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Performance Analysis 2008

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f i

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P f A l i 2008

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P f A l i 2008

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Tripping Analysis

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FORCED OUTAGECY WISE BREAK UP (No. / %)

Heads Cal Year 2006 Cal Year 2007 Cal Year 2008

Pld outage 6 / 5.75 7 / 6.10 6 / 6.09

Grid Rest . +

Dist

1 / 0.002 0 / 0.000 0 / 0.000

Blr Aux 2 / 0.04 6 / 0.14 3 / 0.04

Turb Aux 4 / 0.23 6 / 0.09 2 / 0.23

Elect Aux 7 / 0.34 7 / 0.05 23 / 0.25

BTL 15 / 0.70 27 / 1.25 33 / 1.51

C&I 1 / 0.01 15 / 0.08 8 / 0.02Others 2 / 0.01 3 / 0.01 9 / 0.21

Fd outage 32 / 1.33 64 / 1.63 78 / 2.26

Total Outage 38 / 7.07 71 / 7.73 84 / 8.35

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Action Plan to reduce Forced Outages

CAUSE OF TRIPPING

• U # III : Leakage from

LHS Eco coil no.32

header joint

• Root Cause: Weldfailure.

ACTION PLAN

• Proper marking andrecord of defective

joints afterradiograph

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CAUSE OF TRIPPING

• U # III : Leakage from

LHS SCW T-1&2

above re-heater

regulating stage

• Root Cause:

Attachment weld

failure, sample sent to

R&D.

ACTION PLAN

• Exhaustive DPT andchecking of attachment welds.

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CAUSE OF TRIPPING

• U # VII : Leakage from

water wall (LHS ) tube

no -12 towards rear

from scaffold door at anelevation of 8.5 mt

• Root Cause: Ash led air

erosion due to gap

between LHS & S-

Panel WW.

ACTION PLAN

• Sealing of gapsbetween “S” paneland vertical wall

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CAUSE OF TRIPPING

• U # VII : both ID & FD

fans tripped on “Post

purge fan trip”

protection and unittripped on “both FD

fans OFF”.

• Root Cause: Defective

input cards EB02 in

CRB01 panel

ACTION PLAN

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CAUSE OF TRIPPING

• U # VIII : Unit was de-

synchronised to attend

HRH ERV (no. 23)

passing, manualisolating valve was also

passing.

ACTION PLAN

• New ERV wasreplaced with newone.

• Servicing of manualisolating valve everyoverhaul.

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CAUSE OF TRIPPING

• U # VIII : Leakage

from water wall S-

panel area front side

tube no1 from LHS atan elevation of 8.5 mt

near scaffold door

• Root Cause:

Attachment weld

failure.

ACTION PLAN


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CAUSE OF TRIPPING

• U # X : Leakage from

from water wall (front

side ) tube no -1

towards right fromWWSB No.-45. EL-46

mt

• Root Cause: Shop weld

failure

ACTION PLAN

• Radiography of shop/erection jointsin phased mannerduring overhaul.

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CAUSE OF TRIPPING

• U # X : Unit tripped on “ GT

WTI operated” due to the

actuation of “GT Cooling fan

supply change over fault” relay

• Root Cause: Over current relay

operation of 415 V in both

incomers of ACDB due to the

circulating current flown while

paralleling of both

transformers(11/0.4 KV)

ACTION PLAN

• Review of over-current relaysetting and timedelay.

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CAUSE OF TRIPPING

• U # X : Leakage from

ECO lower bank

bottom, vertical joint of

inner most tube of coilno 1 from LHS at an

elevation of 48 mt.

Root Cause: Erection

weld failure.

ACTION PLAN

• Radiography of shop/erection jointsin phased mannerduring overhaul.

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CAUSE OFTRIPPING

• U # III : Tube

leakage in Re-heater

Regulating stage

Coil no. 80 RHS

bottom centre bend

• Root Cause: Flue

Gas erosion .

ACTION PLAN

• Inspection andthickness survey

of bends at all foursides and middletop and bottom.

• Lifting of 24 coils

every year toinspect middlebends of all 288coils.

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CAUSE OFTRIPPING

• U # VI : Tube


Regulating stage

Coil no. 31 LHS

bottom extreme

bend.


Gas erosion .

ACTION PLAN

• Inspection andthickness survey

of bends at all foursides and middletop and bottom.

• Lifting of 24 coils

every year toinspect middlebends of all 288coils.

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CAUSE OF TRIPPING

• U # IX : . Turbine tripped on

„Cold gas temperature high‟

protection. Both TDBFPs

tripped. MDBFP came on autobut it tripped on protection.

Boiler tripped on Drum level

very low protection

• Root Cause: Air locking in the

TG ECW system

ACTION PLAN

• Presence of NRV betweenECW make uptank and

suction header.shall bereviewed;matter will bereferred to OS-

Engg.

