ML033650372
| ML033650372 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 09/26/2003 |
| From: | Miessi G Structural Integrity Associates |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| PY-CEI/NRR-2758L PERY-03Q-301, Rev 0 | |
| Download: ML033650372 (22) | |
Text
PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I CALCULATION REVIEW FORM Calculation Number/FiI c~y_ 63g2' 30 1 Revision: 0 Review Method: A Design Review l Alternate Calc l Other Scope Item Review Attribute Reviewer: gj,7k I l l (PM) I Wer ,1e inputs correctly selected and incorporated into the analysis?
Yes E1 No by/date: m 7N I 7 ---
Zc 2
27 Are all assumptions necessary to perform the analysis reasonable and adequately de' cribed'.
Yes El No by/date: 7 Are the applicable codes, standards, and regulatory documents and requirements, including edition 7 / 3 and denda, properly identified, and are their requirements met?
_ _ Yes El No by/date:
4 Is theoutput reasonable compared to the inputs?
VI" . . 53 Yes El No by/date:
Are perrect material properties used in the analysis?
5 EtlYes E No by/date:
6 Are tJe acceptance criteria used in the analysis correct?
V 7
E r I Yes El No by/date:
Are cWulations numerically correct?
'/7"E Yes El No by/date:
Are pormation and analysis results accurately transferred from underlying calculati s or documents?
8 F Yes El No by/date:
9 Are De analysis results complete?
Er Yes E No by/date:
Are k wn problems or limitations of the results adequately defined?
1 lE Yes El No by/date:
11 We mputer programs used in the analysis adequately identified, verified, tested, nd controlled?
[T Yes El No by/date:
12 Is the, utput of computer programs compatible and reasonable compared with the inp t?
12 j[ Yes El No by/date:
13 Are aysociated computer files correct, current, and available for archival? ,-m /2-,,/6A2 13 9 A Yes E No by/date: //U I/ /
Documentation Attached: t"zMarkup L1I Memo El Other Comments (attach pages if necessary):
6 n&cLL gj Proposed Resolution (Preparer):
Gwnn5,k *hcoYpo yf -
Reviewer Acceptance*/Date: C 26103 that are referenced inthe attached calculation, were reviewed and approved for use by the PM, nas/hers The project m nager's approval signature, below, also indicates that all design inputs used in the preparation of the attached calculation, and designee.
Project Manager ApprovallDate: q2L7 v {
- _
- Includes agreement that any computer files are current and available for archival F2101R2.D0C
PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I FILE No.: PERY-03Q-301 v2 STRUCTURAL CALCULATION INTEGRITY PACKAGE PROJECT No.: PERY-03Q Associates, Inc.
PROJECT NAME: Emergency Service Water System Pump Shaft Coupling Failure Analysis CLIENT: First Energy Corporation CALCULATION TITLE: Stress Comparison Between a Properly Centered Coupling and an Off-Centered Coupling Project Mgr. Preparer(s) &
Document Affected . . s.p.nApproval Checker(s)
Revision Pages Revision Descripton Signature & Signatures &
Date Date 0 1-20 Original Issue Al Files Page of 20
PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I
- 1. OBJECTIVE A coupling failure has been observed for the vertical pump shaft of the emergency service water system at Perry Nuclear Power Plant. The failed coupling was found to be have been vertically misaligned by 1". The objective of this calculation is to develop finite element models of the properly centered and off-centered pump shaft coupling assemblies, and then perform stress analyses to evaluate the impact of the misalignment on the coupling. The stress analysis results will also be used later to perform a fracture mechanics evaluation of the coupling.
- 2. FINITE ELEMENT MODEL The finite element models (FEM) are developed using the 8-node structural solid (SOLID45) elements of the ANSYS software package [1]. The dimensions of the pump shaft coupling assembly, including the two shafts, two keys, and coupling, are obtained from References 2, 3, and 4. Note that the modeled length of each shaft, arbitrarily chosen as 5" from the end of the key slot, is enough to avoid boundary effects. The split rings are not modeled since their purpose is to transfer the down thrust axial loads, which do not contribute to the stresses on the coupling. The dimensions of the modeled geometry are summarized in Figure 1, and the finite element models are shown in Figures 2 through 5. The cross-sectional mesh for both models are identical (see Figure 6).
