ML20101U314
| ML20101U314 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 01/31/1985 |
| From: | Wood C CLEVELAND ELECTRIC ILLUMINATING CO., SOUTHWEST RESEARCH INSTITUTE |
| To: | |
| Shared Package | |
| ML20101U246 | List: |
| References | |
| OL, NUDOCS 8502070246 | |
| Download: ML20101U314 (91) | |
Text
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n January 31, g TED UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION 85 FEB ~6 p4:h BEFORE THE ATOMIC SAFETY AND LICENSING BOARA ,,,,
N' ST ?
In the Matter of. )
)
THE CLEVELAND ELECTRIC ) Docket Nos. 50-440 ILLUMINATING COMPANY, ET AL. ) 50-441
)
(Perry Nuclear Power Plant, )
Units 1 and 2) ) .
STATE OF TEXAS. )
) ss:
-COUNTY OF BEXAR )
' AFFIDAVIT OF. CHARLES D. WOOD III
- I, Charles D. WoodIII,beingdukysworn, state as fol-lows:
-1. I am the Vice-President of the Engines, Emissions, and Vehicle'Research Division of Southwest Research-Institute.
'(SwRI), a position-I have held sint:e December.of 1983.
My busines's address.is Southwest Research Institute, P. O.
-Drawer 28510, San Antonio,. Texas _78284.
-8502070246 850205 PDR 0 ADOCK 05000440 7 PDR _u
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- 2. I am directly and personally involved with diesel en-gine research, design, and testing at SwRI, and supervise our diesel engine research staff. My experience with diesel en-
.gines ranges from high speed automotive diesels to medium speed railroad and ship diesels. Two twelve-cylinder railroad diesel
. engines and two two-cylinder electromotive diesel engines are-ir stalled at SwRI . These engines are operated by my Division Lfor var.'ous engine research programs, and the experience gained from working with these four engines is transferrable to the -
TDI engines.
- 3. I have overseen the design review work conducted for Cleveland Electric Illuminating Company ("CEI") on the. sixteen
, Phase I components-identified in the Owners Group Program. I
.have visited the Perry Nuclear Power Plant ("PNPP") and ob- '
served the.Transamerica Delaval, Inc.-("TDI") engine installa-- ,
'tions.
I;have personal knowledge of each of the matters set Jforth herein, and believe them to be 'true and correct.
(- f4. I have-been employed by SwRI-since 1962. -I joined
'the company as a Senior Research Engineer in the Automotive Re- o search Department. -I later acted as Section~ Manager for the Department and in'1974 became the Director of the SwRI Depart-g-
~ ment:of Engine and Vehicle Research. Prior'to my work-at SwRI,
-I was employed as.a. test. engineer and,-subsequently, as a.
propulsion engineer at' Ling-Temco-Vought, Inc.
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I have a Bachelor of Science degree as well as a Mas-I terio'f' Science degree'in mechanical engineering.
I t, a member
'of'both'the SAE and the Texas Society of. Professional Engi-neers.; 1 I am a registered professional engineer in the SL te of A statement of my professional qualificat' ions, which
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ITexas.t if includes a listing of my publications and patents I am associ-nated'with, is attached hereto as Exhibit A.
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I. THE OWNERS GROUP PROGRAM PLAN
'6. The TDI Diesel Generator Owners Group Program was
,; . developed to assess _the adequacy of the various TDI engine de-
'~ sign configurations to perform their intended safety-relsted-fu'nctions. 'The. Program involves three_ major elements, which,
~
'by a combined approach-involving design reviews and analyses of-
_ engine components, quality revalidations'of important p attributes', and expanded enginestesting and. component inspec-
$tions,bwillprovidereasonable: assurance 1of-the.abilityofthe
-TDI engines to provide reliable backup power supplies for nu-
~
c1 ear power plant' service. The first ' maj or _ program - element,-
- characterized as Phase-I,-involves the' resolution of poten-
.[ ~tially.genericLknown. problems. -Based on' operational experience- '
- data pertinent to the TDI engines, thel Owners. Group determined-
~
- that'a limited' number of components ^ warranted prioritization
'and consideration as significant: problems'with potentially generic' applicability. -See Affidavit of-John'C. Kammeyer.
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- 7. .The Owners Group prepared task descriptions specifyingjthe analysis and evaluation to be conducted for each Lof these components. This work was completed by Owners Group
. consultants. Final reports have been completed covering each component.
II. OVERVIEW OF SwRI'S ROLE 82 SwRI has reviewed the TDI Diesel Generator Owners Group' Program reports and backup material on the sixteen Phase-I components with regard to their applicability to the PNPP diesel engines. This task was defined by three subtasks requiring review and critique of: (1) the component criticality definition as provided by the Owners Group; (2) the component.
function and attributes as defined by;the Owners Group; and
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-(3) the assumptions, methodologies, codes and standards, re-
- sults, conclusions, and recommendations in the Owners Group re-ports.
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- 9. Staff. members chosen to conduct the reviews were se-
-lected for their experience in the' required disciplines such as engine design and testing, metallurgy, stress analysis, frac-tureJmechanics, and finite. element modeling. Where:necessary, copies lof supporting. materials, such as: calculations, metallur-gical-reports, etc., were also obtained. ;Three of SwRI's staff visited the Owners Group offices in Charlotte,-North Carolina'.
6 (whereLsupporting material and engine drawings were reviewed.
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- 10. Each of the Owners Group reports was reviewed to as-
_ sess the'overall methodology applied, the assumptions and parameters.used, the analytical approaches applied, accuracy of .
analysis,'the. conclusions-derived, and finally, the recommenda- .
- tions made. In some instances,'SwRI made independent calcula-
<tionsiusing different equations, different assumptions, and/or-different parameters.
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' 11. The_following_ discussion concerning each of the com-ponents' reviewed compares SwRI's results, conclusions, and rec-4 'ommendations with those of.the' Owners Group. It incluces:
-(l) the component; function and its critical attributes; (2) its failure history; (3)_a review of the Owners Group and SwRI 4 imethodology,xand a discussion of any differences; (4).a disc'us- ,
l sion"of>any. testing; and (5) a review of the Owners Group and LSwRIrresul's,. t conclusions,-and recommendations,;and a discus--
-s'ionlof any differences.
' ~
III. SwRI REVIEW OF I THE PHASE I COMPONENTS-Rocker-Arm CapscrewL
, A.
.'5 L - 12 1 5The rocker arm:capscrews-infTDI. standby _ diesel gener -
-ators: transmit resultant loads':.fromithe valve-springs,.3 valve
- ~
.: opening pressure,:pushrods, and rocker arm assemblies.to the
< 'subcover;and' cylinder. heads.- In formulating-the. design review.
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~ task description for this component, the Owners Group deter-mined that the critical functional attribute of the rocker arm capscrews was that they have sufficent strength to withstand j preload and oscillation loads without fatigue cracking, unacceptable preload relaxation, or thread distortion.
- 13. The rocker arm capscrews were included among the sixteen Phase I components due to isolated failures resulting from-insufficient preload application in TDI nuclear standby
' diesel engines. Two rocker arm capscrew designs were evaluated byfthe TDI Owners Group, the original " straight shank" type capscrew and a modified " necked shank" design. -
- 14. -A stress analysis was performed for both of the rocker. arm capscrew designs by the Owners Group.1/ The analy-sis included a determination of the_ applied stress and the en--
durance limits of the'two designs, a~ fatigue life analysis, a
- thread distortion analysis, and a thermal stress evaluation.
- 15. _ Satisfactory. fatigue life has been demonstrated ~by several engines'with more than 750 hours0.00868 days <br />0.208 hours <br />0.00124 weeks <br />2.85375e-4 months <br /> (10 7 cycles) of operation. This operational history verifies that'fatigud' failures:willinot be a problem.-
1/ A detaildd' discussion of the. analysis performed is includ-ed-in Stone & Webster Engineering-Corporation, " Emergency Die-sel Generator Rocker Arm Capscrew Stress Analysis,": March, 1984
{and its Supplement,LApril; 1984,z both prepared for the~ Owners Group. -
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- 16. SwRI. reviewed the Owners Group report on rocker arm capscrews ,to verify its applicability to the " straight shank" capscrews in place at PNPP. Design parameters used by SWRI were in agreement with those used by the Owners Group. Certain .
LassumptionsLmade by SwRI in reviewing the design analysis were,
-in general, more conservative than those used by the Owners Group. These assumptions concerned the: 1) modifying factors e
used to calculate the endurance limit (OG: 8.7 ksi, SwRI: 8.6 ksi)'; 2); intake valve spring damper force (OG: 0.0, SwRI: 121 a
lbf./in.); and 3) percent of torque contributing to torsional
' stress ~(OG: 75%, SwRI: 50%).
- 17. SWRI performed a number of analyses on both the orig-inal and modified designs to evaluate their respective u
attributes. The maximum cyclic loading on the capscrews was
+
calculated to be 10,271 lbs. The adequacy.of the capscrews.to
~
' withstand.this loading was determined using a series of stan-3.; dard engineering calculations culminating with the use of the modified Goodman line failure criteria to consider both.mean (original-design: 43.2 ksi, modified design: 42.5:ksi') and-alternating-(original design 2.73 ksi; modified design: 2.02 ksi)lstresses. The-maximum biaxial stresses were1 calculated'
, i for the - capscrews during tightening -to the' specified torque-1(365 lbf.-ft). 'The principal stresses were compared to:the-
~ failure criteria of the distortion energy theory. Analyses n
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-were-also conducted to determine performance under thermal m-stresses,.whether creep would result in loss of preload or capscrew failure, if thread stripping in the subcover was like-ly, and the impact on the capscrew if the preload is lost.
>- These analyses, conducted by SwRI, were to confirm the critical
- functional attributes, namely, that the studs have sufficient strength to withstand preload and cyclic loads without fatigue f'ailure,'and that neither loss of preload nor thread distortion would occur.
- 18. No significant differences between the results obtained in-the Owners Group analysis and those of SwRI were
- observed. There was a difference in the calculated cyclic load on the.capscrews'(OG: 8.3~ksi, SwRI: 10.3.ksi) and the calcu-lated fatigue life safety factors for both the original (OG:
4
-1.61,-SwRI: l'.46) and modified (OG: 1.88, SwRI::1.68) capscrews. The calculated capscrew endurance limits were also slightly different (OG: 8.7 kai, SwRI: 8.6 kai) as were the safety' factors-against. failure during tightening (OG: 1.4, SwRI::1.7). Both. safety factors were satisfactory.
- 19. No significant thermal' stresses will be introduced to 1the capscrew. Resu$ts indicate both thefcapscrew and the rocker. arm shaft will.be exposed to the same temperature and ~
thatsboth have the-same coefficients of thermal expansion.
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~. h-1the therma,l' expansion of the capscrews and that of
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armishafttover,the clamped length.
, . 20. Analyses by SwRI-and the Owners Group also indicate A
that.the maximum operating temperature (190'F) is well below
. -the~ point lof significant temperature effects.(usually 600*F).
The' maximum' operating stress in the capscrew is approximately 38%-of the ultimate strength. This is low enough, when com-4 , .
jbined with the relatively low temperatures, to dismiss creep as.,
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'a{ concern. ,
- 21. Based on1the results of its analyses, the Owners
,(Groupconcludedthat-bothytheoriginalandthemodifieddesigns y
were adequate-for. nuclear service. The modified " necked shank">
- design.was found to be~somewhat more resistant to, fatigue fail .
fj .ure and;less likely;to loseLits preload due to'its; lower cyclicL cload. The threads' utilized for.both designs:were determinedito
- adequately' resist' distortion during preload application.and the material 1 utilized ~forLthe' modified-rockerfarm capscrew' design =
,was' determined to.meetfor exceed.the requirements of: ASTM-A193.
~
LThe Owners Group; recommended ~a. quality revalidation! review'(ma--
'terial verification)'on a'sampleibasis to confirm capscrew ma-
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g ;terial pr$perties'.: .The,0wners Group further recommended-that- -!
tall: materials used in ther" straight shank" design,xiffnot AISI;
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..T4140,2f.have a minimum proof strength of 90,000 psi.
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-% l22. SwRI concludes that either capscrew design is satis-
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I' factory.for use at PNPP'. Neither will fail due to fatigue
-loading, thermal. stresses, or creep, when properly torqued.
jWhile-the modif,ied capscrew design is slightly more resistant j) .e ~
sto/ fatigue' failure, the difference.is slight (15% higher), and Jthe original design, with a safety factor of 1.46, has more
?than adequate fatigue resistance. Both capscrew designs will fail >with a loss of preload. However, loss of preload will not
- occur with proper-maintenance.
Thesubcoverthreadswillnot{_
, . strip with the thread-engagement length provided, and with the
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capscrew properly. torqued.
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.23. .-Because of the acceptability of the original designi 3and.thebfact that there-is only.a slight = improvement associated w . .
with the modified design, SwRI does not recommend a. change--to
'the " necked shank". design at-PNPP. :SwRI.reco$ mends that the capscrews;b~e~retorqued periodically..during! initial engine oper-
_ :ation unti1> no~ movement' is - detected. Torque shouldibe1 checked 4; .
atfevery outage after this initial. period.in accordance with
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}the maintenance' recommendations provid9 d'by the Owners Group; q i for.thelPNPP engines. -SwRI further. recommends;that during:
J2A AISI'.4140.and'ASMT-A193-are comparable >initheir: require- .
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"capscrew' installation, all mating surfaces be cleaned, and the !
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icapscrew threads lubricated with a 50/50 oil / graphite mixture ;
asLspecified by TDI.
B. Fuel Oil Injector Tubing
- 24. The-fuel oil injector tubing on the TDI standby die-
"sel generators transfers high pressure fuel from the individual
- *Jcylinder fuel pumps to the injection nozzles. The fuel oil in-jector tubing was included among the Phase I components due to 90 Eleaks in the low pressure tubing and in one high pressure cir-l'
.cuit. In' drafting the. design review task description for this
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- component,.the Owners Group determined that-the critical func-V tional attributes were: 1).that the tubing have adequate fa-tigue' strength to withstand cyclic pressure and vibration.with-out failure; 2),that.it be resistant to internal corrosion and.
. erosion; and 3) that the tubing connectors be able to withstand the-same conditions as the tubing. :Both shrouded and
-unshrouded-tubing designs were reviewed =by.the: Owners Group.
, PNPPfcurrently has the unshrouded tubing design, however, shrouded tubing ~is scheduled to be installed.
25.- The owners Groupzperformed an analysis to determine
'appliedistresses duetto the pulsating fuel pressure.3) 'A:
3/; 'A. detailed discussion"of the10 wners' Group review of this
! component is contained:in: " Emergency.~ Diesel Generator Fuel oil (Continued Next Page) r 6 n t-
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comparison:of these stresses to the tubing material yield-
. strength and endurance limits was done. A fracture mechanics
- analysis ~was conducted to determine the maximum inner diameter flaw size that would not propagate to failure. Test procedures
'werefevaluatedLto determine those which would detect s
' unacceptable flaw sizes, A separate evaluation of the con-c ,
cnectors and of1the corrosion and erosion resistance of the inner' surface tubing was also performed, a
- 26. The; Owners Group also reviewed the TDI endurance test
-procedures and test results. The test report'from the con-
'nector supplier (Bendix)-was also reviewed. This report in-Lcluded. tests 1 demonstrating that cavitation and erosion were not.
