ML20059M706
| ML20059M706 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/17/1993 |
| From: | Haynes H OAK RIDGE NATIONAL LABORATORY |
| To: | |
| References | |
| RTR-NUREG-CR-4302 OLA-2-I-MFP-012, OLA-2-I-MFP-12, NUDOCS 9311190257 | |
| Download: ML20059M706 (71) | |
Text
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gp __ /z NU REG /CR-4302 ORNL-6193 iy l ,,
? Vol. 2 m re' 90 n e 1 r:
t Aging anci Service Wear of %
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! Check Valves Used in Engineered
- Safety-Fea:ure Systems of Xuclear Power Plants Aging Assessments and Monitoring Method Evaluations
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Prepared by H. D. flaynet Oak Ridge Natinnul I.aboraturj Prepared for U.S. Nuclear Reguhinry Commiwinn
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NucttnP R!CUtMORY CONSSION
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- - . ~ . - - - . ~ . N-AVAILABill1Y NOllCt ,f Avaaatmey of heteeru Mate *iah r "-1in NhC 1%ths .& c' West dowments celed an Nr1C putshcations wts be evenable from one of the fouowv9g sovces W atru n; ton DC 20555 1 The NHC Pubhc Document Room. 212C L Str eet NW. Lower Level 2 The Superintendent of Documents. U $ Gewernment Pretng 0+fice P O fion 37087. wastwngton.
l OC 20013 FCE l 3 T he Nat.onal T echivc al inf ormation Service. Spregfield VA ??t61 Afthoug*i the lsteg that feloes represents the rnalertty of documents CNed e AHC putAcahoes ft h not
- r. ended to be enhaustive I
Referenced documents av&Rable for hspection and copyng f or a f ee from the N AC Public Document Room bclude NRC correspondence and eternal NAC memoranda. NRC 0+fice of fnspect6on and Enforcement l
bufetns, circulars eformation notices. espection and investigation notices Lkensee Event Reports, ven. I dor reports and correspondence: Commession papers, and arrin ant and kceesee documents and corre.
spondence l
The fo nowing cocuments m the NUREO ser6es are svadarse for purchase from the GPO Saies Program '
forman NkC statt and contractor reports. N AC.eponsored conf erence procecongs, and NRC bocMets and br ocrur es Also avadable are Regulatory Guides. NitC segulatk>ns e the ( s.efe er/eaesef hegulafenna. a*d Nuclear lotg.rlaten Comemssion nssuances Documents avanable from the Nat6ona9 Techn6 Cal Information Service ece u de NUAEG series reports and techneca: reports prepared by other federal agencies anc toports prepared by the Atorrec Energy Commes.
sion, f orerunner egenes to the Nuc> ear Regulatory Commission l
r Documents avaGabte from p@c and special techn& cal librarles eclude all open starature items. suc i es books. Journal and pernodical articies, and transactions f ederal Heptster notices. federat and state leg'sta-tion, and corvessional reports can usua ye be obtained hom these Ebranes Docenents such as theses. d,$sertations. foreign reports end translations, ano non.NAC conference pro-ceedengs are averable foe purchase from the organua'non sponsoreg the publication cited Srve cres o' NM ora t reccets r are avatare free, to t%e entent of supr4 upon written reavest tu the 09 c e o' in'c,rma' or ke n;rc e s 4.ravgment. Distribut.cc Section. U S fut;*a* 6egsatory Comssion w a *Ar y
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Cepes c' k-ds.y codes and standards used m a outs tant've manner e the fmC reguiatory process are n aw a nec a' tr a PA*. Let t a y 1921 Noric,* Avenua. f. thesca. Matand and a's ava..at.a tre s' f or ref er.
ence v.e by t*o cut c Code , and standards are usuats c opyngmey and rnar banchased frc= the ,
orig!na te; o ; sN a'ic a c'. ff they s's Aarserican Nationa' Standards, f<orn t' e a merit.an Nat one Standards institu c im F*cadas. . New Yors Nf 10318 . . - . .
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OtSCL AIMER NOTICE This rrw *a , ver.,vM as an account o' wort soormed by an a;per,v cf tes. Urvsm Sta'e .Goenment N+ fit *W tho (Jogd States Government for any agtsrcy tf seesao . Or r isny of ttie t em(;tr,,,ys=e5 rTakt== jia y maa'tarty, f
e 4#c*n1 Or trT4MMI. or a sumM any 6ngal list hty r.f reye.rone,dhty f(1 Dny t'urd Iarty'S spm. or l'e' terdM O te u p o' any .,vor trat.cn. apparatus. prock;ct or prota**.s cskms ei tties tr4r;rt. or tr prevres trut res uvi by %p h t*heri par *y wo;ld ev)( or'Iff enge pr svately Owntw1 recrit*,, ---- -.- .-
NUREG/CR-4302 ls. ORNIA193 Vol. 2 RV l Aging and Seivice Wear of
- Check Valves Used in Engineered
- Safety-Feature Systems of
! Nuclear Power Plants Aging Assessinents and Monitoring j Method Evaluations htanucpt Completed. September 1990 Date Published: April 1991
. Prepared by j H. D. Haynes !
Oak Rx!ge National-laboratory )
Operated by htsrun hianetta linergy Systems. Inc.
i
} Oak Ridge National 121mratory Oak Ridge.TN 37x31-62H5 1
Prtpared for j Division of Engineering
- Omce of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555 NRC FIN B0828 Under Contract No. DE-ACOS-840R21400 4
I 1
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.. a v38 LIST OF FIGURES .............................. ............ ,
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LIST O'F TABLES . . . ..................... .................... 'l xiii ACKNO WLEDO M ENU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,
S U M M AR Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . . . . . . . . . . . . . xv. i 1 ,
- 1. I NTRO D U CTIO N ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ]
1.1 NUCLEAR PLANT AGING RESEARCil GOALS . . . . .. .I . . . . . . . . : 1 1.2 NPAR PR OG RAM STRATEGY . . . . . . . . . . . . . . . . . . . . . . . . . . 2 !
13 NRC INUERES T IN CHECK VALVES . . . . . . . . . . . . . . . . . . . . . . 4 13.1 Check Valve Function and Types . . . . . . . . . . . . . . . . . . . . .
5 13.2 Selected NRC Notices'acd Bulletins .' . . . . . . . . ......... .........6 t 13 3 INPO SO ER 86-03 . . . . . . . . . . . . . . . . . . . . . . . ;
6- ;
13.4 Generic letter 89-04 ............................. 7 i 13.5 EPRI Application Guidelir.cs . . . . . . . . . . . . . . . . . . . . .. . . . 7-1.4 PHASE 1 REPORT
SUMMARY
. . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.4.1 General Information . . . . . . . . . . . . . 8 14.2 Check Valve Failure Modes and Sites of Degradation . . . . . . . .
8- ,
1.43 Surveillance Requirements and Measurabic Parameters . . . . . .
1.4.4 Conclusions and Recommendations . . . . . . . . . . . . . . . . . . . ' 9 It'
- 2. EVALUATION OF Cl{ECK VALVE MONITORING METHODS . . . . . . . 11 '
2.1 GEN ERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 11.
2.2 ACOUST1C EMISSION MONITORINC '. . . . . . . . . . . . . . . . . . . . . '!!
2.2.1 Basic Principles .................................. !
2.;t.2' Detection of Valve Disc Movement .................. '
16 2.23 Ocalitative Leak Dctcction . . . . . . . . . . . . . . . . . . . . . . . .-. 17 23 ULTRASONIC INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 't 23.1 Basic Principles ..................................
17 23.2 Detection of Valve Disc Movement ............;..... +
19 2.4 MAGNETIC FLUX MONITORINO . . . . . . . . . . . . . . . . . . . . . . 19:
2.4.1 Basic Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.................. 19 2.4.2 Detection of Valve Disc Mm ement 21-2.43 Detection of Worn Hinto Pins . . . . . . . . . . . . . . . . . . . . . .
2.5 COMPARISON OF ACOUS'I1C, UL'IRASONIC, AND MAGNETIC
'23; i M ETHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - ,
28 2.6 ODI ER M En{0DS . . . . . . . . . . . . . . . . . . . . . . . . .~ . . . . . .. . . . . j 2.6.1 Radiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 28 .
2.6.2 Pressure Noise Monitoring '. . . . . . . . . . . . . . . . . . . . . . . . . 28 j
2.7 CONCLUSION
S-BENEFTIS AND WEAKNESSES OF 31.
MONITORING METHODS ........................... :
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- 3. D*c2LRIPTION Ol' SELECTED COMMERCIALLY AVAILABLE CllECK VALVE DIAGNOSTIC SYSTEMS . . .......... . . . . . . . 33 33 3.1 CHECKM ATE
- 11 (HENZE MOVATS. INC.) . . . . . . . . . . . . . . . .
33 3.2 QUICKCllECK* (LIBERTY TECHNOLOGY CEN TER. INC.) . . . .
35 3.3 VIP (CANUS CORPCRATION) ..........................
36 3.4 AVLD (LEAK DETECTION SERVICES. INC.) . . . . . . . . . . . . . . .
3..', MINAC.6 (SCHONBERG RADIATION CO.'tPORAT10N) . . . . . . . 37 3.6 PHYSICAL ACOUSTICS CORPCMTION . . . . . . . . . . . . . . . . . . 37
- 4. NUCLEAR INDUSTRY CllECK VALVE GROUP TEST OF CilECK VALVE DIAGNOSTIC SYSTEMS . . . . . . . . . . . . . . . . . . . 39 4.1 G EN E RAL I N FO RM ATI ON . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 39 4.2 SELELTED TEST RESULTS .......................... 39
- 5.
SUMMARY
AND RECOMMENDATIONS ........................ 51-R E FE R E N C ES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Appendix A: REGULATORY TEST REQUIREMENTS AND CURRENT TIGT MlifilODS . . . . . ............. ................... 55
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i LIST OF FIGURlIS l _.
Page Figure 1
N P AR a p p roa c h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 ,
1.2 Close.up of the hinge mechanism of a 10 in. swing check valve 3
that failed to close . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Additional lateral disc movement observed on the same failed check valve whose severely worn hinge mechanism j 3 is s hown in Fi g. 1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 1.4 Typical swing check valve ................................
2.1 Acoustic signal vs time for a 10 in. check valve tested l 12 by Duke Power Company in March 1984 . . . . . . . . . . . . . . . . . . . . . .
2.2 Acoustic cmission equipment (sc .cmatic representation) used 13 by Duke Power Company in 1987 Dow loop tests . . . . . . . . . . . . . . . .
2.3 Acoustic waveform for a check valve during unstabic (tapping) l and stable (Oow noisc only) operations . . . . . . . . . . . . . . . . . . . . . . . 14 l
Time.of. arrival technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4 i 2.5 Check valve closures with new and artificia!!y worn 15 hinge pins . . . . .......................... . . . . . . . . . .
Check valve clostres with two artincial degradations . . . . . . . . . . . . . . 16 2.6 2.7 Ultrasonic signatures during stabic and unstable check valve 18 oper a t ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.h Comparison of an ultrasonic signature with that from an RVDT -
installed on the hinge pin of a check valve . . . . . . . . . . . . . . . . . . . . 18 2.9 Magnetic Dux signature analysis (MFSA) principle of o pe r ation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.10 Comparison of magnetic Geld strength and disc angular position measurements .................................. 21 ,
i Check valve Dow loop (photo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 l 2.11
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Page Figure
....... 23 2.12 Check valve now loop (schematic) .................
24 2.13 . Use of Mi% to deicct disc instability (flutter) ..... . . . . . . . . . . . .
24 2.14 Detecting worn hingc pins using MISA . . . . . . . . . . . . . . . . . . . . . . . ,
2.15 Magnetic'llux time waveforms of a 3.in. wing check' valve -
for inrce hinge pin conditions: normal (top trace) medium worn (middle trace), and severcly worn (bottom trace).
All signatures were acquired using identical internal-magnet and external gaussmeter locations . . . . . . . . . . . . . . . . . . . . . . 25 2.16 Magnetic flux.and acoustic signature.s for a check valve under several simulated operational conditions . . . . . . . . . . . . . . . . . . 27 Pressure probe specifications and points of in tallation ~ . . . . . . . . . . . . 29 2.17 .
Effect of flow rate on pressure nois:: spectra . . . . . . . . . . . . . . . . . . . 29' 2.18 Effect of Dow path on pressure noise spectra . . . ............... 30 2.19 A simplified depiction of the CIIECKMATE* li sptem . . . . ...... 34 3.1 3.2 CllECKMATE" and acoustic signatures for a check valve undergoing backstop tapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 ;
i 3.3 CljECKMATE and acoustic signatures for a check valve undergoing seat tapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7 3.4 Simplified dcpiction of the OUICKCifECK" system ............. 36 4.1 QUICKCHECK* signals for a 12.in. tilling. disc check -
valve in *new" condition ........................ ........ 41 4.2 OUICKCliECK* signals for a 12.in. tilting-disc check valve with 30% hinge pin diameter reduction . . . . . . . . . . . . . .. . . . . . 42 4.3 OUICKCHECK" signals for a 12.in. tilting disc check valve in "new* condition--. expanded scale to show l Sc a tin g t ra nsie nt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 4.4 OUICKCHECK" signals for a 12.in. tilting-disc check valvc. with 30% hingc pin diameter reduction---capanded scalc tc show seating transient ............................. 41 i
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i Pay l i I1gurc l 4.5 VIP (CANUS Corporation) accelerometer traces from .
test 410 (24.in. tilling-disc check valve, full.llow .l 45 conditions, induced flow turbulence, worn hinge pin) . . . . . . . . . . . . . .
4.6 VIP (CANUS Corporation) accelerometer traces from test 420 (2.l.in. tilting 4isc check valve, full.!!ow 46 l conditions, minimal flow turbulence. worn hinge pin) ..............
l 4.7 Two ultrasonic signatures, obtained using the CllECKMATE" 11 i
sysicm for the same valve (10.in. Velan swing check) under different Dow conditions: 2251 eal/ min (top trace) 47 and 1295 gal / min (bottom tracc) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 A CilECKMATE 11 signature for a 12-in. Val-Matic tilting. disc 48 check valve from the full-open to full-closed positions . . . . . . . . . . . . .
4.9 CHECKMATE !! signature for a 12-in. Val.Matic tilting-disc check valve having a stuck disc. The top trace was obtained l at no-flow conditions, while the bottom tiace was obtained at '
l 49 l
2392 gal / min (more than would be sufUcient to move the disc) . . . . . . .