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CAUSE OF TRIPPING• U # X : Unit tripped on

“Loss of All Fuel”

protection.

• Root Cause: Tripping of PA fan-10B on local EPB

operation

ACTION PLAN

• EPBs of all PA, FD,ID fans were checkedfor integrity of fixtures.

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Jun2008

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CAUSE OF

TRIPPING

• U # II Tripped on

“Loss of Excitation”

Root Cause: Reason

could not be

established

ACTION PLAN

Thorough checking

of both the DVR

and control/Power

circuit of

Excitation system

indicates noabnormality in the

system.

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CAUSE OF

TRIPPING

• U # V : Tube


Regulating stage

Coil no. 144 LHS

bottom extreme

bend.


Gas erosion .

ACTION PLAN

• Inspection and

thickness surveyof bends at all four

sides and middle

top and bottom.

• Lifting of ~50

coils to inspect all

288 coils.

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CAUSE OF TRIPPING

• U # IV : . Tube leakage

in Water Wall S-panel

Rear panel tube T161

• Root Cause: Impact of

falling clinker.

ACTION PLAN

• Air distributionplates on RHS(Cor-1,5,4 &8)were inspectedand damagedplates wererectified.

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CAUSE OF TRIPPING• U # VII : Unit tripped on

“Rotor E/F stage 2”

protection.

• Root Cause: Rotor E/Fprotection Circuit

problem

ACTION PLAN

• Rotor E/F stage 2protection bothauxiliary relay shallbe connected to

RA7A panel DCcircuit alone.Proposal has beensent to OS-CC forconcurrence and

approval.

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Jul 2008

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Tripping Analysis

CAUSE OF TRIPPING

• U # V Tripped on

“Flame failure”

Root Cause:

C&I Control card

failure.

ACTION PLAN

• The defective

NPM12 Card was

replaced with

another new

NPM12 card.

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Tripping Analysis

CAUSE OF TRIPPING

• U # II Tripped on

“Loss of Excitation”

Root Cause:

Defective cards in

DVR UM.

ACTION PLAN

• The defectives

Cards were

replaced and the

excitation system

changed over from

Stand-by to main .

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Tripping Analysis

CAUSE OF TRIPPING

• U # V Tripped on

“Cond. Vacuum fail”

protection

Root Cause:

Water particles in the

vacuum switches

ACTION PLAN

• All the vacuum

switches were

cleaned, recalibrated ,fixed back and put

into service after

wrapping all the

switches withsuitable polythene

covers.

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Tripping Analysis

CAUSE OF

TRIPPING

• U # V Trippedon “Cond.

Vacuum fail”protection

Root Cause:

Micro

switchesdevelopedproblems dueto presence of water particles

ACTION PLAN

• The vacuum switches werereplaced with brand new Ashcroftmake vacuum switches. All

associated cables and protectionblock were checked for the secondtime and found normal. 2 out of 3logic was also checked and foundnormal.

• In future, any switch, withpresence water particles, shall bedried and cleaned. If required, thesame shall be replaced

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Tripping AnalysisCAUSE OF TRIPPING

• U # X Tripped on“Loss of all fuel”

Root Cause:

Sudden rupture of strainer change overvalve flange gasket of HFO supply line inHFO control station atBoiler firing floorcausing oil splashingover leading to firebreak out.

ACTION PLAN

• It shall be alwaysensured to replace thegaskets in HFO

system with betterquality gaskets.

• Proper control of HFO pressure shallbe ensured while

taking oil guns intoservice.

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Tripping Analysis

CAUSE OF TRIPPING

• U # IX stopped due tohigh TG Vibration

Root Cause: • Clearances of LP

front gland box washigher probably

because of higherclearances of horizontal keys of LPT front gland box

ACTION PLAN

• The gland box of LPfront was centered.

• Horizontal keys were

corrected after built-upand machining.

• TG Brg 3 was inspectedas a preventivemeasure.

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Tripping Analysis

CAUSE OF

TRIPPING• Station Black-out

Root Cause:

a). Arcing in V-

J#4 R phasebreaker ; b) Busbar differentialprotection for bussection-I,did notoperate eventhough the relaysettings were asper design.

ACTION PLAN

• Measures to prevent arcing in400KV breakers. Matter has beentaken up with M/S CGL (OEM) tostudy the reason for initiation of arc and suggest remedies forpreventing the same.

• Reviewing of current settings forstart relay and differential relaywhich activate the bus barprotection. Communication in thisregard has been sent to GM(PE-Elect.) and M/s ABB

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Tripping Analysis

CAUSE OF TRIPPING

• U#9 : Water wall Tube

leakage

Root Cause:

• Attachment weldfailure.

