Becht Engineering Company, Inc. • Becht Nuclear Services • www.bechtns.com BECHT I AA00000000000"--1 5224 Woodside Executive Court, Aiken, SC 29803 • 803-648-7461 114 Columbia Point Drive, Suite A, Richland, WA 99352 • 509-943-1625 F M RWCU Regenerative Heat Exchanger Piping Repair Patch Analysis Document No. ME-02-13-09 Revision No. 1 Project Number Project Name Client 20144 RCWU Repair Patch Energy Northwest Quality Assurance Open Items Prevedfied Software Used N/A No ANSYS 14.0 Originator Verifier Approver 414/2013 4/4/2013 4/4/2013 Brian Larsen Ken Stoops Jack Cole Calculation Cover Sheet Page I of 19
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RWCU Regenerative Heat Exchanger Piping Repair Patch …ME-02-13-09 Rev. 1 RWCU Regenerative Heat Exchanger Piping Repair Patch Analysis Page 3 of 19 1. Objective and Scope Provide
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Becht Engineering Company, Inc. • Becht Nuclear Services • www.bechtns.comBECHT
I AA00000000000"--15224 Woodside Executive Court, Aiken, SC 29803 • 803-648-7461
114 Columbia Point Drive, Suite A, Richland, WA 99352 • 509-943-1625F M
3. Open Items ............................................................................................................................................................ 3
5.1.1 A106 Gr B. Carbon Steel Material Properties .................................................................................... 45.1.2 W eld filler for Carbon steel ....................................................................................................................... 45.1.3 Allowable Stress for the Pipe and Patch ............................................................................................. 45.1.4 Allowable W eld Stress Criteria ................................................................................................................. 4
6. Modeling and Inputs .............................................................................................................................................. 56.1 Element types ............................................................................................................................................... 56.2 Boundary conditions ..................................................................................................................................... 56.3 Applied Loads ............................................................................................................................................... 5
Appendix A - Evaluation of W eld ............................................................................................................................... 14
Record of Revisions ..................................................................................................................................................... 19
5224 Woodside Executive Court Becht Nuclear Services 114 Columbia Point Drive, Suite AAiken, SC 29803 • 803-648-7461 www.bechtns.com Richland, WA 99352 * 509-943-1625
Provide an evaluation of a proposed patch repair for the leaking RWCU pipe located between two stages of theRWCU heat exchanger.
2. Summary of Analysis Results
The maximum membrane + bending stress of the 4" schedule 80 pipe is 20,526 psi occurring at a stressconcentration in the comer of the 1" x 3" material removed to simulate the corroded pipe area. The maximumdemand to capacity ratio (D/C) is (20,526 psi/22,500 psi) = 0.91. This is a peak value based on the modeling of thesharp comer as shown in Figure 7. The maximum membrane + bending stress intensity of the pipe is 18,551 psi withthat stress concentration removed as shown in Figure 8. The maximum membrane stress intensity for the pipe is11,903 psi as shown in Figure 5.
The maximum membrane + bending stress of the V" Patch is 21,378 psi as shown in Figure 10. The maximummembrane stress intensity for the pipe is 6,679 psi as shown in Figure 9. The maximum demand to capacity ratio(D/C) is (21,378 psi/22,500 psi) = 0.95.
The pipe to patch welded connection requires a minimum 5/16" fillet weld. The fillet weld is within the allowable ascalculated in Appendix A. Two separate weld evaluations are performed each with different methodology. A-1conservatively takes the peak load occurring on a single element of the weld. The peak stress demand/capacity ratio(D/C) is 1.09 as shown in A-I. This peak stress will be redistributed and spread along the line of the weld.Therefore, the line of the weld is evaluated utilizing a Blodgett square weld line calculation is shown in A-2demonstrating that the 5/16" fillet weld has sufficient margin and a D/C of 0.80.
3. Repair Details
(a) The repair analyzed is a fillet welded patch, in accordance with ASME PCC-2 Article 2.12 (Ref. 1.2).
(b) The pipe is ASTM A 106 Grade B, 4" Schedule 80 pipe (4.5 in. OD x 0.337in. wall), (Ref. 4.4).
(c) The design pressure and temperature are 1450 psi @ 575°F (Ref. 4.4).
(d) A cut-out 1" x 3" is removed from the pipe at the location and corrosion size based upon measurementsprovided by field measurements from Energy Northwest. The location indicated in Figure 1, is to simulate apostulated through-wall corrosion occuring in the pipe, approximately the pattern measured above (Ref.4.4).
(e) The pad is sized to be 3.5" x 5.25" x 0.5" thick patch as detailed in Figure 1. A fillet weld is simulated withcombin14 elements attaching the patch plate to the existing nominal 4" schedule 80 pipe at the weldlocation (See Figure 4).
