ML20094P725
| ML20094P725 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  |
| Issue date: | 07/31/1984 |
| From: | Choi K, Hu C, Khlafallah M BECHTEL GROUP, INC. |
| To: | |
| Shared Package | |
| ML20094P713 | List: |
| References | |
| NUDOCS 8408170343 | |
| Download: ML20094P725 (10) | |
Text
STUUT CALCULATION POR STIPF PIPE CLAMP CALCUIATION NO. SR10855-SS27 PREPARED POR HOPE CREEK PROJECT BY BECHTEL POWER CORP.
i PLANT DESIGN STRESS STAPF JULY 31,1984 i
PREPARED BY c.h. au l2 /ch;; chern (W
cxEcxED BY K.~Choi APPROVED BY u1 R.' 2. EhlafAlah j
8408170343 840814 PDR ADOCK 05000354 D
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TABLE OF CDNTSNTS 1.0 Introduction 2.0 Purpose 3.0 Summary 3.1 Primary Nombrane Stresses 3.2 Primary Moabrane Plus Primary Bending Stresses 3.3 Stresses Due to Bolt Preload 3.4 Clamp Design Criteria 3.5 Bolt Loosening Protection 3.6 Stress Due to Constraint of Expansion from Internal Pressure Stress Due to Constraint of Dif forential Thermal 3.7 Expansion 3.8 Fatigue Usage Appendix 1.0 Loading Combination 2.0 Table 1 and 2 Stress Summary 5
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1.0 INTRODUCTION
1 1.1 RACKGROUND ASME Section III Code Subsection NB3645 requires that the of facts of attachments in producing thermal stresses, stress concentrations, and restraints on pressure retaining mesbers shall be taken into account in checking for compliance with stress criteria.
In November 1983, the Nuclear Regulatory Commission issued IE Information Notice 8 3-80, use of specia-lized " stiff" pipe clamps.
The information notice identifies three concerns with stif f pipe clamps:
excessive bolt preload induced stresses in the pipe, small clamp contact bearing areas that could induce local overstress and the ef fect of clamp on elbow stress indices.
Attachments to piping are generally categorized as 1
integral attachments and non-integral attachments.
Lugs and stanchions welded to the pipe wall are integral attachments.
Clamps used Bor attaching nangers and snubbers to the pipe by bolting are non-integral attachments.
For integral attachments, the design calculations are prepared by Bechtel to show that the requirements of ASME Section III Code and code cases have been met.
The code does not provide the design rules for the evaluation of non-integral attacheents:
however,. methods consistent with the intent of the code have been developed to address the concerns of information Notice 8 3-80 and the Code.
1.2 GENEP.AL DESCRIPTION For BOP Nuclear Class I piping systems on Hope Creek Project, Bechtel has used total of 12 "stif f" pipe l
clamps as follows:
i)
$ locations 11)
LPCI 3 locations 4
iii)
RHR System 2 locations iv)
Core Spray 2 locations j
All 12 "stif f" clamps are ITT Grinnell clamps.
None of them are installed on elbows.
By examining the piping stress levels and support loads at the loca-tions wnere stiff clamps are used, and the tempera-ture and pressure fluctuations of the piping system 1_
it is determined that the stiff clamps on 12" and 24" feedwater line are the most severe cases among all the systems identified above.
These two clamp assembly properties are given as follows:
FEEDSGER STIFF CUWEP ASSDSLY PIPE CIJe9 2S. REPORT NO.
IE 101 SA333 Gr. 6 Somaless!
Ibit BOLT ltATIIG,
PE-193-IB DP SIZE PRETUQ 2 KIPS ITT-GLIteE2.L ttG MIVC/D CIJW9 UD IEVEIS IDENTIFICATIGi i 103 24" 1.531" 2 1/2p 200FT-IBSl 120/160/162 Fig. 31544, Size 120 171 12.75" 0.687" 1 3/4W 150-FI-IBS l 33/40.2/
43.22 Fig. 315N, Size 33A l
2.0 PURPOSE j
The purpose of this analysis is to evaluate the impact of piping local stresses induced by *stif f" pipe clamps attached to BOP Nuclear Class I piping systems.
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3.0 SumtARY The piping stresses calculated per ASME Section III 153650 are combined with the local stresses induced by " Stiff" pipe clamp Sor all the operating condi-tions.
The results of calculations show that the primary stress intensities for all operating condi-tions.and the cumulative usage factors meet the code requirements.
The calculated stresses and usage factors are summarized in Appendix 2.
3.1 Primary Membrane Stresses The existence of a pipe clamp will not af fact the calculation for minimum wall, in fact, the primary me2rane stresses is less than that of straight pipe due to clamp reinforcement of of factive thickness.
3.2 Primary Membrane Plus Primary Bending Stresses The primary membrane plus primary bending stresses introduced by the presence of clamp comes from two dif forent loadings.
