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ACOMPARATIV E STUD YO F PLAN T AN D EQUIPMEN T LIF E EXTENSIO NSTRATEGIE S

B YS . A . PATULSK I

WISCONSI NELECTRI C POWE RCOMPAN Y MILWAUKEE , WISCONSI N

JUNE , 198 6 

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ErAASRDOCXE F

Presente d a t EPRI/EI I - Conferenc e o nLif e Extensio nand Assessmen t o f Fossi l Plant s Jun e 2-4 , 1986 , Washington , D.C . 198 6P. 3

INTRODUCTIO N

Som e ma yargu e tha t th e utilit ycommunity , owner/operators , origina l equipmen t manufacturers , consultant s an d specialt ycontractors , hav e bee n engage d i nlif e extensio npractice s fo r a lon g perio d o f time . Earl y198 3 mark s th e perio d durin g whic hthes e effort s becom e formall y recognize d a s "lif e extension" . Organizationa l structure s hav e bee n adopted , an d technologie s enhance d t o mor e directl yaddres s th e issue s surroundin g lif e extensions . Th e fourtee ntechnica l paper s tha t embodyth e consultant' s approac h t o lif e extensio ndra wo nexperienc e gaine d sinc e 1983 . I hav e no t attempte d t o analyz e th e technica l meri t o r critiqu e th e variou s approache s o r technique s discusse d i nthes e papers . Comment s ar e offere d o nth e constant s reflecte d i nth e papers , th e similaritie s i napproach , component s investigated , an d th e failur e mechanism s o f greates t concern . Th e nondestructiv e technique s use d i napproachin g th e lif e extensio ngoal , and som e obviou s anomalie s ar e als o touche d on . Include d i s a summar yo f th e mor e importan t item s t o b e considere d b y th e owner/operato r o f a generatin g uni t whe nmanagin g a lif e extensio n effort . I . CONSTANT S

Anumbe r o f constant s appea r i nth e approache s t o lif e extensio n bein g considered . Som e o f thes e constant s are : 1 . Moder ngeneratin g unit s - thos e buil t wit hfina l steamtemperature s o f 90 0 F an d abov e an d operatin g ove r 160 0 psi g hav e desig nlive s i nth e rang e o f 30-4 0 years .P. 4

Littl e informatio ni s availabl e i ndesig ndocument s regardin g anyoriginall yintende d lif e spans . Failur e mechanism s encountere d i nbenc hmar k survey s indicat e tha t th e engineerin g standard s use d i nth e 1950' s and earl y1960' s wil l provid e uni t lif e span s i nthi s range . Operatio nsignficantl yi nexces s o f thes e tim e span s require s additiona l technical , and economi c effort . 2 . Overal l objective s drivin g lif e extension : Whil e the yvar yfro mutilit yt o utility , al l includ e a t leas t som e o f th e followin g items : deferra l o f capacit yaddition s reduce d financia l ris k whe ncompare d t o othe r alternative s regulator yprudenc yaction s uncertai n loa d growt h(abilit yt o respon d rapidl yt o forecas t changes ) capacit yrecaptur e and/o r repowin g cos t effectivenes s (thi s i s no t th e sam e a s reduce d risk ) improve d therma l efficiencies/therma l efficienc yrecaptur e increase d availabilitie s decrease d operation s and maintenanc e cost s program s ca ntailo r cas hflow s t o availabl e corporat e resource s cyclin g capabilit y change s i nfue l soruc e o r typ e obsolescenc e • 3 . T o formulate , guide , analyz e and implemen t a successfu l lif e extensio nprogra mth e utilit y need s t o commi t a diversifie d group o f in-hous e expertise . Th e followin g discipline s shoul d b e included :P. 5

Corporat e planner s Engineerin g personne l (Centra l Office ) Operatin g personne l (Plan t inputs ) Financia l manager s Environmenta l analys t Lega l staf f 4 . Lif e extensio ni s a flexibl e program . I t ca n accommodate :

Asmal l utilit ywit hon e o r tw o candidat e unit s o r a larg e utilit ywit hdozen s o f units . I t ca nb e time d t o occu r ove r a shor t period , wit hanalysi s and th e star t o f implementatio n occurrin g ove r thre e year s o r less ; o r i t ca n b e extende d ove r a decad e o r more . Th e numbe r o f unit s considere d and th e timin g employe d ar e ofte ndrive nbyth e utility' s objective s a s discusse d i nite m2 5 . Lif e extensio ni s no t a glorifie d maintenanc e program . Som e activitie s ca naccompanyan d complemen t maintenance . Other s ar e unique . Lif e extensio ni s define d i nman ydifferen t ways . On e o f th e mor e concis e statement s o f th e differenc e betwee nlif e extensio nan d maintenanc e tha t I hav e ru nacros s i s forwarde d byWestinghouse : "Goo d maintenanc e program s ar e essentia l t o ensur e reliabl e lif e extension ; however , the ycanno t ensur e tha t critica l component s wil l no t fai l du e t o ag e relate d phenomenon. " "Lif e extensio ni s proactive. "

