A Successful Preventive Maintenance Program

8/18/2019 A Successful Preventive Maintenance Program

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F a i l u r e

R a t e

X I

Preventive Maintenance Plan

. Inspection Plan

. Improvement Plan

. Recommendat on Items

Maintenance Records

Specification o f Equipment

Failure Data

L

e

/ / S

Bilm-in Useful

L i fe Year -oc r

ReZion Reqion

Repion

I

Ciaqnos i s Da ta o f Rena in i rg L i fe

Opera t ion

B

maintenance Data

1 Recomecdat ion o f i z soec t ion . i a o r a v e ~ e f i r

Rel ia b le 0pe ra : ion P la n t s

Fi g.

1

The Need f o r Devel opment of Compr ehensi ve

Preventi ve Mai ntenance Progr am

Thi s sys tem can i dent i f y the fo l l owi ng i tems

f r om t he manufact urer ( Hi tachi Ltd. ) to the us i ng

ut i 1 i ty.

1)

Recommendat ons f or i mpr ovement , or r epai r

i t ems, f or cr i t i cal equi pment and syst ems f rom t he

s tandpoi nt of h i gh ava i l abi l i t y and l i f e extens i on.

(2)

Recommendat ons of i nspect i on cr i t er i a and

i t ems f or cr i t i cal equi pment and components .

(3 ) Recommendat ons f or pendi ng ques t ons and

r emai ni ng mat t er s r el ated to r epl acement ,

i nspect i on of equi pment, and components .

Thi s system i s composed of dat a i nput s on

devi ces used i n the pl ant , the dat a base of each

equi pment , a common dat a base, and t he mai nt enance

pl anni ng and r ecommendat i on syst em

The st r ucture of t hi s syst em is shown in Fi g. 2.

Actual mai nt enance, operat i on, and f ai l ure dat a

of each power pl ant i s i nputt ed to t he dat a center.

I n par t i cul ar , t he mai ntenance dat a i ncl udes

di agnost i c data of deter i orat i on and t he r emai ni ng

1 i f e of equi pment i n t he power pl ant s. Nai nt enance

dat a ar e t hen anal yzed

f o r

t r ends o f deter i orat i on,

r emai ni ng l i f e

o r

i nspect i on resul ts .

Thi s dat a i s st or ed i n the common data base

o r

i n the equi pment dat a base.

The common dat a base i s used f or st or age of common

dat a such as pl ant operat i on r ecor ds, mai ntenance

schedul e and pl ant shut down f ai l ure data.

The equi pment dat a base st ores i nherent dat a of

equi pment such as di agnost i c r esul t s, mai ntenance

r ecor ds, and t r ends of remai ni ng l i fe.

The mai nt enance pl anni ng and r ecommendat on

syst em can prepar e the r ecommendat ons

f o r

r equi r ed mai nt emance i t ems at each pl ant,

systemati cal l y, wi t hout om ssi on, and i n a t i mel y

manner .

I

Pl ant]

1

I RK P an:Short Long Team I

Maintenance Work

.

Detection Crack and Diagnosis

. Nondestructive Test (NDT)

. Calib ration of Instrument etc.

Diagnosis o f Deterioration

and Remainina Lif e

I I

LJ

IMaintenance Records

I I

quipment Data Base

I

Trend of Remaining Life

CY

I I

1

Actual Data from Each Plant

Maintenance Records

Operation Records

1

I

Common Data Base

Plant Specitication

Operation Time

Start/Stop Times

Maintenance Schedule

Operation Plan

Fi g. 2 The S t ruc tu re of Hi tachi Compr ehensi ve Prevent i ve Mai nt enance

P l anni ng Sys t em

1993

PROCEEDINGS Annual RELIABILITY AND MAINTAINABILITY Symposium

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3.

REM

INING LIFE DIAGNOSTIC

SYSTEhIS

Rotor.

Blade.

Cas

ny.

Main Stop

Va ve

We have devel oped t he di agnosti c s yst ems f or

es t i mat i on of remai ni ng l i fe

f o r

bot h pr i mary

equi pment and auxi I i ar y equi pment f r om the

st andpoi nt of preventi ng pl ant f orced out age.