(f) The pipe and patch stresses are presented in Table 1 and Figures 5 through 10. Membrane and Membrane+ Bending stresses in the pipe and the patch plate meet ASME Section VIII Division 11 (201 la) Part 5Section 5.2.2. Section VIII
(g) The weld loads are extracted from ANSYS and at each node location are checked for weld sizing and the5/16" fillet weld is qualified in Appendix A. The weld qualifies to the requirements of PCC-2-201 1 (Ref. 1.2)as documented in Annex 1.
4. Open ItemsNone
5224 Woodside Executive Court Becht Nuclear Services 114 Columbia Point Drive, Suite AAiken, SC 29803 , 803-648-7461 www.bechtns.com Richland, WA 99352 • 509-943-1625
(a) The repair analyzed is a fillet welded patch, in accordance with ASME PCC-2 Article 2.12 (Ref. 1.2).
(b) The pipe is ASTM A 106 Grade B 4" Schedule 80 pipe (4.5 in. OD x 0.337in. wall) (Ref. 4.4).
(c) The design pressure and temperature are 1450 psi @ 575*F (Ref. 4.4).
(d) A cut-out 1" x 3" is removed from the pipe, at the location indicated in Figure 1, to simulate a postulatedthrough-wall corrosion occuring in the pipe per measurements by Energy Northwest (Ref. 4.4).
(e) A 3.5" x 5.25" x 0.5" thick patch size based on pipe corrosion measurements provided by Energy Northwestis shown in Figure 1.
6. Evaluation Requirements
The repair of a degraded pressure retaining component is not covered by the rules of construction codes such asASME III or B31.1. These Codes are intended for new construction. Guidance for repair of pressure components isprovided by post construction codes such as PCC-2, API 579/ ASME FFS-1, or ASME Section XI. The leakingRWCU piping is classified as B31.1. Initially, the proposed repair is a patch plate following the rules of PCC-2 (Ref.1,2). The simplified rules of PCC-2 are not met. Thus the detailed fitness for service evaluation methods of ASMEFFS-1 (Ref. 1.6) are utilized. FFS-1 allows for detailed analysis utilizing ASME Section VIII, Div. 2.
(a) The design pressure and temperature are 1450 psi @ 575°F (Ref. 4.4).
6,1 Allowable Stress
The material strength per Section II of the ASME code (Ref. 1.3) and B31.1 (Ref. 1.1) and the allowable stresses arediscussed in the following sections.
6,1.1 A 106 Gr B. Carbon Steel Material Properties
" Elastic modulus: E = 2.68x10 7 psi (Ref. 1.3) at 600°F
* Yield Strength (ASME): Sy = 27,225 psi (Ref. 1.3) at 5750F
* Allowable Stress S = 15,000 psi (Ref. 1.1) at 600°F
6.1.2 Weld filler for Carbon steel
Weld filler material is compatible with the pipe and fitting material specified. The material identified for use is E70S-2or E7018. The material has a 70,000 psi minimum tensile strength.
6.1.3 Allowable Stress for the Pipe and Patch
ASME VIII Division II (Ref. 1.4) describes the primary allowable stress as developed by use of yield strength. PerASME B31.1, 1971 the allowable general membrane stress is 15,000 psi. The combined membrane and bendingdesign stress is 1.5(15,000 psi) = 22,500 psi.
6.1.4 Allowable Weld Stress Criteria
The allowable stress for each weld type is addressed in Table 2.3 of AWS D1.1 (Ref. 1.5). A description of eachcriterion is shown next.
5224 Woodside Executive Court Becht Nuclear Services 114 Columbia Point Drive, Suite AAiken, SC 29803 ° 803-648-7461 www.bechtns.com Richland, WA 99352 • 509-943-1625
Fillet WeldsShear on the effective area: 0.30 x nominal tensile strength of the filler metal, except shear stress on base metalshall not exceed 0. 40 xyield strength of the base metal
Based on the AWS code and the material properties, the allowable stresses for Service Level A Loading arecalculated as follows. Section VIII, Division 1, Table UW-12 provides joint efficiency factors for ARC and Gas WeldedJoints. The plate fillet weld is equivalent to a Category C fillet. Table UW-12 Type 7 states that E in the designformulas
at = 70,000 psi Filler metal tensile strength per AWScr= 27,225 psi Base metal yield strength per ASME Code at 5750F
Fillet Welds
Oshear = 0.3x70,000 psi = 21,000 psi allowable tensile strength of filler material= 0.4x27,225 psi = 10,890 psi allowable yield strength of base material
Use 10,890 psi
7. Modeling and Inputs
The equipment is evaluated using ANSYS version 14.0, a general-purpose finite element analysis (FEA) program.The finite element analysis technique is used to develop stresses in the pipe, so as to demonstrate compliance withallowable stress limits. In addition, selected hand calculations are performed to check components not analyzed inthe FEA model. A list of input and output files is found in Attachment 1. The units used in the ANSYS model areinches, pounds, and seconds.