- a. problem at-the flow. levels required in the TDI engines. In-addition to-these_ manufacturers' tests, several utility engines-
-with TDI' tubing,have accumulated more than 750 hours0.00868 days <br />0.208 hours <br />0.00124 weeks <br />2.85375e-4 months <br />'(10._ 7
. cycles) of operation. This.provides confirmation that fatigue
-failure'of the fuel oil injector tubingswil1~r.ot be a problem.=
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- 27. ' Based on its' analyses, the,0wners Group determined -
=thatlthe' fuel *oilfinjectorgtubing' meets'the stress criteria'of-
- ASME'III' Class.'2; piping l design?which is that-the maximum 4
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( -(Continued)'
, ; Injector = Tubing,"LApril,11984,Lprepared by. Stone & Webster En-Tgineering Corporation;-
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~ allowable. stresses be less than or equal to the smaller of ei-
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ther-the tubing material tensile strength (12.3 kai) or 62.5%
l of the? tubing material' yield. strength (15.6 ksi). It concluded that fatigue failures would.not be a concern with the maximum
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Longine. cyclic-fuel pressure, which results in a maximum: tubing
' stress:of'11'.6 kai (which is less than the 12.3 kai allowed).
- It.also concluded that' engine and seismic vibration loads are
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not.a' concern.
- 28. The fracture mechanics analysis concluded that a 0.0048 inch deep maximum flaw size could be contained on the inner surface of the tube and not propagate. Because tie testing method (eddy current) used to detect cracks has a reso-
- lut' ion.of + 0.0005 inches, the actual allowabl~e. flaw size detected by this method will not exceed 0.004 inch deep.
- 29. .The compression fittings used to connect the tubing Lto the pump and_ injector:were considered satisfactory, if in-~ ~
stalled' correctly, given their testing and in-service perfor l 3mance. Proper.installationinstructions;areprovibedJinthe:
.TDI maintenance: manual and are utilized at PNPP.
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.30. ;SwRI reviewed the. Owners:GroupLreport on-the fuelioil
' injector tubing.to verifyDits applicability to;the'PliPPren-'
gines. The'assumptionsz-and methods-of analysis used by the l, . , . .
cowners1 Group were acceptable to-SwRI'and no'other.' analyses were
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necessary.
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- 31. JThe. Owners Group recommended inspection of the inner surface:of the high pressure tubing using eddy current tech-f:V Jniques and rejection of an tubing that exhibits a flaw size
.: greater than O.004 inch deep. This inspection has been con-
. ducted on'the_PNPP engines. No flaws were found.
- 2 D32. The' owners Group report and maintenance instructions recommend'that'the: tubing-and fittings be checked visually each
[ monthifor. fuel oil leaks while the engines are operating. .
Also,L the - tiubingi supports should be checked at each outage to
-[ assure that the elastomer ~ inserts are functional and to check for any excessive fuel oil line vibration and deflection. SwRI:
agr'ees with each of these-recommendations. - Although not an
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OwnersIGroup requirementt PNPP will be-installing shroud lines-
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A' ' around theifuel! oil-injection / tubing as'an:added precaution.
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-' * ;C. Main Bearing Saddle,' Bearing Caps,'an'd Fasteners-
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</ ' 3 3 '. The. main bearing saddleJ bearing-caps l; and the:fas-
,tener assembly support-the' engine crankshaft.in the TDI.l standby.
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D idiesell; generators. :The cylinder $ firing pressureTexerts'a11oad-; -
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m ~ontthe engineEpiston which'is' transmitted tolthe main [ bearing
- saddle assembly through the connecting rod ~and the crankshaft. -
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{Therefore,.the entire:loadion.the/ piston is su~pported.byLthe:
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Jsaddle-bearing-cap 1 assembly.. 2 pt ~- ,
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'34. In formulating the design review task description for th'is component, the Owners Group determined that the critical functional attribute of the saddle-bearing cap assembly was that 'ti have sufficient strength to carry the lateral loads im- .
posed.by crankshaft inertia, and to react to the vertical com-
'pression and tension loads imposed by the engine firing and the crank / rod / piston inertia loading. The casting un't pockets for both main bearing studs and through-bolts must have sufficient strength to carry the nut preload, inertia and dynamic loading from the crankshaft and firing loads transmitted from the upper engine. .The studs, bolts, and nuts (fasteners) must have suf-oc ficient strength to carry the imposed preloads, dynamic loads, and-firing loads. The clamping force provided by the mai., -
bearing studs and-nuts must be sufficient to prevent lateral movement'of.the bearing caps under lateral crankshaft loading.
The main bearing caps must have sufficient strength to with-stand imposed crankshaft loads and the base must be suffi-
'ciently rigid to maintain adequate main bearing alignment dur-ing operation.
- 35. The saddle-bearing. cap assembly was included among the; sir. teen-generic concerns due to cracks. observed in the bearing pedestals of DSR-4.inline engines,.a nut pocket failure
-in a DSRV-16-4. engine, and through-bolt failures on a~DSR-46
. engine. JThe cracks:in the bearing pedestals were attributed'to
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- an improper engine disassembly method; the nut pocket failure
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was found to be due to impurities in the casting material; and l the'through-bolt failures were due to insufficient initial torque and accompanying preload.
- 36. The Owners Group performed a stress analysis for both the bearing saddle and bearing caps.4/ A fatigue and fracture
. analysis was also performed for the bearing saddle. A " hole in a plate" model was used for the saddle. The loading consisted of. main bearing' loads derived from a journal orbit analysis, and load due to interference fit between the saddle and the main bearing. To represent the actual loading condition, the base and cap were modeled as an elastic ~ foundation. Variation in the interference load due to differential expansion between the cast iron _ saddle-bearing cap assembly and aluminum bearings was considered.
- 37. .The fatigue and fracture-analysis performed to deter-mine.the fatigue life of the bearing saddle utilized maximum tensile stress and modified Goodman line failure criteria to
-assess the fatigue ~ strength. Finish, size, t'emperature, and-
- other parameters were considered to calculate the maximum 14/ ' -A' detailed discussion of analyses performed is. included in
-* Design Review of Engine Base and Bearing' Caps.for Transamerica Delaval'DSRV-16 Diesel Engines," prepared by Failure Analysis
-Associates-("FaAA") for-the Owners Group.
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alternating value of 7,960' psi and a factor of safety of 1.31.
k The Owners Group concluded that an adequate margin of safety against fatigue failure existed.
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- 38. A similar model and similar procedure was used for the stress analysis of the bearing caps to calculate the alter-nating (17,700 psi) and the maximum positive principal stresses. The maximum stress of 10,030 psi was found to be Twell below the 60,000 psi yield-strength of the cap material.
Based on a safety factor of 3.35, the Owners Group also con-
' cluded that fatigue failure would not occur in the bearing cap.
- 39. For the'through-bolts and-nuts, the bolt, being the weakest;of the two components, tras reviewed by the Owners
. Group. The Owners Group approach was very conservative in that it assumed a very low value for the coefficient of friction.
- j. Stresses were calculated assuming axial loading of the bolts.
Finite element analysis.was used to determine the portion of the firing load carried by each bolt. The fatigue factor of safety _for infinite life was calculated using the modified Goodman line failure criteria. Based on a factor of safety-of
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1.45, the Owners Group concluded that fatigue failure of the bolting would not occur if the~preload torque specifications are met. To ensure that the cap would not move in the horizon-tal direction, the available friction force of the joint was f
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compared with the 1ateral load of 218,000 lbs. The friction force of 3,89,000.lbs was found to be 1.78 times higher than the
. lateral load of 218,000 lbs. It was concluded that lateral movement of the joint would not occur.
- 40. The Owners Group also analyzed the' bearing cap and f- nut fastener system. This system consists of top nut, bearing stud,. bottom nut, bearing cap and pedestal. Strength of the 1
nut, _ fastener behavior under preload, crankshaft vertical load, t
and safety against fatigue failure of the stud were analyzed.
The friction force at the joint and the crankshaft horizontal e
- forces were compared to ensure that there would be no horizon-
,tal displacement of the bearing cap. Modified Goodman cri iria
/
was used to calculate the fatigue strength. Appropriate modi-
. fiers were used to calculate the material fstique limit. From the factor of safety obtained (1.30), it was concluded that the
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?J ' fastener system is safe from fatigue failure. The. friction force of~94,400 lbs was.found to be 1.19 times the crankshaft ,
horizontalLforce of 79,400 lbs. It was concluded that friction force is adequate to resist the cap movement.
<41. .SwRI reviewed the* Owners Group report on the saddle-bearing cap assembly to-verify its applicability to the DSRV-16-4 engines at PNPP. SwRI verified the accuracy and ap--
~plicability of'all of the assumptions made in the foregoing r
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? Owners, Group analyses. The bolt loading values, material spec- ,
, ;s tifications,.and material strength used for the analyses were tappropriate and:were used for SwRI's analysis.
142. One signficant difference between the results
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fobtained+in'the Owners Group analysis and that conducted by ;
- SwRI3was observed.
- SwRI's analysis indicated that the g . interface betweenLthe cap-and the saddlac is much stronger.than ithatfcalculated by the Owners Group. A stronger interface t-jmeans'thatithereLwould be no-lateral movement of the bearing
^ .
y 'E capjunder the influence of the crankshaft horizontal force.
The difference-occured because'SwRI's analysis _also considered
[the; presence ofithe dowel between the saddle and the bearing'
, .' .;+ fcap. lit was concluded that the dowel must. fail before any"lat--
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,, eral: movement :of the bearing cap. Given the dowel's factors of
-2 ;
"J ' safety o'f 7.0 in shear and 2.38 in bending, it.was concluded
.!that.no;1ateral-movement of thecbearing caps will occur.
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. 43. LThe. Owners, Group' concluded that the-saddle-bearing-
'$ T cap assembly is-adequate.for nuclear service.
SwRI also con- >
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.fcludesi hat t the~ assembly is satisfactory for;use at PNPP. In
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'allEcases the. safety factors calculated are' adequate,to con-g ,
!cludeethat:the saddle-bearing cap' assembly hasiinfinite life.
,againstifatigue' failure.
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L44. To increase the factor of safety between the saddle !
I and the'be,aring cap, the Owners Group recommended that the l
' mating surfaces of the base and cap be thoroughly cleaned with osolvent before first assembly and upon any reassembly as a pre-
-cautionary measure to improve the frictional force resisting cap movement. SwRI recommends that the preload torque of both the. bearing cap studs and the through-bolts be checked prior to engine = operation. If the.preload torque is less than that specified by TDI, all the studs should be retorqued.
45 '. PNPP'has conducted a torque verification of the bolts ard nuts. Proper maintenance procedures for engine disassembly have also been.followed at PNPP.
~
'D. Connecting Rod Bearing Shell~
- 46. The babbitt-overlayed cast aluminum connecting rod bearing shells in the TDI standby diesel generator engines pro-vide'theroscillating/ sliding surface between the crankpin and m -the connecting rod through formation'of a hydrodynamic film.
The cylinder firing pressure is transmitted through'the: con-necting rod bearing shells to the crankpin. The force is thus
- converted into engine' torque. =In formulating th'e-design review
-task' description ~for this component, the owners Group deter-minedJthat the critical functional attributes-of the bearing
.shellsswere'that: 1).they have' sufficient fatigue life and j
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'that.during; operation the peak oil film pressure, minimum oil
'filmLthickness and oil film, temperature rise be within accept-cable limits.:
m
~
- 47. The connecting rod bearing shells were included among
-thessixteen Phase.I. components due to failures of the con-
-necting rod-upper shells in the Shoreham Nuclear Power Station o ;DSR-48 engines. Failures occurred due to cracks in the bearing shells after-about 250-hours of full-load operation due to the
- flarge (1/4" x.45~ degree) chamfer on the connecting rod bearing D~ capfand bearing shelis.5,f 14 8 ; A visual non-destructive examination of the bearing.
g
, ,,jshell fromLa utilitylengine with 315 hours0.00365 days <br />0.0875 hours <br />5.208333e-4 weeks <br />1.198575e-4 months <br /> of full-load opera-tion'was performed in the-Owners Group' Phase I. investigation.
This particular~' engine was'a DSRV-16-4 model:with'aq13-inch x:
~ l, .
L ; ?l3-inch crankshaft,nthe'same as.on the PNPP. engines. < Dye a.. - _ .
4 ,
penetrant 1 inspection and measurement o,f wall thickness wasipart-g4 Lof!the non-destructive examination. In..'only;a few cases was edge. loading,_ light to moderate scoring =of overlay, Land ~ overlay.
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removal 1 evident. None of these had any effect on the bearing's ability to, perform its intended function.
- 49. Chemical composition tests and tests for tensile
~
properties of typical failure bearing shells from the Shoreham crankshaft were also performed. The material composition and the tensile properties were found to be in accordance with the TDI material specifications. It was concluded that the materi-al was suitable for its intended application.
- 50. Journal orbit analysis was used to determine the characteristics of the hydrodynamic oil film formed between the
- bearing and the crankpin. The peak oil film pressure in the DSRV-16-4 engine was found to be 25,800 psi.
- 51. Finite element stress analysis was performed to com-pare the magnitude, orientation and location of the largest-tensile stress in the bearing shells. .The maximum tensile stress in the bearing shells.was found-to occur at the inside diameter and had a value of 8,200 psi. Using the results of
'the finite element stress analysis, a fatigue analysis was per-formed. The fatigue life of the bearing shells in the DSRV-16-4 engine was estimated to be 38,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> at full-load ope ration.~- The finite element and fatigue'analysislapplied only to the fully-supported bearing shells which the'PNPP en-
.gines have.9/
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l 6/ 'In the~ fully-supported assemblies, the chamfer in the con-
'necting bore is-1/16" x 45 degrees. . The fully-supported (Continued Next'Page) i L I e == .. .
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152. Using a fracture medhanic analysis, the stress inten- i sity. factor range was used to compute an acceptance criterion for bearing shell castings of 0.050 inch (maximum discontinuity size).
-53. The owners Group analysis concluded that the con-necting rod. bearing shells used on DSRV-16-4 engines, with 13-inch x 13-inch crankshafts and connecting rod bores with 1/16" x 45' degrees chamfer (which fully support the bearing shell) have a fatigue life of 38,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of full-load engine operation. This conclusion is verified 'tur the operating histo-ry of-the engines.7/
- 54. SwRI reviewed the Owners Group report on the-con-necting rod bearing shells to verify its applicability to the TDI diesel engines at PNPP.g/ Design-parameters used by SwRI were in agreement with those used by the Owners Group. The (Continued)
. bearings-eliminate the possibility of edge loading on the bearing shells.
12/ For example,cno_' failure of bearing 1 shells was observed after 12OO hour's of operation of a Grand Gulf DSRV-16-4 engine.
_g/ A detailed discussion of the_ Owners Group analysis is in-cluded in the FaAA report, " Design Review of Connecting Rod
~ Bearing Shells for Transamerica Delaval Enterprise Engines,~"
March,_1984.
J 5
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- assumption made by the Owners Group with regard to firing pres-sure was lower than that utilized by SwRI for PNPP, as dis-cussedLbelow.9/ Other assumptions were consistent.