The di agnost i c syst ems of r emai ni ng

1

i f e f o r

equi pment ar e shown i n Tabl e 1.

By

way of exampl e, t he di agnost i c syst em

f o r

the

t urbi ne and generat or w 11 be expl ai ned.

Tabl e 1

Di agnosti c Systems of Remai ni ng Li f e

f or Equi pment

Equipnent Conponent

I

Diagnostic Het od

-

CREEP

lectric resistance test

Hardness test, Replica method

Replica method FAT GL

Hard etching

Turbi ne

h p

Fan

Shaft X-ray diffraction method

sys em On-condition monitorin g - lh.vibration

Optical micro-crack detection method

Generator I

Stator Coil

Motor D Map nethod

I

H-Y Yap method

Tube

Tube

Eddy current test for tube thickness

Data analyzer

Ultrasonic test (bl) for tube thickness

Trend of thickness with analyzer

(CAT)

El ectri c

Va

Ive

Con t r o l

Rod Dri ve

Mechanism

Packing actual operation data

carbon seal . Trend

of

cooling water teqperature

0 ring Comparison between life test data and

actual operation data

Beat

Exchanger

Pipe

3.1

Diagnostic system

of

remaining life

f o r

turbine

The st eam t urbi nes are operated under sever e

operat i ng condi t i ons, wi t h hi gh t emper ature, hi gh

pressure, da i l y s tar t - s top and l oad f o l l owi ng

operat i on. The mater i al of t he t urbi ne, under

thes e condi t i ons w l l de te r i ora te as a r es ul t of

damage f rom creep, f at i gue and t emper

embri t t l ement . I n the worst case, damage w l l l ead

t o dest r uct i on. Theref ore, t he i nspect i on and

di agnosi s f o r esti mati ng t he r emai ni ng l i f e of t he

t urbi ne i s i mpor t ant ( Ref .

2,

3 ) .

The di agnost i c pr ocess of det erm ni ng t he

r emai ni ng l i f e f or a turbi ne rotor is shown i n

Fi g.

3.

3.1.1

Electric resistance method

I t

i s known that met al l urgi cal changes and cr eep

damage accumul at e duri ng l ong- t erm use under hi gh

t emperat ur e, wher e car bi de compound pr ec i p i tates

and gr ows near gr ai n boundar i es. Thi s

prec i pi t at i on gradual l y decreases e l ect r i c

r esi st ance when cr eep damage occur s. The

el ect r i cal r es i st ance method ut i I i zes the

cor r e l at i on bet ween e l ect r i c r es i s t i v i t y and creep

damage.

3.1.2

Hardness measurement

I n order t o i ncr ease t he accur acy of eval uat i ng

t he r emai ni ng l i f e,

i t

i s necessary to obt ai n a

corr el ati on bet ween har dness deter i orat i on and

cr eep damage. Thi s r el ati onshi p can be der i ved

f rom the tes t of t he same,

o r

s i m l ar mate r i al as

t he or i gi nal one.

3.1.3

Observation

of

microstructure

The r epl i ca method dupl i cat es a condi t i on of

grai n boundary on r ep1 i ca f i l m The mcr ostr uct ur e

i s observed wi t h t he repl i ca met hod and cr eep

damage i s eval uated qual i tat i vel y.

For heat r es i s t i ng al l oy s teel , dete r i o ra t i on

has shown by car bi de compound pr eci pi t at es and

gr owt h near gr ai n boundari es. When t he

det er i orat i on cont i nues, voi ds appear on a t rack

where t he car bi de compound exi st s.

3.1.4

Temper embrittlement

Two met hods f o r measur i ng t he amount of t emper

embri t t l ement have been devel oped f or t he actual

di agnoses. One di agnosi s i s the grai n boundar y

et chi ng met hod. The degr ee of t emper embr i t t l ement

i s measured wi t h f r actur e appear ance t r ansi t

t emperat ure ( FATT) and proport i onal to t he l ength

and dept h of pi t s i n the grai n boundar y af t er hard

etchi ng of t he mater i al surf ace. We have

devel oped t hi s t emper embri t t l ement eval uat i on

t echni que and

i t

i s ready for f i el d use.

