ML19340E460

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Low Pressure Disc Ultrasonic Insp Rept
ML19340E460
Person / Time
Site: Farley Southern Nuclear icon.png
Issue date: 01/08/1981
From:
ALABAMA POWER CO.
To:
Shared Package
ML19340E457 List:
References
NUDOCS 8101140559
Download: ML19340E460 (13)
v • d • e


Text

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ALABAMA POWER CO. ~

FARLEY fl LOW PRESSURE DISC ULTRASONIC INSPECTION REPORT E

REPORT DATE: 1/8/81 INSPECTION DATE: 11/24/80 THRU 12/10/80 I

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LOW PRESSURE DISC ULTRASONIC INSPECTION REPORT (t

INTRODUCTION This report covers the ultrasonic inspection of the disc bores and keyway areas of tae Alabama Power Co., Farley No.1 unit. This unit is of a shrunk on dise design with each disc keyed to the shaft at the disc bore area. The U.T. inspection was performed to detect possible cracking in the disc keyway area. The need for this inspection is a result of recent industry experience where stress corrosion cracking has occurred in machines of shrunk on disc design. Cracking in this disc '

bore area, if allowed to propagate, could eventually lead to a disc burst.

DISCUSSION

~

Ultrasonic inspection techniques have been developed for detecting keyway cracks without the need for unshrinking discs. Two techniques are used; one for detecting crack indications and the other for verify-ing crack indications.and measuring their depths.

The initial technique used is the tangential aim, where an ultrasonic transducer is mounted on a plexiglass block that sits on the disc hub.

The plexiglass block is contoured so that it is in complete contact with the disc hub. The ultrasonic waves are directed tangentially towards the keyway bore region so that any cracks perpendicular to the sound L

beam will reflect the sound. A careful analysis of the time difference discriminationoffalseindication/boreandthecrackallows

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between the echoes from the keyway s.

This time differential procedure is applied by circumferentially scanning the disc (See Figure 1). Since the disc profile is composed of a series of compound radii, a mathematical. model was developed for transducer positioning and alignment. The model was ccmputerized to allow calculating: (1)all needed information for positioning aid aiming the transducer, (2) metal pathlength,elapsedtimetokeyway/etweenkeyway/boreechoand aore echoes, apd time between keyway bore echo and crack echo, (3) time b suspectedspuriousindications,(4)various'angleswithinterrelated.

ultrasonic central ray direction to disc and transducer axis. Because of the disc profile and the need for good sonic coupling' between the disc and the plexiglass blocks (called compound angle wedges) a large number of bl.ocks are required (see Figure 2).

If a crack indication is picked up sonically, the location is determined by the transducer location and its relationship to keyhole / bore echoes (see Figures 3 and 4).

Since the tangcatial aim technique is not suitable for determinin'g(depth

^

of crack, a complementary technique called radial aim is used to: 1) verify cracking detected by the tangential aim technique, and (2) to estimate the depth of crack. In this method, the ultrasonic waves are directed rapidly towards the bore. The radial aim method works because a crack undergoes branching and spreading while it grows. Thus, the

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branching'part' of the crack includes components which reflect ultrasound back to the transducer. Depth of the crack is determired by the time difference between the keyway / bare echo and the flaw echo.

j ANALYSIS After ultrasonic' inspect' ion' has Tndicated a possible disc crack, an_

analysis is made to determine what the indicated crack size is in relat-ionship to the critical crack size as determined by fracture ~

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mechanicst. This relationship is used to detennine Westinghouse recom-mendat. ions regarding continued operation with a disc crack indication.

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-QUIPMENT P ~0; 'l 2 J '-

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Electronic Instruments A

'Krautkramer USIP 11-Ultrasonic Equipment.

8 Tektronix Model 465B or Model 465 Portable Oscilloscope.

.m n u '..g... :... a '.=..,. =

c TRANSDUCERS -

M J.. 4.

.u.:==:

.v.-

n.

  • ~

r t-Transducers' ranging'in. diameter from 1/4 inchh to 1-1/8 inch and in frequency from 2-1/4 MHZ to 10 MHZ as detailed in the specific tables for each of the' BB discs. Other frequencies may be used to further evaluate. indications.

