ML19290E464
| ML19290E464 | |
| Person / Time | |
|---|---|
| Site: | Washington Public Power Supply System |
| Issue date: | 01/24/1980 |
| From: | Renberger D WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| IEB-79-02, IEB-79-2, NUDOCS 8003110323 | |
| Download: ML19290E464 (12) | |
Text
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P W shington Public Power Supply System A JOINT OPERATING AGENCY 3
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Mr. R. H. Engelken, Director NRC Region V
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Suite 202 Walnut Creek Plaza 1900 N. California Boulevard 7l f
Walnut Creek, California 94596
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Dear Mr. Engelken:
Subject:
WPPSS Nuclear Projects Nos.1 & 4
's IE Bulletin No. 79-02, Revision 2,
" Pipe Support Base Plate Designs Using Concrete Expansion Anchor Bolts", and Related Reportable Condition 10 CFR 50.55 (e)
Pipe Support Design
References:
- 1) G01-79-380, Response to IE Bulletin 79-02, Rev. 1, DL Renberger to RH Engelken, dated July 10, 1979
- 2) NRC Letter, IE Bulletin 79-02, Rev. 2, RH Engelken to NO Strand, dated November 8, 1979 Mr. Al Toth, US NRC Region V Resident Inspector, was verbally notified of the reportable 10 CFR 50.55 (e) condition on January 4,1980 by the Supply dy. tem.
As previously notified, the Washington Public Power Supply System has reviewed the related reportable 10 CFR 50.55 (e) condition in conjunction with the response to IE Bulletin 79-02, Revision 2.
The attached contains the requested information in response to Bulletin 79-02, Revision 2 as well as the WPPSS final report on the reportable design deficiency.
If you have any questions or desire further information, please advise.
Very truly yours, D. L. Renberger Assitant Director of Technology LCO:jmh Attachments 8008110923
/D-05
cc: CR Bryant, Bonneville Power Administration V. Stello, Director, NRC Cffice of Inspection and Enforcement Engineering Files 1/4 RS Millne, United Er.gineers & Constructors, Inc.
BD Redd, United Engineers & Constructors, Inc.
AD Toth, Nuclear Regulatory Commission, Region V 1
8
Attachment NRC IE Bulletin 79-02, Revision 2 Pipe Support Base Plate Designs Using Concrete xpansion Anchor Bolts e
The following response to IE Bulletin 79-02, Revision 2 has been updated from the Revision 1 response as indicated in the margin.
Included is the final report covering our verbal notification of the related 10 CFR 50.55 (e) reportable design deficiency.
The majority of pipe supports (approximately 807.) do not require concrete expansion anchors and are attached by bolting into embedded inserts or welding to existing structural members, supplementary steel, or embedded structural shapes.
1.
VERIFICATION TilAT BASE PLATE FLEXIBILITY UAS ACCOUllTED FOR IN CALCULATIflG ANCHOR BOLI LOADS The original design calculations for determining anchor bolt loads did account for the effects of base plate flexibility but not to the extent specified in Item 1 of IE Bulletin 79-02 and not to the extent of considering increased anchor loads due to prying action.
Calculations for all Seismic Category I pipe supports are therefore being reviewed with the assumption that the base plate is flexible unless the distance from the edge of the support member to the edge of the plate is less than 2 times the thickness of the plate (i.e.,
the base plate is rigid).
When base plates have been determined to be rigid, the compressive force is assumed to act at the center-line of the anchor bolt on the compression side of the plate.
(See ). When base plates are assumed to be flexible, anchor bolt loads are determined in accordarce with the calculation basis described in Attachment 1.
This design approach includes consider-ation of prying action in causing additional anchor bolt loading.
The original design calculations utilized the formulas given in with the exception that there was no factor for prying action and the moment arn "h" was equal to d+(a+b).
2 For those seismic Category I supports which have already been de-signed, anchor bolt loads will be recalculated utilizing the approach described in Attacnment 1.
All future designs will util-ize this same approach in determining anchor bolt loads.
Recalculations which indicate maximum allowable anchor bolt loads have been exceeded (See Iten 2 of ti. s rec,ponse) will be rectified by appropriate pipe support redesign, refabrication, and/or field modification as required to meet the maxinam allowable design load.
The current schedule for recalculating anchor bolt loads on existing designs calls for June,1930 completion.
2
Page 2 of 6 2.
VERIFICATI0tl 0F NIllIMUM SAFETY FACTOR FOR BOLT DESIGil LOADS WilP-1/4 utilizes Hilti-Kwik Bolts exclusively for all Seismic Category I pipe supports with concrete expansion anchors.