Another way t o measur e t emper embr i t t l ement i s

t he smal l punch (SP) t est met hod by usi ng met al

sampl i ng and a mechani cal t est. Thi s test i s not a

nondes t r uct i ve tes t , but onl y a- smal l sampl e (l ox

1 OX O. 5

mm

i n si ze) is used. I t i s poss i bl e to

r emove a sampl e f r om an act ual component.

Ac tual l y , i t i s not easy to det erm ne t he degree

of materi al damage, because t he fact ors of f ati gue,

cr eep, and t emper embr i t t l ement are compl ex.

1993 PROCEEDINGS Annual RELIABILITY AND MAINTAINABILITY Symposium

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Ue s t r u ct i v e

1

I

I

E l e c t r i c Ha r d ne ss S amp l i n g

Res i s t ance Test Test

T e s t

T e s t T e s t

Po

ent a

1

Di f f e r e nc e

Decr ease

i n El ec t r i c

es i s tance

ecrease

i n

Har dness

E lemp.

FATT

P

Ener gy

Mai nt enance Recor ds

Fi g.

3

T he Di a gn os t i c P r o c ess of Re ma i n i n g L i f e Ev al u at i o n f o r Tu r b i n e Ro t o r

I n order to r ai se t he accur acy of di agnosi s, mechani cal , and t hermo-mechani cal cycl i ng

var i ous t echni ques ar e i mpl ement ed in combi nat i on. r esul t i ng f rom the st art and st op operat i on.

Mor eover, a1 1 t he procedur es are syst emat i zed on a The I nsul at i on det eri or at i on mechani sms and

comput er- ai ded basi s. Some of procedur es use t hei r detect i on method are shown i n Fi g. 4.

Expert Syst ems usi ng a knowl edge dat a base.

3.1 .5

Application f o r Turbines

r emai ni ng l i f e for t urbi nes have been appl i ed to

50 t her mal power pl ant s , and

250

equi pment du r i ng

seven years . As the resul t o f di agnoses , s i x t o a c r i t i c a l

mai n t urbi ne v l v e s

wer e

r epl aced. Equi pment

w h i c h

est i mati on methods and t hei r exper t syst em of

i nsul a t i on di agnos i s (Ref . 4, 5). These are

wer e eval uat ed and f ound to have adequat e

r emai ni ng l i f e w l l be di agnosed agai n in a f our - d i scussed be l ow

year peri od.

3. 2. 1

N Y Map

method

\\ %en new, i nsul ati on composi t es of m ca- r esi n

are a voi dl ess st ructure. Voi ds i n the i nsul at i on

The di agnost i c syst ems f o r eval uat i ng

t h e

ar e gr adual l y pr oduced by deteri orati on. Some

voi ds become l arge and combi ne wi t h ot her s. The

di el ec t r i c s t r engt h o f m ca r esi n then decreases

turbi ne ro to rs , f i v e t urb i ne

cas ings ,

and

e l e v e n

we have devel oped two new r emai ni ng l i f e

One est i mat i on i s t he N- Y map met hod t hat

caused due to vari ous f actor s af f ect ed

by

t he

n u be r of

star t -s tops

y ) and t he operat i ng t i me

l arge gener at ors i s caused by e l e c t r i c a l , Y ) . The dat a is t aken f rom the gener ator

operat i ng hi story.

3 * 2

emaining f e estimation ystem o f

det er m nes how much i n s u l a t i o n det e r i or a t i on

i s

stator coil in generator

I nsul a t i on det er i o rat i on Of the St at or Co i l s in

1993 PROCEEDINGS

A nnua l

RELIABILITY AND MAINTAINABILITY Symposium

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Part a

d scharge

test

;

Maxi mum

Fi g. 4 I nsul at i on Det eri orat i on Mechani sms and

its

Det ect i on Net hod

f or St at or Coi l i n Gener at or

The mai n f act ors i nf l uenc i ng i nsul at i on

det er i orat i on are the r epet i t i on of t her mo-

mechani cal f orc es due to st ar t s and st ops of the

power pl ant , t hermal agi ng, el ect r i cal s t ress

agi ng, and mechani cal f at i gue due to operat i on of

the pl ant . Each deter i orat i on rat i o o f the

i nsul at i on st r ength caused

by

t he above- ment i oned

f act or s can be obt ai ned f r om many model agi ng

t est s. Then, r esi dual br eakdown vol t age can be

obt ai ned by the pr oduct of the det er i orat i on

r at i os, as shown in eq.

