ML20141D075
| ML20141D075 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 03/05/1986 |
| From: | Mcavay J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | |
| Shared Package | |
| ML20141D059 | List: |
| References | |
| NUDOCS 8604070390 | |
| Download: ML20141D075 (154) | |
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' I SURRY 410 STAINLESS STEEL STUD CRACKING ANALYSIS !
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I March 5, 1986 I
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SURRY 410 STAINLESS STEEL STUD CRACKING ANALYSIS
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FINAL REPORT, MARCH 5, 1986 PP.EPARED BY J. M. MCAVOY,_ VIRGINIA POWER-N0D/0&MS
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PREPARED FOR I
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TABLE OF CONTENTS
- SECTION PAGE Background 1 Failure Mechanism 3
-Material, Stress and Environmental Effects 5 Actions Taken to Define and Resolve the Cracking Problem 9 Conclusions and Recommendations 11 Failure Analysis of SI-241 Cracked Valve Studs Appendix A Failure Analysis of Cracked Studs from Surry Unit 1 Valve SI-1890B Appendix B
. Valve'SI-241 Structural Analysis Appendix C Fracture Mechanics Adalysis For Studs in Valve SI-241 Appendix D Surry 410 S/S Stud Bend Tests Appendix Z JMM/jmj /0M4-64 z - .
Background
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Several ~410 stainless steel studs in valves SI-241 and SI-1890B in the Surry Unit I low head safety injection system were found broken and partially or completely missing from the valves. Due to circumstances surrounding the failure, the initial judgement was that the three 1 1/4" diameter studs which failed in SI-241 had failed by over-torque.
A thorough metallurgical and chemical analysis of the failed studs and foreign material found on the studs (see Appendix A) indicated that the failure mechanism was stress corrosion cracking. It is assumed that rapid unstable crack growth occurred after the critical flaw size was achieved. During the investigation period for SI-241, two (2) 410 stainless steel studs failed in SI-1890B;by the .same mechanism ar.d this failure it documented in Appendix B.
The 513-18908 studs were 1- 7/8" diameter. No leakage in either valve was attributed to failure of the studs. Due to the number of failed studs in SI-241, a detailed structural analysis was conducted which is contained in Appendix C. This analysis concluded that the valve was not in danger of failure due to.the loss of several studs.
A review of the purchase records and markings on the studs indicated that the same manufacturer had supplied the studs for both valves in 1981 as part of a valve stud material replacement program for Surry Units 1 and 2. Furthermore, chemical analysis of studs from both valves, an.d a third valve with similarly marked studs of the same size, indicated that only two heats of material were involved. One heat of material was employed for the 11" studs found in one
[ valve and one heat was employed for the 17/8" studs found in several valves.
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The chemical analysis _of foreign material found ,on the studs indicated the presence of copper which originated from the lubricant. Also, valve SI-241 had experienced leakage w'hich provided the electrolite for the stress corrosion cracking. Valve SI-1890B showed signs of past leakage and/or collection of moisture from the local environment. Many of the studs from both SI-241 and SI-1890B were rusted.
f Mechanical test results from the failed studs were generally within the required values for ASTM A193, Grade B6, the specification to which the studs were purchased (except the minimum tensile strength was specified as 125 Ksi vs the minimum requirement for B6 material of 110 Ksi). In one case a stud was found to show a reduction in area of 44.5% vs the specification requirement of 50%; however, all other requirements were met. A supplementary Charpy V-notch test indicated low notch toughness for studs from both 51-241 4' and 51-18908, and the fracture appearance of the tensile test specimens was abnormal. The chemistry of the studs from both valves was within ASTM A193 Grade B6 requirements, and the hardness values were in the range of 25 to 24 Rockwell C (HRC). Typical hardness values. have been in the range of 28 to 32 HRC which indicates a fairly soft temper for 410 stainless steel.
The combination of sensitivity to stress corrosion cracking, low fracture toughness and abnormal tensile fracture appearance are indicators of a low tempering temperature and temper embrittlement. It appears that the failed studs were tempered below the ASTM A193 Grade B6 minimum requirement of 1100'F, and in a range resulting in temper embrittlement. The studs may have been tempered between 1000 F and 1050 F. In some instances the stud manufacturer appears to have heat treated at a lower tempering temperature l-JMM/jmj/0M4-64
than the minimum specified by ASTM A193 for 86 material to achieve the higher tensile strength of 125 Ksi minimum required by the purchase order. This material was marked by the manufacturer J410. In other instances the manufacturer may have inadvertently tempered the 410 stainless steel studs below 1100 F or ' performed some other heat treatment resulting in temper embrittlement. Some material marked JB6 (indicating that the ASTM A193 Grade B6 specification nad been met), was in this category.
Valve SI-241 was found to have 410 stainless steel studs marked J410, while valve SI-18908 had 410 stainless steel studs marked JB6.
Failure Mechanism The failure techanism observed in SI-241 and SI-1890B involved the growth of intergranular stress corrosion crack (s) to a point where the largest flaw reached critical size and the stud failed by rapid fracture. During the failure a localized " load shed" to adjacent studs occurs. This localized load buildup in adjacent studs was the apparent cause of failure of one (1) additional stud with a stress corrosion crack in SI-1890B. Load shed also may have resulted in the failure of one (1) or two (2) cracked studs in SI-241,
- but this cannot be determined. The load shed affect is not thought to be l
l capable of the failure of an entire group of valve studs due primarily to:
l l 1. The differential stress in the studs due to torquing by use of torque wrenches,
- 2. The difference in crack size in the studs,
! 3. The fact that all studs in a valve are not cracked, and that (due to l'
torquing sequence) the distribution of cracked and uncracked studs is somewhat symmetrical (alternating).
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Only those 410 stainless steel studs have failed which were corroded (rusted).
Such a condition occurs - where there is significant chronic valve leakage and/or moisture resulting from environniental conditions external to the valve.
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A microscopic analysis 'of the failed studs reveals a rust buildup in the thread roots with localized pitting or "troughing" in the root. Stress corrosion cracks initiate from the pits or troughs and extend into the studs at an initial angle equal to the thread pitch'. ,
Cracking in the SI-241 studs was restricted to the lower portion of the studs at the interface region between the stud and the valve body. At this regicn there was a small accumulation of boric acid and copper (CSA) lubricant.
In.the SI-1890 valves, stud cracking occurred at two locations. Most of the
- cracks were located in the lower region of the studs just above, or at, the interface with the bottom nut. This location would be the normal accumulation point for moisture on the stud and the location of excess thread lubricant.
Two studs, one in 18908 and one in 1890C, cracked in the nut. These cracks occurred in the upper portion of the studs and represent the only cracks found in the upper ~ region. One stud crack was 11" into the nut which was apparently holding water. Cracking in this case occurred at the interface between moisture, and thread lubricant, but in a low' stress region.
Material, Stress, and Environmental Effects Intergranular stress corrosion cracking is the result of an interrelationship between the material which is susceptible to IGSCC, a condition of stress in the material which must exceed a threshold value (KIscc), and an environa nt l which contributes electrolite and some corrosive species. An investigation JMM/jmj/0M4-64
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1 into all. three aspects of the IGSCC process was conducted for the 410 stainless steel stud failure at Surry. The important' elements related to each aspect of material, stress, and environment follow:
- 1. Material
- a. Studs were specified to have a minimum tensile strength of 125 Ksi vs th' eASTM A193 Grade B6 requirement of 110 Ksi minimum.
- b. The studs were tempered in such a manner as to result in temper embrittlement, probably at a temperature between 1000 and 1050*F.
- c. The studs have mechanical properties which , generally meet ASTM A193 Grade B6, though reduction-in-area values are marginal.
- d. The studs meet the cheinical analysis requirements of ASTM A193 '
Grade B with a minor exception as shown in Table 3 of Appendix B.
p e. Supplementary Charpy V-notch tests show low notch toughness, with I the . fracture surface appearance , indicating little or no shear 1.
-fracture.
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- f. Supplementary hardness tests of cracked studs indicate a scatter of hardness values between HRC 25 and 34 (See Appendix A to this i
l report). This indicates considerable variability in material properties, sometimes across a single diameter of a single stud.
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- g. Bend test specimens, cut from l'ongitudinal sections of studs parallel to the central axis, indicate v'ery little ductility in studs which exhibit IGSCC, with bend angles between O' and 17*.
a.