- 55. - SwRI performed an additional. analysis to calculate the~ oil film thickness and oil film pressure accompanying an
. increased gas pressure.' These calculations were performed by the Owners Group for a peak cylinder firing pressure of 1450 psig. The PNPP engine data indicated that the peak cylinder firing pressure can be as high as 1700 psig. For this higher
. cylinder. pressure the minimum film pressure for the highest load was calculated by SwRI to be 23,314 psi, which is lower
--than the allowable pressure of 26,000 psi. It was-concluded,
.therefore, that the increased peak cylinder firing pressure Twould not.have a detrimental effect on the fatigue life of-the bearing shells. -
- 56. SwRI agreed with the Owners Group conclusion that the PNPP bearing shells have a fatigue 111fe of at least 38,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of full-load operation.
A/ The SwRI' approach would not have changed the conclusion of, the Owners Group study'that the connecting rod bearing: shells are suitable for the PNPP engines and are safe from fatigue-
- failure.
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Group' concluded that the babbitt-overlayed cast aluminum con-g .. M necting rod bearing shells were suitable for their intended n
-. purpose and-that minor surface-imperfections in the babbitt-A Loverlay~would'not degrade the suitability of the bearing f ~s hells.' Again,.this analysis'was~for fully-supported bearing
' shells,-which the_P'NPP engines have.
J The critical zone of the connecting rod bearing shells was determined to be a circular
- ; band'~on each end of the bearing, beginning 0.4 inch-from the bearing end and' extending 1.4 inches from the bearing end. ~The '
4 JOwners. Group analysis resulted in a recommendation that the
- jo Esize of the~ voids in the casting in this critical zone not'ex-coed.0'.050 inch. Ein the non-critical areas of the.. bearing;
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ishell'1 , and. in the : lightly-loaded lower ~ bearing shell, f 6
.sizeL'cani-be as large.as 0.250 inch. y, s.
% -:5.8. To' assure compliance with the acceptance criterion,-
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lthe' owners Group' recommended inspection.of the bearing.sheils N f --by radiography. .PNPP has performed thistinspection on:its.;en-
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- gines. -Allybearing shells presently installed'in the engines _
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Jbearingshells-be.fnspectedito'ensurethat[the: i .
chamfer--onboth "j"r~ ,
isides;of both of:the; parts does not exceed 10.062: inches x?45'
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- Di E. Emergency Diesel Generator Engine and Auxiliary Module Wiring and Termination Qualification to
, IEEE-383-1974 a m ,
"60. The TDI diesel generator engine an'd' auxiliary module wiringjand termination interconnect instrument,' control, and p'wericircuits o on the diesel generator itself and w'ithin the
- y
-control panels. In drafting th'a design review task description
-forithis component, the Owners Group determined that the crit'i-cal' functional attributes of the wiring and termination were
~ k that': :1)Lthe-conductors, insulation, and termination must be U" '
suitable for'the specified amp rating: 2) the conductors and insulation must be flame retardant; and 3) the material and'in-sulation': rating must be appropriate ~for' engine and generator jf ; applications.
~Y:
-a: 61. The wiring and termination was included'among.the sixteen _ Phase I, components because of a Service Information-Memorandum ("SIM") issued by TDI informing utilites of-two .
potentially defective engine-mounted cables that'did not meet'
- a. .IEEE-383-1974. CEI has implemented the' recommendations of-this SIM and. replaced its. cables with: cables: meeting IEEE-383-1974 standards.,
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[: [, iTDI-generi,c.and~PNPP-specific wiring and termination de-i- 0 . signs.1_Of This analysis included a review of the circuit
. requirements. Included in this analysis was a determination of
' "1^
'the. wire insulation rating, type and rating of termination, voltage, maximum temperature, current flame retardan::y require-
<ments (IEEE-383-1974)i and routing.
" < 63. 'Satisfact.ory performance of the wiring and termina-
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x g tion has! been demonstrated in several utility engines with more / v- 3.. y
-than 750 hours of operation and over 100 starts each. This op-
_} terating. history confirms the reliability of the TDI-generic
^
}.wiringfand termination.. Having implemented the SIM/ PNPP now Emeets all'of the requirements of'the Owners Group review, i swr'I ' reviewed the Owners Group report on wirir'd anc'
~
> 64.
t (terminationJto v'erify its applicability to the PNPPldiese'l g'en -
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cerators.- The' assumptions >and method's-of analysis u' sed $.y..'the; - 4
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. s t Owners. Group were acceptable c to SwRI. 7 ,
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I 0+!/jf.651 ! Based on the' results of':its analysis,Lthe Owners? Group concluded that-the:PNPP; wiring andLtermination were r '
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_ . , , ~#'AT...... , u.n ' N :;10f ?Aldetdiled. discussion of this analysis is included in '
- a 2 1 Stone:& Webster; Engineering 1 Corporation,'" Emergency? Diesel.' Gen- O.-
@7, > erator Auxiliary Module Control, Wiring & Termination. Qualifica-4 4, T ; tion' Review /"; July-1984; prepared for the:Ownera Group. a S pig av (, q -
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,. E 'IP satisfactory. The Owners Group found that all wiring and ter-mination was adequate to meet voltage and current requirements at the elevated engine block (82.2*C) or room ambient tempera-tures (60*C).11/ The Owners Group also found that the wiring met flame retardant requirements of IEEE 383-1974, that routing L was acceptable and that shielded cable was provided where re-M quired.
- 66. SwRI agrees with the findings of the owners Group and concurs with actions taken by PNPP, which included the conduct of.an inspection and the implementation of the recommendations contained in TDI's SIM. No additional action is recommended.
F. Cylinder Head Stud
- 67. The cylinder head studs in the TDI standby diesel generators-transmit cylinder firing pressure forces from the cylinder heads to the engine block'and assure the required preload on the cylinder hea1 gasket for combustien gas and-water : sealing. In drafting the design review task-description 4
'for this component, the Owners Group determined that the cylin-der head studs must have sufficient strength to withstand the
.necessary preload and cyclic firing pressure forces without L ,.
J J11/ These: findings are conservative for PNPP'since PNPP's FSAR
. indicates that maximum room l temperature will only be 49 C.
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fi . preload relaxation or thread distortion. Further, the thread geometry o,f the head stud should provide an upper thread en-
,4gement which is sufficently below adjacent cylinder liner landings to minimize stress concentration in this area.
~
- 68. The cyinder head studs were included among the .
- Phase I components due to isolated failures resulting from in-sufficient preload in some non-nuclear applications. Two dis-tinet head stud designs were evaluated by the Owners Group, the Loriginal, " straight" shank design, and a modified, " necked"
-shank type. CEI has replaced the " straight" shank type supplied with'the. engines.at PNPP with the " necked" shank design.
- 69. A stress-analysis was performed by the Owners' Group on both, head stud designs 12/ The analysis included a determi-nation of.the applied stresses, the endurance limits, a fatigue life' . analysis, a thread distortion analysis,.and a thermal stress evaluation of both stud designs,
- 70. SwRI reviewed ~the Owners Group report onLthe cylinder head studs to verify its~ applicability to-the' PNPP; cylinder
. head studs.' .SwRI performed several analyses beyond~those
'12/' A detailed discussion of the analysis is included'in Stone
& Webster Engineering Corporation,." Emergency Diesel. Generator
'Cylinde'r Head Stud Stress Analysis," April, 1984 and its'Sup-plement', May,-1984, both prepared for the Owners Group.
t *"' 3 _*
r performed by the owners Group for both stud types to further evaluate d,esign concerns. SwRI investigated the potential for thread-stripping in the block and the effect on the stud if
.preload is lost.
'71. The adequacy _of the cylinder head studs to withstand the sum of the. total peak combustion pressure force (419,700 .
lbf.) and the sum of the fire ring gasket and other seal com-pression. forces (356,700 lbf.) was determined using standard engineering design calculations compared to a modified Goodman line failure criteria. This approach permitted both the mean (" straight" design: 46.3 kai, " necked" design: 45.5 kai) and alternating (" straight" design: 3.36 ksi, " necked" design: 2.62 kai)' stresses to be utilized. The Owners Group fatigue analy-sis yielded mean (" straight" design: 45.6 kai, " necked" de-sign: 44.8 kai)'and alternating (" straight" design: 3.8 kai,
~
^
" necked" design: 2.9 ksi) stresses as noted.
- 72. Thread distortion analysis was performed by comparing
- thep' rincipal stresses calculated- from the biaxial ~ stress field 4
during nut tightening-(to 3600 lbf.-ft) with the failure criteria of the distortion energ- .heory. Analyse's.were also
-con'ucted'by d the Owners Group to s ' 'e if thermal stresses
, 'wlereia consideration and whether-cret .suld be aLfactor in causing loss'of preload.
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- 73. Satisfactory fatigue life for the cylinder head studs has been demonstrated by several utility engines accumulating 7
more than 750 hours (10 cycles) of operation. This op-erating history verifies that failures due to fatigue, tightening, and loss of preload will not be a problem.
- 74. A. review of results obtained by the Owners Group and those of SwRI did not indicate any significant differences.
Based on the slightly different assumptions used by SwRI and the Owners Group, there was a difference in calculated cylinder thead stud endurance limits (OG: 10.6 kai, SwRI: 8.6 ksi) that yielded differences in safety-factors for fatigue life of the-
" straight" shank d.esign (OG: 1.35, SwRI: 1.29) and the " necked" deAign (OG: 1.55, SwRI: 1.46). All of these safety factors are
. considered satisfactory. The safety factors during nut
. tightening are also satisfactory (OG: 1.2, SwRI: 1.5).
- 75. SwRI agrees. with-the Owners Group conclusion'that
- j. thermal' stresses would not be significant because,the cylinder
~
head stud and.the head are of the same. material, have the same . ~ coefficients of thermal expansion,.and experience similar change in. temperatures during engine operation. The tempera-
- ture differences. experienced during engine startup will-not' r
m. f, contribute significantly to the mean stud-stress. S .-
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- 76. With maximum stud temperatures below 190"E and with the maximum operating stress less than half the yield stress, creep will not be a factor in reducing stud preload.
- 77. Based on these results, the Owners Group concluded
- that both the " straight" and " necked" studs were satisfactory for nuclear service. The " necked" shank desig.n is somewhat more resistant to fatigue failure and less likely to lose its preload. The " necked" design top thread in the block is lower than that on the " straight" stud, which means that the " necked" design will produce lower stress levels near the liner landing area than the " straight" stud. The Owners Group recommended a
- quality revalidation review (material verification) on a sample basis to confirm that the cylinder head stud meets the require-ments of AISI 4140. This verification has been performed.at PNPP.
.9
- 78. SwRI concludes'that either stud design is satisfacto-207 for the PNPP. engines. Neither~will-failidue to fatigue
' loading, thermal. stresses, or cr$ep when properly torqued. .Be--
cause the " necked". design is less:likely.to. lose'its preloa'd, has a higher safetyJfactor under' fatigue loading, and lowers
-).
thefstresses-in the-block. adjacent to the linerilanding area, itstado'ption is recommended.by SwRI. ~CEI has installed the
" necked"-design. R J
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- 79. Both designs will fail due to loss of preload. How- l l
ever, preload will not be lost with proper maintenance (which includes _retorquing duri.g initial operation and retorcuing
, "during outages). SwRI recommends that the head stud nuts be retorqued periodically during initial engine operation until no movement is detected and therafter at each outage. SwRI fur-ther recomends that care be taken in cleaning and lubricating oof the stud and block threads in accordance with TDI specifica-tions to assure maximum preload is attained.
G. Air Start Valve Capscrew
- 80. The air start valve capscrews in the TDI. standby die-sel genrators provide the clamping force to hold the air start valves in' place on the cylinder heads. In drafting the design
-reviewitask description for this component, the Owners Group determined that the critical functional attribute of the air staht valve capscrews was that they have sufficient strength to s 1 withstand the necessary preload and reaction air loading with-out yielding (and resulting.in-loss of clamping load on the. air start: valves).
181. .he air start valve capscrews were ir.cluded among the Phase I components because one nuclear power plant engine-was-
-found to have'an excessively.long,capscrew'which prevented the R- air start valve from-being properly seated. -This was J.
iC
discovered during an inspection prompted by an SIM issued by TDI which recommended that users measure the length of their engine air start valve capscrews because some capscrews supplied in engines were too long.
- 82. A stress and dimensional analysis was performed by the Owners' Group for the air. start valve capscrew.13/ The analysis included a determination of minimum possible capscrew clearance (given the specified tolerances of the capscrew and
- its clamped parts), the applied stresses, a fatigue analysis and an analysis of stresses during tightening.
- 83. Satisfactory fatigue and operational life has been f demonstrated by several utility engines which have accumulated 7
more.than 750 hours (10 cycles) of operation and over 100 starts. This operating history verifies that capscrew fatigue and operational failures will not be a problem.
- 84. --SwRI reviewed the Owners Group report.to verify its
- appcability to_the air start valve capscrews used in the en-gines;at PNPP. -Design parameters and assumptions used by-SwRI,
' were.in agreement with those used by the Owners Group.
13/.:Asdeta'iled discussion of'this analysis is include'd'in the-Stone'&. Webster Engineering Corporation report, "EmergencyLDie--
- sel Generator Air Start Valve Capscrew Dimensions:and Stress
. Analysis," March 1984, prepared for the Owners Group.
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- 85. SwRI performed a number of analyses to evaluate the functional, attributes of the capscrews. The maximum cyclic load on the capscrews was calculated at 3600 lbf. The adequacy of the capscrews to withstand this loading and the preload was
- determined using a series of standard engineering calculations culminating in the use of the modified Goodman line failure criteria which considers both mean (38.7 kai) and alternating.
' (2.7 ksi) stresses. The maximitm biaxial stress was calculated
-for the capscrew during-tightening to the specified torque (150
' 1bf.-ft). The principal stresses were compared to the failure criteria of the distortion energy theory. An analysis to de-termine the impact of the loss of preload on the capscrew was f
also-performed. 8'6. 'No s'ignificant1 difference in results between the Own-
- ers Group analysis- and that of SwRI. was observed. There were
- slight differences-in mean stresses (OG: 37.5 ksi, SwRI: 38.7 ksi) and alternating stresses (OG: _1.6 ksi, SwRI: 2.7 ksi)_that.
- yielded different safety factors.for fatigue life ~(OG: 2.04, SwRI: l '. 6 ) . Both of these safety factors are satisfactory.
8 7 .' -The' safety' factors during capscrew: tightening were also considered satisfactory (OG: 1.52,fSwRI: 1.88). _The. cafe-ty factor with loss of preload, determined-by SwRI, is 1.58. _ The' Owners. Group concluded that with capscrews meeting current; t .,
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TDI specifications, a minimum of 0.2 inches clearance exists w'ith the" worst case tolerance stack-up between the capscrew and
- the bott'om_.of its tapped hole in the cylinder head. SwRI
~
agrees 1with this calculation.
~88. Based on these results the Owners Group concluded
- thatIthe' air start valve capscrew was satisfactory dor nuclear
, , , '. service. - The design provides adequate safety factors against i fatigue failure and failure while tightening.
'8 9 . SwRI concludes, likewise, that the air start valve
- capscrew is of adequate design to resist failure by fatigue and
..[ 'during; tightening. The capscrew will not fail due to loss of
_ prel'oad.
