ML20030B577

Final Deficiency Rept Re Use of Pipe Shims Around Expansion Anchors in Base Plate Installations.Use of Shims Discontinued

ML20030B577
Person / Time
Site:	Susquehanna
Issue date:	08/11/1981
From:	Curtis N PENNSYLVANIA POWER & LIGHT CO.
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, PLA-890, NUDOCS 8108180305
Download: ML20030B577 (16)

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@ Pennsylvania Power & Light Company Two North Ninth Street + Allentown, PA 18101 + 215 I 770 5151 Norman W. Curtis Vice President-Engineering & Construction-Nuclear 215/ 770-5381 August 11, 1981 Mr. Boyce H. Grier 8

Director, Region I

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U. S. Nuclear Regulatory Commission

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Fp h=I 631 Park Avenue

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\\% "+ mp SUSQUEllANNA STEAM ELECTRIC STATION be f

FINIJ REPORT OF A DEFICIENCY RELATING TO 5;i1MMING f4 BASE PLATES 4

ERs 100450/100508 FILES 840-4/900-10 PLA-890

References:

PLA-646 (3/2/81)

PLA-586 (12/9/80)

Dear Mr. Grier:

This letter serves to provide the Commission with a final report of a deficiency relating to the use of pipe shims around expur.sion anchors in base plate installations. The deficiency was originally reported in PLA-586 and the information contained herein is submitted pursuant io the provisions of 10 CFR SC.55(e).

The attachment to this letter constitutes the final report on the deficiency as prepared by PP&L Nuclear Plant Engineering based upon Bechtel Engineering's final report.

We trust you will find this information satisfactory.

Very truly yours,

[

c Mbd N. W. Curtis Vice President-Engineering & Construction-Nuclear FLW:sab At*.achment

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81G8180305 810811 gDRADOCK 05000387 68l PDR

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Mr. Boyce H. Grier August 11, 1981 cc Mr. Victor Stello (15)

Director-Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. G. Mcdonald, Director (1)

Office of Management Information & Program Control U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. Gary Rhoads U. S. Nuclear Regulatory Commission P.O. Box 52 Shickshinny, PA 18655 l

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Attachment to PLA-890 1

t FINAL REPORT ON i

j SHINMING OF BASEPLATES FOR i

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UNITS 1 AND 2 i

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i PENNSYLVANIA POP.*R E LIGHT COMPANT TWO NORTH NINTH STREET 1

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TABLE OF CONTENTS SECTION DESCRIPTION PAGE Title Page 1

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Table of Contents 2

1.0 Purpose 3

2.0 Background

3 4

3.0 Deficiencies 3

4.0 Safety Implications 4

5.0 Corrective Action and Evaluation 4

Deficiencies 6.0 Field Inspection 6

7.0 Future Installations 6

8.0 Conclusion 6

FIGURE 1 Welding,of Leveling Nut to Pipe Shim FIGURE 2 Shimming of Baseplate Table I Evaluation of Electrical and Instrumentation

'upports S

Appendix A Design Example Using Analytical Method 8

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1 1.'0 PURPOSE _

This report provides the final infor=ation as required by 10CFR 50.55(e) subsequent to the notification of a potentially reportable deficiency.

The subject deficiency is associated with the construction =ethod of providing pipe shi=s around concrete expansion anchors for Q and safety related baseplate installations at Susquehanna Steam Electric Station--

Units 1 & 2.

2.0 BACKGROUND

2.1 In June, 1980, Non-Confor=ance Report (NCR) No. 6154 was issued.

The non-confor=ing condition was due to the fact that for a specific pipe support baseplate installation, pipe shims were placed around the expansion anchors between the concrete and bas.eplate for the purpose of grouting (1"-2") and leveling.

Further= ore, leveling nuts were tackwelded to the inside of the pipe shi=s (see Figure 1).

Further investigation by Bechtel field personnel, as a result of the NCR, revealed that the use of pipe shi=s was videspread. However, the tackwelding of leveling nuts to pipe shi=s (or in so=e instances, velding of pipe shi=s to anchors) was li=ited to the work of a specific crew of pipefitters.

Bechtel field engineering has traced all supports installed by these particular pipefitters during their employment during October, 1978 through August, 1979.

2.2 During the period of 1978 until Septe=ber 3, 1980, it had been standard field practice to install pipe shi=s around anchors between concrete and baseplates of only floor =ounted supports to lift the 4

supports for grouting and leveling.

This practice was followed for the installation of s=all and large dia=eter pipe supports, elec-trical raceway and control syste=s' supports, and instru=ent tubing and instru=ent supports.

3.0 DEFICIENCIES 3.1 Fipe Shi=s The use of a pipe shim around an expansion anchor bolt creates a void, annular space between the pipe shi= inner vall and the surface of the anchor bolt (see Figure 2). The anchor bolt is latarally unsupported within the pipe shi= (1"-2"); thus, reducing the hori-zontal loading capacity of the support. Without the pipe shim, the grout would nor= ally provide lateral resistance just below the baseplate.