- 2. Stress (and crack dimensions)
- d. Based on material notch toughness (from which fracture toughness can be estimated), and flaw size at failure for studs in SI 241 and SI-18908, the failure stress does not represent an over-torque condition.
- b. The presence of cracks in two studs well within that portion of the studs surrounded by the nuts indicates that there is a very low threshold stress intensity (KIscc) value for inWadon of IGSCC in the temper embrittled 410 stainless steel. The K Iscc valuemaybebelow10t;.20Ksidin,
- c. Crack growth rates may not be a function of stress in the '~ studs.
Observed growth rates for cracks in the same general region of a single 410 stainless steel stud are in the range of 2.9 x 10-9 in/second to 4.1 x 10-10 in/second. The lcwer crack growth rates seem to represent locations on stud surfaces above the stud-nut-lubricant interface. The higher growth rates are closer to the stud nut interface and in the region of moisture / lubricant r- JM/jmj/0M4-64
e concentrat. ion.
~d. Since the valves in question at the Surry Power Station were asse-bled primarily by use of torque. wrenches, a high variability is anticipated in preload from stud-to-stud due to the' limits' on torque control possible with a torque wrench, and the use of torque ~ sequence patterns with_ a low number of passes. This results 'in significant variations in net stress from stud-to-stud in each valve. With stud material sensitive to IGSCC at a low K threshold, this is a desirable situation Iscc
- e. There is significant variability in crack shape and size from stud-to-stud and from location-tc-location within a single stud.
The observed cracks grow with aspect ratios (a/l) as large as 0.5 and as small as 0.1 or less.
- f. Failure of a stud occurs when the size of the crack reaches a critical value (a )c based on stud stress and static fracture toughness (KIc). The critical flaws in failed studs have normally been large flaws with an aspect ratio of 0.25 to 0.5. One failed stud with an aspect ratio of less than 0.1 is thought to represent a " load shed" failure.
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- g. Load shedding due to the static fracture of one stud results in loading of adjacent studs. Those adjacent studs with a flaw which becomes critical in size as a result of the new load may fracture.
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e It has been observed, however, that only one (1) or possibly two (2) studs have fractured. This low number of " load shed" fractures is due to: (1) the significant difference in net stress of surrounding studs, (2) the large variation in crack size from stud-to-stud, and (3) the number of uncracked studs in each valve spaced between cracked studs.
- 3. Environment
- a. The studs appear to crack due to the e'lectrolite (water) present from valve leakage, or from a source external to the valve,
- b. Only those studs have cracked which were rusted with small pits in the thread rcots.
- c. The cracks grew out of pits in thread roots,
- d. Cracking has occurred most frequently and more severely at the interface between the stud, thread lubricant (copper CSA), and moisture. Cracking seems to occur more slowly at regions away from the lubricant " pile" at the nut / stud interface.
- e. Detailed analysis of chemical samples removed from bolted connections in the Surry station has shown a wide variety of chemical species. Few of these have any history of causing cracking in 410 stainless steel at hardness values of 25 to 34 HRC. Copper lubricants have been reported in several references as playing some part, yet unquantified, in the IGSCC failure of JMM/jmj/0M4-64
410-stainless steel fasteners in field service and in laboratory tests.
- f. Leach tests conducted on the fracture surface of a 410 stainless steel stud from SI-241 revealed no abnormal pH condition. Also, leach tests on concentrations of leakage residue from a sister valve of SI-241 revealed no abnormal contaminates or pH value.
Actions Taken to Define and Resolve the Cracking Problem
.The following actions have been taken to further. define the extent of this problem and to resolve the problem:
- 1. Studs in valves SI-1890A, B, and C and SI-2830A, B, ar.d C have been removed and have been inspected by non-destructive and destructive (on a selective basis) techniques to determine the extent of the IGSCC. The results of this inspection are included in Appendix B.
Studs in SI-241 were also examined to determine the nature, size, and extent of the cracks and this evaluation is included in Appendix A.
- 2. A detailed search was conducted of the purchase records to determine what other fasteners of 410 stainless steel were supplied by the vendor in question, and other vendors, as part of the valve stud replacement project at the Surry Pcwer Station.
- 3. Valves in ASME class systems within the scope of the original valve change-out were identified where stud size is 3/4" diameter ar.d greater. All such valves were inspected to determine: (1) what JMM/jmj/0M4-64 l
r materials were used for studs on a valve-by-valve basis, (2) where studs marked JB6 and J410 were used, and (3) where possible which vendors supplied other studs of 410 stainless steel. It was determined from field inspection that a relatively small number of 410 stainless steel studs were used in Surry Unit 2; however, a larger number of studs were found in Surry Unit 1.
- 4. During the Unit 1 and Unit 2 maintenance outages, 410 stainless steel studs 3/4" diameter and greater marked JB6, J410, B6 or unmarked, in critical applications, were replaced. Other studs were tested on a sample basis to determine if any were temper embrittled or showed signs of IGSCC. No additional studs were cracked. One stud was found to be _ marginal in ductility which was considered to be an indicaticn of temper embrittlement. All of the studs tested demonstrated superior bend test results to those which were temper embrittled and showed IGSCC.
- 5. Studs in the size range below 3/4" diameter have been removed on a sample basis and tested to prove that they are not cracking by IGSCC and that they are not temper embrittled. It was found that small studs generally did not exhibit temper embrittlement and none were cracked. This is assumed to be because of a difference in the heat treatment process for small diameter studs, and the apparent ease in obtaining desired mechanical properties in these studs by complying with ASTM '.'93 Grade B6 heat treatment requirements. Appendix Z contains the bend test procedure and results including photographs of fracture surfaces.
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- 6. Imediately after discovering the broken studs in SI-18908, all critical safety related systems in both Surry 1 and 2 were visually inspected by a walkdown conducted by station operations personnel.
No further broken studs were observed.
Conclusions and Recommendations With the actions described above completed, it is concluded that the Surry stud cracking mechanism has been identified and the extent of the problem has been determined. Material suspect of IGSCC was replaced and other material which indicated no IGSCC, but which was considered marginal in ductility, was identified for replacement at a later outage. Specifically, the final recommendations from this evaluation are as follows:
- 1. Large diameter studs (3/4" to 17/8" diameter) marked VB6 shcwed no signs of IGSCC, but one stud indicated marginal ductility by the bend test. Since marginal ductility indicates some degree of temper embrittlement, it is considered conservative to replace these large diameter studs at the next refueling outage.
- 2. Small diameter (<3/4") studs tested indicated low hardness and reasonable ductility by bend tests except those studs marked VB6-JC
, which were marginal in the bend test. None of the studs marked VB6-JC were cracked, but it would be conservative to locate and remove this material at the next refueling outage.
- 3. Because of the superior performance of the small diameter (<3/4") B6 410 stainless steel studs as compared to B7 low alloy steel studs in JP94/jmj/0M4-64
I borated water service, it is recommended that no replacement of these studs be made except as noted in 2. above. Where normal replacement is required, due to valve maintenance, 410 stainless steel may be used provided it is purchased to the requirements of ASTM A193 Grade B6. Since this may involved receipt of some materials with tensile strength below 125 Ksi and a low yield strength, the lower tensile and yield strength of the B6 studs must be reviewed and approved by Station Engineering or E&C.
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APPENDIX A FAILURE ANALYSIS OF SI-241 CRACKED VALVE STUDS e
January 16, 1986 l
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EXAMINATION OF LOW HEAD SAFETY INJECTION SYSTEM STUDS FROM VIRGINIA POWER'S SURRY POWER STATION The Babcock & Wilcox Company Nuclear Power Division P.O. Box 10935 Lynchburg, Virginia 24506-0935
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. . Report Documentation Document Identifier: 47-1159842-00 T121e: Examination of Low Head Safety Injection System Studs from Virginia Power's Surry Power Station Date: January 6, 1986 Customer: Virginia Electric and Power Company Customer Order No.: SY-15458-SC B&W Contract No.: 583-7375 Task 039 Prepared By: T.J. Zeh
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Project Manager: D.J. Firth 4
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SUMMARY
Twenty-three studs from two safety injection valves were examined from the Virginia Power Surry Nuclear Power Plant. One set of twelve studs was fabricated from ASTM 193 B6 (AISI Type 410 stainless steel) while the other set was fabricated from ASTM 193 B7 (AISI Type 4140). Three of the 410 stainless steel studs were broken when received. The fractures occurred approximately 2-1/4 inches above the bottom of the stud where the studs thread into the valve flange. Cracks were detected in eight 410 stainless steel studs during penetrant testing including the three studs containing fractures. The studs failed in a mixed mode intergranular and ductile rupture fracture. The failure mechanism is probably related to an unexplained interaction between the 410 SS and a copper bearing lubricant used during valve assembly.