. s ::: ~ -

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WEDGES 1.

- 4. '..

c.

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Numerous' plexiglass. wedges varying in entrance angle, rotational" angle,-

radius of curvature, physical size and rotational direction are provid-ed, as required for each of the BB discs, as detailed in the specific -

tables..c p

.r.-

_ERANSDUCER MANIPULATORS

'. - +. ' ' " ' -

r_.

Transducer' manipulators are used whenever hand scanning cannot be'.- - '

conducted.

A) Wedge Extensions -..

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B) Transducer Manipulators. ~.u C) Charlotte Manipulator-

'. r '. ' -

.s / "-

CAMERA

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Tektronix C-5A Oscilloscope Camera, or equivalent.

COUPLANT Ultragel II..

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CALIBRATION STANDARDS A),3/4 inch x 8 inches long cylindrical rod.

B) Plexiglass Block CONVERSION FACTORS Ultrasonic measurements of distance are presented as time interval measurements on the 4658 oscilloscope. Thus, time measurements in microseconds / division on the oscilloscope must be multiplied by the appropriate factor for shear wave travel to convert them to linear' measurements in inches.

INSPECTION RESULTS LP #1 23A4262 Shaft Test fTN1650 DISC fl Generator End TN1632 Outlet Numerous bore indications throughout the disc were detected.

The worst indications were radially inspected to chart their propagation. The largest indications with the greatest depths are located:-

Balance Hole #4%

2.08" Deep Balance Hole #5 1.28" Deep Balance Hole f5 1.39" Deep Balance Hole #11

.84" Deep Balance Hole #18h 1.32" Deep

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Balance Hole #34 1.35" Deep Keyway #1 1.18" Deep Keyway #14

.77" Deep Keyway f27

.78" Deep DISC fl Governor End TH1935 Outlet l

Numerous bore indications throughout the disc were detected.

The worst indications were radially inspected to chart their propagation. The largest indication with the greatest depths are located:

Balance Hole #11

.48" Deep Balance Hole #18

.51" Deep

.63" Deep Balance Hole #38 l

Keyway #1 Found tangentially, no radial depth Keyway #14 Found tangentially, no radial depth -

t Keyway #27 Found tangentially, no radial depth DISC f2 Governor End TN6056 Outlet Bore indication @ B.H. #8

.26"' Deep Keyway #1, Indication found tangentially, no radial depth Keyway #14 Indication found tangentially, no radial depth l

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i

DISC #2 -Governor End Inlet Side Bore indication 0 B.H. 29-3/4 10" Deep s..

Bore indication 0 B.H. 30 13" Deep DISC #4 'Govenor~End TN6112 Outlet 2

.... Keyway #1 Found tangentially, no radial depth -

E : Keyway #14,'

Found tangentially, no radial depth.

~.'.! _ Keyway #27

. Found tangentially, no radial dept

%.?..,...

No other reportable in'dications were found on any of the remaining discs.,. gf, ;;3...,-

LP #2 23A4263 Shaft Test #TN1649 c.

-., a DISC f1' Goveinor'End TN6097 Outlet

e......

.. _ _ '...r '

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..' '.35" Deep Keyway #1~

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Keyway #27 47" Deep

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DISC fl Generator End TN6060 Outlet

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Bore indicatioon 0 B.H. #25 r.40" Deep Keyway #1

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.11" Deep DISC #2 Governor End

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TN6098 Outlet bohd] indication 0B.H.f18 no, radial depth DISC #2 Gene 5ator'End TN6058 Inlet At,least 20 bore indications the deepest being.68"

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Generator.End'.,.,.._..

__. Outlet

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I Keyway #1

. 04" Deep

- M' Keyway #14.

.45" Deep 4.-

Keyway #27

.40" Deep No other eportable indications were found on any of the remaining discs.

RECOMMENDATION'S Based on the dalculated reinspection time intervals it is recomended that discs 1 & 2 Gov. and Gen. end of both LP rotor be either removed from the rotor or the rotors be refurbished before returning the ' rotors to service.