In the absence of extensive test data, it is not possi-ble to quantify the reduction in the horizontal shear capacity.

However, this reduction could be significant when a support =ust resist high horizontal, seis=ic design loads.

Pipe shi-ing vill have no effect on the direct vertical loading capacity (tension or co=pression) of a baseplate support.

In this case, the load is transmitted directly into the concrete through the anchor bolt (tension) or into the grout (co=pression).

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3.2 Levoline Mut Welded to Fion Shim For vedge/ stud type expansion anchors, after a baseplate has been grouted, final torqueing of the anchor bolt nut is required to completely set the embedded end of the anchor bolt into the con-crete. When a leveling nut is tackwelded inside a pipe shim and this asse=bly is screwed onto the anchor bolt to support and level a baseplate before grouting, proper setting of the expansion anchor cannot be assured. "When the anchor bolt nut is torqued, thia tends to tighten the pipe shim asse=bly agtinst the bottom of the base-plate instead of transmitting the developed tension to the expanding portion of the enbedded anchor bolt.

3.3 Welding of Pipe Shim to Anchor Bolt Taekwelding of a pipe shi= to an expansion anchor bolt prevects proper setting of the anchor (Seccion 3.2) and also =ay reduce the strength of the anchor bolt as a result of the applied heat for welding. The project Specification 8S56-C-72 specif' ally prohibits any welding of the anchor bolts.

4.0 SAFETY IMPLICATIONS The expansion anchors in the floor =ounted supports anchor safety re-lated piping, electrical raceways and instru=entation ite=s.

In light of the deficiencies described in the previous sections, proper functioning of the anchors under design loadings is questionable and/or non-confor=ing.

Since the nu=ber of anchors involved.is significant and the deficiencies will have safety i=plications on the safe operation of the plant, t,is problem is considered to be reportable.

5.0 CORRECTIVE ACTION AND EVALUATION OF DEFICIENCIES 5.1 Immediate Action When this probles' wac discovered, Bechtel engineering notified Pennsylvania Power and Light of the potential deficiency, and Bechtel Quality Assurance issued Manage =ent Corrective Action Report (MCAR) No. 64 An interim rep rc was. issued in November, 1980.

Since November, 1980, Bechtel Field personnel have discentinued using pipe shi=s around expansion anchors under floor =ounted sup-ports.

5.2 Pipe Shims Baseplates, typically using four expansion anchors, have been con-servatively designed on the basis that all applied shear (horizontal) and tension (vertical) forces are resisted by the anchor bolts.

In reality the following other factors resist the applied shear forces along the interface between the baseplate and the non-shrink grout:

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1.

Bond bstwain grout and beszplnto, 2.

Friction bstwsen grout and baseplats--ACI 349 specifica a coefficient of friction of 9.55 for this condition.

3.

Torqueing of the anchor bolt nut creates co=pression at

- the concrete /baseplace interface, and thus, provides additional shear resistance.

Therefore, supports for electrical rad control syste= ite=s, where horizontal shear loads tend to be low, have been evaluated on a generic basis assu=ing that the tension is resisted by the anchor bolt and the shear is resisted solely by the frictional resistance between the basep? ate and concrete.

Bend and torqueing of the anchor bolt nut are neglected, =aking this evaluation so=ewhat conservative.

Thus, assu=ing that the anchor bolts do net resist shear, the void, annular space within the pipe shin will have no adverse effect on anchor behavior.

The analytical =ethod used in the evaluations is given in Appendix A.

The results of the evaluations are shown in Table I.

a All other supports where pipe shi=s have been used will be repaired.

Also, where an evaluation indicates chat tL2 shear resistance due to friction is not adequate, that particular support uf?.1 be repaired.

The repeir =ethod for the bataplate supports which have already been greuted is si= ply to fill the void, annular space with grout.

This will correct the probles by providing the lateral support within the pipe shi= tssu=ed during the original design of r.he support. The holes in the baseplate for the anchor bolts arc o~ersized (1/16" to 1/8") so that non-shrink grout in a paste forn can be injected through this gap between the anchor and hole to fill the void within the pipe shi=.

The grout to be used is "Y.asterflow 814 Cable Grout" manufacturet by F. aster Builders, Cleveland, Ohio.

For supports which have not yet been grouted, and thus, the pipe shi=s are accessible, field 7ersonnel =ay elect to re=ove the shi=s before grout'ing'the baseplates or inject grout into the pipe shi=s as described above to correct the prcble=.

Finally, there is a special category of pipe supports called,

' spring can supports.'

The support design above the baseplate is such that only a vertical co=pression load is transnitted through the baseplate and into the expansion anchors. Therefore, pipe shi=s will have no effect on the support's perfor=ance and no repairs or evaluations will be required.

5.3 Leveling Nut k'elded to Pine Shf=

As mentioned in Sectidn 2.1, the anchor installations perfor=ed by a sp;cific crew of pipefitters have been traced. This crew is the

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only crew that tackwelded leveling nuts to pipe shi=s.