I nth e proactiv e mode , lif e extensio nno t onl yidentifie s proble marea s bu t als o identifie s plan t upgrades , timetables , an d th e operatin g an d maintenanc e technique s require d t o exten d plan t an d equipmen t life .

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I I PROGRA

MSTEP S Beyon d the agreemen t tha t surround s the constants , ther e exist s reasonabl e agreemen t a s t o wha t step s o r division s o f effor t ar e include d i nthe lif e extensionprogram .



## fr The firs t step involve s a genera l revie wo f the "suppl yside "

option s ope n t o th e utility . During thi s step th e utilit y mus t come t o grip s wit hit s syste mload growth , it s source s o f suppl yan

d wha t unit s ar e reasonabl e candidate s fo r lif e extension . Man

yo f th e benefit s ar e weighe d during thi s stage . *& - %'- ***' • 

### The secon d step i s t o determin e the approximat e economic s o f lif e extension ; the valu e o f lif e extende d generation , verse s a probabl e rang e o f costs . Durin g thi s ste

p the shor t an

d long-ter

meconomic s o f lif e extensionfo r the utilit yar e reviewed . Th e result s o f thi s revie wcanlead t o a numbe r o f majo r variation s i nth e following lif e extensio nsteps . Amajo r decisio n normall yoccur s a t thi s point : th e schedul e i s defined . On e optio ni s the tota l uni t assessment/implemen

tatio n approach , the secon d i s proceeding inth e "phased " approac hwit hselecte d items o f equipmen t examined , assesse d an d project s implemente d ove r a numbe r o f successive years .

-.- • 

### Fo r utilitie s choosing t o pursu e lif e extensionacros s a

larg e numbe r o f units , a sub-step ma ynowbe necessary ; tha t o f selecte d a

n orde r (ranking ) fo r unit s t o be addresse d in the lif e extensio n program . Avariet yo f selectio nmethod s an d criteri a ar e availabl e t o accomplis hthi s task .

X: £ A. 

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# I f ' Step thre e i s th e evaluatio no f specifi c component s tha t

compris e a

n individua l generating unit . Regardles s o f the option s selecte d (for singl e o r multipl e units , th e tota l uni t assessmen t verse s the phased approach ) developing a plan t o determin e th e unit' s physica l conditio nnowoccurs .P. 7

Thi s ste p i s compose d o f severa l sub-step s including : Design , operatin g records , an d dat a revie w Sit e interview s wit happropriat e personne l Visua l inspections , wal k downs , and confirmatio no f desig ndrawin g accurac ywit h"a s is " conditio no n critica l systems . Nondestructiv e evaluatio n- Thi s ca nb e eithe r testin g o r calculation s o r both . Samplin g an d destructiv e testin g Performanc e testin g I t i s generall yagree d tha t dat a review , personne l interview s and som e visua l inspection s shoul d occu r whe nplannin g fo r th e initia l uni t assessmen t outage . Thes e activitie s provid e a dat a bas e upo nwhic ha ninspectio npla nca nb e made . Durin g a uni t outa e thi s typ e o f pla ni s neede d t o assur e a smoot h interfac e wit hth e norma l maintenanc e wor k tha t i s t o b e performe d durin g th e sam e outag e timespan . A t th e sam e time , meaningfu l dat a mus t b e gathere d t o arriv e a t accurat e conclusions . Exces s dat a i s costl yi nlabo r and outag e time . Incomplet e informatio nma ylea d t o erroneou s conclusions . I nconductin g thes e inspection s severa l option s ar e ope nt o th e utility . Inspection s ca nb e performe d bya narchitec t engineer , th e origina l equipmen t manufacture r o r th e specialt y contractor . Th e consideration s take nint o accoun t fo r th e selectio n o f a prope r contracto r t o perfor mth e actua l fiel d inspectio nar e varie d t o perfor mth e actua l fiel d inspectio n ar e varie d enoug hfo r a spearat e pape r i nan d o f themselve s s o the yar e no t discusse d here . Als o no t mentione d i nanygrea t detail s i n anyo f th e paper s reviewe d i s th e possiblit yo f utilit ypersonne l performin g thi s work . Whe nchoosin g method s fo r th e detaile d inspectio nth e utilit y mus t remembe r tha t th e dat a gathere d wil l b e use d t o supplemen t and augmen t knownfact s i nsupportin g continue d uni t operation .P. 8