The B7 studs also showed degradation in the same area. Two of the studs underwent severe general corrosion of the stud in the same area where the 410 studs failed. The general corrosion is caused by boric acid leakage. This type of corrosion, however, is readily apparent which could be an advantage in a plant.
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RDD:85:5237-01:01 PAGE 1 a McDermott company
1.0 INTRODUCTION
Twenty-three 1-1/4 inch diameter 6-3/8 inch long studs from two low head safety injection valves were removed from the Virginia Power Surry Nuclear Power Plant. Twelve studs are used to hold the cap to the valve top. The valve carries borated water. The studs were shipped to the Babcock & Wilcr x Company Lynchburg Research Center (LRC) for examination.
The studs were individually wrapped and packaged in a fif tyfive gallon drum.
The drum was labeled #SH 1985-165. One set of twelve studs removed from valve SI-241 was fabricated from ASTM 193-B6 modified tensile strength (AISI 410 stainless steel) material. The other eleven studs were removed from valve SI-243 and were fabricated from ASTM 193-B7 ( AISI 4140 steel) material. For clarity, the studs are designated as 241 and 243 studs throughout the remainder of this report. Three of the SI-241 studs (numbers 2, 4, and 5) tere broken in service. Figure 1 shows a picture of the SI-241 valve insitu.
Note the three missing nuts and broken studs in the photograph. A graphic representation of the configuration of the valve showing where deposits can accumulate if the valve leaks is also shown in Figure 1. The 243 studs were removed from a similar valve but none of the studs were fractured.51) One stu1, however, was lost and could not be shipped.
The studs in the 243 valve had been changed out recently as part of a program to use 87 material for all replacement studs.
2.0 WORKSCOPE The primary purpose of the examination was to examine the failures of the 241 s tuds . The 243 studs were examined on a limited basis. The workscope included the following steps as outlined below.
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o Radiation Survey - 241 and 243
- I o Visual Inspection - 241 and 243 o Macro Photography - 241 and 243 o Penetrant Inspection - 241 and 243 o Scanning Electron Microscopy of Fracture Surfaces - 241 o Qualitative Energy Dispersive Spectroscopy - 241 o Physical Testing - 241
- Hardness Testing
- Full Section Tension Testing
- Tensile Testing
- Charpy Impact Testing o Metallography -241 o Deposit Chemical Analyses - 241 and 243
- Emission Spectrocopy
- Wet Chemical Analysis Chlorides Sul fides
- Leachant Testing for Hydroxides ;
o Bulk Chemical Analysis of Stud Materials - 241 and 243 3.0 RESULTS 3.1 Radiation Survey The studs were surveyed with a R03-A dosimeter in a background of approximately 2.5 millirem (mR) per hour. The radiation levels of the studs ranged from 3 mR to 23 mR including background.
3.2 Visual Inspection The twenty-three studs were visually inspected upon receipt. A Virginia Power representative reported that 241 studs #10 and #5 had been inadvertently
T Babcos;k &WHeox RDD:85:5237-01:01 PAGE 3 a McDermott company switched and mislabeled at Surry. The #5 and #10 studs were switched at the LRC to correct the mistake. One end of the 241 studs was stamped J410 while the other end was stamped NN137. The stampings did not correspond to placement or orientation in the valve and, therefor', were not significant in the examination. The 243 studs did not hate any identifications. Photographs typical of the 241 and 243 studs in the as-received condition are shown in Figures 2 and 3. A photograph of stud #5 wa:. Inadvertently not taken. All of the studs were covered with colored deposits ranging / rom white to whitish-brown to red and copper colored. The white colored deposits were probably boric acid crystals. The boric acid could ha/e resulted from occasional leaks in the valves which carry borated water. The majority of the deposits were located in a band about 1-1/4 to 3 inches long and starting approxhiately 2.5 inches from one end as shown for 243 studs #2 and #5 in Figure 3. General wastage was also observed in this same area on 243 studs #6 and #11 as shown ir. Figure 3. No significant defects were observed for the 241 studs except for the three fractured studs shown in Figure 4.
3.3 Penetrant Inspection The studs were scraped and chemically cleaned in passivated hcl
- to remove surfac,e deposits from the studs. The deposits scraped from the 243 studs and from 241 stud #8 were collected and transferred into separate glass vials for subsequent chemical analyses (Section 3.8). The studs were flourescent dye penetrant inspected according to ASTM E-165-80. The results of the inspection showed multiple indications in the thread roots over the entire length of the 241 studs which could have been caused by small pitting, and tearing of the threads. Possible cracks were detected in 241 studs #1, 2, 4, 5, 6, 8,11,12 in the same 1-1/4 inch band where the deposits were observed during the visual inspection; however, cracks were verified in studs 2, 4, 5, 6, and 12 only.
CPassivated Hydrochloric Acid - room temperature solution of 6N hcl inhibited with 2 g/l hexamethylene/ tetramine.
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i No crack indications were found on the 243 studs even in the wastage areas of studs #6 and #11. Only minor pitting type indications were found on the 243 studs.
3.4 Scanning Electron Microscopy of Fracture Surfaces The fracture surface of 241 stud #2 was removed by dry sectioning a 1/8 inch Wdfer off the end of the stud. The wafer was then quartered to permit the specimens to fit in the chamber of the scanning electron microscope (SEM).
Each of the four quarters was examined in the SEM before and after cleaning in passivated hcl. The examination was performed with an ETEC* SEM. The fracture surface of each quarter had a similar mixed mode' morphology, i.e., a mixture of intergranular, transgranular and microvoid coalescence. Figure 5 is representative of the fracture observed in each quarter and shows the difference between the edge and center areas of Quarter B. There appears to be more ductile fracture at the center of the stud.
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3.5 Qualttative Enfrgy Dispersive Spectroscopy The fracture surface of 241 stud #2 was examined with a KEVEX 8000 energy I
dispersive opdctrometer (EDS) 'ising a detector with a multiple position
- The ETEC Autoscan microscope automatically records pertinent data on the micrographs ,
tdngth Scale Working Distance (mm) hg /'
001.0p /s 05-3 20.0 13 100 118 '
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Ma gni fica, tion
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Accelera tion hgative 5x!O; Voltage ID Number i
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Babcock &WIfcox RDD:85:5237-01:01 PAGE 5 a McDermott company window. Elements with atomic numbers less than 11 are not detected for the window position used. Al, Si, K Ca, S, Cr, Fe, Ni, Cu, and Zn were detected on the fracture surface of the stud. Representative EDS spectra are shown in Figure 6. A replica of one quarter of the fracture surface of 241 Stud #2 was made to remove the surface deposits from the stud. The use of the replica reduced the energy counts from the base metal thereby increasing the accuracy of the deposit analysis. The replica was carbon coated and analyzed with the EDS system. Figure 7 shows an elemental dot made of a copper particle found on the replica. Note, the amount of copper found on the fracture surface was sporadic in nature and found in small discrete particles. A semi-quantitative standardless EDS analysis of the overall replica showed:
Si 1.79%
K 0.23%
Cr 11.42%
Fe 86.00%
Cu 0.56%
Samples of the surface deposits taken from 241 stud #8 and the 243 studs were also analyzed. The results showed major peaks of Si, Ca, S, Cr and Fe on all samples.
3.6 Physical Testing Physical testing including Rockwell hardness testing, full and reduced section tensile testing, and elevated and room temperature charpy testing were performed on 241 stud samples. The full section tests were performed at the LRC while the tensile and charpy tests were performed at an independent la bora tory. The samples were chemically cleaned in passivated hydrochloric acid prior to shipping and testing.
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3.6.1 Hardness Testing Wafers approximately 1/4 inch thick were removed with a water cooled abrasive ~
cut off saw for all 241 studs and 243 stud #8. Five Rockwell hardness readings were taken across each of the wafers according to ASTM E18-74. The _
results, shown in Table 1, indicate that the Rockwell C hardness of the 241 studs ranged from 25.4 to 34.7.