In order to model the interface between the different components, non-linear point-to-point contact (CONTAC52) elements are inserted between the contact surfaces between the coupling and the key, and the coupling and the shaft. The contact surfaces between the key and the shaft that are expected to be in compression due to the applied load are merged; this is acceptable as the detailed interactions between the key and the shaft is not the focus of this evaluation.
- 3. MATERIAL PROPERTIES Reference 3 shows that the pump shaft, key, and coupling material is SA582 Type 416, which has a tested chemical composition of 13.5% Cr [5]. Therefore, the elastic modulus for the Type 416 stainless steel falls in the 13% Cr material group of the ASME Code [6], which is 29.2E+06 psi at 80 F, while the Poisson's ratio is assumed to be 0.30. The material of the coupling assembly is martensitic in structure whether in the annealed or hardened and tempered condition. The ASM Handbook [7], which lists the room temperature Young's modulus of martensitic Stainless Steel Grades 410 and 416 at 29.OE+06 psi, states: "the modulus of elasticity is one of the most structure-insensitive of the mechanical properties. Generally, it is only slightly affected by alloying additions, heat treatment or cold work".
This fact is corroborated by materials reference data sheets from various vendors that report the same room temperature Young's modulus of 29.OE+06 psi for martensitic Stainless Steel Grade 410 in different heat-treatment conditions [8].
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I
- 4. ANALYSIS Reference 3 states that the key is subjected to 42,000 in-lbs of torque, plus a shock factor of 1.1 for torsion. This load is converted to a force couple and applied at the top end of the upper shaft, while the bottom end of the lower shaft is fixed in order for the load to be appropriately transferred. In addition, one node pair between the key and the coupling and one node pair between the shaft and the coupling are coupled axially near the set screw locations to simulate them (the set screws are not modeled) for stability of the model (see Figures 3 and 5). The top end of the top shaft is held axially to prevent any off-axis rotation. The ANSYS input files for the analyses are listed in Appendix A.
- 5. RESULTS AND DISCUSSION The deformed shapes, with the undeformed shapes outlined, of the shafts with the properly centered and off-centered couplings that subjected to the torque are shown in Figures 7 and 8, respectively. The overall hoop stress (SY) distribution on the model is shown in Figure 9. It should be noted that the highly localized maximum stresses seen on the shaft are simply due to the applied torque load at two points at the end of the shaft, which is far enough away from the coupling that it does not affect its stresses. Figure 10 presents the stresses in the shaft and illustrate the localization of the large stresses both in the centered and off-centered configurations.
5.1 Stress Comparison Between Configurations The radial (SX), hoop (SY), and axial (SZ) stresses on the properly centered and off-centered couplings are shown in Figures 11 through 13. Since the primary objective of this analysis is to investigate the root cause of the cracking in the pump shaft coupling, only tensile stresses are of importance. The results demonstrate that all three stress components peak at the edge of the keyway on the couplings, and all of the component stresses on the off-centered coupling are higher than that for the centered coupling.
The comparison between the maximum component stresses is summarized in Table 5-1.
Table 5-1: Pump Shaft Coupling Peak Stress Comparison Coupling Radial Stress (SX), ksi Hoop Stress (SY), ksi Axial Stress (SZ), ksi Centered 48.0 114.4 37.6 Off-Centered 65.1 1 154.9 l 49.8
% Difference 35.6% 1 35.4% 1 32.4%
The above comparisons demonstrate that the off-centered coupling is clearly more susceptible to cracking and failure than the properly centered coupling.
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I 5.2 Primary Stress Comparison to Allowables In the original design analysis of the vertical pump [3], the lineshaft coupling assembly was qualified based on the average primary stresses and allowable stresses presented in Table 5-2:
Table 5-2: Pump Shaft Assembly Original Report Primary and Allowable Stresses Component l Primary Stress Allowable Stress Component (psi) (psi)
Split Ring Axial Stress =21,580 30,000 Key Shear Stress = 12,491 20,000 Shaft Shearing Stress = 13,051 Not applicable Stress Intensity =29,155 30,000 Coupling Stress Intensity < 29,155 30,000 The coupling stress were not explicitly calculated but were determined to be lower than those of the shaft based on a comparison of section properties.