### Secondly , the dat a mus t be assemble d t o provid e informatio n neede d t o identif yalternat e mean s o f achieving additiona l uni t lif e an

d othe r utilit yspecifi c goals . Lastly , the tota l dat a bas e shoul d permi t evaluatio no f the cost s o f a lif e extension . Thi s lead s directl yt o step four i nth e process , the identifi

catio no f improvemen t requirements . Thi s step include s th e identificatio n o f th e physica l requirement s an d equipmen t shortcoming s identifie d i nthe 3 step inspection s an d embrace s al l economi c alternative s for a uni t tha t ar e no t inconsisten t i n goal s o r ar e o f themselve s conflicting . Step 5 i s the indept heconomi c analysi s o f the variou s project s identifie d a s lif e extensio n alternatives . Fo r larg e system s (man yunits ) o r severel ydebilitate d unit s thi s canb e a

n arduou s task . Objective s develope d b ythe utilit yi nstep s 1 an d 2 mus t b e carefull yse t t o ai d i nthe economi c evaluation . Thi s step includes : Quantifying the benefit s fro meac hindividua l recommendation . Determining the revenu e requirement s thes e refine d esti

mate s plac e on th e corporation . Ascertaining howthes e revenu e requirement s migh t impac t the corporatio nan

d the ratepayers . Step 6 i s the implementatio n plan . Financia l dat a combine d wit hphysica l informatio n gaine d vi a inspectio nan d a timetable , resul t i na pla n develope d t o mee t th e need s o f th e specifi c utility . Thi s step shoul d includ e a continuing reviewo f operating data . Thi s reviewpermit s reassessmen t o f the physica l conditio n o f the unit , the utility' s needs , an d the progra m cost s thu s arriving a t additiona l items/recommendation s fo r actioni nfutur e years . Vi a thi s step , limit s on uni t lif e become mor e dependen t on non-physica l factor s sucha s economics , .future regulation sP. 9



### an d the like , the n onfactor s resulting fro muni t generatio n o r equipmen t obsolescence .

III . FAILURE MECHANISM S The physica l investigation s tha t accompan ythe uni t conditio n assessmen t ar e a critica l par t o f the lif e extensio nprogram . Thes e investigation s ar e used indetermining the conditio n o f the existing component s o f a generating unit . Furthe r they contribut e t o th e engineering informatio n bas e fo r extensio n modifications . The failur e mechanism s o f concern during a lif e extensio n effor t ar e varied . 1 . Creep o f highenerg ypiping an

d majo r boile r pressur e part s ar e area s o f prime interes t an d investigation . I nadditio nt o pressur e parts , creep canhave a significan t effec t on turbine rotor s an d casing s tha t ar e expose d t o operating temperature s i nthe rang e o f concern fo r material s o f thei r manufacture . 2 . Erosio n i s a secon d failur e mechanis massociate d wit h lif e limiting conditions . I t i s o f concerni nsuch area s a s hig

henerg ypiping elbows , hea t exchange r tubing , (bothcondenser s an d feedewat e heaters ) turbin e blades , an

d boile r hea t transfe r surfaces . 3 . Corrosion : Th e chemica l dissolutio no f powe r plan t component s canbe a lon g ter mfailur e mechanis mfor man yarea s o f the plant . Condensat e cycl e equipmen t sucha s deareators , condensers , an d feedwate r heater s ar e affecte d a s wel l a s boile r stea mgenerating surfaces . Othe r failur e mechanism s o f concern ar e hig hcycl e an

d low cycl e fatigue . Thes e failur e mode s ar e particularl ysensitive t o pas t an

d futur e operating practices . Stres s corrosion ,P.1 0

tempe r embrittlemen t and insulatio nbreakdow nroun d ou t th e failur e mode s mos t ofte nconsidere d i nlif e extensio nstudies . T o ascertai nth e leve l t o whic hequipmen t ha s bee ndamage d b ythes e failur e mechanism s th e contributio no f mechanis m sugges t th e nee d fo r a variet yo f destructiv e an d nondestruc

tiv e techniques .