3.6.2 Full Section Loading Two 241 studs were tested in the original configuration to determine the effect of the cracking on the overall load carrying capacity of the studs. A -
fixture was fabricated in which the studs were threaded and pulled on a 120,000 pound load frame. The full section tensile tests were performed at a moderate loading (crosshead) rate on one service cracked (241 stud #6) and one q intact (241 stud #3) stud. The actual loading rate cannot be determined on a the Baldwin Universal Testing Machine. The maximum loads obtained are given below:
Service Cracked 241 Stud #6 61,600 lbs.
Intact 241 Stud #3: >115,000 lbs.
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ggy, RDD:85:5237-01:01 PAGE 7 4 WOermott company Table 1 Hardness Results, Rockwell C Scale 241 Stud # Average Hardness Standard Deviation 1 20.88 1.37 Re. check #1 25.42 3.34 2' 27.32 1.26 3 33.08 0.31 4 31.08 1.27 5 29.88 0.68 6 32.50 0.48 7 30.42 0.78 8 30.98 0.53 9 31.12 0.84 10 31.54 0.88 11 34.74 1.88 12 32.74 1.79 243 Stud #8 29.92 2.21
'T'he intact stud did not fail at a load of 115,000 pounds which is reasonable based on the cross-sectional area (approximately one square inch) and tensile I
, strength (140,000 psi) of this material. The 241 stud #6 did fail.
Photographs of 241 stud #6 following the completion of tensile testing are shown in Figure 8. Approximately 35-40 percent of the cross-sectional area of stud #6 was precracked. Using a 40% precrack and an original cross-sectional area of one square inch, the #6 stud should have pulled greater than 84,000 pounds. Normally, most ductile steel alloys exhibit a notched tensile strength higher than the tensile strength of the material. The lower propor-tionai load capability for stud #6 indicates that the material had a high notch sensitivity (high localized stress intensity combined with low fracture toughness) similar to alloy steels tempered at temperatures less than 900 F.(5) SEM fractographs (Figure 9) show that the service cracked region
ah mW RDD:85:5237-01:01 PAGE 8 a McDermott company (dark area of the fracture) of the stud failed in a mixed mode manner of which the majority was intergranular in nature. In the center of the stud where the fracture surface was bright and shiny (signifying a new fracture) the fracture had more areas showing ductile rupture, however, a significant amount of intergranular fracture is also present.
3.6.3 Tensile Testing The tensile tests were performed by Westmoreland Mechanical Testing &
Research, Inc., Youngstown, Pennsylvania, on samples from 241 studs #1 (intact) and #2 (failed), specimens 1 and 2, respectively. The tests were performed in accordance with ASTM E8. The results (Appendix A) shcw no apparent differences in the two specimens (146 to 148 ksi tensile strength) but both show higher tensile and yield strength than normally specified by Virginia Power for 410 stainless steel. Virginia Power normally requested a tensile of 120,000-132,000 psi.(I) The higher strength is probably due to a lower tempering temperature. A tempering temperature decrease from 1100 F to 1050 F or 1000 F could cause the observed strength and hardness values for 410 stainless steel.(6) Note, the samples were mislabeled by the testing laboratory as 413 SS. An SEM fractograph, shown in Figure 10, of stud #1 after fracture, shows an unusual fracture. Note thh axial cracks in the well necked fracture. These cracks could have been caused by high biaxial stresses produced during necking. Higher magnification views showed the fracture to be ductile rupture.
3.6.4 Charpy Testing Room and elevated temperature charpy impact tests were performed by Westmoreland Mechanical testing & Research, Inc. on samples from 241 studs #4 (failed) and #11 (intact). The tests were performed in accordance to ASTM E23. The results (Appendix A) showed no difference in the two studs. Both had impact energies of 14 and 105 foot pounds for room temperature and 400 F test temperatures, respectively, which are reasonable for tempering
gg RDD:85:5237-01:01 PAGE 9 a McDermott company temperature near 1050 F or 1000 F. For example, the expected charpy impact of 120,000 psi material would have been approximately 25-35 ft-lbs. Therefore, the lower shelf energy is slightly lower than expected for the 120,000 psi Case.
There was considerable difference between the fracture mode at the two test temperatu res. The SEM photomicrographs in Figure 11 show a mixed mode fracture for the room temperature fracture while the elevated temperature fracture was mainly ductile rupture. Therefore, the predominantly intergranular fracture is apparently the preferred fracture mode for the 410 stainless steel stud material for impact or cracked tensile at low (near room) tempe ratu res.
3.7 Metallography A metallurgical sample was prepared from 241 stud #12. The sample selected from the 241 stud included a circumferential crack found during penetrant testing. The sample was mounted, ground and polished using normal practices.
Figure 12 shows an intergranular crack observed propagating from the outer surface of the stud in the thread root. The crack was wide at the base as if the prior austenite grain boundaries had corroded away. The sample was then etched in oxalic acid (Figure 13). The resulting microstructure was tempered martensite with no detectable ferrite in the prior austenite grain boundaries.
3.8 Deposit Chemical Analyses All deposit samples from the eleven 243 studs were combined and split into two samples labeled 243-1 and 243-2. The 241 stud #8 scrap sample was left intact. The three samples were ground and mixed with an agate mortar and pestle. The sample labeled 241 stud #8 had a gray black color and was sticky.
Samples from the 243 studs were brown in color.
ggg RDD:85:5237-01:01 PAGE 10 _
a McDermott company 3.8.1 Emission Spectroscopy The chemical composition of the samples was determined by emission spectroscopy (Table 2). The samples were mixed with a buffer containing an internal standard and burned in a D.C. arc. Standards were analyzed in the same way. Line intensitities were recorded photographically. All intensities were ratioed to the intensity of the internal standard lines. The following elements were measured: Zn , Na , V , Sn , Ca , Mo , It , Co , Zr, Mn , C r, Pb, Mg ,
1 Cu, Ni, Fe, Al, and Si. Boron was also observed but emission lines were too intense to quantify. The precision of the method is approximately +/- 20%
relative.
3.8.. Wet Chemical Analysis for Sulfides and Chlorides 3.8.2.1 Total Sulfur Portions of the samples were digested with a mixture of acids to convert all forms of sulfur to sulfate. Acid blanks were treated in the same manner. The sulfate was determined by a turbidimetric method after addition of barium "
chloride. The results are contained in Table 3.
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g RDD:85:5237-01:01 PAGE 11 a ucoermote company y l
Table 2 Emission Spectrographic Anbalyses (weight percent)
Compound
- 241 Stud #8 243-1 243-2 Zn0 <0.1 <0.1 <0.1 Na 0 <0.1 0.1 <0.1 2
V025 <0.03 <0.03 <0.03 Sn0 2
<0.03 <0.03 <0.03 Ca0 0.2 0.. ' O.09 Mo0 3
<0.03 0.1 0.05 TiO 0.06 0.04 0.06 2
C00 <0.03 <0.03 <0.03 Zr0 <0.03 <0.03 <0.03 2
Mn0 2
0.07 0.10 0.06 Cr230 0.3 0.3 0.3 Pb0 <0.03 0.04 <0.03 Mg0 0.2 0. 2 0.2 Cu0 0.3 0.2 0.1 Ni0 15 10 8 Fe230 12 >25 22 Al 23 0 2.1 1.9 1.4 SiO 8 6 6 2
- The compounds listed are based on the standards used. The form of the elements in the sample may be di f ferent.
mggg RDD:85:5237-01:01 PAGE 12 a McDermott company l Table 3 l
Sulfur Analysis Sample # Weight (g) ug/g Total Sulfate Wt %
l 241 stud #8 0.0402 570 +/- 60 0.057 243-1 0.1008 810 +/- 80 0.081 243-2 0.0775 820 +/- 80 0.082 3.8.2.2 Chloride Analysis Portions of the sample were digested with 1:40 nitric acid. Blanks were also prepared. The procedure will dissolve most chloride compounds. The chlorides of mercury, silver, and lead are exceptions. The chloride concentrations were determined by the standard mercuric thiocyanate method. The data are listed in Table 4.