7.1 Element types
SHELL281 elements are used to model the pipe and the patch. These are shell elements with (8) nodes each with(6) degrees of freedom. The element supports both membrane and bending stiffnesses. The pipe shell thickness is0.337 in and the patch thickness is 0.5 in. Element coordinate systems and derived section properties areautomatically determined by ANSYS.
COMBIN14 elements are used to simulate the fillet weld for the patch. These are uniaxial spring elements with (2)nodes each with (3) degrees of freedom. A key option is used to limit each element to one degree of freedom each.Three single degree of freedom (DOF) translation only springs are used at each node and the forces passing throughthese elements are used to calculate the required weld size. Classical methods of evaluating welds do not credit asingle line fillet weld with moment capacity parallel to the weld line; therefore the springs are used to limit effectivedegrees of freedom to translation only. Also, spring elements allow for easy extraction of forces at the weld formanual evaluation. The stiffness of the spring is infinitely rigid and uses a value 1 Ell Ibf/in.
7.2 Boundary conditions
The 4" Schedule 80 pipe is modeled in ANSYS with fixed-fixed ends (Figures 2 and 3). A sufficient length of pipe is20 inches, which exceeds the minimum spacing to a structural discontinuity VDiameter Thick = 1.23 inch. Theend of the pipe at the elbow is located at a vessel nozzle, thus it is rigid. The other end of the pipe is located morethan four diameters from the patch.
7.3 Applied Loads
Internal pressure of 1450 psi is applied to the pipe and patch.
5224 Woodside Executive Court Becht Nuclear Services 114 Columbia Point Drive, Suite AAiken, SC 29803 - 803-648-7461 www.bechtns.com Richland, WA 99352 , 509-943-1625
(a) Thermal radial expansion because the heat-up and cool-down are slow and the metal remains at uniformtemperature.
(b) Longitudinal stress effects have minimal impact in this analysis. Thus, the following loading is not applied tothis analysis: deadweight, thermal bending, and seismic.
8. SoftwareANSYS 14.0 is used to perform the analyses in this calculation report. This version of software has been validatedand verified for use on the computer that ran the analysis.
Computer Description: NSWA-BLARSENDSK
Computer ID: 2UA24523H0
Computer Type: HP Xeon E5-1620 3.6 GHz W7 Pro x64
The in-use test was performed satisfactorily to verify adequacy of the current computer configuration in which thefinal analysis runs were performed.
The input and output files used to perform the analysis and are provided in Attachment 1.
Appendix A - Evaluation of WeldA-1 - Maximum Fillet Welded Patch Analysis at one location
Weld Analysis of 5116" (0.313") Fillet Weld between the Elbow/Pipe Patch and theexisting Pipe.
Maximum ANSYS Weld Loads at Elements 566(FX).610 (FY), and 654(FZ), Maximum Location is shown in Red:
FX = 2401bfKO
FY:- IlIllbf
FZ :=- 12791bfKO
gO
KO KOKO'CO
KO
.KoKO
KO
Weld Loads are in the Global CoordinateSystem (GCS). Maximum weld load at onelocation occurs at weld elements 566. 610,and 654 extracted from ANSYS. The weldwas modeled by using springs to join thenodes of the two parts along the weld path.The two parts are shell elements with a oneinch mesh and mid-side nodes. Springforces were extracted from ANSYS with theminimum node spacing used in thecalculation to determine the weld loading inpounds per inch.
Weld Arnalyal of51 (13WP ) F~le Weld Oewen hebowafflp Pam and the eaiduin PIPe.
Absoi sum dANSYS Wild Loads
Fweldx :- 81411% Force kq91w X-axs KOKO
Id I
Fweldy:- 89391% Force iong hw Y-axis k
Fwsldz .- 19T761b Force aln Ow Z-.a X0
Weld Loads are in 1w Globa C*wor Symm (GCS). The M •mm weld oload is otaned by abss m iulo•in offt troes ex*adsd from ANSYS COCOMBIN4 elem Thewlddwas nodeed by uag COMBIN14 *e*eINlo pin the nodes of11 bw o pris etng lh weld p*. K
WWel walayai for Mbtngeala be weld g
Mated Propues and AkowU" Skesses K
.- 27225pst Yield en br A106 Gr B at 575 "F KO to to KO
SFR -- 000PS Fler rod 7OXX onoW e mal thn e
I Iu:- 0.3 SO* FaSDr WWedb noIDM dlanSle *re0l of i melOW.
I:b-- 0.4 Say bcW aqWd i yield s1rmngdi d base mawiah
wel:Alow "- Ifu.SFR - 21000ps Alowal, show sh'ess on ehdce weld area.
baseAl •w:- fb.Sy• - 108901si Akwab b• se or compIsswO sliess on e tw wld areaWeld Sec*in Proper:es