( 1 ) .

Vr : r esi dual BDV ( Br eakdown Vol t age)

Vo: i ni t i al BDV

Ve: res i dual BDV due to el ectr i cal

Vt : resi dual BDV due to t her mal deter i orat i on

Vh: r esi dual BDV due to heat cycl e det eri orat i on

dete r i ora t i on

The i nsul at i on st r ength est i mati on curves of the

N- Y map ar e shown i n Fi g. 5 ( Exampl e of di spl ay

f am exper t system .

150

16

14

12

S M

tw

U

tb %

10

a

6

4

2

0

lm

0 1 2 3 4

-

q*lrpticil

hours Hr) x10o0O0

162217

hr

=5611 T i a a

VR = 73 54 I

Fi g. 5 I nsul at i on Str ength Est i mati on

Cur ve by N Y Map Met hod

The fi el d dat a was obt ai ned by exam ni ng t he

gener ator coi Is act ual l y used, aft er l ong

operat i on. The measured r esi dual br eakdo m vol t age

( BDV) and est i mat ed BDV of t he N- Y map aer e

compared. Both of them were near l y equal .

Compari son between t he est hat ed BDV usi ng the N Y

map and the measur ed BDV i s shown i n Fi g.

6.

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3 . 2 . 3 E upert system for insulation

diagnosis

We devel oped t he expert systei n wi t h Hi t achi

workstat i on 2050/32 by usi ng a sof t ware

pr ogr amm ng t ool ESI KERXELI W .

I t

has a knowl edge

express i on of a hybr i d t ype consi st i ng of f r ames,

r ul es ( i f - , then- t ype) and C- l anguage program

The sys tem str ucture and j ob sel ect i on o f t hi s

system

o n

CRT di spl ay is s h o w

i n

Fi g.

10.

Each knorvl edge base i tem i s di vi ded i nt o modul es,

and t he system has a t ree- l i ke str ucture.

Thi s st r uctur e makes

i t

easy to add and r evi se t he

knwl edge bases.

After al I i nfer ence i t ems ar e execut ed, t he

i nspect i on r eport s , rvhi ch i ncl ude al l i t ems, are

pri nted out and present t he r esul t s of t he

i nsul at i on di agnosi s qui ckl y .

I .

F ig . 10 Syst emStr uct ure and J ob Sel ect i on of

Expert System

3 .2 .4 clpplicat ion

f o r

Generators

The r emai ni ng

1

i f e es t i mat i on s ys tem of the

gener ator st ator coi l s has been appl i ed to

60

generators over a 1 year per i od. As a resul t o f

di agnoses f or coi l s whi ch have al r eady reached to

l i f e expect ancy or c l ose to l i f e, 21 c oi l s of

pol yest er r esi n and 4 coi l s of epoxy res i n i n

gener at or s have been r ep l aced. Gener at or s whi ch

have adequat e r emai ni ng l i f e

r v i l l

be di agnosed i n

a per i od of f our years .

4.

RESULUTS

The comprehensi ve prevent i ve mai nt enance

pl anni ng system has been actual l y appl i ed to

mai nt enance pl ans of t her mal and nucl ear power

pl ant s . Ve obta i ned good res ul t s by i t s

appl i cat i on. For exampl e, a r educt i on of the

f orced out age rat e of nucl ear power pl ant s

(Boi

1

i ng Water React or t ype pl ant s by Hi t achi Ltd.

as mai n cont r actor ) i mproved f r om

0. 3

t i mes

/ pl ant - year to 0. 16 t i mes / pl ant - year . The f a i l ure

r at e in a t her mal power pl ant s al so i mproved f r om

1.4 t i mes

/

6 mont hs t o

1.0

t i me/

6

mont hs.

Fai l ure 'of a bo i l er t ube af t er i nspect i on ,

di agnosi s and repai r , has not occur red.