;90. SwRI-recommends retorquing at eight-hour intervals
~
during' initial engine operation, as-specified by TDI and the. Owners! Group, until no further' movement is detected; :This-
% .retorquing procedure will assure retention .of a tight.: seal. as '
t
~
- the copper gasket " sets".! SwRI also recommends that.c'are be-c' - .
s Ltaken-inicleaning..and lubricating the capscrew?and head threads-Iiri accordance Iwith TDI- instructions, to . assure - thatb maximum '[ %- 2 preload is-attained. - i
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H. Push Rods 91' . The intake and exhaust main push rods and the exhaust connecting (intermediate) push rods are among the sixteen Phase I components. The primary function of the push rods is to_ provide a portion of the linkage that transmits camshaft lobe motion'to the intake and exhaust valves, thereby control-ling the valve opening and closing cycle. Important functional attributes of the push rods are: 1) that the push rods have sufficient column strength to withstand compressive buckling;
- 2) that the ends have acceptable wear resistence; and 3) that the push _ rod tube and end fitting design minimize the possibil-ity of design defects and be able to function without separa-tion of the tube and end; fittings.
- 92. Three basic designs are in use. 'These are: 1) forged head; 2) ball-end; and 3). friction-welded end. . The forged head
' design consists of a tubular steel shaft fitted with hardened steel _endpiecesattachedtokhetube.withfourplugweldsnear the end of the tube. Cracking in the tube ~ wall adjacent to_the
~
-plug welds has beentfound inLthe forged hea'd design. Concern about the shear capacity of the plug welds has also been
-raised.
- 9 3 '. The_ ball'end design consists of-a tubular steel' shaft fillet-welded to a carbon' steel ball: at each and. The ball end
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' design has exhibited cracking at the interface of the push rod tube and ball end fitting. These cracks have developed in the heat-affected zone of the high carbon chrome steel ball. Com-
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plete separation-between the tubular steel shaft and the push rod ball has occurred upon disassembly. Failures of the forged
~
head and ball end designs have not affected engine operability because the valve train lash has never been sufficient to allow
' the push rod end to escape from the tube.
- 94. The friction-welded design (the design used at PNPP) consists of a tubular steel shaft friction-welded to a solid
' steel plug on each end.
No failures have been reported for the , fri'ction-welded push rods.
- 95. -The Owners Group investigation of the push rods con-
. sisted of a metallurgical analysis of the fillet-welded ball
- end-design, fatigue. analyses and an analysis of the-buckling stability e.nd wear resistance of the-forged head and friction-
. welded designs.'1_4/
_9 6 .- ' SwRI's review offthe Owners Group-effort: consisted of-a review of the push rod ~ criticality status, a review of_the- -
' push rod static-and dynamic loading and a comparison.of this J 14' 'A descsiption of.the Owners Group review ~is contained _'in,
~
- Design Review of Push Rods for Transamerica Delaval Diesel
. Generators", April,;1984, prepared by FaAA.
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i [ r p' s I cloading with calculated critical buckling loads (i.e., the loads that the push rods could withstand without buckling). SwRI's analysis of critical buckling loads included the well-1 known. Euler and short column equations used by the Owners ! Group. SwRI extended the analysis to include buckling under dynamic loading conditions.
- 97. The Owners Group performed a two-part experimental evaluation. The first part consisted of fatigue tests of forged head and friction-welded push rods. The fatigue tests were performed at loads in excess of those expected in service 7
to a' life of-10 cycles. The second portion of the experi-
; mental evaluation consisted of metallurgical examinations of forged head and friction-welded push rods for a comparison with specifications identified in the drawings. The metallurgical examination included: 1) a dimensional check of the push' rod with the drawings; 2) a chemical evaluation of the ends and the tubular shaft; and 3) a microhardness profile of the ends and the tubular shaft.
- 98. The-Owners Group analysis of' push rod loading showed
~
a combined static and dynamic ~ maximum-loading of 2,945 lbs. for the intake push' rod, 7,787 lbs.-for the exhaust main push rod and 13,040 lbs. for the exhaust. intermediate push rod. Calcu-
~1ated' critical loading at which buckling would be expected is-4
n lowest using the short column equation. For the main push rod the critical loading is 18,100 lbs. This gives safety factors of 6.1 :and 2.3 for the intake and exhaust push rods respective- _ ly. For the exhaust intermediate push rod, the critical load-
- ing is'27,560 lbs. which provides a safety factor of 2.1.
- 99. The Owners. Group fatigue crack analysis showed that, under: cyclic loading, no potential fabrication crack is expect-ed.to propagate in either the main or intermediate friction-welded ~ push rods. This conclusion was based on a very conser-vative model that assumed some net tension-during cyclic loading. In reality, the push rods will always be loaded in compression which assures that fatigue crack growth will not
, occur..
100. The fatigue test performed by the Owners Group lon the friction-welded intermediate push rod used a-load cycle ranging from zero to-1.25 times the maximum loading. Radiographic and fluorescent magnetic-particle examinations performed before and
- after-the tests-showed no flaws.- The end connections were sec-
-tioned~and examined after the test. ~Neither flaws norJindica-Etio'ns1were found.
101. The.results of_the,0wners Group metallurgical'evalua-
, tioniof~the' friction-welded design showed the. push rod 1dimen-
= sions to be'within drawing specifications. Chemical analyses 1
C 1 a
- showed that the chemistries fall within the material require-
. ments spec,ified on the drawings. The hardness values on the spherical portion of the end plug were in agreement with draw-ing specifications. Results of a metallurgical evaluation of
'the friction-welded design showed microstructures typical for
- the specified materials. No major discrepancies with the mate-rial. properties specified on the drawings were observed.
102. SwRI's review of-the push rod analysis performed by
~
the Owners Group produced only minor areas of difference.
' SwRI's calculated values for dynamic loading were slightly higher ~(15% for intermediate rod and 8% for the main rod).
This difference, when combined with static loading, yielded a combined increase of only 0.6% for the main and intermediate push rods, which still results in an acceptable safety factor. t
.103. SwRI's extension of the buckling analysis to include an evaluation of dynamic buckling showed that dynamic loading
- would'have no effect on buckling.
~ 104. From the analysis performed,[the Owners Group has - concluded that the friction-welded design is the:most reliable of the-three push rod designs. SwRI-concurs with this selec--
' tion ofLthe friction-weldedEdesign forfthe.PNPP: engines.
w - 5 4 _f. uis-
105..The Owners Group recommended an inspection and sam-pling plan be developed to meet the following criteria: a)- No surface cracks longer than 25% of the
~
circumference (approximately one inch) oshould be allowed along the bond joint be-tween the rod end and the tube. Those rods where the friction weld looks suspicious (i.e., obvious failure to weld, porous wcld area, etc.) should be removed, b) Apprcpriate destructive testing techniques should be. employed on a random sample of friction-welded' design push rods to examine the interior section for lack of fusion which is identifiable by lack of " lips" on the interior of the tube.
~
106. The Owners Group. report also states that any
-friction-welded push rods successfully completing 800 hours of in-service use at full load may be considered qualified _for-continued use.
lO7.iBecause-push rod' failure could result inlan_early en--
~
~
gine shutdown,'SwRI. agrees with the recommendations-of the Own-ers Groupfthat an inspection and sampling plan should be, ,
.~:
4
r g
. g'-' 1 Sm : *u-Jimplemented'and. applied to all push rods. An inspection of all "> . - - tof the: push rods was performed prior to installing them in the- '^
- PNPP' engines to verify that they were of the friction-welded
. design.
I. Cylinder Heads
'108. The cylinder heads in the TDI standby diesel genera-
. tors provide a pressure-tight cap for the engine cylinders and.
provide: passages.and sealing for cooling water, lube oil,. o .. . . f, ^ starting air, intake,.and exhaust gases. In formulating the
~ design review' task 1 description for this component, the owners lGroupTdetermined.that-the critical functional attributes of a sc ylinder h'ead are that it must: 1) serve as a structural-member
~
[ i >
~
- with sufficient stiffne'ss to react-to the cylinder firing-forc- ,
!J . es .without : leakage or damaging deformation; 2) maintain
'. stresses'below endurance-limits; 3) withstand thermal.and me- ,
-chanical fatigue., loading; and 4) be resistant.to impact and corrosion damage.
- g. .
I 4 s109. -The cylinder : heads were included: amongithe l sixteen
- m. Phase:I: components becausetofshead defects:consistinglof. cracks
? in locations such as the: fire deck,- the' exhaust.and' intake
^
I:' ' "O, Lbridges, exhaust; valve seats,;and induction. port.. : Cylinder; 5 heads cast-before, September 1980 were: subject toLeore~ shift,- ~ Lihadequate' control ofa solidification,n.and inadequate' control of
<- , .the' stellite valve? seat weld deposition process.- Headsicast:
S , i
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; p ,' :^ -. *
. f:
before October 1978 were not stress-relieved and were therefore subject to fatigue crack growth in thin sections and/or from fabrication-induced defects. Heads on the PNPP engines were cast pri~or to October 1978. 110. The cylinder heads at PNPP were removed and returned to-TDI where they were inspected for cracks in thin sections. Several were rejected. Heads not rejected were given a stress-relief treatment before being reinstalled. All replacement heads were cast after September 1980. The inspection of and modification to the current cylinder heads installed at PNPP makeLthem-equivalent to those manufactured after September 1980. 111. A metallurgical analysis was performed by the Owners Group.15/ The' analysis included: 1) examination of casting
. shrinkage indications found in a cylinder head taken from a-Comanche Peak engine; 2) examination of a pre-existing shrink-age void.and of a crack'in a stellite; weld deposit,1each found.
.in'a Grand Gulf l head; and 3)-the examination of a crack across lthe~ wall'of the-fuel injector port in'a-head-from an engine at the' Catawba _ Nuclear. Power Station. A review by SwRI of the 15/ A detailed ~ discussion of the analyses performed is includ-ed.in FaAA teport " Evaluation of Cylinder Heads'of Transamerica '
-Delaval,_Inc. Series'R-4 Diesel Engines," May 1984,7 prepared for:the Owners-Group.
W
- Owners Group metallurgical analysis confirmed that the analysis
~
was performed using recognized and correct procedures, 112. An evaluation of thermal and pressure stresses was
'also performed by the Owners Group. This analysis included an l
. initial. determination of the transient and steady state temper-ature distribution in the fire deck, and then a thermal stress
. analysis and a pressure stress analysis. The calculations per-
' formed by the Owners Group for thermal and pressure stresses I
were reviewed for validity of assumptions and calculations. j 113. Modeling of the cylinder head to fit existing well-established equations was performed by the Owners Group using the following assumptions: a) The fire deck is' subjected to steady state mean stresses resulting from clamping the head by the studs and from thermal. gradients. b) The fire deck is loaded in bending by peak gas pres-sure.
.c) The fire deck,'is idealized: 1) as' circular flat
-plate?with clamped outer boundary;12) two parallel decks constrained'to deflect together; and 3) a flat plate clamped at its boundaries having an average
~
thickness of 3/4 inch. y
w+ . 4
- 7. -
..~.4 fSERIlused.a:more conservative approach, assuming that the fire
-l N.; , .
l Q ' deck was two. parallel decks tied together at a number of loca-tions. Oz . cll4.-Analytical results obtained by SwRI and the Owners Group differed only slightly due to the difference in assump~-
- tions. mad'e regarding the fire deck.
The owners Group analysis i
. assumed the fire deck to be a flat plat, clamped at its edges.
!This5model produced a_ bending stress of 115 ksi.
~
The assump-m i.tiontthat the. deck-was supported at the center resulted in cal-Lculations indic'ating that-the-central support would reduce the N. ,
" stress byfone' - half:(i.e., to 58 kai). SwRI's analysis showed
+
..that, using_its, assumption,_the bending stress at the boundary
? .. ,
S- swould be'more than'one half.that of a single plate. However,. _;
. as theinumber of contact-points increase (e.g.,Jintake andvex -
'"! haust posts, thesinjector. port.and: water passages), the stress- ,
a [in the! fire deck wouldLapproach one-half,~ as. concluded by the y _ ,< - Owneirs ; Group. - h ' 3 15.-iThe j ownersLGrodp thermal !stresse analysis, i-review'ed by- a
.e .
_ ._ .. .. . .. w W- LSwRI,;.showed?that the.: contribution.of thermal. stress to high , f"
.m-(
(cycleifatigue'.is quite small_(a 5'.0_ksi' increase in mean: - N ys Jtsess)f. iTheimost<significant thermal! stress is the bending;
+
$:NE.e
' ' g un 'ssresstresultin7 from the1 temperature gradient-in:.Lthe deck--
~
J Ithickness. 5 Calculations - pre'dictla range _ofl bending stressesJof.
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( about 20 ksi-between the exhaust valve ports and 30 ksi between g intake ~ valve ports, both below the yield stress of the materi-al. 116. Pressure stress analysis showed a maximum bending of 58 ksi'due to-pressure loads with a mean and amplitude stress (. of 29 ksi~. The Owners Group calculations for combined pressure and thermal stress showed a maximum of 28 ksi and a minimum. g stress of -30 ksi, both below the yield strength of the materi-al. 117. Analysis of the head design by the Owners Group
~
showed that stresses resulting from combustion pressure loads can exceed the material yield stress. However, the combined stresses resulting from pressure and thermal loading are re-duced to a safe level because the thermal and gas pressure. p bending stresses partially cancel out. SwRI concurs that com-bined stresses;will-have a cancelling effect during steady-E ' state running. During an emergency start, several' seconds are
. required for-thermal loading to develop. In this time period,
.the pressure loading may approach its design _value and conse-
;quentl'y the full benefit of_ combining thermal and pressure. ,
~
g stresses may not be realized. These stress calculations we're
;made using a= number of assumptions to render a veryscomplex
~
thermal and structural problem-tractable.to-hand solution. A-L t . i
~
l i=; _ m . m o,
E I consequence of.the numerous assumptions is that the computed stresses can only be considered as an approximation of the stress rather than actual values. The analysis does serve to identify-an item for which periodic inspections are necessary. No field failures of this kind were documented in the Owners Group component database or the Owners Group report.(which in-clude the ' review of several utility engines with more than 100 7 starts and 750 hours (10 cycles) of operation). 118. The_ inspection, replacement of some heads, and addi-tional stress-relief conducted at PNPP for the cylinder heads assure that-they will be adequate for service. This inspection will be supplemented by periodic checks for water leaks, ac-cording to the preventative maintenance recommendations
-contained in the Perry Maintenance Matrix provided by th'e Own-ers. Group in the.PNPP DR/QR Report. A barring-over'or blow-over procedure will detect water leakage that could occur if head cracks develop. Early detection of leaks will negate any harmful effects on the engines.
J. Piston Skirt- 1
.119. The piston skirt in' the TDI diesel generators trans-
, mits the cylinder gas' pressure force on the piston crown to'the
-connecting _ rod. Also,-the piston sk,irt supports the piston
. crown and guides the connecting' rod'into'the engine's cylinder.
s l
l l 1 I 1The side thrust developed due to the obliquity of the rod is transferred to the piston skirt. The piston skirt provides a o
. sliding friction surface against the stationary cylinder liner.
In the TDI diesel generators, the piston crown is bolted to the
-piston ~ skirt The skirt is, therefore, required to carry the
-bolt preload. In preparing the design review task description
=
for this component, the Owners Group considered the important functional attribute of the piston skirt to be that it have sufficient strength to withstand cyclic loading without fatigue cracking. 120. The piston skirts were included among the sixteen Phase:I components due-to-failures indicated by cracks in the skirt-to-crown stud attachment bosses in 23 out of 24 pistons
. in.a DSR-48 engine at the Shoreham Nuclear Power Station. Each' Lof the failed-piston skirts were-of the AF design. The one
' piston skirt which did not-show any sign of failure was of the AN' des'ign.
