ML20087B855
| ML20087B855 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/08/1991 |
| From: | Galeazzi D, Matthew Mitchell MKW POWER SYSTEMS, INC. |
| To: | |
| Shared Package | |
| ML20087B847 | List: |
| References | |
| REF-PT21-91 10CFR21-0058, 10CFR21-58, NUDOCS 9201130344 | |
| Download: ML20087B855 (15) | |
Text
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a REPORT fio. :
10CFR21-00$8 November 8, 1991 10CFR2? REPORTI!10 OF DEFECTS Air lioll-COMPLI ANCE
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COMPONENT:
Hounting Bolt - EMD #188146 Camshaft Beari 39 Block Assembit Mounting SYSTEM:
All Diesel Generators with EMD 645 Series Engines
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CONCLUSICH:
Defect is Appli: cole only to the Diesel Generators at Southern California Edison, San Onofre Nuclear
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Generating Station PREPARED 9Y:
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DATE Donald D. Ga/eacti, Engineering Manager
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Vann Mitchell, Quality Manager 4
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REPORT HO.:
10CFR31-00$8 DATEt 11/8/91 PAGE:
1 0F 7 l
SUMMARY
This is a f ollow-up report to HKW Power Systems' notification to Mr. Thomas Hurley of the NRC dated 10/11/91 (see Attachment 1).
HKH Power Systems received notification on 10/10/91 that, upon disassembly of the failed San onofre Unit #2B diesel engine, seven (7) camshaft bearing block assembly mounting bolts (END
- 188146) were found to be shorter than the required length.
A total quantity of eighty (80) bolts, four (4) per cylinder, are utilized on the 20 cylinder EMD 645 engine.
The length of the seven (7) bolts was confirmed to be 4.460 inches on 10/14/91 (see Attachment 2).
Bolt #188146 has a nominal length of 4.625 inches with an allowable length of 4.531 - 4.625 inches.
(See ).
f COMRONENT Bolt, EMD #188146, 3/8-24 x 4-5/8" hex head.
CUSTOMERS _AFIECTED Southern California Edison, San Onofre Nuclear Generating Station only.
OEFECT Bolte shorter than the required length of 4.531 - 4.625 inches have been found installed in a diesel engine.
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REPORT NO.
10CPR31-0058 DATE:
A&/8/91 pAGE:
3 0F 7 ANALYSI.S The cause of the installation of the short bolts appears to be related to previous engine work.
According to correspondence from Southern California Edison (see Attachment 4), new bolts were previously supplied by HKW Power Systems, Western Regional International, and Stewart & Stevenson at various times dating back to 1981.
HKW power Systems has researched their records and confirmed that all bolts 1188146 which were supply to Southern California Edison as well as all other nuclear customers were within the allowable length of 4.531 - 4.625 inches.. The bolt length is a criticci characteristic which is verified during congonent inspectic, as part of HKW's nuclear parts dedication program.
HKW Power Ayatems as well as EMD does not have any reports of failures of the camshaft bearing block mounting bolts on any EMD engines which have been in service (nuclear as well is commercial service). contains the engine manufacturer's (EMD's) evaluation of this issue.
In EMD's opinion, the short bolt lengths at San Onofre would probably not have resulted-in engine failure.
If short length bolts are installed and do not strip during initial torquing to the specified torque, then it is unlikely that they will strip or come loose in service.
The above demonstrates that the short camshaft bearing block mounting bolt condition is not a generic problem and is limited to the San Onofre diesel generators.
C0!. RECT LVE.. ACTION 2
Inspect all engines at San onof re where previous camshaf t work has been performed which may have introduced short-length bolts.
All camshaft bearing block assembly mounting bolts shorter than 4.531 inches should be replaced.
Inspect inventory at San Onofre for bolts #188146 which are shorter than the required length.
All bolts shorter than 4.531 inches should be replaced.
?
e REPORT fiO.1 10CFR31-0058
~i DATE!
11/8/91 PAGE:
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6 ATTAcitHE!1T 1 (1 PAGE) f tiOTIFICATIOli TO !1RC DATED 10/11/91
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F october 11, 1991 Mr. Thomas Hurley Director - Office of Nuclear Reactor Regulation 11555 Rockville Pike Rockville, MD 20052
Subject:
potential Reportable Defect for EMD 645 Series camshaft Bearing Block Assembly Mounting Bolt (EMD #188146)
Dear Sir:
on 10/10/91, MKW Power Systems received notification that, upon disassembly of the failed San onofre Unit #2 diesel
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engine, seven (7) camshaft bearing. block assembly mounting bolts (EMD #188146) were shorter than the required length (4-7/16" versus 4-5/8").