The dimensions used in this evaluation are nearly identical to the dimensions used in the original analysis except for the smaller, corroded shaft diameter used in the latter. Thus, for the same operating loads, the design analysis should remain valid.
In order to verify the primary stresses in the coupling assembly, the through-wall stresses from the finite element analysis are linearized at some locations to extract the membrane and bending stresses in the structure. The linearization option is available in ANSYS to allow a separation of stresses across the thickness of the section under consideration into membrane (constant, average value) and bending (linear, variable) stresses. First, the section is defined by a path consisting of two end points, which are at free surfaces, and 47 intermediate points (automatically determined by linear interpolation in the active display coordinate system). Then, the stress results are mapped onto that path and the membrane and bending stresses are extracted. The stress paths for the key and shaft are illustrated in Figures 14 and the paths for the coupling are shown in Figure 15. To obtain the primary stresses, which do not include peak stresses, the stress paths must be taken away from geometric discontinuities of the coupling assembly. Thus, the stress path for the shaft is taken halfway between the end of the shaft and the bottom of the keyway. For the coupling and the keys, the paths are taken at the centerline of each of the component.
The stress intensity calculated for the shaft in the original report includes bending and deadweight contributions, which are not considered in this analysis. Hence, only the maximum primary shearing stresses obtained from the finite element analyses are presented in Table 5-3 and compared to the values calculated in the original report. As expected, for the centered configuration, the stresses are almost equal or less than the stresses calculated in the original report. The off-centered configuration produces V Revision Preparer/Date Checker/Date 0
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PY-CEIINRR-2758L Calculation EA-254 Rev. 0 Attachment I nearly identical primary shearing stresses in the shaft and coupling but 33% higher stresses in the top key and slightly lower stresses in the bottom key. This 33% increase in primary shear stress is in agreement with the fact that only 3/4 of the top key is engaged. Therefore, the finite element analysis primary stresses compare well with the original report.
Table 5-3: Pump Shaft Assembly Primary Stress Comparison Shearing Stress (psi)
Component Finite Element Analysis Original Analysis Centered Off-Centered Top Key 1 12,670 16,830 12,491 Bottom Key 12,660 11,790 Shaft 13,051 12,990 13,110 Coupling < 13,051 5,574 5,733 1Only 3 /4 of the top key is engaged in the off-centered configuration.
The ANSYS post-processing result files for are listed in Appendix A.
- 6. CONCLUSION The stress analysis of the ESW pump coupling assembly demonstrates that very high hoop stresses are generated in the localized regions near the geometric discontinuities of the keyway under normal operating conditions. Figure 12 shows that the maximum hoop stresses are at the keyway groove, the exact location where the coupling cracking was reported [5]. Such high stresses in a crevice-like location, coupled with a susceptible material in a stress corrosion tolerant environment, can lead to intergranular stress corrosion cracking. Moreover, the stress analyses indicate that the improper installation of the coupling on the shafts increases the hoop stresses at the keyway by 35%, further augmenting the possibility of cracking.
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I
- 7. REFERENCES
- 1. ANSYS/Mechanical, Release 6.1 (w/ Service Packs 2 and 3), ANSYS Inc., April 2002.
- 3. McDonald Engineering Report No. ME-454 (Dated 07/20/1982), "Seismic Analysis of Vertical Pump," Including Addendum No. 1 (Dated 04/03/1984), SI File No. PERY-03Q-202.
- 4. E-Mail and Accompanying Attachments from C. Flensburg (First Energy) to A. Miessi (SI), "Pump Shaft Dimensions Rev. 1," Dated 09/11/2003, SI File No. PERY-03Q-201.
- 5. BETA Laboratory Report No. M-03284, "Failure Analysis Report," Dated 09/19/2003, SI File No.
PERY-03Q-203.
- 6. ASME Boiler and Pressure Vessel Code,Section II, Part D - Properties, 1998 Edition, No Addenda.
- 7. ASM Handbook, Ninth Edition, Volume 3, "Properties and Selection" and Volume 8 "Mechanical Testing".