121. The Owners Group performed a detailed analysis of-the AF.and AE type' piston skirts. Basically, the :AF and AE piston l skirts are.similar:in design with identical loading and func-tional attributes. The major difference between the two de- ! signs is in1their fabrication thermal history and the configu-ration oflthe; stud. bosses insideithe' skirt where the washers on; r -
~
m a
.]
]
b . . _ _ _ _ _ _ _ _ _ - _ - _ - - _ - -
th'e crown attachment stud meet the skirt.
~
?- Because of the de-sign similarities, the Owners Group analysis used the data / test
.results in an interchangeable manner whenever applicable.
Originally, the piston skirts used on the PNPP DSRV-16-4 en- . gines were of the AH type. These piston skirts have since been
. replaced with the much superior AE design.
122. In the Owners Group analysis, a non-destructive dye-
- penetrant test was performed on the failed AF piston.16/ The analysis found that all of the cracks were similarly located and oriented on the spot-faced boss. Eddy current tests were used to confirm the presence of the cracks. A destructive ex-amination.was also conducted and the cracks were opened up.
Examination of the fractured surfaces indicated that they were fatigue cracks. This was confirmed by examination in a scan-ning electron microscope. m. 123.-Small specimens from the area near the. fatigue-cracked bosses were pr'operly examined to reveal microstructure. Due tolthe-difference in the-heat' treatments / cooling rates, the microst'ructures for AF and AE piston skirts were different.
-However,;the. differences were~found.to be consistent with the f
16/ A discussion of-the analysis performed by FaAA'for the
-Owners Group.is contained in " Investigation of Types AF and AE'
~ Piston Skirts," May 23,'_1984.
c
=
\
.+
'ba . _
.c difference in the heat treatment of the two piston skirts. The amount of ferrite in the AE piston skirts was only half that of the AF piston skirts.17/ A sample of the piston skirt material !
l was subjected to chemical analyse's. The chemical composition l of the test specimen was found to be as per the design specifi-cations (ductile iron ASTM-8536 grade 100-70-03). Material I hardness and the mechanical properties of the specimen were alsoffound to be in agreement with the design specifications and the heat treatment. Using a dissection technique, residual stress measurements were made on both AF and AE piston skirts. The residual stress near the ridges and boss region on the AF
~
piston skirts was found to be over 11 times that of the AE pis-ton skirts. -The most undesirable residual stresses in AE pis-ton skirt material were low due to the. increased cooling rate imposed after" normalizing the AE skirts.
'124. Experimental stress analysis was performed on both AF
'and.AE piston. skirts. A stress. coat _ technique Uas used to
' identify regions of peak stress. lThese regions were then con-
- centrated upon in'the strain-gauge tests. Appropriate. test set-up was used to' simulate the engine loading on theEpiston crown. The test pressure:of.2,000 psig applied on the piston-l17/ The-lower ferrite makes the AE piston ~ skirts:struc'turally
' stronger.
g
. s t
crown was well -above peak co,mbustion gas working pressure on the piston, crown. The strain gauges on the peak stress area of the AE piston skirts provided information about the pressure required to close the gap between the outer ring and the crown. , LThis information was then used in another set of experiments in which the skirt loading was maximized. During the warming up period,'the loading on the skirt is the highest, when there is a' gap between the skirt and the crown's outer ring. Calcula-tions_were performed to calculate the stresses in the high stress region. The stress at 1,627 psig working pressure was estimated to be -68.7 kai. Peak stres'ses in AE skirts were foundLto be generally lower than corresponding AF values. In addition to gas loading, stresses due to bolt preload were
-evaluated by finite element model and measured on AE piston skirts. Since the. bolt preload was found to have no affect on
-the stresses in the critical area of the stud boss region, it was'omitted from the overall' finite l element analysis of the skirt.
125. Stresses and displacement under gas pressure and.in-ertial-loads were' calculated:for the AE. piston skirt.using.
-ANSYS finite element computer-program. -Two models, a full model of.the skirt and a local model of the crown stud boss, y
~
were prepared. In additioncto these skirtimodels, a finite el-cement,-model of the crown was. developed for placing on the
, - I ~
r- ',.
+ ..
), .:
r
- global skirt model. The Owners Group developed additional x=
' local model's to better evaluate the magnitude and location of
~
? .
1the peak. stresses in the_ stress gradient wherever required.
+1 -
;126.; Interaction between the crown and skirt was analyzed twith the help of the models and the information obtained
[thEbugh'the, experimental stress analysis. The analysis indi-lcatedtthat the' gap between the skirt and the crown closes uni-Jfo rmly . Uniform gap closing means an even distribution of load
.and i therefore uniform stresses throughout the load-bearing e .
. . . Dr ~' areas of the. piston skirt.
127.LThe-peak stress magnitudes computed by finite element. _3 l . . . . . _ m Lanalysis_wereLcompared with the experimental results. The Own ; 9ty an Ters: Group analysisLfound generally _ good agreement between.the , i.expehimentalfand-finite 1elementiresulbs. The average experi-
^
~ mentalj.valueson-AE-sk'irts.were28timesbelowthefiniteele-ment' values. 'TheTdifferences were attributed to1 assumptions-
' ^
- , .suchfas.a rigid
- wrist pin in finite element analysis. The-ex-
~
perimentalL.and finite element stress' analysis 1results(were then)
~
f; '
' appropriately used;with the fatigue'and. fracture properties'ofs
[the; material _'to" analyze _the possibility'of-crack: initiation 11n ~_
^
. . ' - the pistons'kirts. -'A modified. Goo'dman diagram;was plotted for-itwoI different> yield st'rengths_(measured-and specified). The OwnersjGroup finite ~~elementcanalysis predicted 1that althoughL w
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- -53->
s 3 ( . , x ( C , ,
)
2
. - = v . .1
[ y : A * ,. "' 4 % "" , ' " ' * '
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g ".i fhV ^ fatigue cracks may-possibly' initiate in the stud boss region of <f the AE' piston skirt, these cracks will not necessarily grow, because they would propagate into a region of decreasing stresses. "The experimental results, however, predicted that cracks.will:not initiate in AE piston skirts. 128. A crack propagation analysis was undertaken to ana-
' lyze whether the cracks that are predicted (by finite element k analysis) to possibly initiate in the stud boss region of AE
.. piston skirts could substantially grow.' Crack growth calcula-I
-tions.were performed using the cyclic stresses which included
- cold and steady-state running and.the' range of gap (between
' crown'and skirt)' sizes from 0.007 to 0.011 inches. Cracks of depths.up: to O.48 inches were considered for the' analysis. 'The
-result.of this' analysis was a prediction that, in the absence 1.of significa'nt. residual stresses, the cracks will not propa-
, cgate..-'Very-low residual' stresses are present71 n theistud boss
' area of AE piston. skirts, as previously discussed. 'l 129.! Based on the favorable service history,18/ results of.
inspections of engine-operated AE pistoniskirts, and the..re-
'p' sultsfof experimental _ stress measurements and fatigue.and s
I V
, .18/l.AE piston. skirts have accumulated in~ excess of'6000 hours without failure ~.' See Board Notification.84-152,iAugust 29,.
- 1984.
=
^
^
c .
=
w .; fracture mechanics analyses, _ the Owners Group concluded that nthe AE piston skirts are adequate for unlimited life under full su' load. operations. s - 3 s
~
The
'130. No additional analyses were performed by SwRI.
u p^ - J l*
-analyses, results and conclusions of the owners Group were
- found to be : appropriate and applicable to TDI- diesel e'ngine
- pliston' Eskirts at PNPP. No rpecific recommendations were'made
- i
.by the Owners Group. SwRI agrees with the Owners Group analy-2 1A sis'and~therefore also makes no recommendations.
3, -
;y ?- '
.K. Cylinder = Block and Liner.
P
-131.-The cylinder block in the TDI standby; diesel genera-7 tors;makes up the central framework for the engine.
In formu-- ilating.the design _ review task-description for'this component,
- ;the(Owners' Group determined that the critical functional attiibutes.of theiblock are that it provide: _1), mounting sup-
- 1V1
~
, ..;j:
~ port for-the' cylinder-heads;.2)E-support for the cylinder n ner'
~
I 5
?and; camshaft;L3) passages'for. engine-~ coolant;:and.4)E reaction
.\:
ito.thefloads_of the cylinder-firing pressure. 'Thefdylinder= y y
-liner: forms the walls.of2the combustion chamber. Functional'. g
- .y l attributes'of thefliner-are: 1) ability lto'contain the high' &n
~
-4 j Temperature and!high pre ~ssure' combustion gasses (along;with the ' -
fjY - +- ' - rcylinder head'and; piston);p2)-ability;to provide a guide for-' x .. ..
, , lll 5, ^ , 7 ~t '
. -the; piston; Land'3)~abilityito withstand reactive,sideLforces
~ ~
p, _ff. Qr, \: -1
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- . without ' exce s sive' 'we ar e o r ' scuf fing i " , :,~
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~ a 132. The cylinder blocks were included among the Phase I
~
~ components'because of block top cracking exhibited in blocks in Lthe Shoreham Nuclear Power Station engines and other TDI en-gines in nuclear and non-nuclear applications. Four types of
-cracks'were identified in the Shoreham engine blocks: 1) liga-Ement (from cylinder liner counter bore to head stud i counterbore; 2) stud-to-stud;-3) stud-to-end of block; and 4)
_ fcircumferential. cracks at the liner counterbore. All of these
' cracks connected with the block-top surface and could be detected by surface inspection. All three engines at Shoreham had~1igament-type cracks. At Shoreham, one block (from Emer-gency Diesel Generator.("EDG") 103) was.found to have a Widmanstaetten graphite microstructure, discussed below. This block was found to'also have. stud-to-stud and stud-to-end cracks. No other' nuclear engine blocks have been-found to"have
! substandard material. . Ligament cracks have been found in TDI
- 'enginefblocks of other nuclear stations, although the. cracking was not!as~ extensive"as at-Shorsham. Shoreham:is the only lo-
. : cation :were stud-to-stud 'and stud-to-end, and circumferential L:
-cracksLhave.been'found. No instance has been reported where
< cylinderLblock cra'cks'have resulted in failure of'an-R-4 or RV-4 engine. 1 Cam gallery cracks:-were also;found on the.Shoreham cylinder" blocks. LHoweverb the Owners' Group has stated that-.
- theseicracksfare unique to the in-line-R-4 engines and not~of
, . concern wfth,the'V type engines ~ installed at'PNPP.
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133. Since manufacture of the blocks, block to liner
. clearances,have been verified and the liner vertical protrusion above the block top (proudness) has been reduced. PNPP has advised SwRI that the liner proudness has been reduced to the
-specification-currently used by TDI.
134. The. Owners Group analysis included the following
-studies: 1) review of bl.ock-to-liner cold clearance; 2) mate-rials evaluation; 3) block and liner loading; 4) block top
< stress analysis; and 5) fatigue and fracture analysis of bloqk
' cracks.19/. SwRI-reviewed the Owners Group report with atten-
- tion being directed towards the me'thods of analysis used, find-ings andLinterpretation of findings.
- 135. The Shoreham-engine blocks analyzed by the Owners L Group-had-' operated a significant amount of time.at or above the
. nameplate. rating of 3500 kW. As.part of its engine
;requalification testing Shoreham operated each engine 100 hours atLor above the design load. During engine disassembly.~and
; inspection,ethe aforementioned ligament ~ cracks were found.
-; After-. inspection, unit'EDG102;was operated'through-100 starts-
- to, loads greater than 50%. nameplate ~1oad and was then~
~,~. t
, 1_9f, A. detailed: discussion of the analysis performed is,
' contained in-the Owners Group report,'" Design'Reviewtof TDI R-4 and RV-4: Series ~ Emergency Diesel Generator _ Cylinder-Blocks andi LLiners,"(preparediby FaAA.
J f
? -
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' 1J $ _. b _s r4
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1 reinspected. Eddy current examination showed no discernable cextension ,of ligament cracks. In general, cracks were detected
-and measured using visual, liquid penetrant, and eddy-current
- inspection techniques.
L; l136. A cylinder block strain gage test was conducted by theEOwners Groupt on unit EDG103 following a 100-hour-full power endurance test. Measurements of strain were recorded during.
. - preload while the cylinder. head stud nuts were beincJ tightened. <
' Strain measurements were also recorded during steady' operation at 0,s873, 1500, 2000, 2500, 3500 (full load) and 3830 kW. To
~
l measure. effects of thermal loading, strain measurements.were takeniduring at slowfstart, a.. quick start to: full load,-and a start during-a loss of offsite power / loss of: coolant accident ~
;ws '
, (" LOOP /L0CA")? stimulation.
Strain measurements:.during quick' l . w .. starts didLnot exceed the peak'. steady-state values at each' , 4 power levell As a means: of; studying the. effect of' different .
-load' components on.the block top./ stress state,; contributions
~
,. from bolt =preload,' thermal 4 loading and cylinder pressure were I
- fobtained'fromithe test' data. The'results.were used in conjunc-y r Ltion with a scalezfactor developed by the' finite element:analy-q_. ,
- isis:to estimate conservativelyLthe mean_-and. alternating ,
, istresses'at'.the= crack initiation lsitesLof: ligament-and stud-to ' ,
s'tud.L cracks. ff y' a u --'
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fi: 7 137. A metallurgical analysis was conducted by the owners
. Group. The analysis consisted of an investigation of the microstructure, composition and mechanical properties of four TDI R-4 cylinder blocks from three engines at Shoreham. The four cylinder blocks investigated were EDG101, EDG102, EDG103
_( original) and'EDG103 (replacement). It was establinhed that the microstructure of EDG101, EDG102, and EDG103 (replacement) was normal for grey cast iron but the EDG103 (original) block was characterized by an abnormal graphite distribution.
~
, (degenerant Widmanstaetten graphite). It is generally accepted that1the mechanical properties of grey cast iron with the
'Widmanstaetten ferrite are lower than normal. Higher.than nor-mal' amounts of the tramp elements (lead and antimony), were present-in.the EDG103 (original) blocks.
138. Uniaxial tensile tests'and smooth bar axial fatigue tests were performed on representative material for the EDG103 original block and!other material with a normal microstructure.
-Fatigue crack _ growth rate tests were also performed.using com-9
; pact tension specimens. These tests demonstrated that the ten .
~
sile strength-and endurance limit for the EDG103. original material.were significantly below normal. .The-cyclic stress tests on the compact tension also showed a lower than-normal resistance to fatigue crack growth for the EDG103 original 1
' block material.
L .
.' ..m_
~
139. The study described in the Owners Group report was complete in scope'and adequate data was presented to support the observations made. The study clearly showed that the orig-inal,; cracked EDG103 cylinder block was characterized by an ab-
. normal microstructure and that the mechanical properties of that material were substandard.