The bolts have a tolerance of
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-3/32": therefore, the bolts are short by 3/32" from allowable minimum dimension.
A total quantity of-80 bolts (4 per cylinder) are utilized on the 20 cylinder EMD series-engine.
EMD is currently evaluating this issue and we will issue a-report as soon as we obtain the results, i
We do not have any reports of failures of.the camshaft bearing block mounting bolts on any EMD engines which have been in service (nuclear as well as commercial service).
At the present time, we do not believe that the shorter bolts used in this' application will degrade the engine.
Yours very truly, HKW POWER SYSTEMS, INC.
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Vann Mitchell Quality Manager
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REPORT NO.I 10CFR21-0058 DATE 11/8/91 PAGE:
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EMD PARTS LIST NO. D30, PAGE 1 EMD BOLT 108146 l
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.f1iCf8080tiYt D e v ili O N O(Hf8A4 MOfOti CO$#O$& tion Parts 1ist No.1130 CAMSil Al?T llF.AltlNG lill ACKr.TS 12.16.204451:nrines G
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Part Quantity
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N o.
Number Required Description A
12-645 engines B
16445 engines C
20445 engines
'I 832W94 12 16 20 IILOCK ASM... Bearing. Drilled cap 2
8320995 12 16 20 BLOCK ASM... Bearing. Plain cap 3
S071s76 24 32 40 BE ARING.. Shell. Upper half 4
8071176 24 32 40 BEARING.. Shell. Lower half 15 8045976 24 32 40 KEY.. Illock to crankcase. 5000 x.5000 a 21/4 long 6
'10534 24 32 40 SCREW.. Key No.10 24 x 7/8. Flat hes.J. Slotted M7 58146 48 6d 50 ItOLT. 3/h. 24 x 4-5/ 8 het. heaQ b
8373316 48 M
60 WA5!!E R.. Special. Formerly 103321 BRACKET ASM... llearing. Left bank
'9 8253146 1
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BR ACKET ASM... Bearing. Right bank l Accer.sory Drise End 10 8233152 I
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'll 8253259 1
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ilR ACKET ASM... Bearing. Left bank i Camshaft Drive End 12 8253250 1
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BRACKET ASM... Ilearing. Right bank I 13
~29147 8
8 8
DOWEL.. Locating. 3125 x 9/16 lon 14 138294 8
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SCR EW.. Socket head ca 1/2 13
- 2. Formerly 8253973 BEARING.. Shell Upper b f i 15 8237900 2
2 2
16 8237900 2
2 2
BEARINO. Shell. Lower half ; Accessory Drive End 17 8253825 2
2 2
BEARING.. Shell. Upper half t Camshaft Drive End 18 8253825 2
2 2
IIEARING.. Shell. Lower half f
'l9 187697 8
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SCREW. Bracket to crankcase. l/2 20 x 4 3/4. Socket head cap 4 20 8044728 4
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KEY.. Bracket to crankcase. 5000 x.5000 x 13/4 tong.
21 110534 4
4 4
SCREW.. Key No.10 24 x 7/8 Flat head Slotted 22 455012 6
6 6
IlOLT.. Ilex, head Not drilled 1/2 20 x 11/4 Formerly 6028329 23 8028329 6
6 6
BOLT.. Hex, head Drilled. I/2 20 x 1 1/4 For mountmg Ref. Nos, il and 12
'24 8028312 6
6 6
BOLT.. Ilex. head. Drilled. 3/8 24 x 1 For mounting Ref. Nos.11 and 12
'25 8116738 A.R.
WIRE,, Lock. 500 ft.. Currently applied to camshaft drive end only I
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Ifor oversize Crankcase Keyway. use Stepdown Key 8136773. 300010.3623 ster 21l4 fong.
!/ Tor Oversi:e Crankcase Keyway, use Sterdown Key 8166324 3000 to.3623 ster - l-ll4 long.