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LIST OF TAllil3 Tabic Page 1.1 Titles of selected NRC/IE Information Notices . . . . . . . . . . . . . . . . . 5 1.2 Titles of selected NRC/IE Bulletins ~ . . . . . . . . . . . . . . . . . . . . . . . . 6-1.3 Check valve siten susceptible to aging.rclated degradation .......... 8 2.1 Selected diagnostic capabilitics and limitatior,s of three check valve monitoring methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.1 Check valves tested during the NIC muitoring method eva l u a t io n t es ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ 40 4.2 Check valve degradations used in the NIC tests . . . . . . . . . . . . . . . . . 40 4.3 Flow conditions and valve operational modes used in the NIC tests . . . 41 5 I y '$ J. -
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.- S ACKNOWLElX3MiiPCS The check valve Phase 11 studies couki have been carried out only.with the help i
of many people, whom the author wishes to acknowledge.
Appreciation is captcased for the advice and guidance provided during this study by D M. Eissenberg and W. S. Farmer. The author also wishes to thank D. A. Casada for his many contributions, including the preparation of a summary of check valve regulatory.- -
test requirements that is included verbatim in this report (Appendix A). .
ne help provided in the experimental portion of this study by E. L Biddic..Sr.. .
D. E. llendrix and B. K. Stewart is greatly appreciated.
l Much information was obtained from diagnostic system vendors in the form of l In addition, much was learned from product literature and visits to their facilitics.
witnessing one day of check.v.isc tests at the Utah Water Research laboratory. In that -
l regard, the author would lil.r io thank the following peopic for their assistanec:' W. M.
Suslick (Duke Power Corr .any), D. M. Cicsictski and _J. N.~ Nadeau (Henze.Movats, Inc.),
l P. Pomaranski (CANUS C )tporation), D. Manin (I.iherty Technology Center, Inc.), J. W.
l
' McElroy (Philadelphia E!cetric Company), and M. T. Robinson (Chairman-Nuclear Industry Check Valve Group).
%c assistance of Jeanic Sho -r and Janice Asher in preparing this report is '
gratefully acknowledged. f 4
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SUMMARY
s In support of the U.S. Nuclear Regulatory Commasion's Nuclear Plant Aging'-
Research Program, Oak Ridge National Laboratory (ORNL) carried out an evaluation of several developmental and/or commercially availabic check valve' diagnostic l monitoring .
methods. Assessmer,ts were made of the capabihty of cach method to provide diagntatic 1
information useful in deterrnining check valve aging and service wear effects (degradation).
check valve failures, and undesirable operating mixies. Dese methods included j i
e Acoustic emission monitoring.
- Ultrasonic inspection. l e Magnetic flux signature analysis.
- Radiography.
- Pressure noisc signature analysis.
ne evaluations have been focused on the capability of each method to provide diagnostic information useful in determining check valve aging and service wear effects. i (degradation) check valve faNres, and undesirable operating modes. Commercial supplicts . ,
of three check valve monitoring systems recently participated in a comprchensive scrics ofe tats d-signed to evaluate the capability of cach -monitoring technology to detect the )
position, motion, and wear of check valve internals (e.g., disc, hinge arm, etc.) and valve '
seat leakage. Dese tests, directed by the Nuclear Industry Check Valve Group and carried ,
out at the Utah Water Research Laboratory, are describcd in' this report. ,
Of those methods examined by ORNL, acoustic emission monitoring,; ultrasonic, l inspection, and magnetic flus signature analysis provided the greatest level of diagnostic l information. These three methods were shown to be useful in determining check valve . l condition (e.g., disc position, disc motion, and seat leakage), although none of the methods was, by itscif, successful in ~ monitoring all threc. condition indicators. However, the i combination of acoustic emission with either ultrasonic or magnetic flux monitoring yicids 1 a monitoring system that succeeds in providing the sensitivity to dctcct all major check valve 1 '
1 operating conditions. When monitoring check valves using cither of these combinations, it is not necessary to apply both methods simultaneously in order to achieve the combined capabilitice of the twd methods. Commercial versions of all thrt..: methods arc still under development, and all should improve as a result of further testing and c. luation.
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- 1. IKmODUCnON l
1.1 NUCLLAR PLANT AGING RESEARCil GOA13 Tha document describes work performed in support of the U.S. Nuclear Regulatory Commission's (NRC's) Nuclear Plant Aging Research (NPAR) Programc which was established primarily as a means to resolve technical safety issues related to the aging of clectrical and mechanical components, safety systems, support systems, and civil structures used in commercial nuclear power plants.' A comprehensive Phase 11 aging assessment on check valves was performed by Oak Ridge National Laboratory (ORNL), the results of which are presented in this report.
The goals of the NPAR Program are as follows:
- 1. To identify and characterize aging effects that, if unchecked, could cause degradation of components, systems, and civil structures and thereby impair plant safety. .
- 2. To identify methods of inspection, surveillance, and monitoring and of evaluating the-residual life of components, systems, and civil structures that will ensure timely detection of significant aging c'Tects before loss of safety function.
- 3. To evaluate the effectiveness of storage, maintenance, repair, and replacement practices in mitigating the rate and extent of degradation caused by aging.
1.2 NPAR PROGRAM STRA'mGY De methodology employed by the NPAR Program is basically a two. phase approach, as illustrated by Fig.1.1, his strategy is applicable for all components, systems, and structures selected for aging assessments. Research efforts are conducted in accordance with the objectives associated with each phase.
I - . ...
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'lhe objectives for an NPAR Phaw I ning aucument of a component system, or structure are as follows I. Identify and characterize aging and wear effects.
- 2. Identify failure modes and causes attributable to aging.
- 3. Identify measurabic performance parameters, including functional indicators.
Phase I studies result in a determination of whether additional research is needed; if 50. recommendations are developed to identify and guide further studies.
An NPAR Phase II aucument is carried out with the following objectives:
I. Perform in-depth engineering studies and aging aucuments based on in situ measurements.
- 2. Identify improved methods for inspection, surveillance, and monitoring or for evaluating residual life.
- 3. Perform postscrvice examinations and tests of naturally aged / degraded components.
- 4. Make recommendations for utilizing research results in the regulatory process.
The results of a Phase 11 aging assessment are intended to form the basis for implementing improved inspection, surveillance, maintenance, and monitoring methods; modifying present codes and standards; developing guidelines and review procedures for plant life extension, and resolving generic safety issues.
13 NRC INTEREST IN CllECK VALVES
. Check valves are used extensively in nuclear plant safety systems and balance-of-plant (BOP) systems. The failures of these val.cs have resulted in significant maintenance clTorts and, on occasion, have resulted in wi.tcr hammer, overpressurization of low. pressure systems, and damage to flow system components. These failures have largely been attributed to severe degradation of internal parts (e.g., hinge pins, hmge arms, discs, and disc nut pins) resulting from instability (flutter) af check valve Cscs under normal plant operating conditions. For exampic, a post-service examination was carried out on a 10.in. swing check valve from a local installation following its failure to close in service.
The cause of failure was determined to be extreme wear in the hinge mechanism, which permitted the disc to hang up on the valve body before scating occurred. Although service conditions are not known, the wear appears to have been a r.:sult of disc instability (oscillation) during service. A close.up of the hinge mechanism fr.r this valve, which shows the severe wear observed and its effect on disc position is sFown in Figs.1.2 and 13, respectively. Check valve instability may be a result of mis.pplication (using oversized valves) and may be exacerbated by low flow conditions and/o upstream flaw disturhances.8 Present surveillance requirements for nuclear power pl .nt check valves have been inadequate for timely detection and trending of such degrad: tion because neither thc flutter nor the resulting wear can be detected prior to failure. Censequently, the NRC nas had a continuing strong interest in resolving check valve problen.s.
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s Fig.1.2. Oose-up of the hinge mechanism of a 10-in. swing check vahe that failed to close.
ORNL PHOTO 7998-86
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Fig.13. Mditional lateral disc mmement observed on the same failed check valve whose severely worn hinge mechanism is shown in Fig.1.2. j
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l 13.1 Check Valw 1 unctum and Types .
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The function of a check volw is simply to open and thus permit (km in only one directism. When the ihm stops or reseru:s direction, the check valw chees. Check valves I are self actuating, th.it is, they require no esternal mc6hanical or electrical signal to either open or chise. As a result, most check valves are not capahic of being actuated other than l
by changing the (km through' the salve. Several types of check valves are commonly used.
such as the swing : check, piston hit, hall, stop< heck, and dun-check designs. The descriptions of check valve monitoring methods in this report refer in most cases to their .
use on the swing check valve, shtwn in Fig.1.4.- Ih> wever, all monitoring methmis described herein have the potential for being applied to other check valve types. A more .i comprehensive description of check valve types appears in Ref.1.
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. . 5 l.1.2 Selected NRC Notars arml.Hulktins Tables 1.1 and 1.2 tuntam the titles of selected NRC Inspection and Enforcement (IE) Notices and Bulletms over the last 10 3 cars; these notices and bulletins arc indicati ,
of the types of check vahc problems that have tscurred durmg this period and of the l continued interest that the NRC has had m identiftmg and soMng these problems. i I
l Tahic 1.1 'litle of selected NRCJll!Information Notices
- Title Number 90-01 Malfunction ol Ibtg.% irner it ' d Bonnt t Check Valms Caused by Failure of the Samg Arm 8" 62 Malfunction of Ibrg Warner Pressure Seal B<mnet Check Valves Caused 1 by Vertical Misalignment of Disc .
88-85 Broken Retaining Hksk Studs on Anchor Darling Check Vanes 88 70 Check Valve In Sersice Testing Prograic l
l 86 06 Failure of Check and Stop Check Valves Subjected to Low Mow Conditions fE01 Failur'c of Main Feedwater Check Valves Causes less of Fecdwater Splem Integrity and Water !!ammer Damage M.12 Failure of Soft Seat Vahe Seals M 06 Steam Binding of Auxiliary Feedwater Pumps 83 54 Common Mode Failure of Main Steam Isolation Nonrcte,rn Check Valves 83-06 ' Nonidentical Replacement Parts 82 35 Failure of Three Check Valves on Ifigh Pressurc Injec tion Lir.s to Pass How 82-26 Reactor Core isolation Cooling and liigh Pressurc Coolant Injectio-Turbine Exhaust Check Valve Failures 82 20 Check Valve Problems 82 08 Check Valve Failures on Diesel Generator Engine Cooling System i 81 35 Check Valve Failures 81 30 Vclan Swing Check Valves ;
l 80-41 Failure of Swing Check Valve in the Decay licat Removal System at Davis Besse Unit No. I
_. 'I
- nese information notices are available in the NRC Public Document Rtem.
e
\
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i Table 1.2. Bla of selected NRC/II' Hulletim' .
Number Tot -
l M4u2 Streu corrosion crackmg of high haidnen type 4lti stamleu steel mternal-preloaded twitmg in Anchor Dartmg Model SMtlW sumg check sabes or
- $alves of similar design
$ 85 01 Steam bmdmg ot auchan feedwater puml,5 -
i H3411 Check sahe failures in raw water cooling sptems of diesel generators l
80411 Operability of automatie depressuritation sptem ( ADS'. valve pneum.itic
! supply
%e bulletins are asailable in the NRC Public Document Rmim.
1 In particular. IE information Notice 86-01 describes an event that occurred at San Onofre, Unit 1, on November 21, 1985, ne most significant aspect of the event was the i failure of five safety.related feedwater sptem check valves (three main feedwater regulator j check valves and two feedwater pump discharge check valves), nc failure of thcoc valves was the primary cause of a severe water hammer that extensively damaged a portie of the feedwater system. The details of this event have been described in NUREG.1190, Loss of Power and Water Hammer Event at San Onofre, Unit 1, on November 21,1985.* nis
- report presents the findings and conclusions of an NRC incident Investigation Team sent '
to San Onofre by the NRC Executive Director for Operations.
- In 1986, the Institute of Nuclear Power Operations (INPO) issued a significant operating experience report (SOER), numbered 86-03, which recognized the check valve problems facing the nuclear industry and recommended that nuclear power plants establish a preventive maintenance program to ensure check valve reliability. INPO further j
recommended that the maintenance program should include periodic testing.' surveillance ,
monitoring, and/or disassembly and inspection. l
^ e 13.4 Geocric Letter 8944 !
in April 1989, the NRC issued Generic Letter (GL) 89-04 (Ref. 5) in recognition of the differences among utilitics in the scope of valves included in in-service test (IST) programs and concerns about methods of fulfilling the requirements of 10 CFR 50 55a(g),
which requires that certain pumps and valves be tested to aucss their operational readiness in accordance with the Sect. XI requirements of the American Society of Mechanical-Engineers ( ASME) Boiler and Pressurc Vescl Code. GL 89 04 describes potential gencric deficic,cies associated with full-flow testing and back. flow testing of . valves and an alternative to full flow testing (disassembly and inspection). It should be noted that GL .
89 04 addtcases other aspects of IST programs as well. l At present, the nuclear industry, led by the Nuclear Industry Check Valve Group (NIC), is preparing guidelines for exemptions to GL 994M, including methodologies for
~ - - .. _ _ _ . - _ _ , , _ . __
i 4 .ind guidelmes for i estending the u sass mbh .ind mspes tn n entin al ds tined in t el, v8 :
aliennaines i.i tu;l flow and b e.L tion tssim e ii s hisk sab es l
' l.3.5 l .PRI Appbcation Guitk brws l
In January lw. I pRI iwurd a wi of guidtimes for the w !ctiion. installation. and l m.untenante of t hetL sabes in nuclear power plants ' lhe stated mapir objettne of tha document n to prinide auurate teshnnal mloimation to be used by utshines in aucumg the lone. term rehabihts of their chesk sahe mstallations and to aunt them m respondmg l
l to the SOI.R
- lit. It n noted that thn information can alwi be uwd m Selcelmg check
! sahes for new sptems and for plant moditications. The document contams conuderable techn cal information and includes Jewriptions of sescral momtoring methods that were available at the time the guidelints were prepared. 11.e momtoring methods that are described are as follows.
e NoneNihration Monitoring.
' e Acoustic Emission Monitormg.
e Ultrasome Methods.
- Radiogr aphy.
- Fiber Optics.
An An evaluation of four of these monitoring methods is included in this report.
auessment of fiber optics inspection methods was not carried out.
1.4 PHASE I REPORT
SUMMARY
1.4.1 General Informaticm ORNL has completed a Phase I aging assenment on check valves.' Major topics covered by the study included
- 1. Check valve design featurcs.
- 2. Plant operating experiences.
- 3. Surveillance requirements.
- 4. Maintenance practices.
- 5. Failure mtxtes and causes.
- 6. Paramciers to monitor.
Results from this study were based primarily on information from operating experience records. including the Licensec Event Report (LER) file, the Nuc! car Plant Reliability Data System (NPRDS), and the in. Plant Reliability Data Sysicm (IPRDS). In addition to these data bases,information was gathered from component manufacturcrs riy reviewing their literature and participating in discuuiorn with their representatives.