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. ULTRASONIC INSPECTIO OF LP TORBINE DISCS CATEl,fjqg (KEYWAYS AND BORE HUB AREAS) u FORM PtO. PGSO 1049

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DISTRIBUTION:

u _ MILLI AM kEENEY OR00M AU.

4*G.O Quabaf T A..unaseCE. secas aos FIC. LOC AfiOmt u _ CHARLES Reep BIRMING HAM y

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LARAMA Powaa Co.

I bt;Oj, CUSTOMER DURAUCNOFINSPECDON

. STADON Fuony MUC. LEAR UMPF I I

umT LP. NO

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3-t.OCATiON sMpoRD LA.

SHAFTTEST NOYNI N *BB I

eCATY G4 tow.es isTAT.,

. SHOPO DER _23A4262.

PROcEsssPEc MM P1-REv G

TEAMi.EADER(S) _.T. Rewo e.

A.FirrAL C..ksowtes. B.Fosran: BSassswAtr. h.NicMAUD Trau uEusEas3

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. US!PilSERIALNO l1

-55cil.* 2il97-5593 Osci: SCOPE SERIA1.NO.

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RESul.TS OF INSPECTION -

GOVERNOR END GENERATOR END

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INtET-NO Recc:-tableIndlCchenS INI.ET-NO 'Recordoble TnClicctions oise,3 c&b:pi;l(,27becracimC, no oepm cansheti(I$)Vd M-Oli)kw'27-[!78)

.0 sc'v2 INur-fndI(Ohens locofed frilo[ ice.hclC"29-Bo INLET-MO E9Doriable. Ind5CQY1 CMS ~

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cencr-IfdPcatien lccohd bolonceirle "8 cunsr-bioReportabic Indico-hons

' ntEr-Mo Recor+0ble.Irdico+ ions intrr-NO &poriable _Tndicahons i

soisc as centr-%tamomptioorceibenG carttr-No Rescriable..T.nds cc% orts

'nttr-No Remr4able.Tidicohans iutET-MO kger4oble. Indscche,n3 oisc w4 cuntr-2say \\',N,27 in,41001adscpSwo bar, cun.ET-s}c gat %ut faoicahody l

'inarr-No Recerfable TydicohenS INLET-NO Repor4able.~Endica+ ions '

oisc s centr-No Reirriable. Indica +1cns Ot.e.ntr-No Regeriabre J_ndico4 ions DISC #6 REMARKS;f QLSC., J,hpfgf).,'Cf., Mild EUG'4dof @Q.${AVI MUNO MI [UM4bM[

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o POWER GENERAT,'ON SERVICE Day 1R3nu

b DATE [2.[f fgp ULTRASONIC INSPECTION OF LP TURBINE DISCS (KEYWAYS AND BORE HUB AREAS)

FORh8 MQ, PC$Q $O48

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DISTRIBUTION.

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ASTG TOG PAQdECTS. e.4 inst 6 eDFFsCE LDCAT8Gao e asAlb CODEI i

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DURATIONOFI'NSPECTION

THR, CUSTOMER

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UNIT U'. NO STATION LOCATION M

SHAFTTEST NO B

ESTATE 0 SC877 cm Towsoe PROCESS SPEC bN b

aqv SHOPORDER TEAM LEADER (S) 3

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TEAM MEMBER (S) j j

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RESULTS OF INSPECTION GOVERNOR END GENERATOR END l

ttileT-do ence%sLG loptt.kTcopC oltr -L'b Babc26t2 tanuA7 tons DISC s, catkk lacaATics3 kV.fl.36)kel2WM) oc(LERcwncu$ MGkAD] tel,L-(,ll)

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.g, TABLE 1 Alabama Power Co. Unit Farley 1 L-P Rotors Reinspection Interval Reinsoection Time (Mo.)

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Westinghouse' NRC L-P Disc End Procedure Procedure

'l 1

GVN 9.0 8.6 1

1 GNN 1.4 0.0 1

2 GVN 12.6 10.4

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2 1

GVN 5.9 6.7 2

1 GNN

8. l' 12.3 2

2 GNN 9.1 4.8 9

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End 47

TABLE 2 Initial Inspection Interval Farley No.1 L-P Rotors

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Insoection Time (Mo.)