1. The comprehensi ve pr event i ve mai nt enance

pl anni ng syst emhas been devel oped Tor t he

systemati c, t i mel y pr eparat i on of

r ecommendat ons

on

i tems used for per i odi cal

mai ntenance and pl ant l i f e ext ensi on of power

pl ants .

have been devel oped f or t urbi ne r otor ,

gener ator coi , rotor bar , pi pe th i ckness ,

and

so

on.

2.

l he di agnost i c syst ems f or remai ni ng l i f e

3.

The det ecti on t echni ques for mater i al

f ai l ure and remai ni ng

1

i f e assessment al so

have been devel oped. That is:

(a) Combi ned ass ess ment met hod usi ng the

resu 1t s of el ec t r i c r esi s tance

measur ement , r ep1 i ca and har dness.

deter i orat i on wi t h t he N- Y map and t he

map met hod.

(c) Detect i on method of corr os i on pi t t i ng.

(b) Esti mati on method of i nsul ati on

The pl anni ng system can make a l arge

cont r i but i on t o a pr eventi ve mai ntenance progr am

of power pl ant s , especi al l y i n decreas i ng pl ant

f orced out age r ates wi t h th i s sys tem and

its

cont i nuous use.

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RELIABILITY AND MAINTAINABILITY

Symposium


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REFEREMES

1.

K. Onoder a, Mai ntai nabi 1 i ty Desi gn Techni ques,

1989; Uni on of J apanese Sci ent i st s and Engi neers

( J USE

.

2.

S

Mori et al . ”Di agnost i c Techni que f or

Remai ni ng L i f e of Operat i ng Power Pl ant s”, Hi t achi

Revi ew,

Vol .

69- 10, 1987

Oct.

pp

83- 88.

3. T. Tan et ai , ”Pr eventi ve Mai ntenance Technol ogy

f or Turbi ne Components” , Hi t achi Revi ew, Vol . 40,

1991 Apr i l ,

b . 2 .

pp103- 110.

4. S h i , L T an i g uc hi , ” Di agnost i c Techni que

f or Remai ni ng L i f e of Lar ge Rotat i on Coi l ” , The

Proc. of 17t h J USE Rel i abi l t y and Mai nt ai nabi l i t y

Symp. ,

1987

J une,

pp

295- 300.

5 K. Onoder a, ”Expert System and Appl i cati on f or

Re1 i ab I i

ty

and Mai ntai nab

1 i ty”,

Re 1 i ab i ty,

V01. 9-3, 1987 NOV. pp 44- 51.

BIOGRAPHIES

Kat sushi ge Onoder a, PhD

H tachi Works, H tachi . Ltd.

Operat i ng Pl ant Servi ces Cent er

1-1 ,

Sai wai - cho 3-chome. H t achi - shi , I barali i -Ken, 317 J APAN

Kat sushi ge Onodera i s

a

mannger

in the operati ng pl ant

servi ces center. Si nce j oi ning H tachi h’orks in 1961, he has

been i nvol ved i n re1 i abi I i ty anal ysi s and

qual i

ty assur ance

acti vit y in

a

nucl ear power pl ant.

H s PhD in engi neeri ng is fr omTokyo Uni versi ty in 1990:

hi s

B S.

in El ectr i cal Engi neeri ng is f romYamagata

Universi t y in 1961.

He

is

a member

of

I nternati onal El ectr otechni cal

Commssi on(1EC)- Dependabi l i t y ( I C- 56), and

a

di rector of

Rel i abi l i t y Engi neeri ng Associ ati on of Japan(REA ).

Yoomei Katoo, PhD

H tachi Works. H tachi , Ltd.

1-1 Sai wai - cho 3-chome.

H t achi - shi , I baraki - ken, 317 J APAN

Poomei Kat oo is a chi ef engi neer, Corporat e technol ogy i n

H tachi works. Since j oini ng H tachi , Ltd. in

1956,

he has

been engaged in i nstr umentati on and contr ol t echnol ogy

sect i on of nucl ear povi er and chemcal pl ant

i n

H tachi

Research Lab.

hi s

B. S.

in el ect ri cal engi neeri ng is f romKanncawa

Universi t y in 1956.

H s PhD in engi neeri ng is f romOsaka Uni vers i t y i n 1984:

1993 PROCEEDINGS Annual RELIABILITY AND MAINTAINABILITY Symposium

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A Successful Preventive Maintenance Program

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