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1
Q l.4.2 (hk Valve I ailure %=les and Sites ut ikgsadatum
- 1 ne shc6L salse f.ntute ni. Jo us es ederitde(d t'i the l'hw I studi
- 1. I:ailure i.i open
- 2. 1.ulure to time
- 1. Plugged (limited or no llow through a norm. dis open satsel
- 1. Reserse (internal) leak. ige,
- 5. ISteinal leakage.
Sescral check valve sites were identified as being susteptible to aging related degradation. These sites and the corresgunding agmg mechanisms are presented m Table 13.
1.43 Surwillance Requirements and Measurshic Parameters Test requirements for nuclear plant check valves were covered briefly in the Phase I report' and are summariecd in this section. A more detailed description of the regulatory requirements related to check valve testing is presenied in Appendit A of this report.
Testing requirements for nuclear plant check valves are contained in the plant Technical Specifications and are in accordance with Sect. XI of the ASME Boiler and Table 13. Check valve sites susceptib c to aging-related degradation Site Aging mechanism Body anembly Body wear, crosion, corrosion Fastener kiosening, breakage Internals Ilinge pin wear. crosion.
corrosion liinge pin fracture Ilinge arm wear, fracture Disc nut husening. lightening Dise nut breakage Disc wear. crosion. corrosion Seat wear, crosion. corrosion Forcign material Seals Cap gasket deterioration w -w Ve- e e W
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i j l'rcuure \ esw I (iide .\oisIc tw \ . (tain of the AMil ( ude dexriben m wrsice impettom j requirements for thct L uhes. tho requirement umsats primarsh of cierciung the sahe .l j to scrih obturator le g. dist trasel to or trom the tull open and fulliciosed pimitums as
, ment may i required to tuttill the uhei isolain n lunttion. Contirmann n of obturator -e ssures m the be bs snual obsersation, a pnituin indnator. obwrsation of reis s ant c
- miem. or other panoe means.
Some thetk whes uwd for sontamment imlation are aho required to be tested
] >
I m accordante with-Iti Cl R .'11. Appenda J. Jihew tesis imohe preuurumg the check .
2 uhe loi.alh in the same' direction as. when the sabe o required to perform its safety tunction and (omparingt le.ikage rates through the uhe with the specified standard.
Ihew tests are miended to demomtrate ' ctk sahe op:rability under test conditions hut do not i..isure thetL whc actuation as required under other anticipated opetatmg j
condition . In addition, these tests are inadequate for timely detection and trendine, of-theck vahc degradatam.
Check valve measurable parameters ident:6ed in the Phase I report' as important 1
for culuating operational readmen include force or torque apphed to move the obturator; '
j Guid lesel, temperature, preuure, preuure differential, and flow rate, reverse leakage rate; l j humidity; and noise. Additional parameters identified as being neccuary for positive failure-cause idemi6 cation and for enhancement of capabilities for degradation tracking and l
]
- incipient failure detection include dimensions. appearance. roughness, cracking.~ and bolt l torque.
l.4.4 Concluskms and Rexx>mmendatkms l
hree major methods that are used for check valve failurc-eause identification were identified in the Phase I report.' Dese methods are external visual examination, inspectkm i during normal maintenance, and periodic disassembly and inspection. Potentially useful measurabic parameters for detection of degradation and incipient failure were identified.. l The effectivenen and acceptability of these parameters were to be determined by further study (e.g., the Phase 11 aging assenment).
1 i
. . _ _ . ~ _ _
11
. 1
- 1. liVAl.tlA~l10N 01: Citin val.Vh MONIlURINO MisillODS 2.1 ' GEN!!RAL INIORMA110N j
De primar) 56;ectne of the Ph.ase 11 theck salve agmg assessment' program in to .
j identity and rtcommend methods 'ol inspection. survtiltante ~and monitoring that would .
~
proude timely detection .of check v41 e degradation and semcc wear (aging) .so. that.
maintenance or replacement could be performed prior to kms of safety function (s). In that .
regard, ORNL has carried out an evaluation of several developmental andA>r commercially avail.ihle check ' valve diagnostic momtoring methods, in particular, those based on measurements of acoustic cmission, uhrasimies, and magnetic Ous. Juc evaluations have been focused on the capability of each method to provide diagnostic information useful in !
determir.ing check valve aging and service wear effects (degradation) fcheck valve failu'rcs,-
and undesirable operating modes.
A description of each monitoring method, including examples of test data acquired under controlled laboratory conditi(ms, is provided in this report. In some. cases, field icst data acquired in situ are also presented. De methods are compared, and suggested arcas in need of further development are identined.
2.2 ACOUS11C EMISSION MONT1DRING-2.2.1 Basic Principk:s Acoustic cmissions (pressure waves) can be generated in a variety of ways. _ Of1 l particular interest are those generated either when solids contact cach other or when liquids or gases now through pipes and Gttings. Acous ic emissions arc deiccted by , sensors, such .
as piezoelectric. type accelcrometers or microphones, which respond to pressure waves over -
a wide range of frequencies. Signal.cond;tioning clectronics can be used to amplify selected .
acoustic signals while attenuating others, e.g., t nwanted environmental background noise.
Analyses of acoustic emission signals'obtained from' check valves can be used to monitorL ch 4 valve disc position movement,, and mechanical condition, J asi wr!!' as' internal -
Dow/lcakage through the valve. Various ' methods of obtaining and analyzing data are availabic. Dese include Sitering, fast Fourier transform (FFr), computer analysis, etc.1 2.2.2 Detection of Valve Disc Movement Acoustic emission monitoring has been shown to detect check valve disc movement.
As an example, Duke Powcr Company (DPC) installed an' acoustic sensor on top of a 10 in. - !
cold. leg accumulator discharge check valve.* A schematic representation of the installation . j is given in Fig. 2.1. After initially charging the accumulator to 100 psig, the motor operated - ';
- W. M. Suslick, DPC, " Proposed Technique' for Monitoring Check Valve Performance." presented at the INPO Check Valve Technical Workshop, October 30-:tt,-
1986.
12 j
OHL DWG H St00 E10. 1 SYSTEM SCHEMATIC
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- O M AC W W M CYC1E ilST OF A TFN INCH j COL D LEG ACCUMUL ATOR I'ISCHARGF CHECK VALVE ;
MOTOROPE RATE D VALVE OV DUKE POWER COMPANY l*4 MARCH 1984 lSIROKE TIME .10 SECONDS) s l 5 MONITORE D CHECK VALVE I P TO RF ACTOR VESSEL ,
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ACOUSTIC EMISSION SIGNATURE THROTTLING NOtSE FULLY OPEN CLOSURE >
g V EY FLOW NOISE-m h h ML i I d ,
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Fig. 2.1. Acoustic signal vs time for a 10'm. check valve tested by Duke Power
~
Company in March 1984. Source: W. M. Suslick,~ " Proposed Technique for Monitoring Check Valve Performance.' presented at the INPO Check Valve Techr.ical Worleshop.
October 30-31. 1986.
discharge valve was cycled. The acoustic sensor output during this cycling was processed and displayed on a strip chart recorder. He resulting acoustic signaturc (Fig. 2.1) shows that the sensor dctccted the metal.to-metal contact occurring at the'end of both the opening and closing strokes.
DPC has also carried out check valve acoustic emission testing under controlled flow loop conditions and with the introduction of various implanted defects that simulated severe aging and service wear.* Accclerometers were strapped to the bodies of three check valves in a manner depicted in Fig. 2.2. %c following diseission summarizes the results obtained from those tests.
- W. M. Suslick,11. F. Parker, and B. A. McDermott, CoC, " Acoustic Emission Monitoring of Check Valve Perfor nance," presented at the EPRI Power. Plant Valves Symposium. October 11-12,1988 Charlotte, NC.
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- A cE*.E ACVE *10 ui Fig. 2.2. Acoustic cmission equipment (schematic representation) used by Duke Power Company in 1987 flow loop tests. Sumre: W. M. Suslick,11. F. Parker, and B. A.
McDermott," Acoustic Emission Monitoring of Check Valve Performance," presented at the EPRI Power Plant Valves Symposium, October 11-12,198M, Charlotte, NC.
Tapping of the valve disc against la backstop was casily detected and distinguished from background flow noise, as shown in Fig. 2.3. In addition, by using two (or morc) valve. mounted acoustic sensors, DPC was able to approximately locate the source of the tapping based on a comparison of the ' time of :rrival" of 6e acoustic signals acquired from the two sensors. An exampic of this technique is shown in Fig. 2.4.
By using the acoustic emission check valve monitoring method demonstrated by DPC, it appcars iikely that the fo!!owing check valve operational conditions can be determined:
e Valve rapid opening (backscat impact).
- Valve disc tapping during reduced flow, e Ilinge arm tapping during reduced flow.
- Valve rapid closing (scat imp. sci).
Although a fully open check valve could be assurr w My the existence of flow noise without the presence of tapping. the absence of detectahl. t i ping noise is itself no guarantec that the check valve is fully oper since the valve disc may be oscillating without tapping in midstroke, may have fallen off, or may be stuck in a position that prevents it from impacting the valve body at any kcation.
Several tests were carried out by DPC on an 8.in. check valve in new condition and with simulated degradation. Ilinge pin diameters and disc / hinge arm cicarancca were both varied during valve cycle tests that generated acoustic emission signatures during
14
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Fig. 2.3. Acoustic waveform for a check valve during unstable (tapping) and stable
(!)ow noisc only) operations Sourre: W. M. Suslick.11. F. Parker. and B. A. McDermott.
" Acoustic Emission Monitoring of Check Valve Petforrrance." presented at the EPRI Power Plant Valves Symposium. October 11-12.1988 Charlotte. NC. .
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C s . 134 g fisAE 7APPtNG SENSOA AESPONotNG LOCATCN TO PAE55UAE W AVE FaRST HrNCE PM THE cHE NEAPEST THE PNCE PN I
BAcx5f0P fWE ONE NE AAEST THE BAcK$ ROP j
Fig. 2.4. Time.cf. arrival technique. Sourre W. M. Suslick. it. F. Parker. anct B. A.
McDermott. " Acoustic Emission Monitoring of Check Valve Performance," presented at the EPRI Power Plant Valves Symposium. Octohcr 11-12, 1988 Charlotte, NC.
15 Vaht it.amss wah new and .utitaiath worn hmee pins are illustrated in hg 2 5.
thn hgure shows that. wah the worn innge pun, an acoustis tranuent pseteded the seat impac t. 'thn uanuent may result from impa6t between the hince pm and hmge arm ~
surf aces as a result of the intreeed ticarance between these two parts A umilar tranuent esent occurred .n a result of increased clearance between the dne stud and hmge arm. as illustrated m I'ig. 2.ri. Alm shown h a ohnure of a check salve .
hatmg Nith a worn hmce pin and 4 Imne disc hmge arm connection.
In prattite. DPC has momtored cheti sabe acoustie emnuon at three plants l'or
-1 3 ear uung vahe. mounted accelerometers whose outputs are recorded on tape (at the check sahey. Recorded ugn ds are then played back remote.from the vahe (e.g. in an ollice) to both an oscilloscoje and a loudspeake for audio interpretation. Valve instability n then detested as tapping (clicking) noises heard on the loudspeaker and is quantified by the oscilloscope.
DPC uses acoustic emission monitoring primarily to identify vahes that are operating m an unstable manner. Those valves are then targeted for close inspection (disassembly)
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Fig. 2.5. Check valve closures with new and artificially worn hirge pinn. Sowre W. M. Suslick. II. F. Parker, and B. A. McDermott " Acoustic Emiuion Monitoring of Check Valve Performance." presented at the EPRI Power Plant Valves Symposium. October 11-12.198H. Charlotte NC.
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tudE Fig. 2.6. Check valve closures with two artifcial degradations. Source: W. M.
Suslick. H. F. Parker, and B. A. McDermott," Acoustic Emission Monitoring of Check Valve 11-12,1988, Performance," presented at the EPRI Power Plant Valves Symposium, October Charlotte, NC.
at the next convenient time. Roughly 10% of the valves monitored by DPC were determined to be operating in an unstable mode. After disassembly, roughly 90% of these valves showed signs of degradation (wcar).
2.23 Oualitadvc Leak Detection Acoustic emission techniques have long been uwd to detcet fluid leaking through a valve. Philadciphia Electric Company (PECO) has been using acoustic techniques to detect valve leakage in their nuclear power plants since 1974.* Their test procedure consists of acquiring two sets of valve acoustic emission readings, one while the valve is The noise unpressurized and one with a pressure difference across the (closed) disc.
associated with a leaking valve is then determined on the basis of the difference in readings. '
PSCO has had good success with a portable, hattery. powered data acquisition unit for leakage monitoring. The acoustic data collected from baseline (unpressurized) and pressurized tests arc downloaded into a computer for analysis, trending, and archiving.
M l
"J. W. McElroy, PECO," Light Water Reactor Valve Performance Surveys Utilizing j
Acoustic Techniques," presented at the EPRI Power Plant Valves Symposium, August 25-26,1987, Kansas City, MO.
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23 UtilRASONIC INSI'IUl10N 23.1. Ittsic l'rinciples '.
Ultrasonic inspettion msolses the introdu6 tion of high frequency sound waves into a part being esamined and an analpis of the characteristics of the reflected beam.
Typically, one (puhe etho) or Iwo (pitch catchl eiltrasonic transducers are used which proside both transmiuion .md recching (sensingl capabilities. The ultrasonic signal is injected from outside the sahe by the transmittmg transducer and passes through the valve '
body, where it is reflected by an internal part (e.g., disc hinge arm, etc.) hack toward the receiving translucer. (Note: When one transducer is used in a pulse-echo mode,it provides both transmittmg and resching capabilities.) !!) knowing the time required fer transminion-of the ultrasonic signal from the transmitimg transducer and back to the. receiving transducer. the tranviucer hication(sl. and other valve geometries, the instantaneous disc J
puition may be determined.
in gener.it, signal processing circuitry must be used to Glter out undesirabic ultrasonic signal redections present in the raw received signal sa that the resultant processed signal provides a more casily interpreted valve disc puition si,anature. Various methods of obtaining and analyzing data are available. 'Ihese include littering. fit. computer analysis, etc.
23.2 Detection of Valve Disc Movement Ultrasonic inspection techniques can be used to produce a time wavciorm' display from which disc position and movemer t may be casily determined. ' A properly conditioned ultrasonic signal time waveform can be used to deicci the folk) wing check valve operational .
modes:
Occrational Mode Sinneurc Characteristic l i
, Full open or full closed Steady signal Free flutter Variable signal with rounded peaks Backstop tapping Similar to free Gutter but
- with Dattened upper
- peaks Scat tapping Similar to frec Hutter but with flattened lowcr' peaks '
' Dependent on mounting position of the ultrasonic transducer (s).
