBINE & AUXILIARIES
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TURBINE & AUXILIARIES
MAINTURBINE
CF trip oil line modification for proving ATT, & TurbineGoverning characteristics checking,
Turbine actual over speed testing
TDBFPs Euroflex coupling inspection, Turbine actualoverspeed test, MDBFP-2C discharge NRVreplacement, ACV & MCV pilot valves servicing &recirculation control valves inspection & repairs.TDBFP-2A&2B exhaust duct insulation & plastering
DMCW & ACW DMCW pump-B overhaul & suction strainers cleaningDMCW,ACW & CW system butterfly valves servicing(600 NB: 6 no.s, 800 NB : 8 no.s) PU coatinginspection & repairs, Self cleaning filters inspn
CONDENSER Condenser Water box tube cleaning, FRE lining inspn
Hotwell & Deaerator cleaning & condenser flood testCEPSs suction strainers cleaning.
CW DUCT CW duct PU coating inspection & repairs.
VALVES Turbine MAL valves, HTPRDS spray valves
OFF SITES (MECHANICAL)
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OFF-SITES (MECHANICAL)
CW PUMPS CW pump- 3,4 & 5 volute inspection for
poly -glass coating.
CW pump butterfly valves inspection &operational checks
CW DUCT CW inlet & Outlet duct inspection &PU coating repairs.
COOLING
TOWER
CT nozzles inspection / cleaning
CT nozzles & drift eliminators repairs /replacement.
CT basin cleaning.
EM LT SWGR
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EM-LT SWGR
LT switch gear sections overhaul
Bus/Modules/breakers/relays/contactors/transducers/timers
Cable shifting / interchangingTesting of protections of incomers/
bus couplers / auto change over
schemes as per LMI
EM SWYD / HT SWGR
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EM-SWYD / HT SWGR
Insulators replacementCTs replacementBus tightnessHT switch gears PM
EM GENERATOR
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EM-GENERATOR
Stator & Rotor InspectionCore inspectionHydrogen & Exciter coolers servicingExciter servicingTesting of excitation as per LMIInspection & protection of water cooled
generator stator winding
Prevention & detection of generator rotorearth faults as per LMI
TRANSFORMERS
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TRANSFORMERSTransformers cleaning
OLTC, Conservators cleaningProtection elements checkingSilica gel replacement
Oil samplingOil flushingTesting
HT & LT M t
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HT & LT Motors
Overhauling of motorsServicing of motorsBearings
Oil replacement / GreasingLugs inspectionFan inspection
LIGHT-UP TO SYNCHRONISATION
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LIGHT UP TO SYNCHRONISATION
ACTIVITY UNIT-1(2003-04)
UNIT-2(2004-05)
UNIT-1(2004-05)
UNIT-2(2005-06)
UNIT-1(2005-06)
LIGHT-UP TOSYNCH.
25 Hrs 24.5Hrs
20.8 Hrs 20.0HRS
18 Hrs
LIGHT-UP TO
SAFETY V/VFLOATING START
7.2 Hrs 6.7 Hrs 6.5 Hrs 14.4*
HRS12.5Hrs
SAFETY V/VFLOATINGDURATION
5.5 Hrs 5 Hrs 3 Hrs 4.5HRS
4.4 Hrs
SAFETY V/VFLOATING TOTG 3000 RPM
5.2 Hrs 3.3 Hrs 4.5 Hrs 0.8HRS
0.9 Hrs
ELECTRICAL
TESTS DURATION
5 Hrs 7.75
Hrs
6 Hrs 5.0*
HRS4.3 Hrs
PRESSURE PARTS (Cont’d)
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PRESSURE PARTS (Cont’d) QUICK ERECT SCAFFOLDING
UNIT-1(2003-04)
UNIT-2(2004-05)
UNIT-1(2004-05)
UNIT-2(2005-06)
‘QES’
ERECTION8.5
DAYS7.0
DAYS
5.5DAYS
5.5DAYS
‘QES’
DISMANTLING4.5
DAYS2.0
DAYS
2.9DAYS
3.0DAYS
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FUEL OIL CONSUMPTIONUNIT YEAR HFO
KL
LDO
KL
TOTAL
KL
# I 2003-04 228 224 452
# I 2004-05 243 38 281
# II 2004-05 251 151 402
# II 2005-06 148 141 289
# I 2005-06 - - 170
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THANK YOU