W
.140. The Owners Group fracture and fatigue life evaluation produced a cumulative. damage analysis which' takes into account a cumulative Fatigue Damage Index ("FDI"). This index accounts
'_for. hours.of operation at each power level and the corre-sponding'mean stress and cyclic stress driving the crack at each power level The index quantifies the effect of differing fatigue crack growth rates of different materials. This allows comparison of the test period experience on the original
- Shoreham EDG103 block, with its documented degraded fatigue re-sistance, to the expected behavior of.other type cylinder
- blocksihaving the fatigue resistance characteristic of typical
~
grey.castLiron un'er d required test and postulated LOOP /LOCA
-conditions. . Application of the-~ cumulative damage' analysis can
~ be used to. set. future engine operation limits. Safe operation
; can be; assured during_a; LOOP /LOCA based'on Shoreham benchmark Ioperations in combination with past-operation of the, engine C
provided proper: procedures are-followed as referred to in the ,' .OwnerstGroup report.20/_ F
- 20/' This may. involve-non-destructive examination, and material.
._ properties evaluations.
t
e , j ...
' 141~:The. Owners Group analysis of circumferential cracks
~
shows these cracks to'be the result of loads applied to the fcylinder linerLlanding. Liner landing pressure is controlled mainly by the interference of the liner collar (proudness) above;the block top. PNPS engine blocks.have been reworked to reduce this interference to the current TDI specification. The Owners Group finite element analysis shows that stress perpen-
'dicularcto the plane.of.each postulated crack was found to de-crease with distance from-.the corner ~and to become fully com-pressive at a depth of less.than 0.5 inch. The original EDG103
- block, with inferior material properties, developed cracks less
~
'than,3/8. inch deep after. operation in excess of 1000 hours. It is concluded.that~circumferential' cracking in blocks of nominal EdimensionLand material' properties will' slow down-and arrest and will not impair the operationtof-the TDI diesel generators'.-
- 142. SwRI'has reviewed the'OwnersLGroup stress' analysis and agrees:with'the1 assumptions, methods, procedures and re--
suits.- Recommendations set'forth'by the Owners Group'and con-
~ '
ccurred with by.SwRI are the following:
. Per' iodic inspections are necessary to demonstrate
.that!each' cylinder head block is:capableLof meeting:
.its' intended' function-as?a component'in a diesel; gen-at erator in nuclear standbyLservice.
. 'All. blocks-should be' metallurgically evaluated'to verify that.the microstructure'is; characteristic of-
, typicalfgrey; cast. iron.
_Y.-. a q w 'a9s4 m n 7mmw v e rn. ---e-, e me n --A - - - - - - - - - - - -
- a. : ,
, 4 w .-
3 . Cylinder blocks that are inspected and found to be
-free of ligament cracks can operate without-addition-al inspections for combinations of load and time that -< produce less than the excess cumulative damage index that has'been; demonstrated by its operation at the time of the' latest. block top inspection. Blocks of engines that have operated without block top inspec- ~
tion or,for a-time beyond the last inspection in ex-cess of the allowable fatigue damage index should conservati.vely-be assumed to have cracked ligaments.
. For blocks with known or assumed ligament cracks, ab-sence of detectable stud-to-stud or stud-to-end cracks.between the-heads should be established before 4 Lreturning the engine to emergency standby after any operation in excess of 50% nameplate load. Any stud-to-stud or stud-to-end crack indications must be evaluated with detailed inspection to assure that
'they extend less than 1.5 inches from the block top i
.before returning the engine to emergency standby s after any. operation inLexcess of 50% nameplate load.
It is necessary,to evaluate the microstructure to en-
~
.sure typical cast-iron.
The:above: recommendations.are being implemented at PNPP. L. Turbocharger 143.'The turbochargers on the TDIistandby diesel genera-tors utilize' exhaust gas energy to drive the turbine which
^ drives a compressor-on a common. shaft to pressurize the engine intake 1 manifold ~ . This forces =more air into the combustion a
chamber,-permitting more fuel-to beJintroduced-which results'in: n Lhigher? combustion pressures.and net engine output than that' possible with natural aspiration. TheiTDI inline~DSRV-4 series
; engines.use-assingleiturborcharger while the DSRV-4-series en-gines use-.-two1turbochargers, one for each bank. : The PNPP
'DSRV-16JenginesusetwoElliott.Mogel190Gturbochargerseach.
ce
-621 $- F I .A w __
4
.g.
'144. In1 drafting the design review task description for this' component, the Owners Group determined that the critical Efunctional attributes were that: 1) the turbocharger components
; have adequate strength and fatigue resistance to react to loads imposed by flowing engine exhaust gases; 2) the turbine and
- components have the ability to withstand a high temperature corrosive environment; 3) the lubrication system have the abil-
-ity to supply sufficient oil to the bearings quickly after start up and and. continuously while running, and maintain ade-X .quate' discharge oil temperatures; 4) the cooling system must
. provide' sufficient water flow and pressure to maintain adequate component temperatures; 5) the external piping must not trans-
'mit excessive thermal loads to the turbocharger-casings; and
- 6) the turbocharger must--be sized to avoid surge during opera-tion.
f
.145. The turbochargers were included among the Phase I components because of fthrust bearing, -nozzle vane, nozzle ring.
capscrew'and' washer, and nozzle' ring failures on TDI nuclear-standby diesel' engines. Non-nuclear TDI' engine applications also show failuresidue to the above problems and other causes 4 that-are addressed'in the. functional' attributes.
~"
'146. The' Owners Group performed analyses 21/ to:
' 21/D A detailed discussion is included in the FaAA report "De-
. sign Review of Elliott Model 90G Turbocharger Used on
.(Cont'inued Next Page) p l <
4 V
'=n.
, 1)' determine the~ loads on the thrust bearing and the nozzle
' ~
- ring. assembly from_the aerodynamic forces of the exhaust and
-induction air gases and the preload on the nozzle ring capscrews; 2) determine the load carrying capability of the
~
thrust and radial bearings under both transient (startup) and steady-state conditions and the lubrication and cooling
~
requirements in terms of the type of oil, oil flow rate, oil (temperatures and oil pressure; 3) compare the loads imposed on (the.' thrust bearing with the bearing load carrying capability and d'termine if the thrust bearing design is adequate under
^
e all operating modes; 4) determine the dynamic response of the
-rotating mass under;startup, normal operation and overload con-
"ditions and. compare _this to the rotor systems natural modes and
- -imbalance specifications to ascertain whethur deflection end
+
subsequent thrust bearing performance degradation or. vibration would be a problem. 1147. In addition to these analyses, the Owners Group per-L c
-formed-inspections of. thrust bearings 1from nuclear engines that^
?had experienced a series of starts and some-operating time.
1The thrust bearings from:an engine that used the drip s s (Continued) Transamerica Delaval DSR-48 and.DSRV-16 Emergency Diesel Gener-- ator: Sets", prepared for the Owners Group.
- n g i 4
m p r y *T"---
k I- y,e x.
=
ON ; pre-lubrication system only experienced measurable wear on.the Eorder-of 0,.002 inches with 67 starts and 85 operating hours. gThe thrust bearing from an engine with a before and after (b &
, ; a). lubrication system, activated manually for two minutes prior ,
, _ :to-start, and with 32 starts and 275 operating hours, experi-
~
E cenced:no(measurable wear. x 148. The. Owners Group concluded from its analyses that the _ thrust _ bearing would provide adequate service if a
. <prelubrication system with a b & a pump and with a drip provi-p ision was. installed.and used during non-emergency starts. The-
- Owners' Group-found'that both the thrust and radial. bearings Lwere.of. adequate design, given proper lubrication, to operato t
.at the loads: introduced by the exhaust and induction air gases-4
- (w Lduring' transient', normal operating and overload conditions.
'TheLOwners. Group recommendedL that the-thrust bearing be-in-
' fspectediat each 5-year overhaullintervaltor after 40 emergency
-(withoutithe.use of.b & a. pump)-starts. The recommendation'for 2 inspection'afterE40cstarts is1 based:on findi'ngs fromLnuclear
^ Longines?that have undergone 100.tol300Lengine starts without-y - r
# \ithe $ & a pump l-(but with drip prelubrication) before. thrust-
~
- 6. ' bearing failure. . The-Owners Group also-recommends, based on
~
ithis same: data [ that:the drip prelubrication' system, with'at-
.least;O.1-gallons-per? hour-(gph)~oilfflow, be; retained 1for p .eme'rgency. starts. '
f
' } 4 "
! 1 u w '), 7- 1 A /
57 , 4 :. 149. The Owners Group found no problems with regard to the dynamic performance of the rotor assembly. While the
- turbocharger passes through five critical speeds during startup,-all of these are heavily damped and are passed through 1quickly. There are no critical speeds near the normal and overload turbocharger speeds of approximately 16,500 rpm.
; Analysis shows that r) tor imbalance to 1.0 oz-in (the maximum allowable by the manufacturer is 0.06 oz-in),.would not impair operation'of the turbocharger. Thrust bearing deflection due to rotor! shaft bending wil].not occur. Operation of the turb'ocharger'is sufficiently removed from the surge line on the compressor performance map to preclude reverse loading damage.
150. The-Owners Group reported on the nozzle = ring 7;-: capscrew,. washer and vane failures in a' supplement to the orig-
~
-inal report. They investigated the failures of these compo-nents at several nuclear power plants. Their analysis conclud-
-ed-that the nozzle vane failures were due to high cycle fatigue introduced by engine vibration or exhaust gas pulsations. - The EOwners: Group report also concluded that while. isolated vane
, Lfailures may occur, they'have not resulted in any degradation q in diesel; generator. performance or a shutdown among the nuclear Jengines investigated.22/ No cause for the cracked washer was f 22/' Maintenance' performed during every outage'would permit identification of;1oose or missing. vanes or capscrews.
l 9 N. O
+s , - .
. . : a? .
e an , :. >
&f -
J+ I LI < g _ found.2g :The failure.of-the capscrews is attributed to im-zproper.preload.- The single ring failure is attributed to prob-
', :able' impact from a. broken vane. The Owners Group recommended
!thatialisturbochargers be inspected for nozzle vane damage and cthat all.-capscrews be properly torqued to the 18 to 22 lbf-ft a -
"" specified' byj Elliott. In addition, the Owners Group recom-mended that;the-exhaust temperatures be monitored and correc-NU _ ;<tive actions taken if they exceed the values recommended by
. . -l,Z3I .
aw e
* : .n
!151.-SwRI reviewed the Owners-Group analysis to confirm V fits applicability to.the PNPP engines. The methodologies and I n assumptions'were examined :in detail: to determine if they con-fonned to accepted engineering practice and supported -the Own-SwRI is'in agreement with the Owners
, ers' Group conclusions.
' Group results.andLconclusions.
~
SwRI would, however, add to the-
~
.' Owners. Group recommendations an inspection'to assure an ade-
;quateilubrication supply to the thrust : bearings. . Based on an
' ! independent?analysisL of the ' thrust bearing, : SwRI recommends.
._that,PNPPi 1) assureithatsthe oil supply to=the turbocharger.is filteredLto 10 micronsf as specified by Elliott; 2)l perform:
ispectrochemical analysis of~the< engine oil,-as recommende'd by' ,
^ ,G X: Failure ~of a washer:would?notfcause'any degradation of
<diese17generator ~ performance.
~
' ~
, - 1 C <
/n
' 9 f
.' > N
._0~ ,,,
1
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p- i the owners Group, to~ detect the copper level which would indi-
~
cate degradation of the thrust bearing; 3) confirm that the b & a pump provides at least 0.5 gallons per minute flow;
- 4) confirm that the oil pressure to the turbocharger is between 25-35-psig and that the pressure, 10 seconds after start, is at least 10 psig; 5)-that the oil inlet temperature is less than 180*F and that the coolant temperature rise is less than 215*F;
- 6) lhat the coolant temperature is less than 190 F and that the
. coolant temperature rise is less than 30 F.
~
152. Given application and use of_the drip and b & a prelubrication systems, compliance with the above mentioned (turbocharger coolant and oil parameters, and adherence to the Owners Group maintenance. recommendations, SWRI feels that the Elliott Model 90G turbochargers will perform satisfactorily on' the PNPP engines.
. Jacket Water Pumps 153. The jacket ' water pump,, taking suction from the j acket standpipe, delivers coolant (treated _ water) at the required pressure and flow rate to the engine jacket water header. In so doing, the pump'provides the. coolant circulation needed to cool the' engine cylinder assemblies, exhaust manifold,.
-turbocharger, intercooler,'and engine lubefoil cooler. A water
; pump failure would result in diminished or complete loss of I
o ,.
; coolant flow with subsequent overheating of critical engine systems. With loss of coolant and/or high coolant tempera-
=
/' tures, : the engine would eventually shut-down.
154. The:particular water pump design used on the DRSV-4 engine.does not have a history of failures. However, the jack-
~
- et' water pump used on the TDI standby generators equipped with the in-line diesel engine, model DSR-4, has a documented histo-ry of shaft failure in nuclear service. These failures oc-curred at the Shoreham facility, and resulted in the Owners Group conducting a design review of both pumps even'though they differ in several areas.24/ Besides the difference in size of the pumps, other notable differences are: 1) the impeller di-ameter;and impeller material; 2) the method of securing the im-pellerLto the pump shaf t; and 3.) the shaft coupling mechanism used to interface the pump to the engine. These differences -
are important in that they limit the applicability of design
' evaluation and failure history to a particular pump. In other words,. conclusions derived from analysis of the DSR-4= pump-failure do not directly. apply to the DSRV-4 pump.
l 24/ A detailed discussion of the analysis is included in. Stone and Webster Engineering Corporation, " Emergency Diesel Genera-tor Engine. Drive Jacket' Water Pump Design Review," April 1983,.
~
and its supplement,-June 1984.
- ) .1
-:0 .. lhl < si L ,; ,
- 155.'In! formulating the design review task description for the; j ack'et water pump ( s) , theEwnersGroupdeterminedthatthe
- ~ z
, m- . .
- ' critical functional attributes consist of the following:
S - 31)fthat.the pump ~ drive gear and shaft coupling be adequate to ,
.c transmit--the combined torsional loading, and 2) that the pump 2' shaft deliver the required torque to the impeller given the fluctuating nature of the. input. torque.to the drive gear. To
.n ensure:that pump design was indeed capable of performing these
; critical functions, the design review for the DSRV-4 pump fo-4 1 ccused;on,the2 torque transmitting components. The analyses in-scluded a' torsional analysis to determine maximum alternating
/ -ltorqueL(1595 lbf-in) and gear tooth loading (863 lbf), an anal-
" ~
Lysis-to determine mean impeller torque (2426 lbf-in)'at rated speedLand{flo'w, Sand a stress analysis of the shaft coupling and
'. --impeller-to-shaft interface using.the calculated torque values.
m , ,
- The results;of the analyses-indicated more than adequate design o m tmarcin;in the components (' design. factors greater than threeLin tall cases)'.
M - 4156.JIt should also be-noted that the Owners Group report '
, for the DSRV-4 pump reflects the use of.two different-impeller:
d'iameters; .eitherE12.1- inches or 10.75 ' inches.
~
This
% variability;is duejto differences:in plant? specificationJand
~'
; the consequential l coolant flow- requirement for: the- standby; gen .-
n oerators.. lIn addressing;the impactL of: the. difference in1 diesel:
, r
_ - L > s f ' 1 f
;( , f= ,
a ..
" gg ; o .
- 5. L ' : [*
Ai . s impeller; diameter on the review, the Owners Group used a con-
'servative approach.- one based on. analyzing the system with the 7
g[ , . larger 1 impeller. This situation represented "the worst case"
~
-in:. terms'offshaft.and coupling loading. Consequently, the l : stressilevels in'those pumps with the smaller diameter (such as
- m. tther10.75minch impeller at PNPP) would actually be less than "x icalculatedrin the review.