Table 4 Chloride Results Sample Weight ug/g Chloride Wt %
241 stud #8 0.0487 84 +/- 17 0.008 243-1 0.1000 152 +/- 10 0.015 243-2 0.0517 109 +/- 15 0.011 3.8.3 Leachant Testing Portions of the samples were transferred to clean teflon bottles. Two teflon bottles were used as blanks. 100ml of deionized water was added to each bottle. The bottles were capped and placed in an oven at 85-90 C for 24 hou rs. The bottles were then removed from the oven and allowed to cool. The water in samples from 243 stud was brown in color. The pH of the semple and blank solutions was measured (Table 5). The pH of the samples was greater l
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than that of the blanks so the deposits were slightly alkaline. However, since the pH of the sample solutions was (8, the hydroxide and carbonate alkalinity was essentially 0. Hydroxides and carbonates would have raised the pH over 8, therefore, all alkalinity was ascribed to bicarbonate. The alkalinity was measured by titrating the sample with a standard acid solution (Table 5). For convenience purposes, the results are listed as the amount of CACO 3 precipitate formed during the titration.
Table 5 Leach Test Results Sample # Weight pH ug/g CaC 3
i Blank ------
5.24 0 Blank 2 ------
5.50 0 241 stud #8 0.2460 6.10 1380 +/- 270 243-1 1.0813 7.36 13220 +/- 180 243-2 0.7306 7.42 10320 +/- 140 3.9 Bulk Chemical Analysis Samples were sectioned from 241 studs #1, #2, #11, and 243 stud #8 and sent to Ledoux and Company Teaneck, New Jersey, for chemical analysis. The results (Table 6) show the 241 studs conform to the ASTM 193 B6 Specification and the 243 studs conform to the ASTM 193 B7 Specification.
a man ,. ,ar a g g g RDD:85:5237-01:01 PAGE 14 a McDermott company Table 6 Bulk Chemical Analyses (weight percent)
Element B6 Spec.* B7 Spec.* 241 #1 241 #2 241 #11 243 #8 t
C <0.15 0.37-0.49 0.134 0.151 0.132 0.30 Mn <1.00 0.65-1.10 0.46 0.35 0.39 0.50 <
P <0.04 <0.035 0.010 0.010 0.010 0.014 S <0.03 <0.040 0.006 0.006 0.008 0.014 Si <1.0 0.15-0.35 0.47 0.44 0.45 0.29 j Cr 11.5-13.5 0.75-1.20 11.52 11.64 11.50 0.92 N1 ----- -----
0.13 0.14 0.13 0.31 Nb ----- -----
<0.003 <0.003 <0.003 <0.003
- Specifications per ASTM 193 - 86 and B7 4.0 DISCUSSION The cracks in the 241 studs from Surry's low head safety injection valves were probably initiated by a stress-corrosion cracking (SCC) mechanism; a stress h overload, however, was almost certainly responsible, for an unknown portion of fracture propagation. The fracture surface examined in the SEM (241-#2) had a l mixed mode intergranular and ductile rupture morphology normally typical of SCC. There were multiple circumferential cracks along the stud axis in an area where deposits collected (see Figures 2 and 4). The cracks were highly i
branched with secondary cracks occurring at near right angles from the cain crack which is again typical of SCC. SCC occurs most often in aqueous environments. Some studs were probably exposed to an aqueous boric acid solution during valve leakage. This is evident from the gross localized wastage in the 243 studs and the deposits found in the flange area of the l studs. It was determined that the low temperature precracked tensile and impact modes for the 241 stud material are predominately intergranular (see Figures 9 and 11). However, simple tensile overload was probably not s responsible for both crack initiation and propagation even if it is assumed
RDD:85:S237-01:01 PAGE 15 Babcock &wiscox i a McDermott company that the thread would be an adequate notch and that a sufficient source of tensile stress was available. This conclusion is based on the observation that many of the studs show partial cracks and more importantly the fractured studs (2, 4, and 5) also show partial circumferential cracking. Tensile overload would not produce partial cracking of the type seen and particularly for f ractured studs. However, several multiple cracks in conjunction with i fracture is typical of SCC initiation. SCC is a mechanical-environmental failure in which sustained tensile stress and chemical attack combine to initiate and propagate fracture in susceptible material. Failure by SCC can be caused by simultaneous exposure to a seemingly mild chemical environment and to tensile stresses below the yleid strength of the material. This synergistic action causes failure in less time than the separate effects of the stress and environment. Sources of stresses can be from manufacturing (casting, welding, thermal processing, surface finishing, etc.) or service (stress risers, temperature differentials, assembly, external sources, etc.).
The requirements for SCC (as indicated above) appear to be present for the 241 series studs. The studs were retorqued and possibly reused which could have subjected the material to stresses near or above the yield strength of the Odterial. It Was reported that the valves leak periodically and that the studs may be subsequently retorqued to a higher value.II) This could result in sufficiently high tensile stresses in the studs to rapidly propagate existing SCC initiated cracks.
The cracking probably initiated in pitted regions in the thread roots on the outer surface of the 241 studs. The outer surface is exposed to various environments carrying unknown chemical contaminants. Microchemical analysis of the fracture found evidence of aluminum, silicon, calcium, and copper on the fracture surface. High levels of Ni, A1, and St were found in the scrapings of both 241 stud #8 and the 243 series studs (Table 2). Low levels of Cu and Mg were also present. Based on the bulk chemical analysis of the stud materials (Table 6), none of these elements can be considered corrosion products, therefore, these elements must result from either application of
T RDD:85:5237-01:01 pAGE 16 h &WHcom a McDerraott comparty
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antiseize Compounds, Valve leakage, or general accumulation of area contamination. Aluminum, silicon, sulfur and calcium are commonly found in boric acid lines. Nickel-based lubricants are used during installation of studs which accounts for the high level of Ni seen in all scraping. Copper bearing antiseize compounds were used praviously,(I) however, complete removal of this material would be difficult. This explains the low level of Cu present.
Martenistic 410 stainless steels are susceptible to SCC in some environments.
The material is usually considered crack resistant at the hardness levels observed, but cracking has occurred during exposure to very alkaline environments or in conjunction with copper based antisetze compounds when the hardness was in the 40 Rc range.(2,3) The cracking which occurred during exposure to copper based compounds was supposedly controlled by lowering the hirdness of the material to approximately 25-30 Rc. This resulted in an apparent life increase of three years. Extended test results for longer periods were not available. The failure mechanism is thought to be related to an electrochemical interaction between the Cu based antiseize compound and the 410 stainless steel, but this has not been proven. Long term elimination of the problem by reducing the hardness levels also has not been proven.
Therefore, SCC cracking appears to be present in the 241 series studs, but definition of the mechanism arid influence of slight environmental and/or mechanical property changes would require testing in a laboratory environment.
The 243 studs underwent simple localized wastage apparently caused by localized concentrated boric acid leakage from the valve. Alloy and mild steels are susceptible to a high level (>50 mils / year) of attack from this source.
Babcock &WHcom RDD:85:5237-01:01 PAGE 17 4 MCDermott Company
5.0 CONCLUSION
S
- 1. Crack initiation for the 241 series studs apparently was caused by some type of stress corrosion cracking mechanism. This type of attack is very unusual for 410 stainless steel at the low hardness levels listed.
However, a high level of stress was probably present, at least for some studs. The stress level combined with the unknown environment present apparently was adequate to cause crack initiation in the eight studs noted.
- 2. The 241 series stud material appears to be quite crack or notch sensitive at low temperatures. This is indicated by the room temperature charpy test results, the full section tensile test results (stud #6), and the intergranular fracture surfaces observed.
- 3. Final fracture (an unknown percentage of the cross-section) for studs 2, 4, and 5 was apparently caused by stress overload.
- 4. Prior use of Cu based antiseize compounds during stud installation may have contributed to 241 series crack initiation, but this cannot be proven i because of the low hardness levels and the generally uncontrolled stud environment.
- 5. The 243 series stad wastage was apparently caused by localized concentrated boric acid corrosion due to valve leakage.
Eh &WIOCENr RDD :85:5237-01:01 PAGE 18 a McDermott company
6.0 REFERENCES
- 1. Conversations with Joe McAvoy, Virginia Power, throughout the investigation.
- 2. Metals Handbook, Failure Analysis and Prevention, Volume 10, Eighth ,
Edition, American Society for Metals, Metals Park, Ohio,1975, P. 476.