IV . • NONDESTRUCTIV E TECHNIQUE S Nondestructiv e an d i nsom e cases , destructiv e technique s fo r equipmen t conditio nassessmen t includ e th e followin g overal l areas : Record s revie w Industr ydat a revie w Visua l inspectio n Performanc e testin g Mathematica l modelin g Nondestructiv e examinatio n Destructiv e testin g Nowher e els e i nth e literatur e comprisin g thi s group o f 1 4 paper s suc hdiversit yo f opinio nabound . Thi s diversit y include s th e area s o f nondestructive/destructiv e testing , mathematica l modelin g (finit e element s and crac k propagatio n analysis ) an d t o som e lesse r exten d performanc e testing . Th e disagreemen t includes , wha t metho d o f analysi s t o use , whe nthes e method s shoul d b e applied , wh o i s bes t t o appl y eac hmethod , an d lastly , wh o and wha t typ e o f interpretatio n shoul d b e employed .P.1 1

V . ANOMALIE S I n al l wel l ordere d group s ther e appear s th e exceptio nt o tha t order . No t necessaril ywrong , bu t different , I prefe r t o refe r t o thes e case s a s th e anomalies . 1 . Lif e assessmen t effort s ca nb e quit e differen t fo r mino r powe r generatin g facilities , les s tha n2 5 MW , (typica l o f smal l municipa l o r industria l plants) . Thes e facilitie s usuall yhav e signfican t system s o f support, tha t i s large r utilitie s fro mwhic henerg yca n b e purchase d a t a neconomicall ycompetitiv e level . Fo r thi s typ e o f situation , record s review , industr y dat a revie wand visua l inspection s hav e bee nemploye d t o determin e th e plan t status , expecte d remainin g lif e an d projecte d costs/benefit s fo r lif e extension . Thi s approac hprovide s usefu l informatio nt o th e plant' s owner/operato r withou t mor e length yan d costl yphysica l investigatio nan d plannin g phase . 2 . Equipmen t Populatio nPredictio n- Thi s approac hpermit s an assessmen t o f uni t conditio nbase d o n pas t performanc e o f othe r simila r units . Economic s ar e base d o nimprove d maintenanc e performanc e and therma l performanc e o f th e equipmen t involved . 3 . Fatalisti c Approac h- Tie s int o th e equipmen t populatio n approac ht o som e exten t an d say s tha t afte r a predetermine d tim e perio d a norderl yreplacemen t progra mi s needed . Al l tha t remain s t o b e determine d i s ho wt o d o th e replacemen t wor k o na neconomica l basis . 4 . Othe r Plan t Upgrade s - Th e belie f tha t anylon g ter mconfi

denc e i nth e lif e extensio ntechnologyi s flawe d and postu late s tha t thi s belie f i s bor nou t b yshor t ter mfailure s i n younge r plants . Thi s belie f i s couple d wit hconcentratin g o ndesig n upgrade s i nth e area s o f controls , turbin e wate r inductio n preventio nan d wate r an d stea mchemistr ycontrol .P.1 2

VI . SUMMAR Y

Amajorit yo f approache s t o th e lif e extensio nquestio nfollo w a commo napproach . Variation s tha t exis t ar e o nth e whole , no t substantial , an d ar e th e resul t mor e o f th e need s o f an individua l utility . Whil e unanimou s voic e canno t b e give nt o th e lif e extensio n technology , mos t contributor s believ e tha t factor s othe r tha n physica l limit s wil l determin e th e futur e en d o f live s fo r generatin g unit s a s lon g a s a continuin g and proactiv e lif e extensio n effor t remain s i nplace . Th e continuin g effor t i nlif e extensio nb yth e utilit y communit yha s lea d t o a rapidl yevolvin g technolog yand continuin g competitio namongs t th e AE's/OEM's/an d specialt y contractors . Thi s situatio ni s goo d fo r th e powe r generatio n industry . Finally , th e utilitie s themselve s mus t continu e t o respon d t o th e challenge s tha t uni t lif e extensio npresents . Realisti c goal s fo r th e progra mmus t b e establishe d i nconcer t wit hth e regulator ypressur e an d financia l demand s o nth e corporation . Projec t managemen t mus t b e an d remai ninnovative , challengin g t o it s staf f an d contractors , an d entrepreneuria l i nit s approac ht o solvin g technica l problems , meetin g regulator y limit s and achievin g financia l goals . Lastly , a s th e lif e extensio neffor t come s o f ag e a s a technology , al l partie s concerned , utility , AE , OE Mand specialt ycontractors , shoul d b e cognizan t o f th e fac t tha t continuin g equipmen t managemen t i s neede d t o optimiz e an y lif e extensio neffort . Lif e extensio ndoe s no t en d wit h projec t implementation , i t reall ybegin s ther e anew .