Figure 2.7 shows ultrasonic signatures taken from a swing check valve installed in -
a laboratory now loop at two disc positions: full open and partially open. It is noted that the disc was fluttering (unstabic) in the partially open position and that the Dutter was cl::arly detected using the ultrasonic method. Figure 2.8 illustrates the similarity between disc motion signatures acquired with an ultrasonic sensor and with a specially installed rotary variabic differential transformer (RVDT) attached directly to the~ hinge pin to provide a direct measurement of disc position.
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t 4n-CHECWMATE v5 RvDt et4 wiPCE Pe4 s O*'- RvDT
. Y **q ', / g, / / \ [ \ /
c4*-
i i i
- 52-
'$ 22 24 28 32 36 40 i
- d '9 '2 D.'E m Fig. 2.M. Comparinon of an ultrasonic signature with that from an RVDT installed on the hinge pin of a check valve. (Used with the permission of lienze Movats. Inc.)
F J
t i
_ _ . _ . . . - . ,-- - _ , , ,. ,.r-# - , , . , _ . . , , , , , ,,,,,,,--.m., , , ,, ,- .. ,
ps Ultramn" inspettion tethmques tan be used to deteu a miume or stuck dne. For '.
esample, it the dnc is miumg. no uenal will be acturned u6ticsted) inom the doc. howeses, it the hmge arin rem.nns on the sahe, the hinge arm lmution tan be se died by ultramme inspection tethmques. l urthermore, under umilar flow conditions, a hinge arm without an attathed dne will tlutter at higher frequencies than if a dne were attached.*
Dise stud wear can be detected by ultrasonic inspection by monitoring the motion .
of both the dne and hinge arm usmg ultrawnic transdusers, one' sensing movement of the dne and the other senung hinge arm mosement. Incre. sed clearante betweer, the dise stud and the hmge arm can result m increased mosemsnt of the dne relatne to the hmge arm.
~
2.4 MAGNI llc l't.UX MUNI'lORING 2.4.1 Basic Principles Rescatsh tarned out by ORNI. .n part of the NPAR Phee il study of check vahes h.n led to the idennlication of a new thetk sahe diagnostic technique, m.ignetic ilus ugnature analpis (Mt SA).t Mi SA is based on correlating the magnetic lield strength sariations momtored on the outside of a thetk sabe with the gesilion of a permanent magnet placed on a mesmg part inude the check vahe (Fig. 2.91 In the proof-ol pimeiple tests. . llall-cifect gaussmeter probe was used outside the check vahe to detect the magnitude of the magnetic Geld produced by a sinall cylindrical or rectangular (barn permanent magnet attached to the hinge arm. he liall effec. probe detected both tonstant aad sarying magnetie Gelds and thus continuously monitored Imth the irwtantaneous poution and the mohon of the check valve dise. Various methods of obt.iining and analysing data are available. nese include filtering. FFr. computer analpis, etc.
2.4.2 Detectkm of Valve Dio %m: ment MFSA prmides the ability to monitor dise position through an entire valve stroke using one externally mounted sensor. A comparison of disc position measured mechanically (by an angular displacement transducer attached to the hinge pin) with that obtained by M FSA is ' awn in Fig. 2.10 for a 3-m. swing check valve whose disc was moved rnanually.
MFSA has been applied to several swing check vahes heing different body materiak and ranging in si/c from 2 to 10 in.
MFSA aho provides indication of dise llutter. This was demonstrated by tests carried out by ORNL on a 2.in. swing check vahe that was installed m a water flow kmp.
nc ORNL check valve flow hop, illustrated photographically in Fig. 2.11 and schematically in Fig. 2.12. utiliecd a centrifugal pump that i capable of delivering >300 gal / min through a 2.in. nominal-diameter linc (>30 ft/s).
- R. D. Ryan, CilECDIA TE ll-A Diapmuic Tool for Cha k l'alces. Ilenie.
Movats. Inc.. Technical Resources. May I'r80 til.11 lla>nes and D. M. liiwenberg. ORNI ~ Performance Monitoring of Swing Check Vahes Usmg Magnetic Ilus Signature Analpis," Information Package Contaimng belected MIM Test Results. May 1989
20
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. ~ .
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(
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I
/ O (N i,/e . -
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I% FLOW l Fig. 2.9. Magnetic Dux signature analysis (MFSA) principle of operation.
Flow rate through the tested check valve was controlled by means of three ball valves located downstream of the check valve and a manually operated gate valve located in a short. 3 i.n. nominal-diameter bypass pipe circuit. Low Dow rates through the check valve were achieved by fully opening the bypass gate. If needed, the How through the check valve was further throttled by the ball valves. Conversely, higher now smics throu;h the che:k valve scre achieved by throttling the gate valve.
The llow loop contains threc Dowmeters: a 24 gal / min rotameter, a 60. gal / min rotameter, and a turbinc flowmeter. At now rates less than approximately 20 gal / min through the check valvc (<2 ft/s), th'c turbinc Gowmeter does nct provide a stahic, accurate measure of flow rate; thus, under these circunutances, the rotameters are relied on for flow rate measurements.
At flow rates excceding the combined fullscale reading of the rotameters (24 + 60 = 84 gal / min), the turbine flowmeter provides an accurate means of .
monitoring now rate through the check valve. Bypass flow rate was not measured.
De flow loop also includes a drain and cold water supply, the latter being a tank located above the ceiling of the room. Under normal now operations, the loop water temperature increases because of the energy supplied by the pump. Flow loop water temperaturcs were stabilized by adjusting the water supply and drain flow rates so that the necessary heat reinoval was achieved, ne acquired magnetic flux signatures (see Fig. 2.13) showed that at a low now rate (insufficient to open the valve fully), the disc fluttered considerably in midstroke, !
whereas at a higher Dow rate, the same valve cchieved a fuily open and stable condition.
-- .J
i 21
..... r. . , . .c s m ,
e 3 FC4 SWNG CHECX VAL',1 OtSc L*'ht0 unAJALLY n
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30 35 40 0 s to ts 20 25 f NE tel 5 WASURED WCHANICALLY (ANGULAA DISM.ACEWNT TRAN500cEM 8 GAU55 METER. MO8E L .AuED ON yALVE cM Fig. 2.10. Comparison of magnetic ficid strength and disc angular position measurements.
2.4.3 Detectim of Worn Hinge Pins .
Experiments carried out at ORNL have shown that MI'SA techniques can be used tu detcet hinge pin wear. Figure 2.14 illustrates a technique for detecting worn hinge pins l
that
- s me cf .wo Hall effect gaussmeter probes, mounted so that cach probe provides l
l an independent measurement of instantaneous hinge arm pcsition. When both probes are mounted on the valve cap at locations equidistant from and perpendicular to the projected l
I hinge arm travel plane, both gaussmeters should provide identical signatures when the hinge arm moves in a purely swinging motion as the valve opens and closes.
In addition to swinging, the hingc arm moves in a sidc.to-side rocking motion as well, as a result of flow turbulence and the cicarances between the hinge pin a~nd hinge l
arm. As this cicarance increases (e.g., because of hinge pin wear), the propensity to rock increases. Thus, the increase in hingc arm ncking is detected as increased deviations from the single line (pure swinging) relatior. ship between the probe outp'it signals, as shown in Fig. 2.14.
q 22 i ORNL PHOTO 8234-G v
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i Fig. 2.11. Check valve flow loop (photo). '
Another technique that appears to be useful for detceting worn hingc pins is based on an analpis of the magnetic flux time wavcform (signature) act ired by a single probe during a full valve stroke. Figurc 2.15 illustrates that tne time waveform changes appreciably when different hinge pins are installed. This tellects changes in hingc arm position due to differences in cicarance betacen the hinge arm and hinge pin. During an opening or closing of the valve, the magnet (which is mounted on the hinge arm) rotates and translates along a difierent path that is determined by this clearance.
Figure 2.15 shmus that, even when the normal. sized hinge pin was installed, the magnetic field strength varies with valve position in a nonlinear manner. In fact, when the l
valve is near the full open position, the same magnetic field strength reading is reached at two distinctly different valve positions. The relationship between the external. magnetic ' :Id -
i reading and valve position when the normal-size.1 hinge pin was installed is different than that previously discussed (see Figs. 2.10 and 2.13). This relationship was seen to bc l
l approximately lin:ar and witho it any ' humps" in the time waveform that would result in two valve positions c::isting for the same magnetic field reading. The differences in these signatures are simply a result of kicating the gauumeter at a slightly dificrent position.
i l _ . . _ _ . _ _ _ _ _ _ _ _ _ _ . . _ . . _ _ _ _ _ _ _ _ _ _ . _ _ - . _ _ . - _ _ . _ , _ . - .
23 .
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itst 51i110% ,
- m :l g Pl!MP '_ ,, '_
oman i.p s
s DR AIN g Fig.111 Check vahe ikw loop (schematic).'
During ther.c tests, it was noted that the magnitude of the.* hump
- could also be affected by the rate at which the valve opened and closed. - For exampic, the faster the valve opened, the smaller the hump became even though the fullopen signal magnituoc
-~ ' J remamed the same. ,
Thus, when using MFSA, the relationship between magnetic field strength readings and disc position is determined from several factors, including the locations of the internally installed magnet and the externally attached gaussmeter and the clearance between the hingc arm and hinge pin.
15 COMPARISON OF ACOUS'I1C, ULTRASONIC, AND MAGNETIC MimIODS The preceding three sections of this report have provided descriptions of three check valve monitoring methods that are useful in determining check valve position, motion, ;
and leakage. These methods, based on acoustic cmission, ultrasonic inspection, _ and magnetic flux monitoring function according to different principles of operation and thus ,
provide different (and complementary) diagnostic information. 'Itc currently calimnted capability of each monitoring method to detcet various check valve operational conditions is given in Table 2.1.
. . . , . - , , . , . . - . - . - ,.-,.,n, , - - .-.
, 2.s onNL.owo e15:04 L70
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w 04 w
9
- 03 W
D 5
a 02 01 i
PUMP STARTED HIGH FLOW RATE 0.0 -
(OPENS VALVE FULLY) 0.1 TIME (2 SECONDS DIVISON)
' Fig.113. Une of MFSA to detect disc instability (Dutter).
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l 0 60
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x caussucita Fig.114. Detecting worn hinge pins using MFSA.
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Fig. 2.15. Magnetic Dux time waveforms of a 3-in. swing check valve for threc l hinge pin conditions: normal (top tracc), medium worn (middic trace), and severcly worn .1 (bottom trace). All signatures were acquired using identical internal magnet and external (
gaussmeter locations. ,
1 I
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Table 2.1. Selected diagnostic capabilitics and limitations of three check valve monitoring methods" .
' Detects Sensitivity Monitors disc Detects Works Detects .11 uttering to position throughout valve . '
ambient the full range. with intornal internal (no impacts) Nonintrusive conditions' of doc travel all fluids Method leakage impacts Yes Sensitive to No -- Yes Acoustic Ycs Yes No externally .
emission generated noise / vibration Yes - Yes Unknown Not in all No Ultrasonic No Yes cases-becaux: of inspection (indirectly) !#
limited Awing angle of transducer No-tequires . Sensitive to '. cs Yes MFSA' ~ No: Yes Yes -
(indirectly) initial - .
nearby ~
installation of external ~
permanent magnetic ficids..
magnet inside (e.g, from the valve motors)-
' *P- %i, and ' pressure noise analysis methods are not summarized in this tahic. ~Ihis table does not reDect
. other attributes such as cost, casef o use, etc. This table tcDects the judgment of the author and is h= d on all
~
-informiam available at the time this report was prepared.-
Temperature and radiation effects are unknown.
4
_ _ _.-_--_L__--.__ ..---___i ~ - _ _ . _ < . - - ,
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27 i
As indicated in Table 2.1, although no single technique has the capability to detect ,
all. check valve operational conditions well. a combinatam of acoustic emission with cither:
ultrasonic inspection or MFSA can yield a monitoring _ system that succeeds'in prcmding sensitivity to detect all major check valve operating conditions.'Ikith acoustic / ultrasonic and ..
acoustic / magnetic combinations have been tested.
lhe combination of acoustic emission and uhrammie mimitoring methods is described ,
later in this report where commercial spiems are discussed. . 'The combinatkm of acoustic '
cminion and magnetic Ilus monitoring methods was tested by ORNL on a check valve -
l whose dise was moved manually to simulate disc 11 uttering at different disc pnsitions.; .
As shown in Fig. 2.16. the acoustic signature dia .mt provide direct indication of disc gwnition when the valve's dise was stationary in the f ully open and fully closed positions. .
f nor did it detect the slowly moving disc or dise llutt'cr in midstroke. .In all .t hree tapping; modes (seat tapping. backstop _ tapping and. hinge arm rocking). the acoustic signature- .
detected the tapping but not its location. The magnetic signature did not unambiguouslyf detect the tapping but 'in conjunction with the acoustic signature.- identified its location.
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Fig.116. Magnetic flus and acoustic signaturcs r<w a check valve under several simulated operational conditions. ,
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1 28 2.6 011(liR MtilllODS 2.6.1 Radiography ne use of onventional c and new *high-energy" radiographic techniques ' for monitoring the condition of check valves is described in Ref. 2. De following is- a' summary, of the information presented in that reference. .
Conventional radiography has been successfully used by several nuclear utilitics toi detect certain types of failurcs and degradation of check valve internals. - Exampics of swing check valve failures that were detected with conventional radiography include missing valve discs, locking devices. and nuts; broken disc studs: discs stuck in full.open' position: etc.* In addition. the integrity of discs and guide pins in globc. type stop-check. valves has been-verified wah this technique. It was pointed out that these cases involved relatively small (6 in. or smaller) valves and that when' applied to larger valve sizes, the interpretation .of..
the radiographic film becomes more difficult (because of decreased resolution) and thus may _
not provide reliable results.
De major drawbacks associated with conventional radiography, identified in Ref. 2, include
- 1. Inability to radiographically inspect steci sections in the ficid that are thicker than approximately 5 in.
- 2. Execuive exposurc time (and outage time) for field radiography.
- 3. Inability to acquire good radiography quality in. field ' practice under adverse plant environmental conditions, particularly those of high temperature and background ionizing radiation typical of nuclear generating units. .
liigh.cncrgy radiographic equipment has recently been developed which overcomes -
the limitations of conventional radiographic techniques, and it has been used by a nucicar utility to determine the integrity of swing check ' valve'!nternals.' his new technology is described later in this report where commercial diagnostic systems arc discussed.