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REPORT No.1 AOCFR21-0058 DATE:
11/8/91 PAGE 6 0F 7 t
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s ATTACHMENT 4 (1 PAGE) i F-SCE CORRESPONDENCE-ABOUT PREVIOUSLY SUPPLIED BOLTS
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October 16,1931 Frank Amend i
MKW Power Systems Phone 919 977 2720 FAX 910-4461134 Sub}cet:
Emergency Diesel Generator Camshaft Boaring Block Bolts San Onotto Nuclear Generation Station, Unit 2 i
Por our telnphono conversation,7 camshaft bearing block bolts removed from the Emorgency Diesel Generator woro tound to bc approximately 4.460'Instead of tho nominal 4.625' length. The canishaft of the engino has been worked in the past with the installation of some now bolts. Inus, tho short bol.is may, or may not, bo original installation. Although we have not located all the procurement records of new cam boating block bolt Installations, we have havo found past procurement records for now bolts with MKW Power Systomt PO OH100056 eind Western Regional intomational PCs BE2N4030, BA095015, and 8E124085. Also,it appears Stewart & Stevenson supplicd new bolts in 1981 for repairs attor a camshalt failure, John D. Osbome 714 368 6681 D r.u sric a :
mno dae.ksrwrs surrueo 1%rs e 188/40 udoat bes Ro. 4Hosso20 Ysa br=a>ecucco A o GHIOM" pro ^/or Have Mrs st /89/4 6 -
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REPORT No.:
DATE:
11/8/9A PAGE:
7 op 7 ATTACHMENT 5 (2 PAGES)
EMD EVALUATION l
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OCT 2 81991 ELEC1RO-MOTivt
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C 0 M N U H._I_Q..A T I O N DATE:
October 25, 1991 TIMP.:
TO:
Frank Amend FROM:
C. J.
Farbor MKW/PS EMD LaGrango, IL Fax:
(919) 446-3830 Fax:
(708) 387-5845 l
Following this covor page, there will be page(s) transmitted (SEE MEs8 AGE BELOW).
If problems occur in transmission or all pages are not received, please contact us at (708) 387-5884.
If GH Network service is available, please use 8-563-5484.
===========================r===============z=========
Subject:
EMD E!3GINEERING OPINION REGARDING SHORT CAM DEARING BLOCK DOLTS (p/N 188146) FOUND ON S.O.N.G.S. UNIT /2B This letter is in responso to a request from our distributor, MKW-PSI, to evaluate the possible risk to EMD engines in nuclear installation from undersize (short) camshaft bearing block bolts.
A root cause failuro analysis of the engine failure which occurred at the San Onofra Nuclear Generating Station (S.O.N.G.S.) on the EMD 20-645E4 engine (part of the tandem diesel gonorator unit 28) concluded that the failure started with the loss of clamp load on the bolts of the roar-most left-bank camshaft bearing block.
The longths of both bolts were moauured and reported to be undersize at approximately 4.460 inches.
the length specification for the 4-5/8 nominal bolts is 4.531 - 4.625 inches.
The inboard tapped hole in the crankcase was reported stripped, however, the outboard hold was not stripped.
The failure analysis suggestod that the short bolts coupled with distressed / degraded throads in the tapped bolt holds were the most probably cause of the loss of clamp load.
In the opinion of the writer, another highly probably contributor was improper torquing of the bolts.
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Five other short bolts of similar length were reported found at the second, third, sixth, and eighth can block position from the left-bank-rear corner (cylinder locations 20,19 18, and 17).
No other short bolts woro reported.
IN the opinion of the writer, it seems likely that the short bolts are actually 4-1/2 nominal longth bolts (specification:
4.406 - 4.500 inches) which were introduced into the Icft-bank-rear quadrant of the engine during one of the times when the camshaft nogment at the location wan
Trank Amond October 25, 1991 Page 2 changed out at S.O.fl.G.S.
Consequently, this condition may be isolated to the subject engine only.
Regarding the risk of similar-lenoth bolta entanoid ir La 1**
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..nete, is cannot to stated with certainty that the resulting throad engagoment length would be sufficient in all application.
A toleranc'e study of the appropriate components (bolt, Washer, cap, block, bolt chamfer, and tapped hold chamfer) showed that the actual thread ongagoment vill fall in thu range of.261 -
.479 inches when all components are within spoolfication.
Statintically, the actual production thread engagement should fall very close to the center of this rango.
Stresn calculations of the minimum required thread engagement (using minimum material proportioc)l show that the crankcase threads may strip in this application if the engagoment length is loss than.254 inches.
given the approximete.125 inch difference in longth between 4-5/8 nominal and 4-1/2 nominal bolts, obtaining thread engagements near this minimum in a real possibility.
However, since thin application involves a very stiff clamping system (no soft gasket), the low upward dynamic forces within the cam block during operation will manifest themselves in relaxation of the forcon between components and natas significant additional loads to the bolts.
Therefore, it seems reasonable to conclude that if
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a given bolt did not strip during initial torquing to the specified torque, it will not strip or como loose in service (unless subsequent to some other failure).
If it becomes necessary to renew camshaft segmonts/ bearings. It would be prudent to inspect and remove suspected short bolts before retorque in order to avoid potential distress to the crankcaso bolt-hold threada.
R e a t s,.
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C.
Farber l
Service Department Power products CJF:blb/frnkamnd I
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