The original design calculations required that the design tension load be less than or equal to the maximum allowable design load (MADL) where the MADL is defined:
t'ADL =F u SF Where, Fu = ultimate static capacity of the anchor based on the manufacturer's static test for the applicable strength of concrete SF h safety factor of 4 for Hilti-Kwik Bolts 2
(shell type anchors are not utilized for Seismic Category I supports on WilP-1/4)
When both shear and tension act on the anchor a straight line shear-tension interaction is assumed as follows:
-h + h 5 1.0 Where:
T = Design Tension Load V = Design Shear Load Ta= f1ADL in Tension Va= MADL in Shear Based on test data generated on WilP-2 and WNP-1/4 it became apparent that wedge type concrete expansion anchors (Hilti-Kwik Bolts) slip well below the yield strength of the bolting material and utilizing one-fourth of the ultimate static capacity of the anchor (based on the manufacturer's static test data) does not provide a safety factor of four against slip.
The design criteria for the maximun allowable load on Hilti-Kwik Bolts was therefore revised as shown in Attachment 2.
All concrete expansion anchort are designed for worst case loadings which include casideration 2
of SSE loadinos.
Design loads calculated in accordance with Attach-ment 1 must be less than the naximum allowable load shown in.
This approach accounts for shear-tension interaction, minimum edge distance, and proper bolt spacing.
3.
DESIGil REQUIREMEilTS FOR AtlCHOR BOLTS SUBJECT TO CYCLIC LOADS l10 specific calculational requirements for seismic loads or high cycle operating loads exist for anchor bolts other than identified in Note 2 of Attachment 2.
As a general rule, the use 'of concrete expansion anchors is discouraged for high cycle operating loads.
All anchors will have an initial preload tension applied which is 2
Page 3 of 6 greater than 1.5 times the naximum allowable desion load identified 2
in Attachment 2.
The method of obtaining bolt pre-tension will be torquing.
Concrete expansion anchors for Seismic Category I hangers / supports currently being installed are torqued to the following minimum values after nuts have been turned a minimum of three turns past the finger tight position:
NOMIflAL BOLT DIAMETER MINIfiUf1 INSTALLATION TORQUE 1/2-inch 30 ft. lbs.
5/8-inch 60 ft. Ibs.
3/4-inch 130 ft. lbs.
1-inch 155 ft. lbs.
I 1/4-inch 230 ft. lbs.
If torque vs. creload tests to be conducted by UE&C indicate that the minimum torque values identified above do not provide the required 2
preload tension, anchor bolts installed to the above torque require-ments will be re-torqued as required to achieve proper preload.
4.
VERIFICATION THAT DESIGN REOUIREMENTS HAVE BEEN MET FOR EACH ANCHOR BOLT BASED ON EXISTING QC DOCUMENTATION The installation of concrete expansion anchors is controlled by the installing contractor's (J. A. Jones - Contracts 211 and 257) installation and inspection procedures.
The inspection of concrete expansion anchors is included in JAJ-ITI-005, Paragraph 4.3 which includes the inspections and documentation (refer to Attachment #3) necessary to verify that the design requirenents have been met for each anchor bolt in the following areas:
4a)
Cyclic Loads Have Been Considered (i.e., Anchor Bolt Preload Is Equal To Or Greater Than The Bolt Desion Load As indicated in the response to Item 43, all concr;te expansion anchors are torqued to the minimum values shown.
Torque is verified by the installing Contractor's quality control by checking the torque on a minimum of two bolts on each assembly.
Utilizing the formula for determining required wrenching torque values to obtain a given bolt preload, the maximum allowable design load for tension per Attachment 2, and preliminary torque vs. preload data, a comparison between contractor's minimum installation torque.and the calculated torque reouired to obtain an anchor bolt preload of 1505 of the MADL is as follows:
CONTRACTOR'S f1!NIMUM TORQUE FOR 150; MADL BOLT DIAMETER INSTALLATION TORQUE (TENSION-ALL LOADS) 1/2-inch 30 f t. lbs.
23 - ft. lbs.
5/8-inch 60 ft. lbs.
42 - ft. lbs.
3/4-inch 130 ft. lbs.
34 - ft. lbs.
Page 4 of 6 1 - inch 155 ft. lbs.
149 - ft. lbs.
I 1/4-inch 230 ft. lbs.
240 - ft. Ibs.