2.6.2 Prcssure Noise Monitoring-Early in the Phase 11 study, pressurc noise (e.g., fluid pressure perturbations) v,At identified as a measurabic parameter that might be' useful-in ~ check valve diagnostic ~
applications. Hus, an evaluation of pressure noisc' signature analysis wanarried out by ORNL using a 2-in. Stockham swing check valve installed in a cold water flow loop located .
in Oak Ridge. _
Preuurc noise was senacd by two piezoelectric pressure probes, one located upstreem and one located downstream of the check valve. Figure 2.17 illustrates a typical'.
installatien of the two proocs and gives a list of selected probe specifications ^ Droughout .
the I ow tests, the distance from.cach probe to the check valve was varied, as well as the depth of insertion into the flow stream.- . ,
Early tcat results indicated that pressure noisc spectral characteristica were noticeably ;
affected by flow rate. Figure 2.18 illustrates typical noisc spcetral signatures of both probes for two flow rates,20 and 40 gal / min. with both probes located 10 pipe diameters from the -
check valve centerline. - Among the featurcs seen were relatively. sharp frequency peaks representing pressure perturbations at the pump shaft frcquency (motor speed) and at the
~
pump vane pass frequency. .
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~
.i Fig.117. Pressure probe specifications and points of installation.
i ORN1. DWG 90 3997 ETD ;
M0W Thnv LAndur ROTAW1ER ;
l LOC A ~
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= EU
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Fig. 2.18. EITect of ikm rate on pressurc 'noisc spectra.
30 In addition to these peaks. the pressure noise frequency content of both probe signals, especially above 2tXI lie, varied in amplitude (by up to a lactor of 10) as of changes in flow rate. Since the check valve disc position also changed with (km rat it seemed likely that certain pressure nois: signature features (i.e., thusc affected by now rate) might directly renect check valve disc position. Ilowever, it was .ioon discovere signature repioducibility was not very good because of high sensitivity to many fac; including
- 1. Flow path.
- 2. Water temper.. e.
- 3. Tank water level (*ptcm pressure).
- 4. Pressure perturbations induced by pipe vibrations.
5 Air in the system--cspecially that which collected in the check valve bonnet.
For examp*c. l'ig. 2.19 :llustrates the effect of now path on preuurc noisc spectra. At the same Dow rate (60 gal / min), the pressure noise spectral characteristics changed noticea as a result of varying the now path from (a) through the la'ge rotameter to (h) through the ball valve.
Preuure noisc spectra thus were found to be complex signatures that were grcally .i Cons <;quently. a large effort .was made to innuenced by many sptem parameters.
understand (and eliminate. if possibic) many of these effects. For exampic, tests were 00fJL DWG 'O 3998 f ID 60 GPM C _ C. J,B d. '.O.. l a..,A_1.. C. . PM.S . .
L.C'.". A. . . . .N.B.
,, ..g PROSE A g . . . . , n r. , . ,
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Fig. 2.19. Effect of ihm path on prcasure noisc spectra.
I
31 carried out at a constant loop water temperature. Care w s taken.in establishing reproducible tank water levels and flow paths. Pipe vibrations were monitored by accelerometers, and the spectra were compared with the preuure noise spcctra.
In addition, various signal analysis techniques were esplored in"an attempt to ,
develop a means of arriving at a diagnostic signature that provided maximum' sensitivity to.
check valve ef fects while having minimum sensitisity to other influences. .%ose techniques included determining e the prenure probe ugnal ratio (P,Y,,). where P4 is the pressure signal from probc *N (down.tream trom check sahe) and P,,is the pressure signal from probe "If (upstream from check sahe);
e the pressure probe ugnal difference (P - P,,l. and e the correlation between preuure probe signah.
Rese methods, while initially promising, also suffered from nonreproducible results.
In conclusion, pressure noise spectra were complex signatures that were highly semitive to many splem effects and apparently to' other (unidentilled) effects as well.-
Prenure noise signature analpis thus was judged to be an unattractive monitoring method for check sahe diagnostics and was not considered for f urther studies, primarily because of -
a lack of reproducible results.
2.7 CONCI.USIONS-Ill!NiilTIS AND WliAKNiiSS!!S OI:MONrIORING MimIODS nis chapter has described several check valve monitoring methods' and has identitled their strengths and weakneues. hose methods are acoustic eminion, uhrasonic inspection, magnetic flux monitoring, rad;ography, and pressure noise monitoring. Of those methods, the acoustic emission, ultraumic impection. and magnetic flux monitoring methods - ,
provide the greatest metall diagnostic apabilities.
Radiography certainly provides unique information in the form of images that can be serv useful in verifying the integrity of check valve internals or in detecting failures or degradation. liased on information available at the time this report was prepared,its major drawback is the lack of a high. resolution display that provides quantitative information on the psmon of the check valve internals, especially over a'short time frame onduring a a transient (opening or closing of the valve).
Pressure noise monitoring is intrusive-a tran ducer must' be installed which .
penetrates a preuure boundary (e.g., pipe). In addition, pressure noise monitoting was shown (on a laboratory scale) to he overly sensitive to extraneous inputs (flow rate, flow path, iluid. temperature, pipc vibrations, etc.).
%e main limitation of acoustic emission is that the absence of detectable tapping noise does not by itself guarantee that the check valve is fully open and stable since the disc may be oscillating in midstroke without tapping, stuck in midstroke, or detached from the hinge arm and lying still in the bottom of the valve. A minor limitation of this method is the necessity of using multiple senutrs to' determine the kication of a tapping event.
U!irasonic impcction, using a single transducer installed at a fixed position, muy not provide valve dise position information over the full travel of the disc because of the I;mited ,
viewing angle of the transducer. Furthermore, a low density fluid, such as steam, may result in severe attenuation of transmitted and retlected signals and, ultimately, poor transducerL response.
i 1
32 l
It is generally more dimcult to apply ultrasonic inspection techniques on stainicas !
steel valves than on carbon sicci valves since ultraumic signals are attenuated (scattered) more when passing through stainless steel than when passing through carbon stccl. Thick -
wall stainleu steel valves (e.g.,15(XI. psi scavice) prennt the greatest dimculty; however,
~
additional research needs to be carried out in order to fully explore thc4c limitations.
- 1 MFSA rey'uires the installation of a permanent magnet inside the valve; thus, the
~
method is intrusive, impacts between the valve disc and valve boly may result in time ini a demagnetization of the attached magnet. Furthermore, if the magnet (and/or magnet i l assembly) detaches from the check valve, it may presc.it a serious problem. De nterna -
magnet may attract and hold small metallic particles. ; nc particles can. build up, and can 1 affect the magnetic fickl dispersion' pattern, thus possibly changing the strength of the ~ ;
measured external field. Metallic particles may also accumulate around the internal magnet '
in a manner which could affect the operation of the check valve.; Finally, the magnet Gus signature features may he diliicult to observe under licid conditions because of the presence .
of nearby ambient magnetic ficids. .
A check valve methodology that combines scoustic eminskm monitoring with cither ultrasonic inspection or magnetic flux monitoring provides the folkwing general capabilitics: j
-1
- l. Detecting leakage through a closed valve. (Acoustics) -
- 2. Detecting impact 2 occurring within the check valve during How operations. -(Any .
methou) i
- 3. Detecting disc position at all times, whether the valve is experiencing full. flow,' partial ll l l Dow, or no Dow. (Ultrammics or magnetics) i When monitoring check valves using cither of these combinations, it is not necessary'to !
i l
l apply both methods simultaneously in order to achieve the combined capabilitics of the two methods. Two check valve diagnostic systems that arc based on the combinations described -
above are commercially availabic. Dese and other commercially available systems are described in the next chapter of this report.'
I
33
.t. Dl!SCRilmON OF SELICRD COMMERCIALLY AVAllABIE -
CllECK VALVE DIAGNOS'nC SYSTEMS-In order to adequately describe the commercially available check valve monitoring systems, infarmation was_ requested from several vendors of diagnostic systems, including those discussedLin this chapter. The descriptions provided below are based on the information provided by the vendors.
3.1 CIIECKMA'IE" 11 (IEENZE MOVATS, INC)"
At present, CllLCKMATE* 11 is the only commerciallyf availshic check valve De 'systens is available from monitoring system that is based _on ultrasonic inspection. ~
Henze Movats, Inc of Kennesaw Georgia.. His system represents an upgrade of the original CHECKMATE
- system. .. According :to the. vendor, the new system- utilizes .
improved hardware and softwarc' that provide a metins of. more casily l acquiring :and '
analyzing check valve signa'turcs. Figurc 3.1 provides a simplified drawing that illustrates the basic operation of the CICCKMATE* 11 system. - One ultrasonic taansducer is used (pulsc-echo type) which provides both transmission and receiving (sensing) capabilities,'
His system utiliscs signal proccuing circuitry that filters out undesirable ultrasonic !
signal reflections present in the raw rcccived signal so that the resultant processed signal ~
provides a more casily interpreted valvc disc position signature. According to Henze.
Movals, Inc., since March 1987, approximately 200 valves in 21 power plants have been -
tested using CHECKMATE
- and CHECKMATE * !! systems. . -
According to Henze Movets,'Inc., .in addition : to discTposition indication, the CHECKMATE
- 11 data analysis program cart.also provide estimates _of hinge pin wear. '
rates and fatigue damage of valve internal parts. ._
Henje.Movats, Inc., has recently used acoustic ' emission monitoring with their.
ultrasonic inspection sptem. The result of using the combination of these methods is seen in Figs. 3.2 and 3.3,t which comparc data from the tvo sensors obtained for s' check valve tepping its backstop and its seat, respectively. In both cases, the acoustic signature detec the tapping but not its location. De ultrasonic signature did not"""cicarly detect -
the tapping,"
but, in & injunction with the acoustic signature, identified its location. '
3.2 QUICKCIIECK" (IJBERTY TECHNO1DGY CENTER, INC)
Another system that utilizcs _ ; a combination of . monitoringi methods is OUICKCilECK*, a check valve diagnostic system' available- from Liberty Technology ,
- 1.ctter from J. N. Nadeau, Henee.Movets, Inc..' to 11. D. Haynes, ORNI.,
Subject:
Motor. Operated Valve and Check Valve Systems Informati(m dated March I.1990, tLetter from D. M. Ciesieldi, Henze Movets, Inc..Lio_ H,'D.2Haynes,10RNL,7
'~
Subject:
CilECKMATE" System Information. dated July 22 1989.
34 OHNL (We to 3539 LTD i
til THASONIC THANSDUCER COMPUTER-BASED UllHASONC SIGNAL SIGNAL ANALYZER GENERATORIANALYZER 3
1 m , r-~~
r ,.
- t. .
((-ROW) ';
l Fig,3.1. A simplified depiction of the GIECKMATE* 11 systcat i
i l OH8vt Dwo 904000 t10 0 24 -
OM ig $
~ 4 24 '. ,e \, \ \ /l
-a st -
4 ?i -
i 1 EKSTOP TAPPesG BACKSTOP TAPPING 8ACKSTOP TAPMNO t o 68 -
g 9.71 -
" f f N
f4 89 9 .
VST3 '
L
' I 0 00 --
20 24' 28 32 34 4.0
"' "c o 04 08 12 to T&8E (s)
Fig. 3.2. CIECKMA1E" and ecoustic signaturcs for a check wive - ' wi; backstop tapping. (Used with the permission of Henic.Movats, Inc.)
M i
-e
. ._ .. . .- , , .- ~ - - - ~ .
35.
4 e me I w , e 4-ir i n ,n ON' CMCM14 ATE v2\Ts .
O 00 D ffi [.byg., ..' ,
- 4 3. .
s, s
l l
.0 7, *
.i tal SEAf T Af'peeG SEAT TAPPwoo. Sr.AT TAPP98G -
'{
12 53
, . 3, .
k.
, k b d E" .
00 04 09 12 IS 20 -28 1 32 38 .da ,
rant t.o Fig. 33. CIIECKMA'IE" and acoustic signaturcs for a check valve undergoing.
scat tapping. (Used with the permission of Henze.Movats, Inc.). .
Center, Inc., of Conshohocken. Pennsylvania.' QUICKCHECK*,' depicted in simple form -
in Fig. 3.4, utilizcs a combined acoustic / magnetic dual sensor to monitor simultaneously the .;
structurally transmitted acoustic noise that results from flow and intemal part impacts and -
the position and motion of an encapsulated magnet that is permanently installed on a chec.k :
valve internal part (c.g., hinge arm, disc, etc.). Data acquisition hardware includes the dual sensor (s), signal conditioning ciectronics, and a digital audio tape recorder. ' Recorded - -
signals are then processed. displayed, and analyzed with a computer based system that .
providc .!ctailed analysis capabilitics for both acoustic and magnetic signals.'.~ . .
,, l 33 VIP (CANUS CORPORA' HON)
CANUS Corporation of Laguna Hills, California, has developed aLeheck' valve -
diagnostic system called Valve Inspection Program (VIP).' VIP utilizca acccicrometers (from - ,
2 to 12) and associated clectronics (charge amplifiers, signal conditioning) to obtain check :
valve acoustic emission information ~that is stored on a digital audio tape recorder. for subsequent manual and automated analyses.t Real. time, high-resolution displays of the' acoustic waveforms are provided by a digital graphic recorder. In' addition.' headphones are.
used to monitor the signals for qualitative anscamments of flow noise, valve tapping, etc.
' Letter from D. Manin, Liberty Techriology Center, to H. D. Haynes, ORNL,l
Subject:
Motor. Operated Valve and Check Valve Systems Information,. dated March li 17M1.
,, r. .
,, . . . n , , . .. , . ~ t : r W t q e ,, . ., ,i:,,,, ',,, iT n --itiivn c y O tt N fL
<.n, , . ,. ~
1
, )
36
- OltNL.DWG 90 3540 ETD e i
! DUAL SENSOR l (ACOUSTICS / MAGNETICS) ;
l
! . SIGNAL .,
I CONDITIONING COMPUTER
. . . . . . . . . . - 8ASED-l, DIGITAL SIGNAL BASEm AUDIO ANALYZER. .
i a
TAPE 4 RECCRDER '
! / .:h 1
i 3 ' r MAGNET r .,
j Q
-- / -
l \.... ,iI, l : m.,
. .t,i, . ,,
l f,. FLOW
- ,. c i ;l
- t a
i Fig. 3.4. SimphGod depiction of the QUICKCHECK" system.
i ,
j According to CANUS, over the last 3 years, they have used this method to test' i
j approximately 150 valves at five plants. Deir tests has e provided indications of c j
degradation and check vahe operating modes that would lead to degradation.
CANUS is ' presently devcksping neural network programs ' that could provide j
i automated interpretation of acoustic cmission signals.
1 1
3.4 AVLD (LEAK DITIECTION SERVICES, INC.)
kak Detcetion Services, Inc., of Annapolis,- Maryland, has developed an _ acoustic' i a valve leak detector for ura aboard U.S. Navy submarines; it has also been used to detect - l j
internal valve leakage at several commercial nuclear and fossil power plants. ;De device permi:s the operator to observe the acoustic emission signals en a meter and to re them on an 1.y plotter, De device provides the ca'pability for acquiring acoustic signals j
i from two sensors simultaneously, one sensor mounted on thc. valve and the other mounted on the pipe about 10 pipe diameters away from the valve.' De two channct responses are
! e i
then adjusted, and the background noisc signal (acquired by the' pipe. mounted sensor A positive signature _is an- ;
j clectronically subtracted from the valve. mounted signal.
