ML20072D181

Comments on Agenda Items for 820625 Site Meeting Re Technical Aspects of Torque Wrench Calibr.Motor Operator/ Yoke Connection Tightness Check,Torque Wrench Calibr Accuracy & Expansion Anchor Installation Discussed

ML20072D181
Person / Time
Site:	LaSalle
Issue date:	06/26/1982
From:	Rodabaugh E E.C. RODABAUGH ASSOCIATES, INC.
To:	Terao D Office of Nuclear Reactor Regulation
Shared Package
ML20072D133	List: ML20072D170 ML20072D181 ML20072D189 ML20072D193
References
FOIA-83-89 NUDOCS 8306230031
Download: ML20072D181 (6)

Text

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~* ** Attachment G E. C. d?odaGaugA cassociatas, Dna.

• 4625 CEMETERY ROAD e HILUARD, OHIO 43026

- 614/876 5719 June 26,1952 Mr. Cave Terao Mail Stop P-522 Mechanical F.ngineering Branch U. S. !!uclear Regulatory Cc::issica

ashingten, DC 20555

Subject:

Meeting at LaSalle Flant, June 25, 1982 en Technical Aspects of Torque tirench Calibration Cear Iave:

A copy of the Agenda is included as F.nclosure 1. My ec cents cen-cerning each Agenda ite: follow.

1. Motor Operator / Toke Connection Tightness Check Roger Lan'esbury (:.?.C, Regien III) found (6/18/E2) that two nuts on a =cter operator / yoke connection vere " finger tight". ( A pessible reascn is that it was necessary to recove the operator for clearance during con-structicn and all of the nuts vere not re-tightened during replace:ent of the operator.) The Applicant has co_:itted to checking all safety-related motor operated valves inside contairment (2/. valves) 12:ediately and all safety-related noter operated valves outside contairment within 6 :onths.

Fmelesurs 2 is a listing of meter operated valves inside contairment.

It includes a colu:n headed "Terque Spec." Apparently, this ir.fo::aticn was obtained in the last week er so and, prior to then and presu= ably during the tine of the alleged lack of accurate torque vrench calibration, there was _n,9,specified torque for these particular bolts when, or if, they were icosened during plant construction and then re-tightened. A discussien of the technical significance of the torque vrench accuracy, if in fact a terque vrench was used in the re-tightening, is irrevelant" r

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2 Considerable discussion occurred at the meeting as to what was meant by "Urenchtight". In my opinion, "Wrenchtight" is an adequate instruction to any competent workz:an. However, the Applicant agreed to put "A value" in place of "Urenchtight". Once that specified torque is established (as it is for'two of the four valve manufacturers as shown in Enclosure 2),

the technical significance of the torque wrench accuracy beco=es relevant.

Fre: a technical standpoint, torque during bolt tightening is a =ethed of trying to achieve an appropriate cla ping force. As brought cut by Mr. Hood of SPS Technologies, the relationship between torque and cla: ping force, for a given no:inal bolt geometry (size, threads per inch, thread tollerances, etc.) can vary videly depending upon the coefficient of friction.

My own experience (en flanged bolt bolting) indicates that if one first' calibrates torque versus cla: ping force using a seasonably good thread and other =ating surfaces lubricant, then if one continues to use that sa:e lubricant and noninal bolt geccetry,the clasping force can be predicted fres the torque within a scatter of 2305 vith about 905 confidence.

However, 1f' the lubricant is not controlled, then fro: what I have read it appears that the cla: ping force, for a given torque, could easily vary by a factor of 4 or =cre.

Fortunately, the safe operation of bolted connections of the type under consideration are not very sensitive to prelcad cla: ping ferees.

To the exten , that leads are cyclic, it is desirable to have the preload higher than those loads so that the bolt stresses vill remain essentially constant and fatigue of the bolts vill not occur. In addition, even if no leads are anticipated in paper calculations, most power plant equip-cent operate in an environ =ent of at least low-level vibration and bolts should be tightened sufficiently so that the nuts do not vibrate loose in service. Tnese consideration: establish mininu: decired pre 10 ads.

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"'he maxi:u= preload =ay be significant if ,by any chance, prying effects are not properly evaluated in calculating loads. Ecvever, if leads are appnpriately cal.culated and bolt sizes are selected to accc: o-date those loads, then maxi =us preload is not significant in a loading i

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] sense. Sone bolting materials such as SA 193 Grade 37 can be susceptible ,

to stress corrosion cracking and excessive preload may contribute to such cracking. (A perhaps necessaiy co-condition is lack of adequate heat treat-cent control in =anufacturing the bolts.)