Subsequent to completion of the WNP-1/4 torque vs. preload testing program, installation torques will be revised as re-quired to assure a minimum preload tension of 150% of the MADL.
Anchors which have not been torqued to the minimum values established by torque vs. preload tests will be re-torqued as required.
2 b) _Specified Desian Size And Type Is Correctly Installed (i.e.,
Proper Embedment Depth Refer to Attachment 3.
The installing Contractor's inspection checklist includes an inspection hold point to verify that the proper hole depth and diameter exist prior to installation of the expansion anchor.
This approach eliminates any incentive to nodify the anchor to accomodate hole depths which are less than the minimum speci fied. Additionally, expansion anchors are identified with a length code number by the manufacturer so that bolt length can be verified visually af ter installation.
In those cases where anchors do not have the length identifying code number the actual installation of the anchor into the hole is witnessed by the Contractor's quality control inspector.
It should be noted that WNP-1/4 uses only Hilti-Kwik Bolts for all Seismic Category I pipe supports which require concrete expansion anchors.
In addition to bolt hole depth and diameter, bolt size, and bolt length, inspection parameters also include verification of the following (refer to Attachment 3) to substantiate that anchor bolts have been properly installed.
PARAMETER INSPECTI0fl PROCEDURE-PARAGRAPil Full thread engagement (JAJ-ITI-005 - 4.3.4)
!!ut not shouldered out (JAJ-ITI-005 - 4.3.4)
Spacing and edge distance correct (JAJ-ITI-005 - 4.3.2)
Conformance with detail (JAJ-ITI-005 - 4.4)
The project will conduct a 100% verification of bolt embadme.,t length for all concrete anchor bolts installed prior to the published requirements shown in Attachment 2.
Any deviations will be reviewed and dispositioned on a case-by-case basis.
2 5.
EXPAtlSI0ft ANCHOR BOLTS USED Ill CONCRETE BLOCK UALLS Concrete expansion anchors are not used on concrete block walls to attach piping supports in Seismic Category I systems.
Page 5 of 6 6.
P_IPE SUPPORTS WITH EXPANSION ANCHOR BOLTS USED UITH STRUCTURAL STEEL SHAPES Many of the pipe supports with concrete expansion anchors have used structural steel shapes instead of base plates.
The design of these supports, however, is consistent with the criteria of IE Bulletin 79-02, Revision 1.
7.
COMPLETION OF ITEMS 1, 2 AND 4 FOR OPERATillG PLANTS Not applicable to WNP-1/4 8.
COMPLETION OF ITEMS 5, 6, AllD 7 FOR OPERATING PLANTS Not applicable to WNP-1/4 9.
COMPLETION OF ITEMS 1-6 FOR INSTALLED PIPE SUPPORTS WITH CONCRETE ANCHOR BOLTS Seismic Category I pipe supports are supports used in ASME-III, Class 1, Class 2, and Class 3 piping systems.
Concrete expansion anchors are being installed and inspected in accordance with the installing contractors procedures JAJ-WI-010.1 and JAJ-ITI-005 2
respectively.
Existing QC documentation verifies that anchor bolts have been properly installed with respect to the following:
o minimun anchor embedment anchor hole diampter o
o anchor length o
anchor to anchor spacing o
anchor diameter o
anchor to edge distance o
anchor torqued a
full thread engagement.
All supports with concrete expansion anchors c.re being reviewed to assure compliance with items 1 through 6 above. As previously reported, a verification analysis showed that two hangers required design modification namely, CSS-14-RG-22 and NSW-12-RG-3.
The modified design has now been completed.
Installation of ASf1E III supports will continue.
A verification analysis is being perforned concurrent with construction activity.
Page 6 of 6 The scope of the analysis includes the design adequacy with respect to current design guidelines. Among the items addressed are:
o concrete expansion anchors
- prying action
- shear tension interaction o
frictional loads o
weld designs o
allowable stress limits o
embedment plates.
While performing this review some supports have been found which will 2
require design modifications.
It is because of these design modi-fications that a 10 CFR 50.55 (e) condition was reported on Jan. 4, 1980.
The purpose of reporting was to notify the fiRC of the ongoing design review and results of the review to date.
See Attachment #4.
If a d2 sign modification is required on a hanger, the hanger will be placed on " hold" until the exact modification required has been specified and hardware is available to implement '.he modification, i.e.,
the modified design will be installed.
Testing to obtain torque vs. preload data is scheduled to commence during February,1980, wi?E completion in time to support a June,1980 resolution to all existing designs as stated in Item 1.