> : . .. : . . ,, . a . .. . . . .. i, . . t ., ,, ,._
i
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5 1
l
- d. - . . _ . _ . _ . _ , _ , ._.,._...u.., .. ..,.,;,,~...-.,,,,,,,- .. - . , - - .
4 i
'i
- 37 1 .j 1
3.5. MINAC.6 (SCllONHERG RADIA110N CORPORA'110N)
-lhe MINAC-6 portable linear accelerator system, available from Schonberg Radiation Corporation of Santa Clara, California, provides several advantages over canventional industrial radiography systerr.s.' It is a portable, high.cncrgy (6 McV, 300. rads / min at I m) system that is capabic of prcxiucing radiographic images through a 12-in. section of steel with a 10 min exposure time and through a 14.in.~section in 45 min.
The MINAC system was developed in cooperation with the Electric Power Research l
Institute and, since 181, has been used at approximately 20 nuclear power plants in the United States for inspection of heavy wall components, including large piping, valves, and .
pumps. In particular, the system was used to verify the integrity of internal parts of several main steam check valves at the Diablo Canyon Power Plant (Unit 2) while thc. unit.was on. ,
line. t
)
3.6 FilYSICAl. ACOUSTICS CORPORN110N ,
Phpical Acoustics Corporation (PAC), of. Princeton, New . Jersey, manufactures -
acoustic leak detection it. truments as well as prosides field test services for leak detection '
survep. PAC has developed a dual channel. acoustic valve leak. detector that has been; used by utilities to detect valve leakage for more than 10 years.t;' "Ihc detector uses acoustic sensors attached to the valve body to determine the acoustic signal levels;us well as frequency content. The output is recorded on an 1-y plotter showing signal amplitude and frequency.
9 l
~
I i
' Product catalogs, ~ "MINAC 1.5, 4/6. PortabicL Linear ' Accelerator Systems," f 4
Schonberg Radiation Corporation Santa Clara, CA.L
- tLetter from Sam Ternowchek, Physical. Acoustics Corporation, to H. D. Haynes -
ORNI.
Subject:
PAC Leak Monitors, dated December 14, 1990.
l
- me i
c uy-3 , y.,~- , , ,,----% ., r+ .- t ,-~ - - -e v e n-. ,w- v- v- r-- -- i, ,e r &w <=.-45.'w
+,- =
)
~. .'.W '
1
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1
- 4. NUCLEAR INDUSTRY CllECK VALVE GROUP 'mST .
d OF CllECK VALVE DIAGNOF11C SYFmMS ,-
Y E s
2 4.1 GENERAL INFORMA'I10N
~
3 l Three commercial supplicts of' _ check valve _ monitoring ' cquipment recently l
j participated in a comprehensive scrics of tests designed to evaluate the capability 4 j
monitoring technology to detect the position, motion, and wear of check valve internals '
2 (e.g., disc, hinge arm, etc.) and valve seat leakage. Dose vendors were Hense.Mov (ultrasonic / acoustic cmission); Uberty Technology Center, Inc. (magnetic / acoustic
) and CANUS Corporation (acoustic emission). . Dose tests, which began,in late January .I i
1990 and were completed in mid. March 1990,3cre directed by the Nuclear Industry Chec Valve Group (NIC) and were carried out at the Utah Water Research Laboratory locat'lj l on the Utah State University campus. .
1 Dis chapter presents a brici discussion of thcsc tests,' including descriptions of thc
! check valves used in the tests, the test conditions used, and selected vendor data. It should j
j be noted that this discussion is based on a limited amount of information primarily from the diagnostic system vendors directly. De results from these tests w described in a final report that will be distributed to' the NIC ' utility members that -
i j participated in the funding of the activity. ' Because of the heavy involvement of~
in those tests, a comprehensive review and assessment of the NIC. test methodologies,~.
j- vendor test data, and NIC conclusions should be carried out by NRC after NIC issues their '
+
I final report. .
Eleven check valves were used in the tests; Table -4.1 indicates their: size, -
i manufacturer, and type. !
Dese tests were carried out using water as the process fluid.1 Check valves were . ;
j initially tested m "new' condition and then with one or more simuisted degradations and/or j
operational failurcs. Several flow conditions (resulting in several check valve operational modes) were also used. De check valve degradations used in the tests are listed hiTable 4.2. Flow conditions and valve operational modes are indicated in Table 4.3.
It is recognized that data analysis and nonintrusive. testing. technology for check l valves are evolving. After the NIC test results are made availabic to NRC, the results of i
liscsc tests should be reviewed; if necessary, an updated report will be issued. ,
l -
4 i 4.2 SELECED "EST RESUL'IS l' illustrates acoustic and magnetic' signatures obtained ~ bye the Figure . 4.1 QUICKCHECK* system for a 12.in. tilting-disc check valve in "new' condition.' ' De-acoustic trace contains a transient (spike) indicative of the impact that occurred when flow J
(through the valve) was shut oli and the valve closed (seated). De magnetic trace shows 1 -
1 1
I
' Letter from D. Manin, Liberty Technok>gy Center, to H. D.' Haynes, ORNL.T i
Subject:
. Mror. Operated Valve' and Check Valve Systems Information, dated March 1, 1990.
I -
40 Tab e 4.1. Check valves testext during the NIC monitoring method evaluation tests Check valve type Ikxly material Siec (in.) hianufacturer .
Swing check Carbon steci 10 Cranc Val.htatic Tilting disc - Carbon steel 12 Velan . Sv.ing check Carbon steel 4
Duo-check (split Carbon stect 10 hiission disc) -
Vebn Swing check- Carbon stect -
10 Tilting disc Carbon stect -
16 Rockwell. :
i Val-hfatic Tilting disc . Carbon stect 24 Carbon stect 24 Atwtal & htorrill Swing check Atwtul & htorrill . Sving check Carbon steel 20 6 Powell Swing check Stainicssitcci 6 Crane. Tilting disc . Carbon steci Table 41 Ched vaive degradations used in abc NIC tests e -Induced seat Icakage e 157c and 30fo hinge pin diameter reduction -
- a. ,,
e 15cc and 30re disc stud diameter reduction -
e Broken spring (for valves having springs) e Disc stuck open e Combinations of the above degradations e hiissing disc
1 41 Table 43. Ilow conditions and valve operational modes used in the NIC tests l
- Zero flow :
f e Backstop tapping with and without cavitation e Two mid. stroke flow conditions ,
e Seat tapping e Simulated pump start and trip e Reverse flow 3 e Maximum flow
- Minimum flow to opec l .. ..w..,a.,,.
3 . _ - _ .
l 3 ,
IMP ACT WHEN VALVE CLOSES d-c.
.w ,
N 5-in 1
i 9 . -l -I
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a O !
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) ___
75*,'. FLOW rg g - \ - NO HINGE '
- f. I- .
WEAR '
I Y \
- z - i
\
! 0 l m i O
P
~
. VALVE SE ATED
[-
E :sVALVE LEAVES '
0 SEAT 5
e i i .i
' TIME Fig. 4.1. QUICKCIIECK" signals for a 12-in.' tiltin'gdisc chock vahe in 'ncW".-
mndition. (Used with the permission of Liberty Technology Center, Inc.)
i i
I
F ,
l l l l ~ 42-i
. {
!- direct indication of dise travel in the closing direction prior to the detected impact. ;.The '
two signals _together thus confirm that the valve closed. When Dow was restored through the valve, the valve opened, as indicated by the~ magnetic tracc. According to Liberty .
Technology Center, Inc., the decreasc in the magnetic signal magnitude, observed when the valve initially hits off its scat, indicates that the valve had .bcen. fully scated prior ~ to . ~
opening. . . .
Figure 4.2 shows acoustic and magnetic traces for the same valve, but using a hinge:
pin with a 3ti'.i reduction in' diameter. . Changes in features were observed in both signals, .
including the absence of a momentary decrease in magt .: tic signal magnitude as the valve opened. nis, according to Liberty Technology Center, Inc., indicates that the valve's disc ' ,
did not fully seat; instead,it hung down past the seat because of the smaller . hinge pin.j As1 the valve opened, acoustic impacts were recorded.which wcre a result of the increased ,
clearances between the hinge arm and the hinge pin. In addition, when the smaller hinge . ~
pin was used, disc flutter was observed to occur when the valve reached its open position. '
as shown by the magnetic traec.
! 1,
. . . . . . ., ..,e ,
3-s 2 :
1 '
l 4
5 2
' LARGER IMPACT DUE i7) , TO 30% HINGE PIN WEAR '-
9
, ;/
$ ___ J .
_.Sa .'
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i -
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3 1 l LARGER FLUTTER D'JE ' 1 l TO 30% HINGE PIN WEAR - ,
9-v> .. .
.r r
o VALVE NEVER SEATS -
G - DISK HANGS DOWN TOO FAR'-
E [' V THEREFORE. DISK IS NOT >
i 0 -
ABLE TO SEAT j 2 'l i i. .i j TIME Fig. 4.2. QUICKCitECK* signals for' a 12-in." tilting-disc check vahe with 3&E , ..,
hinge pin diameter reduction. -(Used with the permission of Liberty Technology Center.1 i inc.)
i 1
...,.. , - - , y-, . , . . . , . - , , , , , , y ,- .e,, , . . . , , , ,,,m., ,y r.. , ..M,,,. , , ,, _ . , y .. - - ~$
- . =- - _ -
r I
43 hat l'igures 43 and 4.4 show the dif ferences in the valve seating acoustic signatur :
occurred as a result of the dilferent hinge pin sites. Figure 4J shows that a single acoustic transient occurred during disc closure when a normal hinge pin was used. Figure 4.4 shows that, when the smaller hinge pin was installed, multiple impacts (resulting in several acoustic signal transients) occurred.
1hese examples further illustrate the complementary information that can he obtained from using both a disc position (in this case magnetic) monitoring method and an-impact (acoustic emission) monitoring method.
~lhe following two examples also illustrate the benefit of acquiring diagnostic data-simultaneously from multiple sensors of the same type-in. this case, accclerometers, mounted at different locations. CANUS Corporation used several aceclcrometers installed on the body of each test valve at severa' .. .:ations -including e Left and right side of the hinge pin.
l e Left and r'ght side of the open stop position (either on the body or 'hc bonnet.
depending on valve type).
e Valve seat.
i 3
e n B .". I g - n
< e 1, o
i < i z _
o i l-u) i o g h~
D _ _
l
- _ .,I NN O .
O I
< t i
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E -
i a===
Y z _
o j 2
05 N-m
~ __
= -!
o
< t l p
' TIME Fig. 43. QUICKCIIECK" signals for a 12-in. tilting #ac _ check vahe in "new" condition-crpanded scale to show scating transient. (Used with the permission of Liberty I
-w * +-w or e e g
. i a
44 .
- i
.0 t 1 e .I 4 T.
s E '- I
't, -
d ,}t i I 5- ,di 5
o f\, 3 i
g -
/ -\ i
\.J m J . .N_- _ -
g a g , ,
~ >
e ha I
f5 E~
'i Y j z -
9 m
9' O~
=
o N.*%.N _ _
i i b -
Fig. 4.4. QUICKCllECK" signals for a 12-in. tilting disc check' valve with 30% l
- - ' ! scale to show acating transient. (Used with the hinge pin diameter reductie -
permission of laberty Technology Center, Inc.)
l Figurc 4.5 shows traces that were obtained from four acccicrometers during one test carried out on a 24 in. tilting disc check valve.' . His test was = mrformed undu full-flow t conditions acconipanied by
- xcd flow turbulence. As shown in the figure, a hard impact '
was detected by the acccicromcict mounted on the left side of the hinge pin'. : A similar .
impact was not indicated by the accelerometer mounted on the right side of the hinge pin.-
Dus. CANUS* interpretation was that the hinge pin was worn. nc hirge pin was,in fact, .
degraded 157c during this test, verifying CANUS'.. prediction. .
Figure 4.6 shows traces from the same four accclerometers' mounted on the same valve, but now operating under full flow conditions with only a small level of turbuleace. :
- Peter Pomaranski CANUS Corporation, ' Preliminary Overview of Findings and Results on Acoustic Emission Nonintrusive' Check Valve Testing-Performed at the Utah-Water Rcscarch Laboratory, tegen. Utah,' presented at the Nuclear industry Check Valvel Group Spring Meeting. April 24.1990.
-v'"-* "
T y ' *- e
'Mr* -F '.'-"Y P *R 7 *'*t- t+'+ + " - * < fa*** 6 ~- -' * ' ' =d * * ' ' ' * - - * *
. _ _ _ _ . ~ _ . ._
l i i on owr.n cos tin Series No. 7c Test No.410 Trace #2 l
100% w! Turbulence Espanded C3 10KHZ !
Date: 22790 Time: DAT 2.07 Sample: 0.7 sec.
l l
h%", ^ ' ,y.;4/$" ,f '. 7 ; '.',"? ,"r 1^^- ^-
d- 1-?._' - -Q . .f-'; *i_'i ^j.7 ",. --j 7
^T OPEN STOP RIGHT i .
I .._,.a. .t. A e _ _ a s. in. L m . _e_ '-I r- .i . . . i.ll .atu LL u m nt..t
- , m ,- , r.-
.. r
- ,,-r m :v ; r,c ,.,, ,pv. , v. , .. . , g%g.ti y;-v._. r m v
- CPEN STOP LEFT HINGE PIN RGHT u
' TAP t.2 A u , _ .n t. 2- m . . . , _ _ w
.* +- m._. .m u 6,t _ A _.m h i i_P. L. a.. _-
7 r is, , r n .. .- r -
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v1 = - 6, y r, 6. - rr HINGE PIN RIGHT g' i '.
3 mmm . - __m.m... _, m- 2 1. , ; .. 1 - . ._ , ha =='w_ m u
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r, _-- ., ,- 1, e -. n, . . , . . .-,.,,,r g,w , .,
j HtNGE PIN LEFT
- - HARD tt.'P ACT HtNGE PIN LEFT . _ ._ _
Fig. 4.5. VIP (CANUS Corporation) acmc*m .4:r traces fmm tcst 410 (24-in.
- tilting-disc check valve, full-Dow medations, induced Gow 'turbulcoce, worn hinge pin).
Sowre: Peter Pomaranski, CANUS Corporation, " Preliminary Overview of Findings and Results on Acoustic Emission Nonintrusive Check Valve Testing-Performed at the Utah Water Research Laboratory. I.ogan, Utah," presented at the Nuclear Industry Check Valve Group Spring Meeting. April 24,1990.
9
- _ _ _ _ _ _ _ _ _ _ _ _ ._- .- + _ m .
4 CHN! CWG 9C 4" E ID Series No. 7d Test No.420 Tape #2Trece #2 100% wJSmall Turbulence Espanded @ 10KHZ Date: 2/27/90 Time: DAT 8:15:17 Sample: 0.7 sec.