- 3. Czajkowski, Carl J., " Testing of Nuclear Grade Lubricants and their Effect on AS40 824 and A193 Bolting Materials", NUREG/CR-3766, Department for Nuclear Energy, Brookhaven National Laboratory, Upton, Long Island, New York, March 1984.
- 4. Corrosion Data Survey-Metals Section, NACE, 5th Ed.,1974, p. 34.
- 5. Metals Handbook, Mechanical Testing, Volume 8. Ninth Edition American Society for Metals, Metals Park, Ohio,1985, p. 27.
- 6. Metals Handbook, Properties Selection: Stainless Steels, Tool Materials, and Special Purpose Metals, Vol. 3. Ninth Edition, American Society for Metals, Metals Park, Ohio,1985, p. 29.
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I BABC0CK & WILC0X RDD :85 :5237-01-01 PAGE 25 23 ";ctl 3ES T TT4:53 l Preseto 400 secs Vert. "000 c ount s Dasse ! Ceao* 1 fles s as. 400 secs l
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BABC0CK & WILC0X RDD:85 :5237-01-01 PAGE 34 APPENDIX A Mechanical Testing Results
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BABC0CK & WILC0X RDD:85 :5237-01-01 PAGE 35 WESTMORELAND MECHANICALIESTING & RESEARCH lNCORPORATED SPECIALISTS IN MECHANICAL TESTING
' N== _
P.O. BOX 388, Youngstown, Pa.15696 Telephone: 412/537-3131 ORDER NO.: 16923 UC
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mTR seniEs NO; 4094 ON!=1"ar,2!t#1@o'*al#an0' ES*oIEd$llAUwTTE".EOEE"' I 2 SHEET _ of DATE 10/30/E5 The Babcock and Wilcox Ccepany g , A Lynchburg Research Center Work Completed p: - P.O. Box 11165 Lynchburg, VA 24506 Certified By, fu fgdp { ATIN: Mr. Tim Zeh ] TENSILE TEST CERTIFICATION MATERIAL Submitted As 413 S.S. 413 S.S. HEAT NUMBER SPECIMEN NO. 1 2 LOAD, LBS. (TENSILE) 7,330 7,480 HARDNESS TEMPERATURE *F Room Room SOAK TIME, Min. TENSILE STRENGTH 145,725 147,534
.2 y. s. 125,646 127,613
.02 y. s.
ORIG. GAGE LENGTH, In. 1.00 1.00 FINAL GAGE LENGTH,In. 1.22 1.19 ELONGATION, % 22.0 19.0 ORIG. DIAMETER, In. .253 .254 FINAL DIAMETER, In. .140 .140 REDUCTION IN AREA, % 69.4 69.6 MACHINE NO. 4 4 TEST LOG NO. 23507 23508 LABORATORY COMMENTS: All machining and testing done at WKr&R, Inc. SPECIFICATION: ASDI E8
BABC0CK & WILC0X RDD:85:5237-01-01 PAGE 36 T WESTMORELAND MEcuAnicAt TESTING & RESEARCH INCORPORATED SPECIALISTS IN MECHANICAL TESTING tg/ ~ h)
.h. ' P.O. Box 388, Youngstown, Pa.15696 s'" Telephone: 4121 537 3131
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a'a=,':ltutawai:?a:Li?11r"u11:!=",!! amirs $ni?!sfra'l,""
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Machine is certiflad to Watertown Specifications. ORDER NO.: 16923 UC The Babcock & Wilcox Company WMTR SERIES NO.: 4094
- Lynchburg Research Center P.O. Box 11165 2 2 SHEET of Lynchburg, VA 24506 ATI'N
- M . Tim Zeh 10/30/85 DATE CERTIFICATION OF IMPACT TESTING DATA l
Y LS PE T MATERIAL HEAT SAMPLE SPECIMEN TEMPER. E Submitted As NO. NO. TYPE ATURE pousos o*Ausio~ ramcruas 413 S.S. - 4 V-notch +75 F I 10.0 10
' 14.0 l l 413 S.S. - 4 V-notch +400 F 105.0 60.0 60 413 S.S. 11 V-notch +75 F 14.0 10.0 10 413 S.S. -
11 V-notch +400 F l 105.0 60.0 60 i ! l i l l l l l l l I l t l i I i , I i i I l LABORATORY COMMENTS: All machining and testing done at WI'&R, Inc. SPECl EN SIZE. Standard l SPECIFICATION: ASTM E23 Work Completed By: b Certified By: M%
N e i L APPENDIX B i FAILURE ANALYSIS OF CRACKED
. STUDS FROM SURRY UNIT 1 VALVE S1-1890B )
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jlm/32/MCAV0Y
/ FAILURE ANALYSIS OF CRACKED i STUDS FROM SURRY UNIT 1 VALVE SI-1890B i L . A failure analysis was conducted on two cracked studs from valve SI-18903 in a the Surry I safety injection system. The valve is located in the Unit i valve pit adja, cent to the containment. (- The failure of the two (2) 1 7/8" diameter x 14.5" long studs was noticed , during a periodic system inspection conducted by operations personnel. The broken studs were provided by station management to N0D/0&Ms for failure I ar,alysis. Assistance in the analysis was provided by the Performance Services-4 Chesterfield Metallurgical Laboratory. The following tests and inspections were performed on the failed studs from valve SI-18908:
- 1. Visual inspection and photography of fracture surfaces,
- 2. Magnetic particle inspection of the uncracked portion of the two studs, as well as all remaining 14 studs from valve SI-1890B, and studs from sister valves SI-1890A, and 1890C; also, Unit 2 studs from valves SI-2890A, 2890B, and 2890C were inspected.
- 5. Tensile and hardness tests, and chemical analysis were performed on cracked studs from valve SI-18908.
jlm/32/MCAV0Y _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ J
) 4 Charpy V-notch tests were performed on the cracked studs from valve SI-18908 at 40*F, 80*F and 120*F.
, 5. Bend tests and hardness tests were performed on sections of studs which showed magnetic particle indications from valve SI-1890A.
t
- 6. Optical metallography was conducted of the microstructure of studs from SI-1890A and SI-1890B.
{ Test Results:
- 1. Visual inspection of fracture surfaces revealed stress corrosion
}
cracking at the root region of threads in 51-18906 similar in location and nature to the cracking previously observed in valve SI-241 (See Appendix A to this report). Cracking occurred at two locations along the stud length. Most of the cracks were located in the lower region of the studs just above, or at,- the interface with the bottom nut. This location would be the normal accumulation r point for moisture on the stud and the location of excess thread lubricant. One stud in 18908 cracked in the nut. This crack occurred in the upper portion of the stud and represents the only i crack found in the upper region. The location of the crack was 1 1/2" into the nut which was apparently holding water. Cracking in
& this case occurred at the interface between moisture, and thread lubricant, but in a low stress region, jlm/32/MCAV0Y
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ J
( f e The 410 stainless steel studs which have failed were corroded (rusted). Such a condition occurs where there is significant chronic valve leakage and/or environmental conditions external to the valve. A microscopic analysis of the failed SI-18908 studs revealed a heavy rust buildup in the thread roots with localized pitting or "troughing" in the root. Stress corrosion cracks initiated from the pits and troughs and extended into the studs at { an initial angle equal to the thread pitch. One stress corrosion crack in a broken stud from SI-18908 had an aspect ratio of .1875"/1.406" (see Figure 1). A second broken sted had an aspect ratio of 0.032"/1.967", and this latter failure is assumed to have been a result of " load shed" from the initial failure. Crack growth rates are shown in Table 1 for IGSCC in studs for valves SI-241, SI-1890A and SI-18908. The pattern of broken studs in SI-18908 was alternating, i.e. two broken studs separated by one unbroken stud.
- 2. Magnetic particle inspection (MT) of the studs from the SI-1890 and SI-2890 valves revealed the following:
Valve Inspection Results F 4- 1890A 2 studs with MT indications 1890B 2 studs found broken, 1 stud broken when removed, 3 studs with MT indications
Il r 1890C 1 stud with MT indications (. 2890A No MT indications 2890B No[MTindications 2890C No MT indications
- 3. Mechanical test results from two (2) studs in SI-1890B are presented i- in Table 2, with data from 12 studs in SI-241 and one (1) stud from SI-2890A. The mechanical test results generally meet the minimum requirements of ASTM A193, Grade B6 except for the reduction in area (RA) valve for'SI-18908 which is 44.5% vs. the specification requirement of 50%. Figure 2 shows the abnormal shape of the tensile fracture. Note that the SI-2890A stud from the same heat as the SI-18908 stud met the minimum requirements with a RA value of 50.8%. Supplementary Charpy V-notch tests for 'SI-241 and SI-18908 studs show low notch toughness, with the fracture surface appearance indicating little or no shear fracture, as shown in Figure 3.