2 -157. Based on their findings, the Owners Group concluded ~
~
02 @t 'that'the pump design was adequate-for nuclear service. The re- [' isultsidid show, however, that~certain aspects of the design had
. limitations, but that these were overcome by redundancy in com-
^
' ponentifunction. The drive fit of the impeller onto the.sh' aft =
i taper-(At'aEspecified torque of.80 ft-lbs)-was determined to'be .
! adequate to res'ist- the -torsional loading. The. key and' keyway, as The
~ ~
however,Ewere of:sufficientsstrength to. transmit the load.
~
, . actual ratio.of working stress to the material yield strengths was~1ess'thanil/3'. Forfthis case, it was' assumed that':the.
drive fit would-help. prevent:theLkeysfromj" rocking"'and'wearingL , both?itself!and the' keyway.. - Furthermore,fthe analysis-did:not-ireflectLanytrotational influence ofithe impeller on the' degree d
. c .
d
- of? interference at operating' speed. f i
158..Theidrive_ fit _of the external spline;on'its shaft- - l
.g, itaperg(at:specified-nut: torque-of1120 ft-lbs) was:'also.found.to:
m .
+
t e - { - I 4r
' ". !) (
u
~ _
- _ - = - . - . .- .. .. -.
4' y. Lbe inadequate for. transmitting the total torque; it too re-
~ ~
l quired the, key to transmit the load. The analysis also indi-cated that,.because of the locking feature of the nut, it was possible:(during assembly) to have an installation torque .
. higher than specified. Accordingly, the Owners Group recom-
~
mended;that the installation procedure reflect both a minimum
' torque of 120-ft-lbs and'a maximum torque of 660 ft-lbs.
Stresses at the maximum torque were calculated to be approxi-
'mately.2/3 of the shaft yield strength.
159. SwRI reviewed the Owners Group report on the DSRV " jacket water pump to verify its applicability to the pumps at PM?P . The Owners Group. methodology.was found to be consistent with accepted engineering practice. In conducting the review,
~
.SwRI took.into' consideration the actual diameter of the PNPP pump impellers which.are 10.75 inches in diameter. Addition-ally,-SwRI considered-the impeller rotation and the effects of the stressec due to centrifugal force on the drive fit. The-concern.was that'the impeller might become loose on-the shaft taper and accelerate keyway wear. .
1 160. SwRI concluded that the Owner's Group review.was ap- , plicable'to theLPNPP installation. The smaller impeller diame-terthad'little effect on the torsional calculations as the dif-
,ferences l'n assumed mass moment of inertia were small (OG: 665 l
i
'_ v 1_ o ' .
--- - - - - = - - - - - - - - - - - - -
rc c g y:g, ,~,c , - y_.
+
p' , *
.y .; ?
-' , f,q n-q L -
'l1bm-in2,'SwRI~: 616 lbm-in2). The effect of impeller rotation y
m~ -
.on'the drive' tit at the impeller end was more significant.
3 Further~ assessment of this assumption indicated that thermal
~
expansion?of'the shaft would compensate for the rotational ef-2 facts.and maintain ~ adequate interference with the impeller hub
/to' prevent-accelerated wear of the keyway.
~ '
SwRI recommends, y however,gthat the-impeller' keyway be inspected at each outage
=to detect any key and keyway. wear.
. Crankshaft
?. -
w - 5 l'161'.?The crankshaft in TDI standby diesel generator en-gines; converts reciprocating motion, component inertial forces
/ Jand-gas pressure piston forces to-rotary motion and torque at
~
ithe output'. flange. In formulating the design review task de-
;scription for this component, the owners ~ Group-det' ermined that
", the critical functional attributes'of '.ne' crankshaft were that f
k - , ~1t have. sufficient. structural-stiffness to maintain acceptable o - u' .stressescinfthe-crankpin. web and main-journaliareas, maintain isystem natural frequencies sufficiently removed from Longine op-r i 7 Lerating speeds, Land that the design be able:to withstand' normal (main bearing mi'salignments.: Also,"the main bearings and-
. a
~
N .-crankpin areas must:be large enough.to maintain proper-tiubricatingioil film pressure but,small enough.to prevent .
. .endwear!of the bearing; sleeves.. The material.of the crankshaft
&g 4 -
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e and ,the'> surface-finish should be sufficient to resist fatigue crack:init,iation. 162. The 13" x 13" DSRV-16-4 engine crankshaft was includ-ed among the Phase I components due to three crankshaft fail-ures in non-nuclear ~ applications. There have been no failures
'of 13"'x 13" crankshafts on DSRV-4 engines in nuclear service.
The failures were attributed to torsional fatigue cracks initi-
.ated in the oil holes of-main journal numbers 6 or 8. Only the smaller 11" x 13" crankshafts on the three Shoreham Nuclear
~
. Power Station DSR-48 engines failed.
5163. The Owners. Group analysis was performed for the 13" x
.13". crankshafts in the emergency diesel engines at Grand Gulf-L; Nuclear Power Station. The engine types and the crankshafts of 7PNPP-are of identical design.to those at Grand' Gulf.
164. The crankshaft is required to meet the recommenda-- l .
<tions'of the Diesel Engine Manufacturers Association ("DEMA").
~
The Owners Group reviewedithe' design' calculations and torsiograph. test.results of TDI1for compliance with the DEMA
~ recommendations. The.DEMA recommendati'ons statei
- a. .In the caseLof~ constant speed units,:such as gen ~
erator sets, theJobjective is to-insdre that'no harmful
'1 torsional. vibratory stresses l occur within five percent above;and below rated speed.
r-
-_ j
- b. LFor crankshafts, connecting shafts, flange or coupling _ components, etc., made.of conventional materials, torsional vibratory conditions shall generally be consid-ered safe when they induce a superimposed stress of less
-than 5000 psi,. created by a single order of vibration, or
- ,_ a superimposed stress of less than 7000 psi, created by tlue' summation of the major orders of vibration which might come into phase periodically.
il65., Diesel generator' torques due to dynamic response are calculated in two steps. In the first step, TDI determined the
'* natural frequency of the crankshaft. TDI used the well-established Holzer method to. calculate the system's first three natural-frequencies. The first natural frequency of Grand Gulf's crankshaft'was found to be 28.8 Hz which~ produces e4th order-resonance at 432 rpm of the engine. In the' case of the PNPP engine the_ corresponding figures are 29.23 Hz and 438 engine' rpm due.to'the unique PNPP generator rotor and flywheel mass moments'of inertia. In-the'second step of torsional crit-ical stress analysis TDI determined the dynamicctorsional re-7 sponse'of the crankshaft due to gas pressure and inertia load--
Ling. In the' case of Grand Gulf, TDI performed the calculations for each order offvibration up to the 12th order. -In the case o5 the PNPP~ engines, TDI'provided the normalized values of'the Etorsional loading'for significantiorders. These values were
7, .: w
's A'
. :g ~ V,
.n
.' compared by-the Owners Group with those recommended by Lloyd's LRegister'of Shipping. -The largest single order was measured to ;
;c- .
I be(within 4% of those computed using TDI's value of normalized
, t'orsional loading. TDI used an empirical form of calculation f= .m Lto;er ure?that the diesel generator can be brought up to op- y 1erating speed without undergoing excessive-stresses as critical
< speeds are passed. In the case of the PNPP, engine, the 4th fh a- i ' order? critical speed of 438 rpm is important. The Owners Group -t e
/ analysis concluded that in'this particular type of design (V-16 "P is l engine'withl articulated. connecting rods) the 4th order loading-i from one' bank cancelsithe other, which significantly reduces
~
< the excitation. However, the excitation is sensitive to the
' balance between the two banks.
t i <g s s 166. The' nominal shear stresses for the significant orders
-.were. calculated. The largest single order. nominal shear stress
^
. 'of.1956 psi was found to be well'below-the-5000 psi allowable-m
- by[DEMA. The' corresponding stress. level'in PNPP' engines was x
,calculatAd:-to be 1780 psi.: The'torsiographidstests= performed-p oon the Grand Gulf: engine by TDI: were reviewed by the owners'
< . m
' Group.2_5/ On(theiGrand' Gulf engine the first natural frequency'
~
(h
~
was found'to.'bec28.7.Hzfwhich compared.very well with TDIs
-r r.
L
, -25b A;torsiographic' test'will be performed-at PNPP during.the "c; '
engine pre-operational period. See' Affidavit of-Gary.R.
-Leidichiatil 20.;
l' 4 g
~ . 'd
~
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' ?'
s , c p. - 1 s a s
.x . ~
computed value of 28.8 Hz. The TDI analysis established that the nominal shear stress is 8540 psi per degree of free-end vi-bration for the Grand Gulf engine. The Owners Group calculated a vector summation of orders 1 through 8 for the PNPP crank-shaft of 0.583 degress amplitude which would yield 4979 psi ac-i
. cording to SwRI. This is less than the 7000 psi maximum DEMA allowable stress. The largest single order stress of 2028 psi
- was found to be less than the DEMA allowable stress of 5000 psi. The corresponding figure for the PNPP engine was 2118 psi
- - also less than the DEMA recommendation. A good agreement was
' found between the TDI calculated stresses and the measured 4P stresses.
167. The Owners Group verified data to make sure that the crankshaft stresses are within the DEMA allowable for a speed
- range of 440 to 450 rpm +5%. For the PNPP engine at 7000 kw power rating and 95% of rated speed the maximum nominal shear stress was found to be 2281 psi. At 7000 kW power rating and
'105% of~ rated speed the maximum nominal stress was found to be 3296 psi. The amplitudelof both.these stresses is well below the DEMA allowable stress-of.5000 psi. The Owners Group analy-sis has emphasized the importance of adequate engine balance
~
' and the necessity of not operating the engine below 440 rpm ex-
' capt during startup and shutdown., The Owners Group analysis concludes.that the balance specifications provided by TDI may
_ _ _ J
O 4 I be' adequate, however, it has cautioned against a possible con-clusion that all. engines will respond identica11y to this bal-ance. .The torsiograph test planned for the PNPP engines will l determine whether these engines are balanced satisfactorily. Ll68. The Owners Group performed a dynamic torsional analy-sis of the crankshaft to determine the true range of torque at
'each crankthrow. The Owners Group developed a torsional model e of the crankshaft to supplement TDI's conventional forced vi-i bration calculations. In order to compute the true summation of the stresses due to various orders, the model included com-putations for phase relationships between the various orders.
The first three natural-frequencies of the PNPP crankshaft were calculated. The natural frequencies were found to be in agree-- ment with those computed by TDI. 169. The Owners Group analysis' considered th; harmonic loading onJthe crankshaft. cas pressure, inertia forces and frictional loading were considered for_the harmonic loading s : calculations. The dynamics of-a V-16 engine are such that.the
'9 4th order load components from the left and right banks almost cancel. .In practice, however, due to various reasonsLsuch as manufacturing tolerances'and. individual cylinder timing, the
- balance is not complete. To simulate the unbalance the Owners
' Group applied ~one degree delay in'the:right bank; cylinder, 'In .
pl.*am
_ y ...
~ ' M. ,
m ' .; s 4 s 9'
- _ , - +
H: , m -9 btheLabsence.'of torsiographic test data, the calculated ampli- , x
;tudes;are not compared with the measured amplitudes. The model
~
Lwas used tc calculate the range of torques at each crankthrow.
+
?Thetskress.~1evellwasfoundtobehighestbetweencylinders3 l
'[ ~'-- : an'd 4,?55and 6,f.7 and'8. .The highest nominal shear stress.am-p Lplitude of 5335 pai-was found to be lower than the 7000 psi al-
'I $1'wableiby/DEMA.
o For the PNPP crankshaft, the critical speed i.was found to be 438.4 rpm. The Owners Group performed calcula-Etions to determine.the amplitude of free-end vibration and the s associated.nomin&l shear. stress at 7000 kW power and at a crankshaft critical: speed;of 438.4 rpm. The highest nominal
' ~
' t shearfstressiamplitude of 5128.8. psi was found to be lower than-l the:7000cpsi' allowable by DEMA.
'170' The Own re s Group performed a mo'dal~ superposition U ~ analysis of:the crankshaft for PNPP. Pressure loading was.
~
obtained from the. dynamic test at Shoreham. This analysis. cal-i
. culates the nominal'. shear stresses at each crankpin and main-
- 'journel location. [The maximum ~ amplitude'of nominalistress wasi
. found-:to be;5335 psi between cylinder. numbers 5 and 6-~for'a load at 7000 kW.; The nominal" stresses were found.to satisfy-
, , theDEMA requirement,oand are less.than,5000fpsi for a single Jorder, and lessJthan'7000 ps1 for combined orders.
~
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fc F f~ Wll l. [ ,' - i171. The owners Group analysis concluded that the TDI cal- [ t t culations are appropriate and show that the crankshaft stresses
.)
are-b'elow DEMA recommendations for U single order. The dorsiograph. tests performed on a DSRV-16-4 diesel generator set- .
. Latbthe: Duke' Power Catawba Nuclear Generating Station showed the
. y I'[
w ;; , . . (peak-to-peak crankshaft stresses to be'within the DEMA recom-
;mendations.
-mG 4 - ?h-
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~
172. The Owners Group; analysis is appropriate and applica- [ bliito the PNPP engine. SwRI did not find it necessary to per-
' form any; additional analyses. Considering the similarities-of-the1 crankshaft design and the similarities of TDI's and the
- Owners' Group results,:SwRI has concluded that the PNPP. crank-
~_ lsh'afts are adequate for their intended service provided'all of
.thelOwnersiGroup recommendations.are followed. SwRI recommends.
i f, - ', .that;a-torsiograph test be. performed and the results compared
- . Lwith both the owners Group analysis and TDI's calculations.
m.J :The.results'of the'torsiograph test:should demonstrate:that the- "
~ %,,, crankshaft stres'es; s meet:DEMA, standards and that they are close itolthe TDIland'0wners Group val'ues.s-Individual cylinder timing.
shouldi beladjustedkto-: accomplish'enginb balance and bring the stress. values inL.line'with'thoseMof TDI'and the: Owners Group., 1 Thelsetpoint 'of-:the- governorfis above1the' critical speed of 438 '
.g "4 / rpm. ,
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< Connecting Rods -
sig - 173.'The' connecting rods used in the TDI standby diesel m _ 1 generators" installed at'.PNPP transmit engine cylinder firing -
. ~ , t g- , forcesjfrom the pistons to the crankshaft such that the g '
. ..fh . r
)
; reciprocating, motion of the pistons induces shaft rotation and me .
- ~ . . .
% J_ ~ _outputitorque. . By. virtue of the V-cylinder configuration, the ,
,g , 1 imechanism'rel quired to perform this. function consists of two w a
- (connecting rods' arranged in.a master-articulated manner. This -
f airrangement- requires 'more sophistication in bearing design and , T ~ e , 1 Eassembly' methodology than that found- with in-line type engines.
.Such complexity makes the.' design analysis more involved and re-1'
' ; quires-that-there be substantial operating experience and/or q .
~
l experimental.. data to confirm thefdesign integrity.
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;174. Initially, theiconnecting rod. assembly:was produced- .
, . . f-(withfl-7/8~1nch! diameter bolts':tofsecure the main assembly.
2jointX(master-rod boxJto; link' rod box). : Operating' experience- :
,c
- s. .