ACTION PLAN

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Aug 2008

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Tripping Analysis

CAUSE OF TRIPPING

• U#4 : Economiser

Tube leakage

Root Cause:

• Maintenance weldDefect.

ACTION PLAN

• Proper marking and

record of defective

joints after

radiograph beingdone.

• Welder wise defect

rate being

maintained for

control.

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Sep 2008

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Tripping Analysis

CAUSE OF TRIPPING

• U#1 : Unit tripped on

“Furnace Pr. Low” as all

running RCF came to

minimum loading.Root Cause:

• Momentary disturbance

in “Node-2” 24 V supply.

ACTION PLAN

• Supply block for“Node-2” has beenreplaced.

• Controllers‟ supply for RC Feeder will besegregated in 03different panel (02RCF from each panel.)in next overhaul byC&I department.

i i A i

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Tripping Analysis

CAUSE OF TRIPPING


“GT winding Temp

high”.

Root Cause: • Power cable joint of

main supply to GTMB

failed and caught fire,

due to which GT

protection control

cables got damaged.

ACTION PLAN

• During Unit O/H

inspection of cable tray in

GT yard area will be done,

joints will be identified andnew cables will be laid.

• b) Control cable and

power cables will be routed

through different trays

wherever such discrepancy

is found.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#1 : Stub joint leakage

of Regulating stage

Reheater coil # 1.

Root Cause: • The cause of failure is

uneven load on hangers.

ACTION PLAN

• Regular DPT is donein all stubs and if required stubs arereplaced.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#4 : Water wall Tube

leakage

Root Cause:

• Attachment weldfailure.

ACTION PLAN


T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING


“Low Forward power

protection”

Root Cause: • Wiring problem and

termination problem in

the load transducers.

ACTION PLAN

• Duringrecommissioning

joint calibration byEMD & C&I will bedone to ensurehealthiness of loadtransducers.

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Oct 2008

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING


“Furnace Pr. High”.

Root Cause:

• Sudden dislodging of accumulated ash into BA

hopper .

ACTION PLAN

When ever slaggingtendency is observed :

a) proper and timely de-

ashing will be ensuredby increasing thefrequency.

b) Frequency of wall

blowers operationshall be increased.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING


a) “Excitation field

failure protection”

b) “Stator earth fault”

Root Cause:

• Voltage fluctuations

caused due to defectiveBus PT of R and Y

phases.

ACTION PLAN

• The bus line PTs shall be

checked individually and

shall be included in the

testing check list.• New bus line PTs

procurement action shall be

initiated.

T i i A l i

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Tripping Analysis

CAUSE OF

TRIPPING

• U#2 : Unit tripped

due to Gen bkr. Trip

while taking UAT inservice.

Root Cause: Exact

cause of trippig can

be established after online supply change

over, if the problem

persists.

ACTION PLAN

• a) Control wiring checking

shall be done to find out

cause of “Gen Internal fault”

protection operation duringopportunity.

• b) UAT change over

scheme to be checked during

opportunity.

• c) In SOE, the status of unit

and station breaker contacts

shall be incorporated.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#2 : Unit was manually

tripped as light reflection

on GT R-phase bus duct

was suspected as hotspot.

ACTION PLAN

• At night, hot spots areto be confirmed bymaking thesurroundings dark.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#5 : Radiant S/H

Tube leakage

Root Cause:

• Short term overheatingdue to blockage.

ACTION PLAN

• End caps to beprovided whilecutting the verticaltubes.

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Nov 2008

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#2 : Unit tripped on“All ID Fan trip”protection due totripping of LOPs.

Root Cause:

• The CA busequipments got trippeddue to intermittent

voltage drop as R-phase contact of 415VCA bus reserveincomer breaker was

damaged.

ACTION PLAN

• The ageing Russian make 415V LT breakers (reserve) needs

to be replaced, Proposal shall

be initiated by 31/12/2008. for

replacement of reserve

incomer breakers and

sectionalizing breakers in

phased manner.• Availability of supply to

standby lub oil pumps/

equipments from other source

shall always be ensured.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#3 : Unit stopped due

to RH Reg stg T/L from

RHS center bends of

Coil # 134, 135, 137 &LHS center bends of

Coil # 137

Root Cause:

• The suspected cause of

failure is Flue Gas

erosion.

ACTION PLAN

• Inspection and thickness

survey of bends at all four

sides and middle top and

bottom.• b) Lifting of ~50 coils

every year & balance based

on inspection and thickness

survey.

T i i A l i

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Tripping Analysis

CAUSE OF TRIPPING

• U#4 : Unit tripped twice

on “Turbine trip

protection”.

Root Cause: TheOverheating of TTS

supply supervision relay

due to partial release of

one of the Turbine tripmanual push buttons in

the control desk

ACTION PLAN

• The Turbine trip manual

push button was checked

and released properly.