All of these installations have been rejected and reworked with new anchors.

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In order to assure that this cor struction =ethod was not f ollowed by other crafts =en, Bechtel *ield engineering inspected 25 each of pipe, electrical, and instranentation supports (75 supports total) selected at rando: and found that on none of these supports were leveling nuts welded to pipe shi=s e7 pipe shi=s welded to anchor bolts. Therefore, with reasonable assurance, it is considered that welding of shi= or nur does not exist on supports othcr than iden-tified above.

5.4 Welding of Pipe Shin to Anchor Bolt Welding of the pipe shi= to t?e anchor bolt was perfor=ed solely by the sa=e crew mentioned in Section 5.3.

These anchors hava been traced, rejected and replaced with new anchors.

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6.0 FIELD INS?ECTION

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In order to co=plete the idencifications, evalusticas, and corrective actier.s concerning the use of pipe shi=s, 3echtel field personnel (Field Engineering and Quality Control) have initiated a re-inspection progra=

as of January, 1981.

Existing pipe shi= installations can be identified in the field by re=oving an anchor bolt nut on a particular baseplate and probing the space between the bolt and baseplate hole with a thin wire.

If the wire passes below the botto= of the baseplatc, a pipe shim is evident.

The inspection, any engineering evaluation and/or the necessary corrective action is schedried for cc=pletion by Nov. 27,1981 for Unit 1 and co==on oniv.

The, schedule for Unit 2 ins ~pections will be estabitshed in' th.e,near future.. Based,cnt,the. inspection.resu.ts so f ar, the total nu=ber of Q and safe-y related. anchors using pipe shi=s is anticipated to approach 3,000.

7.0 FUTURE NeTALLATIONS Bechtel field has discontinued. '.use.of pipe 'shi=s 'and leveling nuts f5r any installation of baseplates since Nove=ber, 1980.

Si=ilarly, training sessions have been conducted.at the lobsit.e f.or field personnel, in-cluding crafts =en, to e=phasize this' point.

8.0 CONCLUSION

Upon co=pletion of the evaluations and corrective actions described in the previous sections, all existing Q and safety related baseplate in-stallations will be assured of adequately supporting their design loads.

Si=ilarly, pipe shi=s of any kind will not occur in future Q and safety related installations.

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SHIMMIiG OF BASE PLATES MCAR l-64 p,iR 13 '61 jjy17h EVALUATION OF ELECTRICAL SUPPORTS

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NorATICtE 4

M 13 '61 83 70 a = Distance between

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= s/2 + b/2 + L C = Resultant cmpressive force due to external mcznent d = Distance between column face and edge of the base p10te s = Anchor spacing L = Distance between column face and 'C' K = Bolt / anchor stiffness.

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[ = Coefficient of friction between grout and base plate

= 0.55 T = Resultant tension in ancFors due to e: sternal moment P = Applied horizontal load.

H = Vertical distance betwen applied load and base plate M = APFlied morrent n P.H MR= Reisting moment /coucle.

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= 0.55 C A = Bast plate width / length t = Base plate thickness Ta = Resultant tension u one anchor = T/2 l

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.uR 19 'c1 136178 Assumptions:

1.

Base plate has symmetrically placed four anchors of the same size and type.

2.

Anchors do not transfer any shear.

3.

Applied shear is resisted solely by the frictional resistance between grout end base plate.

4.

Bond between grout and base plate and also the pretension in the anchors, which will also resist applied shear, are not considered.

Reference:

1.

Specification 8856-C-72 for allowable loads of the anchors.

2.

Appendix B of ACI 349-76.

3.

' BOLT' program developed by Bechtel in response to NRC IE-79-02.*

ME'IHOD

i. Compute

'L' L = 3.5 [(t/d) 2/3 (44/kb) 1/3] d *

= 1.75 (t/d) 2/3 d where L is less than d.

2.

Compute a = s/2 + b/2 + L 3.

Conpute C and T = Wa 4.

Compute tension in one anchor = Ta.

5.

Conpute resisting shear = 0.55.C 6.

Compute area of canpression block = 2 (d

• ).s 7.

Conpute design compressive / bearing stress =

C 2 (d-L).s 8.

Conpute allowable bearing stress = 9. (0.85). f'c

= (.7) (.85) (4000)

= 2 80 rsi.

ACCEPTANCE CRITERIA 1.

Ta shall be lec.s than the allowable lod per Spec. C-72.

2.

Applied shear mest be less than the resisting s' ear.

3.

Design bearing stress shall be less than 2380 psi.

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m is si J36178 CENCIIJSION If the acceptance criteria is met, the anchors will be considered acceptable.

l If not, the pipe shims will be repaired / grouted.

NOIES 1.

Ebr simplicity purpose, in the above method only one horizontal force is considered to be acting.

2.

However, in the design /evduation of the existing support lateral forces may be acting in two direction in addition to axial loading.

'Ihis method has been appropriately modified to take account of the additional forces.

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