AT.TACHMEffT fl - AflCHOR BOLT LOAD CALCUATI0fl BASIS if N
o (MT t.- a. 'r M
I OA F
t actr l
i y
I I
I L
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Yt T= di 14 hc W
t Where: T = Anchor Design Tension Load V = Anchor Design Shear Load M = Moment Acting on Connection F.= Shear Acting on Connection P = Axial Force Acting on Connection fl = fiumber of Tension Anchor Bolts 1
N = Total flumber of Anchor Bolts 2i = Index to Identify Base Plate Flexibility i = 1 for Rigid Base Plates
~
i = 2 for Flexible Base Plates hi = Moment Arm 1 = Centerline Distance Between Bolts h
=
d'+ 2t not to exceed h1 h
CLl= F$ctor to Account for Prying Action for Base Plate Flexibility CCg= 1.0, CLt = 1.2 fl0TE' Where the connection is subject to biaxial loading the above design approach must be repeated for the other principal plane and the absolute sum of the bolt reactions combined.
4
ATTACHMENT 2 - MAX 1 MUM ALLOWA8LE DESIGN LOADS DESIGN CRITERIA FOR HILTI KWIK BOLTS
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I 24 3
PART NO.
DIA.
EMBEDMENT ALLOWABLE LOAD CENTER T0 EDGE DIST. FROM
( I N..)
(IN.)
(LBS)
CENTER DISTANCE PREVIOUSLY TENSION SNEAR SPACING (IN.)
DRILLED (WT.5 THERM)
(WT.& THERM)
(IN.)
H0LE (IN.)
TENSION SHEAR (ALL LOADS)
(ALL LOADS) 610 740 12 - 512 1/2 2 3/4 1220 1480 6
5 1
890 1070 5/8 - 812 5/8 4 1/2 1780 2140 7 1/2 5
1 1/4 1490 1580 3/4 - 10 3/4 6
2980 3160 9
5 1 1/2 1980 2540 3960 5080 12 6
2 1 - 12 1
6 2565 3395 1/14 - 12 1 1/4 7 1/2 5130 6790 15 7 1/2 2 1/2 NOTES: 1.
Embedment is defined as the distance from the bottom of the anchor to the top of the concrete after the anchor has been set.
2.
Allowable is equal to 9.375% for dead weight and thermal loading or 18.75% for total loading of ultimate strength (interpolated between concrete 0 2000 psi & 4000 psi).
REF: Abbot A. Hands Inc., Testing Laboratories Report #8783-R March 24, 1977.
For dead weight and thermal loads the allowables are based on a factor of safety of 4 against slip and 10.66 against ultimate failure.
For the total loading in-cluding all seismic loads the factor of safety against slip is 2 and 5.33 against ultimate failure.
3.
For center to center distance less than distance in table the capacity is reduced on a straight line basis down to 50% at 6 diameters center to center anchor spacing.
4.
For combined shear and tension use the following interaction formula:
S (act)
T (act)
S (all)
T(all) '
I
+
- Where, S (act) = Shear Load Applied S (all) = Shear Load Allowable T act = Tension Load Applied T all
= Tension Load Allowable
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Report of 10 CFR 50.55 (e) With Respect to ASME III Pipe Supports
Background
While undertaking a review of ASME III Seismic Category I supports for the NRC IE Bulletin 79-02 Rev 0 it was discovered that there were some inade-quate designs of concrete expansion anchors. This led to further investigation of pipe support design calculations which indicated that there were other problems with support designs.
Description of Deficiency The generic cause of the problem is that earlier design guidelines were not specific enough to assure that the designs adequately addressed frictional loads. The current design guide is much more detailed and is consistent with the IE Bulletin 79-02 response.
This current design guide is the basis for the review.
Other problems were discovered in the design review these are isolated errors which do not recur.
As of January 10, 1980 459 supports have been reviewed and 45 require modification.
These modifications are relatively minor in nature, typically requiring additional weld length or a knee brace.
Of the 45 supports requiring modification the following types of problems have been found:
25 Welds 11 Concrete Expansion Anchors 11 Stress 37 Total The reason that the total number of deficiencies in the various categories exceeds the number of supports which are unacceptable is that several supports were deficient in more than one category.
Safety Ijuplications No attempt has been made to determine if this condition would have caused a significant safety hazard since we are modifying the supports as the deficiency is discovered during the review of each support.
Corrective Action Taken A design review of all ASME III, Seismic Category I pipe supports has been undertaken and will be completed by June, 1980. Necessary design modifications will be ongoing during the review and completed by July,1980.
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