The operation of pushbuttons checked and

cleared.

• Turbine trip to Generator

trip timer was replaced.

Tripping Anal sis

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Tripping Analysis

CAUSE OF TRIPPING

• U#8 : Unit was manually

tripped as drain line

(MAL-12) before HPCV-

2 got sheared just abovethe erection weld joint.

ACTION PLAN

• Sample being sent toR&D for analysis.

Tripping Analysis

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Tripping Analysis

CAUSE OF TRIPPING

• U#8 : Water Wall Tube

leakage on (RHS) near

WWSB No.-75 Right

Tube no. 1 at anelevation of -18.5 mt.

Root Cause:

• The suspected cause of

leakage is Shop Joint

failure.

ACTION PLAN

Shop joint to beinspected andradiographed inphased manner.

Tripping Analysis

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Tripping Analysis

CAUSE OF TRIPPING

• U#10 : Water Wall Tube

leakage on (LHS) tube

no -1 towards right from

WWSB No.-18 at anelevation of 50mt.

Root Cause:

• The cause of leakage is

attachment weld failure.

( Membrane welded with

the failed tube was

having weld defect.)

ACTION PLAN

Refractory holdingplate weld will bechecked thoroughlyin the wall blowers

area and repair work will be taken up asper condition.

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Dec 2008


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CAUSE OF TRIPPING

• U # VIII (08/12/08):TL in Platen S/H panel# 13 and 14

• Root cause : Bulgingdue to suspected longterm overheating.

ACTION PLAN

• Regular S/H & R/H MetalTemp monitoring beingdone and reviewed inDPM.

• Metal temp to bemaintained withinprescribed limit bykeeping burner tilt down

and by giving adequate HPspray.


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CAUSE OF TRIPPING

• U # IX (09/12/08): TLin W/W “S” panel.

• Root cause : Ash ladenAir Erosion form thenarrow gap betweensealing strip and LeftWater Wall (This gapshave been sealed

during last OH,however, onetrapezoidal piece founddislocated.)

ACTION PLAN

• Sealing of gaps between“S” panel and verticalwater wall to be ensuredduring every OH.

• In U#10 the above gaps tobe sealed during overhaul.


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CAUSE OF TRIPPING

• U # VI (10/12/08):

Unit got tripped on

„Loss of excitation‟

• Root cause : Failureof DVR-UM Pulse

Final stage Power

supply module-1

ACTION PLAN

• Reason for failure of pulsefinal stage power supply

module is to be ascertained

to avoid recurrence of such

failures. Matter has been

taken up with OES M/S

BHEL


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CAUSE OF TRIPPING

• U # VII (12/12/08): TL

in water wall front side

tube no 11 from RHS

at 46.5mt.• Root cause : Long

Term Overheating due

to Partial chocking at

Ring Header Orifice(30% of the orifice

area was blocked with

corrosion material)

ACTION PLAN

• During OH ring headerorifice to be removed and

water wall flushing to be

ensured as per practice.


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CAUSE OF TRIPPING

• U # V (13/12/08): TL

in SCW near M/H # 14

• Root cause : Erection

joint failure.

ACTION PLAN


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CAUSE OF TRIPPING

• U # IV (17/12/08):Unit got tripped on“Generator field brkr.Main exc. trip”

• Root cause : Highervoltage drop whenstandby exciter wastaken into service. Alsovoltage could not be

built up in time

ACTION PLAN

• Revision of LMI regardingChange over of exciter inview of the R&M of unitswith DDCMIS. The LMIfor Exciter changeover

will be reviewed andrevised as per the Unitload conditions

• b) Reason for failure of

power supply card is to beascertained to avoidrecurrence of such failures,Matter has been taken upwith OES M/S BHEL


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CAUSE OF TRIPPING

• U # X (18/12/08): TL

in Spacer tube in

between Re-heater

panel # 1 & 2• Root cause : Spacer

tube in between Re-

heater panel # 1 & 2

pin-hole fracture inerection joint.

ACTION PLAN


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CAUSE OF TRIPPING

• U # VIII (28/12/08):

Unit stopped due to

gasket leakage from

drum manhole (RHS).

ACTION PLAN

• Manhole cover bluematching to be ensured

during OH.


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CAUSE OF TRIPPING

• U # VII (30/12/08): TL

in water wall front side

near Soot blower no 5

at 43mt

• Root cause : Due soot

blower erosion

thickness got reduced

in T4 towards rightnear WWSB no 5. That

created fish mouth

i i h f il d

ACTION PLAN

• Following checks are to bedone during /after everywall blowing :

– Rotary motion of wall

blower to be ensured, – Poppet valve closing to

be ensured after blowing,

– If a Wall blower gets

stuck-up inside thefurnace, steam to beisolated immediately andmaintenance personnel to

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