(inLnon-nuclear 7applicationsJindicated(that:the: design =was vul .. , 1F . .. - .s e
^
_;nerable-to1 failure by'onelof'two' mechanisms <- ' either by.: loss-4 x ~ .. _ ,. .
.1. ~
_ iof bolt (preload resultingfin bolt-failure or by;the fatigues f - I m, !failure o'f: the: master rod box with. cracks Minitiating at? the , thread roots.'-iTo_ compensate-for~the loss'of bo'lt' prelo"ad,5the p43 4. J"'
!installationLtorquoispecification1forLtheijo'nt bolts was=in-lt, g -
q . - . i
.a , .
m _ f, i - 1 , acreasedL' Corrective action-for the' fatigue o~f the master rod' - - 9>
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if'. t' F
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.,y, c ee-w 4 .os w--~w.s...e~___-ee.. .-= 41 -.
o, L
,. box'iesulted in a design revision with 1-1/2 inch diameter
' bolts, torqued to 1700 lbf-ft to provide the same clamping ic J' force obtained-with the 1-7/8 inch bolt configuration torqued to-2600 lbf-ft. Elis change in bolt diameter provided a greater material section and consequently reduced the stress
$;i .' levels'in the master rod box. PNPP is supplied with the 1-1/2
,. inch bolts.
175. In light of the failure history compiled with I non-nuclear application of the connecting rod and the fact that a rod failure would require immediate shut-down of the engine, (the Owners Group includhd the connecting rod in the Phase I
- components. The scope of the review included engines with both ztypes of rod assemblies (i.e.,- those having the 1-7/8 inch bolts'as'well as'those having 1-1/2. inch bolts). 'In formu-
- lating the design review task description for the connecting.
- rod assembly, the Owners Group. determined that the system must provide 1three functional-attributes in order-for,it-to be
.e acceptable for nuclear standby usage: 1) it must be of suffi :
;cient buckling strength and fatigue resistance to' withstand the expected-firing forces and inertial loads; 2)'it must_be of
-sufficient dimensional uniformity so as not to distort lubrica -
tion' performance-and/or the clamping effectiveness _of mating-o- surfaces;fand 3) itLmust utilize fasteners and torque'specifi-1
-cations that support the_ combined loading without fatigue,
'preload relaxation,oor severe thread distortion.
b
}
l 5 , 176. The design review conducted by the Owners Group to 6, verify the functional attributes focused on three aspects:26/ 1):a detailed physical examination of failed components to ver-
-ify failure mechanisms; 2) finite element stress analysis to i i
~
' predict _ performance'under those engine operating conditions dictated by, nuclear service, and 3) comparison of the recults from'1) and12) above with experimental data and operating his-
. s
. tory to= establish credibility.
177. The analysis conducted by the owners Group indicated i i
- that both rod assembly designs were acceptable for nuclear ser-
' :vice. --In the case of the 1-7/8 inch bolt configuration, the
-fatigue sensitivity exhibited (in terms of actual failures) was
. confirmed through physical-examination of failed parts. Sup-i .
- Jporting analytical docum'entation quantified the failure process
~in: terms of the maximum operating. stress level for the 1-7/8
~
bR^ inch bolts (taean: 11:kai, alternating: 4.94 ksi) and.for the n.:
~
1-1/2' inch ~ bolts-(mean: 8.82 kai, alternatine: 4.51 kai) and its-relationship toJthe modified Goodman line failure criteria.
- The G5odman linerwas-defined:by the ultimate strength of the iconnecting-rod. material'.(AISI 4142)'of 115 kai and a calculated iendurancel limit-at the bolt hole. location'of 5.213 kai.
~ ~
[ M 6 2_6/. - A; detailed description ofithis-analysis is included 11n:
.FaAA report "DesignLReview of Connecting Rods:for Transamerica-
. 'DelavaltDSRV-4 Series Diesel. Generators," August 1984,: prepared =
-for the-Owners Group.
4 ,
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r-Comparison with the Goodman criteria showed that the material would indeed have a finite life. This observation was further supported with calculations of crack growth rate, which showed that the effective stress intensity factor range was 5.27 kai1TEI. which is within the fatigue threshold range of this ma-terial of from 5.0 to 7.5 kaiYi5$ 178. The methodology outlined above was also applied to
' the 1-1/2 inch bolt configuration. The results, however, showed that the 1-1/2 inch design was not vulnerable to fatigue failure under the same engine load conditions. Application of the same Goodman line failure criteria yielded a safety factor of-1.08 for the 1-1/2 inch bolts. While a safety factor of this magnitude is low, field experience with connecting rods with 1-1/2 inch bolts.has been favorable.
179. For both designs, the owners Group. recommended that each rod assembly be inspected with nondestructive techniques to. confirm the absence of flaws. In.the case of the 1-7/8 inch o-bolt system, the inspection should be performed.at intervals of 200 engine hours. ForLthe 1-1/2 inch bolt' system, such as that used at PNPP,' the inspection need only be done initially to confirm the_ absence'of pre-existing flaws. Beyond these , t T
- F F.
iw _
m .
!- i T qp inspections, the rod assemblies need only be checked for proper i bolt torque at installation. '
180. SwRI reviewed the Owners Group report on the cen- l
> necting rod assembly to verify its applicability to the con- f
~ necting rod' assemblies in place at PNPP. The methodology and cassumptions were examined in detail to ensure consistency with E ' accepted' engineering practice and to ascertain that the find-
.ings did indeed support the' conclusions. No exceptions or
-unresolved differences regarding the report and its conclusions Sere-found. Furthermore, SwRI concludes that the Owners Group
. findings with'. respect to the 1-1/2 inch rod configuration do
~ -
l apply to - the PNPP diesel generator units. The rod assemblies
~
are'. suitable for their intended application provided-the main-
-1tenance recommendations of the Owners Group ~are e,bserved.
These recommendations are that: 1) the bolt holes be initially- . i
. .a -
inspected to. verify'.the absence-of pre-existing. flaws, 2) the
,.c .
1 protocol ~forJ. torquing the rod-bolts'_reflectn.the importance e2
~
- - cleaning J the'threadedTsurfaces and using e. threadrlubricant'as
,n Lspecifiedfin the TDI instruction manual, 3) the bolt torque"be-
~
i
- f
-checked;at each outage to. ensure:that bolt preload has not been Ilost;landf4)La<compreh'ensive inspection ofithe connecting: rods?
4
. .~
[belconducted at each eng'ine overhauluinterval, 1 15 g g 1i .
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IV .' - CONCLUSIOMS AS TO THE TDI DIESEL GENERATORS' RELIABILITY 581. In' order for the PNPP TDI diesel generators to per- [} form reliably, they must meet the following requirements:
-l(1).they must start on demand, attain rated speed, and accept ' ~~
load.within;the specified time; and (2) they must have the ca-L- 'Jpacity to supply power continuously to the equipment needed to S : maintain the' plant in a safe condition. SwRI has concluded
,N thatithe sixteen Phase I. components in the PNPP engines are of
_ ! satisfactory design and will perform their intended safety - relate'd function based ~on a. review of the Owners Group reports
, . .e. _
fand backup-material, analyticalfanalysis of various component N .1_. .
' attributes,Jand' discussions.with Owners Group and PNPP person-ne l'. - Based'on its: investigation, SwRI concludes that the PNPP
. engines will] permit the< diesel generators to perform reliably
[ /as" defined-by th'e requirements listed above. t .- - . ,
~
'182. Achievement of reliable'dieselTgenerator performance
.~ .
[ '
-alsoLrequiresthatiPNPP implement the. recommendations of the. ,
T .'OUne'rs. Group.and-SwRILwith regard to inspection and mainte . .
~
Initialiinspections. recommended'by the: Owners Group'and:
. 27 nance.
m, , . SwRITpriorJto diesel generator. operation'have be'en1 performed at , aC .R - wp ;;;;; + Other inspections.;and:mainte'nanceSactions require'dCp~eri '
- 7 ,, ~
,w .
-s JPNPP. ..
wa -
.m.. m . . .
iodicallyJduring:the operationalTlife:of'the dieselsihave b'een JG ,1 , .
>a.
~
- 6. aD[f v, ~ e ;)elineatiedin:thAfOwnersjGroupMaintenanceyMatrixtforthePNPPc
_ -. - n:
- N;$ ' , ,
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3 m-s~
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7 *t= , y;
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. . _ . .lY% ,
- ht ,; ' e + ,
- s. s engines which is included in the PNPP DR/QR Paport. Other
. inspections and maintenance actions recommended by SwRI, as outlined.in the preceding paragraphs, will also be implemented at PNPP.
/
f Charles D. Wood DI Subscribed and sworn to before me this 8/6 dayI of January,1985. C(cdz h t-yt.b a ' 3 Notary Public My commision expires: , ,a , Louis Rediguez ' I a- .: .- .. u; zilli35 a a..ir.... a..eu,s
. a f.:1 Cc.':2..Mca Ephs11/7!35 a ,
k: - 6- .
* ~
Exhibit A CHARLES D. WOOD III Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas Professional Experiences o Vice President of Engines, Emissions, and vehicle Research Division at Southwest Research Institute (SwRI) (1983-Present) o Director, Department of Engine and Vehicle Research at SwRI (1974-83) o Section Manager, Automotive Research Department at SwRI (1967-74) o Senior Research Engineer, Automotive Research Department at SwRI (1962-67) 2 o . Propulsion Engineer, Ling-Tesco-Vought, Inc. (1961-62) o Test Engineer, Ling-Temco-Vought, Inc. (1958-62) Education: B.S. in mechanical engineering, Rice University, 1956 JM.S. in mechanical engineering, Southern-Methodist-University,:1962
. Professional-Qualifications:
~ Registered Professional Engineer'in the State of Texas.'
- Professional Associations:- ,
L' o SAE (formerly Society of Automotive Engineers).
' Positions held with SAE Advanced' Power Plant
- L . Committee,. Diesel Engine Committee, Chairman of South Texas Section.,
o Texas Society of Professional Engineers. { ; l r
- - ~ - .. . . . - . .. . --.. - - - - - _ . _ . . . - _ _
Publications:
"An Unthrottled Gaseous Fuel Conversion of a Two-Stroke Diesel Engine," by T. E. Ritter and C. D. Wood, SAE No. 730139, February 1975.
l
" Design and Development of a Lightweight Winch Drawn Bulldozer,"
by T. E. Ritter, C. D. Wood and 3. W. Colburn, 3r., International Society for Terraln-Vehicle Systems, Proceedings of the ISTVS Conference, Vol. HI, June 1973. aMechanisms of Dust Erosion," by C. D. Wood and Park Espenschade,
- SAE Transactions, Vol. 73,1963.
I
" RED 500-Techniques and Performance," by C. D. Wood, SAE No.
730830, September 1973. -
"An Analog Heat Release Computer for Engine Combustion Evalua -
tion," by R. A. McFarland and C. D. Wood, SAE No. 760333,1976.
" Improvement of Automobile Fuel Economy," by C. W. Coon and C. D.
Wood, SAE No. 740969, October 1974.
"Unthrottled Open-Chamber Stratified Charge Engines," by C. D.
Wood, SAE No. 780341, February 1978.
"An Experimental Investigation of an Open-Chamber Stratified Charge Engine," by C. D. Wood, presented at the Central States Section,1978 5pring Technical Meeting, The Combustion Institute, March 1978.
" Performance of a Stratified Charge Engine," by C. D. Wood, SAE No.
790434, February 1979.
" Performance of Coal Slurry Fuel in a Diese! Engine," by K. Tatalah E and C. D. Wood,5AE No. 800329, February 1980.
1. l- " Direct Injected Methano! Fueling of Two-Stroke Locomotive Engine," by C. D. Wood and 3. O. Storment, SAE No. 800328, February 1980. l "A Simplified N Model for Spark ignition Engines," by C. D. Wood, ASME No. 8 - 43, February 1980. .
" Alternative Fuels in. Diesel Engines - A Review," by C. D.-' Wood, Reprinted from $P-480 " Alternate Fuels," February 1981.
'" Experience on the Use of Fuel-Alr Explosions for Controlled Earth-moving," by C. D. Wood, A. R. Nye, R. B. Melton and D. L. Craft,
. SAE No. 710160, January 1971.
s " Erosion of Metals by the Higi Speed Impact of Dust Particles," by C. D. Wood, Institute .of Environmental Sciences' 1966 Annual Technical Meeting Proceedings,1966. l w, ..,a.- . w- y U.- g -% ._.,,,,%-...-.y,
4 -
"Yehicle Diagnostic Systems -The State of the Art," by Robert N.
Hambright and Charles D. Wood, ASAE Paper No. 73-144, presented at the 1973 Annual Meeting of the American Society of Agricultural Engineers, June 1973. i, " Alternate Forms of Energy" by Conan Furber and Charles Wood presented at the Railway Fuel and Operating Officers Association, Technical Conference, Chicago, Illinols, September 22-24,1980. I 1
" Trends in Diesel Power," Oral Pmsentation by Charles Wood to the 33rd International Convention of the Association of Diesel Specialists in Houston, Texas, September 24,1980.
4 Inventor or Co-Inventor of the Following U.S. Patents:
- 3,372,273 Apparatus for Breaking a Layer of Ice on a Body of Water by Repetitive Combustion Explosions, C. D. Wood 3,600,116 Alt-Contro! 5ystem for Apparatus Displacing Material by l Combustive Explosions, C. D. Wood,3. M. Clark, and A. R.
Nye. 3,680,287 Air Filter, C. D. Wood,5. A. Olsen, and 3. C. Potter. 3,744,018 Method of an Apparatus for Producing a Repe'titive Seismic Impulse, C. D. Wood. 3,750,837 Explosive Selsmic Energy Source and Quick Release Valve, C. D. Wood. 3,732,240 Method of an Apparatus for Proving an Impact to a . Vehicle-Carried Penetrating Tool, C. D. Wood and John M. [ t Clark. l 3,736,416 Apparatus Having a Filter _ Panel Disposed Across a Fluid Passageway, C. D. Wood. . 3,787,144 Explosive Pumping and Dredging Method and Apparatus, C. " D. Wood. 3,801,346 Method for Applying Particulate Coating to a Work Piece,- C. D. Wood, R. B. Melton,3. M. Clark, R. 3. Mathis, and W. D. Weatherford. 3,839,848 Method and Apparatus for Cleaning Air, C. D. Wood and 3. M. Clark. 3,880,368- Combustion Method and Apparatus for Generating l Repetitive Explosions, C. D. Wood,3. W. Colburn, and R. B. Melton. l ( _ ~ v.--, . - - - - , - - , _ . , , . - - - ,
o ~ , ;
, 3,913,381 Method and Apparatus for Applying Particulate Coating Material to a Work Piece, C. D. Wood,3. M. Clar, R. B.
Melton, R. 3. Mathis, and W. D. Weatherford. 3,918,937 Particulate Lead Trap System, C. D. Wood,3. G. Holloway,
- H. W. Barch, and M. B. Treuhaft.
3,918,944 Lead Trap, C. D. Wood and M. B. Trethaf t. 3,924,897 Earth Ripper Employing Repetitive Explosions, C. D. Wood, R. 3. Mathis, A. R. Nye, and 3. W. Colburn. i 4,011,886 Sleen Valve, C. D. Wood 4,194,374 Draf t Power Sensor, H. 5. Benson and C. D. Wood s I l i N l l-i L
..}}