- 8. Materials Reference Data Sheets from:
- BodyCote Materials Testing, "Stainless Steel - Grade 410", www.azom.com
- AK Steel Corporation, "410 Stainless Steel Product Data Sheet", www.aksteel.com
- Ferguson Metals, Inc., "Technical Data Stainless Steel Martensitic Type 410 UNS(S41000)", www.fergusonmetals.com
- Allegheny Ludlum Corporation, "Technical Data Blue Sheet, Martensitic Stainless Steel Types 410,420, 425 Mod, and 440A", www.alleghenyludlum.com SI File No. PERY-03Q-204.
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I symmetry Line 5.5955.
2.690' 1 I-4.002" Figure 1: Dimensions of the Pump Shaft Coupling Assembly
(* indicates assumed dimensions; all other dimensions are obtained from References 2, 3, and 4)
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I ELEMENTS MAT NUM U
Figure 2: Top View of the Finite Element Model of the Shaft with a Properly Centered Coupling (Blue color represents applied displacement constraints: top shaft end is axially held, bottom shaft end is fixed in all translational degrees-of-freedom)
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I Figure 3: Half-Sectional View of the Centered Coupling Model (Green color represents applied axial couples simulating the set-screws)
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I Figure 4: Top View of the Finite Element Model of the Shaft with an Off-Centered Coupling (Blue color represents applied displacement constraints: top shaft end is axially held, bottom shaft end is fixed in all translational degrees-of-freedom. The coupling is 1" below its center position.)
Revision 0
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I Figure 5: Half-Sectional View of the Off-Centered Coupling Model (Green color represents applied axial couples simulating the set-screws)
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PY-CEIINRR-2758L Calculation EA-254 Rev. 0 Attachment I ELEMENT S MAT NUM Figure 6: Front View of the Model Showing the Cross-Sectional Mesh (Both models have identical cross-sectional mesh)
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PY-CEI/N RR-2758L Calculation EA-254 Rev. 0 Attachment I DISPLACEMENT STEP=1 SUB =2 TIME=.
RSY8=1 DMX =. 044264 SEPC=32. 291 1
F STRESS ANALYSIS OF THE CENTERED COUPLING Figure 7: Deformed Shape of the Shaft with a Properly Centered Coupling DIS PLACEMENT STE P=1 SUB =2 TIME=1 RSY8=1 DoX. 047242 SEPC=32. 041 F
STRESS ANALYSIS OF THE OFF-CENTERED COUPLING Figure 8: Deformed Shape of the Shaft with an Off-Centered Coupling V Revision Preparer/Date Checker/Date 0
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PY-CEI/NRR-27 5 8L Calculation EA-254 Rev. 0 Attachment I NODAL SOLUTION STEP=1 SUB =2 TIME=1 SY (AVG)
RSYS=1 -322791 DMX =.044264 SMN =-322791 -251060 SMNB=-585159 SnX 322793 SMXB=585160 -179328
-107597
-35865 35867 107598 179330 251061 322793 STRESS ANALYSIS OF THE CENTERED a) Centered Coupling NODAL SOLUTION STEP=1 SUB 2 TTME=.
SY (AVG)
RSYS=1 -322795 DMX .047242 SMN -322795 -251063 SMNB=-B5162 SMX =322789 SMXB=58157 -179332
-107600
-35868 35863 107595 179326 k 251058 322789 STRESS ANALYSIS OF THE OFF-CENTERED COUPLING b) Off-Centered Coupling Figure 9: Overall Hoop Stress Distribution on the Models V Revision Preparer/Date Checker/Date 0
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PY-CEI/N RR-2758L Calculation EA-254 Rev. 0 Attachment I NODAL SOLUTION STEF=1 SUB =2 TINE=1 SY (AVG)
RSYS=1 DMX=.042787 SMN=-322791 SSVX=322793 I'
-30000 -16667 -3333 10000 23333
-23333 -10000 3333 16667 30000 STRESS ANALYSIS OF TE CENTERED COUPLING a) Centered Coupling NODALSOLUTION STEP=1 SUB 2 TIME=l SY (AVG)
RSYS-1 DMX=.046024 SH =-322795 SMNB-585162 SMX =322789 SMS95 85 157 F
-30000 -16667 -3333 10000 23333
-23333 -10000 3333 16667 30000 STRESS ANALYSIS OF THE OFF-CENTERED COUPLING b) Off-Centered Coupling Figure 10: Overall Hoop Stress Distribution on the Models (Gray color represents areas where the stress is beyond the range in the legend)
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I NODAL SOLUTION STEP=1 SUB =2 TIME=1 SX (AVG)
DMX =.033474 SHN =-157904 SMNB=-255261 SX =48049 SHXB=107220 t..dX~~~ -iV.