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ERRATIC RING
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--- OPEN STOP LEFT - - . . . . HINGE PIN . . . . . _
2 4 Q .i- T j- - .^ 9 "' . _ ;: ,'
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- HINGE PIN LEFT Fig. 4A VIP (CANUS Corporation) arrelcioux..cr traces from test 420 (24_in.
tilting <iisc ch valve, fut-Gow conditions, minimal Dow turt>ulence, worn hinge pin).
- Source: Peter Pomaranski, CANUS Corporation. *Prcliminary Overview of Findings and Results on Acoustic Emission Nonintrusive Check Valve Testing-Performed at the Utah Water Research Laboratory, logan Utah," presented at the Nuclear Industry Check Valve ~-
Group Spring Mc:: ting April 24,1990.-
l i-t r--..-2 e_ _._ m__m__m__. ___m.___ _ _ _ _ _ _ - _.w__ w_ - _ - . - o 44 -s -4 . - - - - - , o ___ -_.__.__ __6
41
*the decreased now tuibulence can clearly be seen by comparing the reduced signal noisc 5
-*1 level in these traces with the much noisier tracca shown in 1ig. 4.5. His Ogure also 5 an impact that was. detected by all acceletorneters; however, the right side hinge pin accelerator detected an erratic ringing pattern rather than tne dear ringing pattern indicated by the left. side hinge pm accelerometer. His feature also led CANUS to predict that the hinge pin was worn. which. in fact, it was.
Figure 4.7 shows ultrasonic signatures, obtained by the CllECKMATE* 11 systeri during the NIC tests, for the same valve under two dill'erent now conditions. As shown in the Ogure, the degree of dise flutter varies with the Dow rate with the' largest llutter occurring at 1295 gal / min. Disc Dutter is quantified in both plots as a measure of the disc angular minement per unit of time (e.g..'at 2251 galimin the flutter is 2.R1 degrees /s, .
whereas at 1295 gal. min, the flutter is 3.65 degrees /s. At 2251 gal / min, the CllECKMA;E il - signal magnitude (.. 2sionally res:ches its maximum value ("f '
apprmimatcly 1435 in.l. indicating that the valve is tapping its backstop. It is noted that the restricted movement of the dise (as a result of tapping) results in a lower overall Hutter magnitude. In this case, the ultrasonic transducer was located on the bottom of the valve; therefore, the largest signal was produced when the dise was at the open position (at the position furthest from the transducer).
liigure 4.8 illustrates that Clil!CKMATE'" 11 can b: used to track the' motion of a check vahe disc (e.g.. ia this case, the disc of a 12.!n. Val.Matie tilting-disc check valve) from the full.open to full. closed position. In contrast to I'ig. 4.7, the ultrasonic transducer ,
was located on top of the vahe; therefore, the largest signal was produced when the disc
<..i,..',......
! Hi Ca 84 A ff
- g o rf . pin.s t uf*C 3Jiut MI
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Id 3 *' '
h! f , ,
- .r M *nate i p 5 u as as esma t }
- 4 1;' ]
sl * * .e ; e '..a
- c i
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. v i . ...
~
.i 1L I *a l / 8,ti . S ttS 1.* ,E 1's '.e c s O"C 0 i:*
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fg ,f ~{
9q, *
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) n ]
- au.
n yi p ;ny , .
. .o o.
c ..,e
't r i. o., we ,r,e so.c
.j t 'sw
. ,,n,e,,,,,,.,
" *:* Uc : is / e4 i s: 4' s,es 9' m. ~ / o.. / 19 sce.s I;g. 4.7. Two ultraumic signatures, obtained using the CIlliCKMA*IT* 11 system . '
for the same valve (10.in. Velan swing check) under different flow conditions: 2251 gal / min (top tracc) and 1295 gal / min (hottom trace). (Used with the permission of IIcnze.Movats, Inc.)
i
..-. . _ m.. .. _. _ . .. ..
4N ,
... v. . 4 e s es C. 8 s es A *(
- a . t . .e - c
, ,y at ,*e . . A i.1 .
,. , . . . ..-.3_
. .t . e l4 I 1l JJae . .
,,,s,.,,,%_, , ..
,,, 9,,,_,g 1 I Ut L ( l O SI l' 1i , vgoo *.ame ,.
10 811s l ** * "' "
- N - .
. i , sm . . . l 10 300* l t n l.
9 791, a i.
e i
i
- [ l
., . c, !
'i' e 7e . 1' s
'l.
a 8 .!a d * .l-.-
4
.4
- 7. //s /
l
" A FULL OPEN
~
0 d~72J 55 f El .[ 91 6 14 1 Jb - Sets .
1
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Fig. 4.8. A CIIECKMA11*. D signature for a 12.in. Val-Matic tilting <lisc check j
valve) from the fullopen to full-closed positions.. (Used with the permission of Henac.
Movats. Inc.)
was at the closed position. It is recognizeds however, that la single ultrasonic transducer i (instal:cd at a fixed location) may not provide valve' disc position information over the ful!
trr. ; of the disc of some valves because of valve gwm :try and the limited, viewing angle , ,,
of the transducer.
Finally, Fig. 4.9 illustrates that 'a stuck check valve disc can be detected simply by comparing the CHF.CKMATE" 11 signatur; obtained at no flow to a CHECKMATE" 11 signature obtained at a significant flow rate.
I t' gf
- 49 a, i ..-,: uis I m Ca st t*xin a 11 8.e.
- t m a' e '. 6 4".s t u"* l'l u t l%)
valve M
.a e #! va e*K L7* f 9
, y, ,
1 te m .. .. . . . .
am SM stunt asun it 4Wupt
- frece Name.
.' % 101- .....s.
y P te1 0 < PS
- ~ ~ ~
i.
0 000 - - . ~
,a* a s* -- '1 e ,e' ~ ~ ~ 4- '41
- ^ ^ ~ ~
'i 14 *~~~~*~~~~~'"se'.s.
I h oa t,,
. . .-.~
valve 10 vaLW #f w it' f 9
. . - - . p, ,
/ 71,* p . .
e 8 se ens eq=st assa et ougs se 1eace Name
. - 5 161 < n .. m 2.
2.5Rt< l 2M2 assa -
7.16 Sec9 0 0000.00 ---.-----45 3 65 6.14 t PJ 2 4 91 Fig. 4.9. OECGA*m" 11 signature for a 12.in. Val-Matic tiltingdisc check vahe having a stuck disc. The top trece was obtained at no. flow conditions, while the bottom trace was obtained at 2392 gal / min (more than would be sulTicient to move the -
disc). (Used with the permission of flcrize.Movats, Inc.)
i ,
i .
51 1
4
' ^
- 5.
SUMMARY
AND RECOMMENC'A110NS i
The pie.. iry objective cf the NPAR Program Phee 11 check valve aging assessment
- is to kjentify and commend methods of inspection, surveillance, and monitoring that.will j provide timely detection of check valve degradation and service wear (aging) so that
- maintenante or replacement can be performed prior .to loss of safety function (s). In ..
l support of the NPAR Program, ORNL has evaluated several developmental and/or
- commercia
- l> available check vatve diagnostic monitoring methods. In each case, the
- cvalu t'ons , haw: heen focused on the capability of eac'i method to provide diagnostic j information useful in determining check vahe aging and service wear effecta (degradation), -
check vahe failures, and undesirabic operating modes. Of those methods csamined.
acomtec emiukm momtoring, ultrasonic inspection, and magnetic flux signature analysi: -
1 provided the greatest icvel of diagmstic informatkm. These threc methods were shown to i he scful m determining check vahe condition (e.g., disc position, disc motion, and seat j leakage), ahnough r.one of the methods was, by itscif, successful in monitoring all three
- condition indicators flowever, the combinatkm of acoustic emission with either ultrasonic j or magnet c flus mimitoring yic'ds a monitosing system that succeeds in providing the
- semitinty in detect all mapr check volve operating comlitions. When monitoring check j vahts wing either of.tha combinatkms, it is not necessary to apply both methods j simultancomly in order to achieve . t
- sc combined . capabilitics of the two methods.
~
Commere:41 versions of all three r cthods arc still under development, and all should
{ imprms as a result of further testing and evaluation. . . ..
i The NIC test ;toduced a large wilume of scrut check valve diagnostic ~ data from i three commercial spicms; however, rx iest data werc .vailable (from NIC) for our review j prior to tM preparat on of this report. 'Became of the significance et the data obtalacd j and its impact o*i determining operatonal readinesa of nuclear plant check valves, it is i recommended that a . comprehemtvc review and anacssment of the. -NIC test l j results-<ncluding NIC test methodologks,' vendor test data, and NiC conclusions--be !
carried out ly NRC after NIC inves. its final report. In addition, any inues not addtcased j j
i j adequate)v by the NIC tests and decraed important in regard to safety.rclated issucs should
- be considered for further study.
i
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i
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i i
4 I
4 s
i ..
53 REIERENCES ,
I. U.S. Nuclear Regulatory Commiuion, Nuclear Plant Ag&sg Researth (NPAR) Progmm Plan: Components, Systems and Structures. USNRC Report NUREG 1144 Rev.1.
September IW7. Availabic for purchase from National Technical Information Service, SpringGeld, Virginia 22161.
- 2. MPR Associates, Inc., and Kalsi Engineering. Inc., Application Guidelines for Check Vah es in Nuc/ car Power Plants Electric Power Research Institue, Inc., Report NP 5479, January 1988. ' Available for purchase frcm Research Reports Center (RRC), Box
.W'm, Prio Alto, California 943nt
- 3. %. L Greemtreet, G. A. Murphy, R. B. Gallaher, and D. M.' Eissenberg, Martin Maricita Energy Spicms. Inc., Oak Ridge Natt. La' Aging and Service Wear of Check Vahes Used m Engineered Safety.Featurr Systenu of Nuclear Ponsr Plants, USNRC '
Available for Report NUREG/CR 4302, Vol.1 (ORNL-6193NI). December 1985.
purchase from National Technical information Service SpringGeld. Virginia 22161.
- 4. U.S. Nuclear Regulatory Commission, L4m of Power and Water Hammer Eient at San onofer Unis.1, on November 21,19#5, USNRC Report NUREG.1190, January 1986.
Awlable from National Technical Information Service. Springficid. Virginia 22161,
- 5. L:: ct from Stesen A. Varga. NRC, to All *dolders of Light Water Reactor Operating lacemcs ' and Comtruction Permits.
Subject:
. Guidance on Developing Acceptable-Imcr*c Testing Programs (Generic Letter No. 89 04), dated April 3,1989. Availabic :
in NRC Public Document Room for impection and copying for a fee. I
- 6. J. G. Dimmick and J. M. Cobb. "Ultraumic Leak Detection Cuts Valve Maintenance Oan.* Power Engineering 9(R), ?5 ( August 19H6). - Available in public technical librarics.
I 1
l l
i l
_. _ _ _. - _ . _. . .~. . _ _ _. _ __ . __
3
- j. O!
1 l 55. ,
O i,
! Appendia A:- ;
5 REGUIAMRY 1EST REQUIREMENTS AND CURRENT *IEST MEntODS 4
i REGULAWRY TEST REQUIREMEN11i There are three distinct regulatory requirements related to check valves. 'These are .
-l j the in.scrvice testing (IST) requirements, containment isolation valve leak test requirements, ,
j and reactor coolant pressure boundary isolation valve leak tcat requirements.-
4 l In4crvice Tcsting Requircascots '
x . '
N .
I Plant Technical Specifications, which invoke the authority of to CFR Part 50.55a,-
require that pumps and valves be tested in accordance with Sect. XI of the 'ASME Code.
l The scope of valves to be included in the IS".* program'is defined in Article.IWV 1000 of- :
l Sect. XI to include valves *. . which arc reqc; red to perform a specific function in shutting .
i down a reactor to the cold shutdown cr,1dition er in mitigating the consequences of an:
i accident." .
Valves are categor' zed by function and functional requirements in Article IWV 2000.' :'
j .
j All check valves fit in Category C ~ valves which arc scil. actuating in response to some '
} system characteristic, such as pressure (rctici valves) or flow direction (check' valves).* + In -
addition, some check valves may be defined as Category A' valves
- valves for which seat- :
I i leak:;;r is limited to a specific maximum amount in the closed position of fulfillment ofu '
their function." . . . .
j Article IWV.3000 of Sect. XI provides test requirements for valves in general,:and i Article IWV 3520 specifically identifies' those requirements that are particular to check:
valves. In essence, check valves are required to be demonstrated to be ahic to move to l their safety.rclated position when system conditions so warrant.: Testing is required to be -
performed quarterly; however, valves that cannot be tested. quarterly are to be'. tested 'at ~
, cold shutdown. Each plant must submit a test program to the NRC which designates valves . :
that are to be tested in accordance with the cmc and which identifies exceptions to Code requirements. .
j Containment Isolation Valve Leak Tcsting Requirescota -
k Plant Technical Specifications also invoke the authority of 10 CFR 50,- Appendia J, l
and require that containment isolation valves that are ' subject to
- Type.C". (not to be confused with
- Category C' valves identified in the 'ASME Code) _ tests be leak tested
! biennially. De valves that are specified in Appendix J arc *. . those that:
1
- 1. Provide a direct connection between the inside and outside atmospheres of the primary l
reactor containment under normal operation, such as purge and . ventilation, vacuum -
l
- relief, and instrument valves; l 2. Arc required to close automatically upon rcccipt of a containment isolation signal in response to controls intended to effect containment isolation;.
- 3. Are required to operate intermittently under postaccident conditions! and j'
i-a
- . . _ _ . _ . . . . ~ . . . _ . _ . _ _ _ . _ , ..._.. ,_ -... . , _ ...-,_.- .,....,~. ,
i-i 56 3
e .
1
- 4. Arc in main steam and Icedwater piping and other systems which penetrate containment . ~
i .
of direct. cycle boiling water powc: rewetors."
a De specific containment isolation valves that are actually " Type C' leak tested are l l normally identified in the individual plant's Final Safety Analysis Report. i j
i !
Reactor Coolant Pressure >=tary isolathm Valve Testing Requirements q l -
a ~
%nt Technical Specifications require that' ccrimin valves that provide isolation ,
between the reactor coolant system (RCS) and connected kiw. pressure systems. (e.g., the - j residual heat removal system) be leak tested periodically. The test' intervals are variable, i
j depending upon plant and valve operation conditions, but testing is rcquired pt least onc .
.j i
per refueling outage. De maximum allowable leakage rate- for each RCS pressure - ,
boundary isolation valve is specifically designated in the Technical Specifications.1 i 1 Dere is overlap between tocac three test requirement' sources. For example, since :
l l containment isolation valves are needed in mitigating the consequences ofan accident,~ ~
j they would fall under the auspices of both the 10 CFR 50, Appendix J, requirements an i :l the IST requirements. In' general, the IST requirements cover the broad range of check L l valves to be tested, while the containment isolation and RCS pressure boundary isolation
- valve leak tests apply specific limits to select valves.i l t
j l.