Supplementary hardness tests of all cracked studs indicate a scatter of hardness values between HRC 25 and 34. This indicates considerable variability in material properties, sometime across a single diameter of a single large stud. Bend tests performed on SI-241 and SI-1890A studs indicated poor ductility with bend angles between 0 and 17', and fracture 4 jlm/32/MCAV0Y
h k appearance being nearly 100% cleavage. (See Appendix Z to the major report, and Figure 3 to this report.) L These conditions indicate a temper embrittled 410 stailess steel material.
. 4. Optical metallography of the microstructure of a stud sample from
[ SI-241, SI-18908 and SI-1890A indicates no abnormality, the structure is basically tempered martensite with zero percent ferrite. A microstructure from a SI-1890A stud is shown in Figure 4. t
- 5. The chemical analysis of the studs meets ASTM A193 Grade 86, requirements as shown in Table 3, with one minor variation, c Conclusion The failure mechanism observed in the SI-1890B valve involved the growth of
, intergranular stress corrosion crack (s) to a point where the largest flaw reached critical size and the stud failed by rapid fracture. During the failure a localized " load shed" to adjacent studs occurred. This localized load -buildup in adjacent studs was the apparent cause of failure of one (1) additional stud with a stress corrosion crack in valve SI-18908, i
The low number of " load shed" fractures is due to: (1) the significant difference in ' net stress of surrounding studs, (2) the large variation in crack size from stud-to-stud, and (3) the number of uncracked studs in each valve spaced between cracked studs, jlm/32/MCAV0Y
L t p The IGSCC in valve SI-18908 studs, as well as those in valve SI-1890A and SI-241 was the result of the temper embrittled condition of the 410 S/S in L' conjunction with a moist environment and the copper thread lubricant. A very low K ISCC value is thought to be operative, so stress plays only a minor role in the failure, (i.e. the studs do not' require an over-torque condition for failure). Given: (1) the estimated fracture toughness of the temper embrittled valve studs (based on notch toughness values) of 30 Ksi d in, (2) a normal torque stress', (3) and a IGSCC crack growth rate of approximately 2 x 10-9 in/second,
. these studs would be expected to fail in 5 years or less of service, where exposed to a corrosive environment. ~
i ke{TWo J. M. McAvoy N0D/0&MS jlm/32/MCAV0V
F lt References Consulted (1) Metals Handbook, Failure Analysis and Prevention, Volume 10 Eighth [ Edition, American Society for Metals, Metals Park, Ohio,1975, P. 476. (2) Czajkowski, Carl J., " Testing of Nuclear Grade Lubricants and Their Effect on AS40 B24 and A193 Bolting Materials", NUREG/CR-3766, Department for Nuclear Energy, Brookhaven National Laboratory, Upton, Long Island, New York, March 1984. (3) Metals Handbook, Mechanical Testing, Volume 8, Ninth Edition, American Society for Metals, Metals Park, Ohio, 1985, p. 27. (4) Metals Handbook, Properties Selection: Stainless Steels, Tool Mate- ials, I and Special Purpose Metals, Vol. 3 Ninth Edition, American Sociery for Metals, Metals Park, Ohio, 1985, p. 29. (5) ASTM Standard A370-77, Mechanical Testing of Steel Products, In Annual Book of ASTM Standards, Part 4, ASTM, Philadelphia. a r jlm/32/MCAV0Y b
( TABI.E 1 CRACK GROWTH RATES (. l
- 1. For valve SI-241, installation was on 5/22/81, time to/during cracking was e 1536 days ~ (removed from service 8/5/85). For four studs evaluated the crack growth rate was as follows:
Cracking Crack Stud # Crack Size Time (Seconds) Growth Rate 1.3271 x 10 8
~
2 .4375" x 1" - 3.2967 x 10 in/sec 4 .250" x .5" 1.3271 x 10 0 1.88 x 10 -9 in/sec 1.3271 x 10 8
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5 .250" x .750" 1.88 x 10 ' in/sec 2.1928 x 10 ~9 in/sec. 8 6 .315" x .866" 1.3271 x 10
- 2. For valve SI-1890B, installation was on 3/31/81, time to/during cracking was 1744 days (removed frca service 1/8/86). For three studs evaluated the crack growth rate was as follows:
Cracking Crack Stud # Crack Size Time (Seconds) Growth Rate A .1873" x 1.406" 1.5068 x 10 8 1.244 x 10 ~9 in/see 2.1237 x 10-10 1,f,,, 8 B .032" x 1.967" 1.5068 x 10 C .062" x 3/4" 1.5068 x 10 8 4.1147 x 10 -10 in/sec
- 3. For valve SI-1890A, installation was on 3/31/81, time to/during cracking was 1758 days (removed frcm service 1/22/86). For two studs evaluated the crack growth rate was as follows:
Cracking Crack Stud # Crack Size Time (Seconds) Growth Rate 8 ~9 A .4375" x 1.4375" 1.5189 x 10 2.88 x 10 in/sec 3.086 x 10 -10 g,j,,e
' 8 B .0469" x .4063" 1.5189 x 10
- 4. For valve SI-2890A, installation was on 12-29-81. Two studs were reported to have failed on or around 8-2-83. The fracture surfaces were rusty and no critical flaw size could be determined. If it is assumed that these studs failed by 1GSCC, the time to failure of the studs was approximately 7
581 days or 5.02 x 10 seconds. JMM/jmj /0M4-67 ) a
i-( ( 'i L r L TABLE 2 MECHANICAL PROPERTIES OF STUDS SI-241 SI-1890B SI-2890A
. (Ksi) Tensile Strength -145.7-147.5 144.8-140.8 142.0 (Ksi) Yield Strength 125.6-127.6 121.8-120.3 118.5
% Elongation 22-19% 15% 17.0%
% Reduction Area 69.4-69.6% 44.5% 50.8%
Charpv V-Notch"(ft-lbs) 75'F 400*F 40*F 80*F 120*F , Sample A 14 105 6.1 5.6 8.0 None Sample B 14 105 4.8 5.4 5.9 biu min m ii i p .. ._ .. ._
{T I f. 4 TABLE 3 CHEMISTRY Valve - Element (Weight %) SI-241 C Mn- P- S Si Cr Ni Nb Mo Comients Stud 1 .134 .46 .010 .006 .47 11.52 .13 ' 003 Stud 2 .151 .35 .010 .006 .44 11.64 .14 ' 00 3 --
. -broken Stud-11 .132 .39 .010 .008 .45 11.50 .13 '.003 -- broken SI-1890B Stud "A" .15 .74 .034 .005 .33 12.06 .13 .16 broken Stud "B" .15 .74 .028 .004 .33 12.10 .13 .16 broken SI-2890A Stud "A" .16* .82 .033 .002 .32 12.06 -- - - - - broken General comments:
a) SI-241 studs appear to be from the same heat. b) SI-2890A and 1890B studs appear to be from the same heat. It therefore appears that only two. heats of material are involved in the SCC failures in the two and possibly three valves.
-This value is 0.01% C above ASTM A193 Grade BG requirements.
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Figure 1A: Fracture surface of SI-18908 valve stud of 410 S/S; thumbnail IGSCC in upper portion of photograph. 2X magnification. or49P/. ? T *Y ,* h' f ( s.