Westinghouse ttRC (L-P End Dise Procedure............_ Procedure i; g..-... :--

m. c 1:
GVN.

g1;

- 63.6,.,

. 3 2.._6.... -

h-GNN-1 48.6 " -'

7 3.2

'l GVN

-2 72.5 39.7 1

GNN

.52 90.9 40,4 2

GVN c.1, 48.5 29,9

., ^

2 GNN 1

53.1 33.0

- ' 2 GyN 32.

90.1 36 3 2

GtJN J2 79.6 40.1 G'-

Initial Inspection Interval Farley No. 2 L-P Rotors Insoection Time (Mo.)

Westinghouse NRC L-P End Disc Procedure Procedure 1

GVN 1

54.4 28.0 1

GNN 1

36.4 19.2 1

GVN 2

77.3 58.1~

l GNN 2

96.0 61.6 2

GVN 1

67.2 31.4 2

GNN 1

53.0 27.2

^

2

.GVN 2

55.2-48.4 2

GNN 2

84.2 50.6 l

Initial Inspection Interval Harris No.1 L-P Rotors Installed In Farley No.1 Inspection Time (Mo.) -

l Westinghouse NRC L-P End Disc Procedure Procedure 1

GVN 1

48.1 24.0 1

GNN 1

48.9 23.8 1

GVN 2

79.1 61.8 1

GNN 2

65.4 49.4 2

GVN 1

41.5 18.7.

2 GNN 1

52.5 21.5 2

GVN 2

62.0 52.6.

2 GNN 2

86.7 66.7 l

1 1

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l 5pd32 L

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Transducer i

Circu=ferential Scan

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1 Edge of key' sole Transducer Transmit Position pulse f,

l a t, - t,-to 1-2 l

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- i At = t -t 3

3 o 2-3 3

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t) l*

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FIG. 1 Sequence of Appearance of Echoes, During Circu=ferential Scanning, fro = Keyhole with Off-Apex Flav.

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1 1

a b

y 1

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'6 : 7 Transducer 8,8.

ks en E = 0 CC11 aim

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keyhole h

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i FIG. 2.

Input Para.eters !! ceded to Calculate Direction.

Angles 8. and $ for Compound-Angic 1.* edge. -

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IMAGE EVALUATION TEST TARGET (MT-3) l 1.0 528 EM y l8 EE l.l

[5 HM l.8 1.25 1.4 1.6 lc 6"

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  • S$; N/

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TEST TARGET (MT-3)

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1.0

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1

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<4 g;7 >$j777 f,v 4

(.

d 2

d,d o1 Transducer

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A d

d' d

0 2

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o t

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l

+

b r

y h

i a

a.

m t

I 15 N

h - axial distance fres 3 in. (9.6 ts) hub face to a reflec *

  • - R

=

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b = traasducer ter near the apex of axial distance-the keyhole from, hub face' T.= Time of arrival of reference echo at. side of the keyhole 'ar b; propagation O

. path length - d

  • O

- T. = n=a of ar&al of. echo from a reflector near the apex of the keyhole at h; 3

propagation path length = d

  • 2

[Ty = Ti== of arrival of echo-from the corner of 'the keyhole; propagation path'le$ th' = d.

4 y

V - velocity of shear wave's in steel.

3

'f~

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= Angle of incidence of ultrasonic rays on radial through the keyhole

{[do+Rg (1-sin y)]2 + b ) 1/2, d 2

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{[do+Rg (1--cos y)]2 4. (h-b) } 1/2

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=

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FIG. '3 Relationship of Keyhole Ec1 oes as Function of 3

Transducer Location.

mm m

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v.

L.. (,

y A..asonic ra.s I

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t

- time to echo irc= side

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of keyuzy (.Teterance r.

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Signal)

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)-

a

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- Refraction angle I

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d.

l

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r-

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entry of

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central ray..

i c-

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. central ray.on disc 7m g

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FIG. 4-Transducer Position (h,b) and Align =ent Paraneters (S '#)

6 to Exa:r.ine Wevvav Tarrer (<M

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