4 '
j CURRENT TEST MET 1tODS 1
Utilitics write and impicment procedures to meet 'the. regulatory requirements - l 1 .
associated with i. heck valves. The procedure used to verify a particular valve's operability .
l may range from a simple test requiring little or no test setup or data analysis, to's com;:!cs L 1 )
test evolution involving systein realignment, partial draining, application of special testing -
l ,l equipment, post. test filling, venting, and realignment, and considerable data analysis.
~ -'
l i
Depending upon what function is to be demonstrated (e.g., closing or opening on L demand or seat leakage less than allowabic), a number of r.onditions arc monitored to- j indicate valve functionability. %csc include, for example,.
l ..
- a. Measuring the seat leak rate. .
f b. Observing upstream temperature (as is .donc routincly, for exampic,in the' case of j
auxiliary feedwater check valves). .
{ 1 j c. Verifying that the required flow rate can be passed through the ' valve.
j d. Observing reverse pressure differential.
j c. Listening for the valve to slam shut on cessation of Dow.
Observing that the valve is sulticiently' closed to ensure that the rate of 16w delivered :
j f.
downstream of the valve to a given t*rget is' adequate to meet system demands.
j ~
~
For check valves that are required to transfer from ' closed to open' to satisfy their safety.rclated function, testing is conducted by passing the required flow rate through the i i volve, when practicable. De NRC has historically accepted full-Gow testing as evidence that the valve has been full. stroked (it is recognized, however, that in some applications,- ti
} ;l valves may not fully open, even undct' maximum system flow). Valves thatare required to
{ 1 4
1 1
~
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1
- _ .. . . . _ - . . _ . _ _ . . . _ _ ~ _ . _ . _ . . . . _ _ _ . _ _ _ _ _u. u__
- c. ,
' 57 1 l
i
! transfer from open to closed are normally tested by applying a reverse pressure differential l
! and observing some system parameter for ir.Jication of ekmure. "
~l '
l Typically, a relatively small fraction of the. check valves used in' safety.rci.ated l D applications are leak tested to determine a quantitativc' leak rateJ ORNL conducted'ai ;
i sampic review of the IST programs' for four units. . Included inJthcL review were two- !
i pressurized water reactor units and two' boiling water reactor units.;There was a total of - .
466 check valves at the four units.. . Only 118 of these valves were identified as ASME ,
l
- Category A valves, that is
- valves for which scat leakage is limited to a specific maximum; 'l
' amount _in the chised position of fulfiltment of their function.UAll 118 valves that were l
~
'l
}- designated to be seat leak tested arc tested under the suspices ~of cither 'he t containment ;
! isolation valve or the RCS pressure boundary isolation valve leak testing programs, with no ; ~
l additional leak testing specifically for IST purpses.l Ooantitative seat lcakage testin9 ;
i conducted by pressurizing the downstrear side of the valve with 4 test pressure source (e.g., = 4 1 i instrument air 'or a compatible water source.fincluding, in 'some - cases. the. existing ; 9 t
j downstream pressurc) and observing the leak rate by opening an upstream connection. . ~
- It should be noted that the safety.rclated function of somc valves that are not1
- quantitatively leak: tested involves only allowing forward. flow; neverthcicas,' a significant ! l
! number of valves for which thc' safety.rclated function includes closing in response to l i
reverse differential presure are not designated as requiring leak testing. his includesi .;
3 valves such as safety.rclated pump discharge check valves.. ..
4 Seat leakage for valves in applications where quantitative leak rate is not required to be measured but where the valve must still be demonstrated _ to close in response to -
~
reverse differential pressure is typically addressed in a qualitative manner.- For exampic, the - l pressure differential across a pump discharge check valve may be observed while' the pump is idle and a'paralici pump is being run' (or the downstream section of the ' check ' valve's . [
piping is otherwise pressuriacd). 'Al_tcrnatively, the adequate functioning of a valve,in terms of scating, may be demonstrated by verifying that the required flow rate is delivered through-i the demand flow path (therdy proving that' the ' valve in_
z question ,provided sufficient , :
isolation). ~L ..
1 In'the event that the required testing is not practicabic during normal operation, the 1 valve may be partially tested during normal oneration (c.g., t y passing a flow rate that is something less than that required to satisfy the safety function) and then tested'st the : ;
required flow rate during cold shutdown or refueling. It should he noted that some valvesL 1 cannut be cven partially tested during normal operation because of the adverse'cffect that: I test conduct would have on the plant. 'l 3
It is important to note that the current tcst requirements' arc not oriented toward '
trending or detection of conditions that may lead to valve failure. Disk flutter.due to .
operation under turbulent conditions'with thc valve not_in a' fully open position (pinned.
against the backstop, for exampic)'has been recognized as a cause of, wear at the hinge pin pivot area. Substantial hinge pin or pin' holder wear can' occur without being detected - I by current monitoring. Other degradation' mechanisms,Lauch as disk pin wear,' may also not - i be detected. Even catastrophic failure can go undctocted for valves in certain applications (e.g., a check salve that is forward !)ow tested only may pass'its flow test with the'~ disk having broken off and fallen to the bottom of the valve body or traveled downstream).' Inh addition' to the inability to detect some degradation / failure sources by.use of historical; monitoring methods, it is important to recognize that in some system' designs / applications,-
it is simply not feasibic, because.of inadequate testability provisions in the system design,L to conduct testinr, at the required condithms at any time. :
h
, em %, m-,4,,,,w.-.my..,,--r ,w-~ -.m.w.,- w,, .v.,+. . -._,,,+m. 4ww..-,-.,...,m - . e- . -w m .4 *e -<~m- -
, r
~58 .l In recognition of the weaknesses in historical monitoring capabilitics and the Edi!ity to test certain valves, utilitics'have undertaken, at the urging of both the NRC and INPO,-
t periodic disassembly and inspection. Disassembly and inspection has normally been used > >
on a sampic basis-that is,. a representative valve' of a ' group' of valves of similar - 'j design / application is disassembled during a refueling outage. During the following outage, . '
another in the group is inspected, and so on,' until the entire group has been inspected. i Typically,' group sia: and sampling rates arc such that all valves m a group.are mspected- '
within 4 to 6 year . ,
While disassembly and inspcction provide better information abSut valve ' condition -
in many respects than can be obtained through any other available method, there~are a .;
number of drawbacks associated with disassembly.' Dcsc include, for casmpic scheduling . '
additional maintenance work during airc ; busy outager, additional radiological burdca, as well as can'ccrns that reassembly crrors can go undetected (for valves that cannot be tested with flow). .! l De need to improve the knowledge of check' valve operating conditions without .
requiring disassembly has resulted in the development and improvement of several
- nonintrusive diagnostic techniques. It is important~ to re,ognize, however,'that for those '
applications in which the utility has determined that current system configuration does not- i permit valve stroking, neither the historical nor the newer techniques are able to conGrm - '
valve operability.
I i,
I' 4
1 2
i l
1 l
I i
59 -
J NUREG/CR-4302 v olume 2 ORN16193/V2 Dist. Category RV Internal Distribution -
- 1. J. M. Asher 52. R. C. Kryter
- 2. h. l Diddle, Sr. 53. K. II, Luk
- 3. S. H. Buechler 54. J. C. Moyers
- 4. D. A. Casada 55. G. A. Murphy
- 5. D. F. Cox $6. C. E Pugh 6 16. D. M. Eissenberg 57. ORNL Patent Omcc
- 17. E C. Fox 58. Central Research Library
- 18. R. H. Greene 59. Document Reference Section i 19-49 11. D. Ilaynes 60-61. Laboratory Records Dept.
- 50. D. E llendrit 62. Laboratory Records (RC)
- 51. J. E Jones Jr.
External Distribution
- 63. G. Sliier, Electric Power Research Institute, P.O.10412, Palo Alto, CA 94303
- 64. J. W. Tills. Institute for Nuclear Power Operations,1100 Circic 75 Parkway, Atlanta, GA 30339 3064
- 65. J.11. Taylor, Brmkhaven National Laboratory, Bldg.130, Upton, NY 11973
- 66. A. B. Johnson, Battelle-PNL, MS P8-10. P. O. Box 999. Richland, WA 99352
- 67. Brian Stewart,557 South Walnut, Apt #8, Cookeville, TN 38501.
- 68. J. P. Vora, U.S. Nuclear Regulatory Commission, .Omcc of Nuclear Regulatory l Research. Electrical and Mechanical Er:gineeriag Branch, 5650 Nicholson Lane, Rockville. MD 20852
- 69. G. II. Weidenhamer, U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Rescarch, Electrical and Mechanical Fngineering Branch,5650 Nicholson Lane. Rockville. MD 20352 -*
- 70. E J. Brown, U.S. Nuclear Regulatory Commission, Omcc for Analysis and Evaluation of Operational Data, Reactor Operations Analysis Branch, Maryland National Bank Building,7735 Old Georgetown Road, Bethesda, MD 20814
- 71. C. Michcison, Advisory Committee on Reactor Safeguards,20 Argonne Plaza. Suite 365. Oak Ridge TN 37830
- 72. M. Vagins, U.S. Nucicar Regulatory Commission, Omcc of Nuclear Regulatory Research, Chief. Electrical and Mechanical Enginccring Branch, Division of Engineering. 5650 Nicholson Lanc, Rockville, MD 20852
- 73. W. S. Farmer, U.S. Nuclear Regulatory Commission, Omcc of Nuclear Regulatory Research, Electrical and Mechnical Engineering Branch. 5650 Nicholson Lanc, Rockville, MD 20852
- 74. M. J. Jacobus, Sandia National Laboratories, P.O. Box 5800, Division 6447, Albuquerque, NM 87185
j . - (&
' 75. II. L. Magleby. Idaho National Engineering Laboratory, MS 240ti. P.O. Box'!625, Idaho Falls, ID 83415
- 76. Joseph N. Nadeau,Ill!NZE.MOVNIS. Inc.,200 Chastain Center Blvd., Kennesaw, GAL ' '
30144
- 77. Richard 11. Tult, l.iberty Technologies. Inc.. . Lee . Park,11tK) E licetor Street, Conshohocken. PA 19428
- 78. Peter Pomaranski. Canus Corporation. 23030 Lake Forest Drive, Laguna Hills, CA 92653
- 79. W. M. Suslick, Dukc Power _ Company, McGuire Nuclear Station, P.O. Box '488, Cornelius NC 28031
- 80. John W. McElroy, Philadelphia Electric Company, Testing & laboratories Division..
P.O. Box 650, Valley Forge, PA 19482
- 81. Richard J. Colsher EPRI M&D Center,3 Industrial Ilighway, Eddystone, PA- 19013 ,
- 82. Ron D. Endicott, Public Service Electric and Gas, P.O. Box 570, Newark, NJ 07101. !
- 83. Richard G. Simmons Tennessec Valley Authority,1101 Market Strcct, BR SS73A.C. .
Chattanooga. TN 3tM02 2H01
- 84. Michat.1 T Robinson, Baltimora Gas &' Electric Company, Routes 2.& 4. Lusby, MD : ~!
20657
- 85. Bob Parry,- Public Service of New Hampshire P.O. Box 300, Scabrook Station, '
Scabrook, Nil 03874 -
- 86. T. F. Iloyle, WPPSS Mail Drop 520.3000 George Washington Way, P.O. Box 968, ,
l Richland, WA 99352 l
l
- 87. Office of Assistant Manager for Energy Research and Development Department of ' ,
Energy, Oak Ridge Operations Office, Oak Ridge,TN 37831 88 89. OfGce of Scientinc and Technical Information. P.O. Box 62, Oak Ridge, TN 37831.90-419. Given distribution as shown in NRC category RV (10 - NTIS) e
+ -w * , -
i-t- e r- , --s., ,w, .,m
l
!j ,)
ren..in u s Nuctian ascutatoav coess o* ' yjg,*.1,siy , i,a, y m: .,, - -~ -,, . .
ns . .3 BIBLIOGRAPHIC DATA SHEET - . NUREG/r't-4302. Vol . 2 <
.s........a,....... ORNI.-6193/V2 J f eist a*.y ket.t s 3 Daf t a:Pont PUBLisalo Aging and Service Wear of Check Valve.s .3.. q .....
Used in Engineered Safety. Feature Systems - Apr11: 1991 of Nuclear Power Planist Aging Assessments: , , , , o , c . ,, ,,ys., g .
and Monitoring Method Evaluatioru 80828
% a vtwomis' 6 igrt os atron,
. Topical l Il. D. II.iynes P4 aioo co eio. n a. . l d
m
. ,i a . o... c o c a s z . i m . 4v t as o ao o a t ss . ..e r-- o-~~~~ .w- i s a- ~ ~ ~ <- .-t --- -~ ."-~- ~.+
- . - . . ~ . .
Oak Ridge Nat'mnal Laboratory ,
Oak Ridge,'IH 37M31-6285 j b.
, spo.us. cam.e onc,asitav.o . vt . o aoc=iss .....c ..,. s . .. . . . . c .w - . . . s - . c.~
~ ,
Division of Engineering -:
Office of Nucicar Regulatory Research )
. U. S. Nuclear Regulatory Commission j Washington DC 20555 10 sue ttastNtaa, .sof t s ,
l 1
- 19. a$s? R ACT N00s m .w.
Check valves are used extensively in nuclear power plant safety systems and balance-of plant systems.iThe '
failurcs of these valven'have resulted la significant maintennoce efforts and, on occasion have rosulted in water hammer. . .
overpressurization of low-pressure systems, and damage to flow system components.f Thcac failures have largely been ' i attributed to severe degradation of internal parts (e.g., hinge pins, hinge arms, disa, and disc not pins) resulting from -
instability (flutter) or check valve disa under normal plant operating conditions.' Present surveillance requirements for nuclear power plant check valves have bcen inadcquate for timely detection and trending of such degradation because, neither the flutter not the resulting wear can be detected prict to failure. Consequently, the U.S. Nuckar Regulatory Commission has had a continuing strong interest in resolving check valve probleens. . .
In support of the Nuclear Plant Aging Research Program. Oak Ridge National Laboratory has carried out an '
evaluation of several developmental and/or commercially available check valve diagnostic monitoring methods, in:
particular, thoac based on measurements of scoustic emission, ultrasonics, and magnetic flux.JIn each case, thec evaluations have been focused on the capability of each method to provide diagnostic information usefulin determining -
check valve aging and service wear effects (degradation), check valve failures,' and undesirable operating modes.
A description of each monitoring method is provided in this report, including examples of test data acquired.
under controlled lahoratory conditions. In some cases, field test data saguired in situ are also presented.- The methods are compared, and kuenested areas in need of further devekmment are identified.
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