-157904 -112137 -66369 -20602 25166
-135021 -89253 -43486 2282 48049 STRESS ANALYSIS OF THE CENTERED COUPLING a) Centered Coupling NODAL SOLUTION STEP=1 SUB =2 TIME=1 SX (AVG)
RSYS=1 OMX =. 03298 SHN =-240404 SHNB=-397648 SHX =65123 SXB=171733
-240404 -172509 -104614 -36719 31176
-206456 -138562 -70667 -2772 65123 STRESS ANALYSIS OF THE OFF-CENTERED COUPLING b) Off-Centered Coupling Figure 11: Radial Stress Distribution on the Couplings, SX Revision 0 CiIIzj' Preparer/Date FHK 09/26/03
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I NODAL SOLUTION STEP1=
SUB =2 TIME=1 RSYS=1 DMX =. 033474 SMN =-109874 SMNB=-192454 SMX =114434 SMXB=163638 x
-109874 -60028 -10182 39664 89511
-84951 -35105 14741 64587 114434 STRESS ANALYSIS OF THE CENTERED COUPLING a) Centered Coupling NODAL SOLUTION SUB =2 SY (AVG)
RSYS=1 DMX =. 03298 SMN -150411 SMNB=-3018=7 SMX =154895 5MXB221244
-150411 -82565 -14719 53127 120972
-116488 -48642 19204 87049 154895 STRESS ANALYSIS OF THE OFF-CENTERED COUPLING b) Off-Centered Coupling Figure 12: Hoop Stress Distribution on the Couplings, SY Revision 0 Preparer/Date FHK 09/26/03 Checker/Date GAM 09/26/03 File No. PERY-03Q-301 Page 17 of 20
PY-CEI/N RR-2758L Calculation EA-254 Rev. 0 Attachment I NODAL SOLUTION STEP=1 SUB =2 TIME=1_
SZ (AVG)
RSYS=1 DMX =.033474 SMN =-78746 SMNB=-176102 SMX =37614 SMXB=83194
-78746 -52888 -27031 -1173 24685
-65817 -39959 -14102 11756 37614 STRESS NALYSIS OF THE CENTERED COUPLING a) Centered Coupling NODAL SOLUTION STEP=1 SUB 2 TIME1=1 SZ (AVG)
RSYS=1 DMX =.03298 SMN =-103047 SNB=-239880 SMX =49782 SMXB=153730
-103047 -659085 -35123 -1161 32801
-86066 -52104 -18142 15820 49782 STRESS ANALYSIS OF THE OFF-CENTERED COUPLING b) Off-Centered Coupling Figure 13: Axial Stress Distribution on the Couplings, SZ Revision 0 Preparer/Date FHK 09/26/03 Checker/Date GAM 09/26/03 File No. PERY-03Q-301 Page 18 of 20
PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I I a) In the Key Ch:wft I I - Ib) In the Shaft Figure 14: Stress Linearization Paths in the Key and Shaft V Revision Preparer/Date Checker/Date 0
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I CoupH2 Figure 15: Stress Linearization Paths in the Coupling V Revision Preparer/Date Checker/Date 0
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PY-CEI/NRR-2758L Calculation EA-254 Rev. 0 Attachment I APPENDIX A - ANSYS INPUT AND OUTPUT FILES DESCRIPTION Input File Description SHAFT CENTER.INP Finite element model geometry for the properly centered coupling SHAFT-OFF.INP Finite element model geometry for the off-centered coupling STR CENTER.INP Stress analysis of the centered coupling model STR OFFINP Stress analysis of the off-centered coupling model LINEARIZE.INP Post-processing file to extract linearized stresses Output File Description LINEARIZECTR.OUT Linearized stress output for centered coupling analysis LINEARIZE OFF.OUT Linearized stress output for off-centered coupling analysis Revision 0 Preparer/Date FHK 09/26/03 Checker/Date GAM 09/26/03 File No. PERY-03Q-301 Page Al of Al