In su==ary, a preload not less than calculated loads is desirable and, regardless of calculated loads, the bolts should be tight encugh to pre-vent loosening due to vibratien. Overtightening could be a proble: if

, stress cor-osien cracking is a pessibility. With controlled lubrication, a specified torque could be useful. Without controlled lubrication, "Wrenchtight" is probably better than specified torque. In view of the large variations of cla= ping force for a given torque, torque vrench accuracy of *203 is adequate.

2. LaSalle County Expansion Anchor Insta.11ation and :nspection Values i

Sargent a:d Lundy's description er their basis for setting installa-tien and inspectica specified torques for concrete anchors ( specifically, Eilti Wedge Anchers) indicates to se that torquc vrench accuracy of 20%

is adequate.

3. Terque Urench Calibration Accuracy (*25 + d65)

'"he t25 is the c="bration fixture accuracy and the 36% is the linits within inich a torque vrench cust be accurate as deter =ined by use of the calibration fixture. In principle, the torque wrench accuracy is *S$.

Based on personal use of torque vrenches some years ago, I suspect that in " tight" places inere the torque vrench can not be pulled on in the sa:e canner as in the calibration, additional inaccuracies could occur.

However, in view of the vide scatter in torque versus cla: ping force

'without controlled lubrication, whether the torque urench is accurate to

• S5 or *203 ( as used in tight places) is a relatively trivial consideration.

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. 4 Incidentally, there is a good discussion of preloading of bolts in flanged joints in the AS!E B&PV Code,Section VIII, Division 1, Appendix S.

That Appendix gives an equation that gives an indication of what "urenchtight" means in ter=s of cla: ping stress in the bolts.

S = 45000/ 6 (1) where S = probable bolt stress developed can"ay when using standard wrenches d = -- *-e7 die eter of bolt.

Equation (1) was developed by E. C. Petrie in 1937. It :.s li ited to d 61/2" and prcbably to d 6 2"; vell lubricated threads and other nating surfaces; : 0 threads belov d =1", the 8 thread per inch series above d=1".

Yours Very Truly D S1%Y E. C. Rodabaugh Inclosures 1 and 2 .

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T.1 RAT.TR COUNT! STATION C0K:0LTiLTE EDISON COMPANT/ NUCLEAR EDOULATORT CO'C".ISSION MISTING JUNE 25, 1982 - 1:00 P.M.

i P12TICIPARTS: Nuclear Heralatory Co-'ssion (NEC)

NEC Consultants Co=envealth Idiscs Co=cacy

! Sargent & Lun:iy E=gineers

1. Motor Operator /rche Connection Ti@tness Check

2. !aSalle Co=ty E=pansion Anchor Installation and. Inspection 7alues 3 Torque W e:ch Calibratics Accuracy (1 2% + d 6%)

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Rx CONTAlllMI:ltr MO'lOlt OPEllATOR/VAINE YOKE ISOLTING TIGilTNESS REQUIRE!!ElfrS ,

VAINE NUMBERS SEL SPEC. MANUPAC'lVRER 10RQUE SPEC. t[TORQUESPEC. REFERENCE lH33-F023A J-2500 G.E /Atwood&Morrill 110 Ft.-Lha. Instr. Manual Part IX Step 12 IB33-F023B IB33-F067A 1833-F067B 1D21-F016 J-2938.ol Anchor-Darling Wrenchtight Instr. Manual - Confirmed w/ John Chappell, IE12-F009 .

A/DV Eng'g. Manager IE51-F063 1G33-F001 IG33-F100 ~

1G33-F101 1G33-F102 1G33-F106 IWR179

, IWR100 IVPll3A J-2940 Plsher Controls Wrenchtight llo Instr. Manual Reference; Info. Obtained IVP113B From Glenn Ilyatt IVPil4A IVPll4B 1D21-F001 J-2950.Ol Anderson-Greenwood 75+10 Ft-Lbs. Drawing BNO3-6492-500, Rev. B IB21-F002 3B21-F005 lE12-F099A IE12-F099B .

1E51-F076 150110 In-Lbs. Drawing $NO3-6490-510, Rev. C t

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