First, the loading transmitted from pipe through the clamp pad to the support structure.
This bearing load will result in local i
stress in the pipe wall.
Secondly, the constraint l
of tne clamp on the pipe under internal pressure will produce local stress in the pipe wall.
These stresses are conservatively calculated and added to the membrane,and overall bending stresses camputed by equation 9 of the code.
Satisfying equation 9 will prevent collapse of the piping systen due to loads that produce primary stresses.
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f 3.3 Stress due to Bolt Preload 1
The preload will produce stress in the pipe wall whan the clamp is initially installed on the piping system j
and the bolts are tightened.
Although local stress s
produced by preload is nonrecurring secondary type in natura it could result in damage to a pipe if a clamp was poorly designed.
Stresses of this type need not be included in the stress evaluations required by NS-3600.
Calculations have been made to ensure that bolt proloads could not result in local plastic deformation of the piping.
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3.4 Clamp Design Criteria The stiff type clamps were designed to provide a high strength attachment for the pipe which would not slip and would fit on the smallest practical length of pipe.
Clamp design of the strap type are too wide to fit in many locations and required lugs to hold them in position.
The stif fness of a capact high strength clamp is inherently greater than that of a strap type.
In fact, all the clamps used are stif fer than the snubber attached to it.
The stif f-ness requirement does not govern the design of stif f type clamps.
3.5 Protection from Icosening In order for the clamp to hold its position during vibratory loads, it must grip the pipe with enough force to prevent sliding.
All the bolts have double nuts to prevent backing of f of the nuts.
In addition, stresses have been calculated conservatively to assure the bolt will well remain in elastic range to prevent permanent deformation.
The bolt material was selected to resist relaxation at the temperature of Concern.
1 3.6 Stresses due to Constraint of Expansion from Internal Pressure Clamp induced stresses caused by the constraint of pipe expansion due to internal pressure have been added to other appropriate primary and secondary j
stresses to satisfy the required criteria.
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3.7 Stresses due to Constraint of Differential Thermal Expansion l
Clamp induced stresses due to dif ferential tempera-l tures and material expansion coef ficients have been calculated and added to other operating secondary and peak stresses.
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3.8 Fatigue Usage The fatigue usage at the clamp locations has been conservatively computed taking into consideration
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clamp induced stresses from pressure, temperature and support loadings.
The clamp induced stresses were added to the stresses computed for each load set pair using equation 10 and 11 of N8-3650 Cumulative fatigue usage was computed by the code.
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APPE[ DIX 1 Loadina Combination for Hope Creek Feedwater Lines Desian Ioadina Combinations condition PD Design Level A/B PO + DW + OBE PO + DW + OBE Imvel C PO + DW + (SSE2 + Ap2)1/2 Level D 1
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s APPENDIX 2 Table 1 - Stress Summary Hope Creek Feedwater Line (d.p. 103, O > 24 in.)
Item Highest Ratio calculated /
Allowable Actual Evaluated (1)
Usage Factor Limits Allowed Primary Stress Eq. 9 11.5 Sm Not governing'
. Design Condition Primary Stress 10744 29180 0.368 Eq. 9 11.5 Sm Level A/B Primary Stress Eq. 9 <l.8 Sm Not governing' Imvel E Primary Stress 16914 58350 0.290
- Eq. 9 13.0 Sm Imvel D Primary + Secondary 29213 58350 0.501 Eq. 10 33.0 Sm Cumulative Usage (2)
Factor fl.0 0.111
- 1. 0 0.171 1
(1) All equations ussd are from ASME B&PV Code, Sec. III-N'3-36 50.
(2) To minimize the calculation all similar stress cycles are combined and the enveloped stress range is used in fatigue evaluation.
As a consequence the usage factor is very conservative.
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APPENDIX 2 I
Table 2 - Stress Summary Hope Creek Feedwater Line (d.p.171, OD=12. 75 in. )
(
r Ratio f
Highest Calculated /
Allowable Actual Item (Psi)
Limits Allowed Evaluated (1)
Usage Factor Primary Stress Eq. 9 11.5 Sm Not governing Design Condition Primary Stress 29180 0.507 14805 Eq. 9 11.5 Sn Imvel A/B 1
Primary Stress Eq. 9 11.8 Sm Not governing Imvel C Primary Stress 20820 58350 0.357 Eq. 9 13.0 Sa I4 vel D Primary + Secondary 55107 58350 0.944 Eq. 10 13.0 Sm Cumulative Usage (2) 0.288 1.0 0.288 Factor 11.0 f
(1) All equations used are from ASME B&PV Code, Sec. III-NB-3650.
(2) To minimize the calculation all similar stress cycles are combined and the enveloped stress range is used in fatigue evaluation.
As a consequence the. usage f actor is very
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conservative.
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