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Tempered martensite, 200X, Kalling's Reagent.
g...... s ( i-L APPEt401X C VALVE SI-241 STR_UCTUPAL ANALYSIS
BWNP 20697 (6 85)
"*" E MICOX DOCUMENT
SUMMARY
SHEET a McDermott company l DOCUMENT IDENTIFIER 32-1159425-00 pp r VEPC0 6 Inch Cehck Valve Analysis PREPARED BY: REVIEWT.D BY: { NAMr G.L. Weatherly er D.E. Costa ( stGNATURr - [1) slGNATURr ' yp , Engineer IV yp.k2/12/85 nur Engineer II 37,12/12/85 ( TM STATEMENT: RbdEWER INDEPENCENcE _g l Cost CENTER 308 REF. PAGrim 38 , PURPOSE AND
SUMMARY
OF RESULTS: (
Purpose:
To deterine the stud Stress level and leakage rate for VEPC0's 6 inch check valve 241 (in the broken condition). This valve had three stud failures and two cracked studs and the potentisi for excessive leakage or failure existed if flow would have been initiated through the valve. Summary of Results: The minimum gasket load for the br6 ken stud configuration (assuming the cracked ( studs break) at T = 1700F, P .= 03 psi is 82% of the gasket load for the. no broken stud case. This residual gasket load should be adequate to prevent leakage if flow had been f nitiated thrcugh the Valve. The stud stresses for the low preload - condition satisfy both the Nomal a9d Faulted condition stress limits, liowever, for the high pecicad condition, the stud stresses can satisfy only the faulted condition stress limith Cracked studs, of course, do not meet ASME criteria. See pages 33 & 34 for a more detailed sut,rnary. Note: The design data used in this anlaysis is based on cor.Nr$,tionE with VEPCC Engineers (Joe McAvoy), gasket manufacturers (Dick White), and valve vendors (Chris Ulley). The information received from these in.dividuals is assi>med to be correct and any deviation from this informathn will invalidate the conclusions of this analysis. a- - __ .= :: = THE FOLL%G CpMTUTER CODES DAVE BEEN USED iN ThtS DOCUtKNf: 6 COct / VERSloiu REV Cl)oE / VEPsiCN / RE'i ANSTS/4/1C _ m y m _f q ,-. mu>w en PAGF- h OF 3
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- P05 21036 3 (9-84) i s.n ua wucox GENERAL CALCULATIONS
' ""'~'*"""' Nuclear Power Division ooc. i.o. 32-1159425.-00 I,o rNT Re bu c Tro n) Stud fellutes have. been obs erved in tA e. bolfing fin a otta cliin*a tb e. c over Velve 2. +/ 9+ .tb e. Po us e t 1 to fr a n . Tb e.to failures in c./u d e tArc e. Sdrkn b ra h s tu ds an d two e.co e. fred s tu d s . Sin e e. \ th e. Failures gre in a n on -s#m eltr e fle. pa fen 4; eI fa c es ces.siv e. /eo /rog e a r va tve Fei e.n isfe d i; &tous w ould A ave. Leen inihefed + bro ug peHern, lute.d th e. ve lve.. Th e. p u rp os e. o f tbis te.porY is to de fermin e th e s Hess level in the. .sfud.s 9ncl the v e los le.a kag e re fe for tl< can$ryutolion e; b to ir < n /g .a d s +u el.s as re rar4e d b y VEPco. I l PatPAnto sy g47, M M I a .vi .. . . . OC o.,, #Adr ...~o. 3
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{ s.ac.ca a wiscox GENERAL CALCULATIONS i - - - - " ' Nuclear Power Division ooc. i o. 32-1159425.-00 f L 2.0/16T/lo b oF A AlA LYsz,s { ko sin;+e elem en + mo dels w e t e. u+ulised in rd;s ( va lve. anal,s;s : n an a x ; s y mm e.+ri e mode / s 4 Yde. V a } vs. c.over, a potfich o f tb e. V alv e. Aad y o n el Ybe S fuc!s - 2. ) a 3-b m o del a-f t b e v elv e,. eover a n el l+vds . Tle. axisymme hri c model (na sfud.s b roir en ) u.s a s used to predict tde ma xim us.7 refalion o f +4 e. valve body due +o p relo a a an d in f ern a l press ute. tai.s to foli on c.o u s e s Sfuel l ben eling .sfret ses a n d ten d.s to op en tAe j o in t af tbe 5 a.ske t la ca /> en fAv.s el e. c te e s in# a tde ga.skei logcl. Tle 3 fu cI b e<; ding stresses and disp al cem en + o f the. va lue. 6ody at +4e. g a we. -F Joealion een f e. con.s erva f;v ely .s vp e r- im d on the. re.su/F.s f com t h e. 2-b eover m o d e /p as eand tbus
\ avoid developing a 2-r m. del o+ the v s /v e boby and f b e. c.o tresj o e nding in c r e o 3 e. in C.ompubc(
'lI m e.. I'n a delihi on f b t. a 't. i S m m t $ti C. m o cI tl 4) * .1 U1 e.$ fa 6$e rm in e. fbe e. echS o $ join f~ hriCl ion h e+w e en th e. c. o v e r a n d v olv e. bo dy .
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.Ln addi}lon , a lo ad J+ep w a .t run w i-l b P = 19 6 0 p s ig -
l Ternp = 17 0 'F Torgue = 700 ff-/b.s
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l PDS-21036-3 (9-84) s e awucox GENERAL CALCULATIONS [' Nuclea o Division o o c. i.o. 32-1159425.-00 r 40 6- B o M E T R v # l
& long>tua:n l c ross - s e eli on af nehe+yc,,;c i Velan 4are ed Ll+ed b onn e l swing k jalve. is .5fown in l=ig-te. /. .s in < e fAe.
d e.+e ile d d t.s w rn y .1 6r V 2 7 C o '.s \ 6 in c l c bce\t e. le k vo/V e. nare c.on sid e,' e d p ro p i e }el? In regui re d dim en sion.s for fl>i.s f aima tialv e ficuen e t t. ' tlr e. e d ( c lfoin ham T o e. he Ava (U EPCo) en el Cbris (Jlle (tie.lqn, u.s in 'o Velen b reusing !c? - 7 e 2 o 4 $ Th e- d imensi os s ole o.s Skown ^in /=ig u re 7, in melcllfrca TI L ho/loving E im en s io n ,5 a t e* he-p uir e b :
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Eolf Cire It di a m e le r ; // Y8 in. Bolf b ole. biome let in cover = l f/]4, in.
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PDS 21036 3 (9 4) I secock a wncox GENERAL CALCULATIONS s Nuclear Power D. . .ivision ooc i.o. 32-1159425.-00 s.o M ATERIAL S t Tbe malerials are. g;ven a $ e.en s & c fi o n o .s ( R e.S. To e. M c A voy (v ePc.o) ) :
%Ive cover and ba d '
/r5 T/1 h 18 7- F 3/6 ss f 5 Y4 d.S T 41o AJ /~57 j S ir,il/ o t 7o Al93 66 I-4btIcer)$ ' fe/ pro A)-/000 TEMP ( *F) foo a ao 200 +oo Soo 6co
(() %l\1c E (le'e s > 0 28./ 27.6 L 7.0 16.S zs.8 z e.'s d(/din/;o/a/=) 354 8.97 9, 6 o (2) 6 76 9.t/ f. 4 L v (assua.,e C) s. 3 .x ( Sfwd 5 G) E (lo 2.7. o 28 5 t). 7 17 3 z g. 7 z 6./ (6) d(loh5U in/;nla/=) s. f 8 4. /5 4. 3 o d 4- o 4 48 4 r.3 (f) 4 (hs0 3 4.96 33.3r s a. t+ 3/.tr s o.3 7 29. st. y nr (a s s un,ef) o. s (1) Ref. ) T able. r -6.0 a us ten ; + t c.s L2) R e f. l ,, T e b l e r - s '. o t u r -i t ui- z.h. (3) Ref. l , Table r-4 0 .straig l w ehra n,i u n, s+ eels (+) 8ef. l ToS/e I-S. o / '$ C I (5) lielt I' T9 5 / e. .T_ - /. ~3 5 Ar - / 9 3 6-r /5 6 aeljuste d to accoesn f f-o r higher y j eld 5,,, = /z3s3 5,,.,
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POS.21036 3 (9-84) s s.n m a wiscox GENERAL CALCULATIONS Nuclear Power Division ooc i.o. 32-1159425.-00 IuhM con f hM Lhl on Lo ek hi C len f a = o./ Fat Fe.jp to U-1 a o o , R e.$. C ( for b ty enth4l fc ene conhqC f , o hri C. ll 0/1 c.a e Hi t t e n t o f m = o.hq) 7+ 11 u s e d , R ed. & , l p ag e. 3-37, T 9 b le. I hot milcl $$e e l an m l lc
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- 1) h,x 970 f f - Id.s 2.) G ; , 1 7 oo f f - /f.s Tbe. .sh d utel she ss for .r h e s e. two + org u e l v a lu e s a r e. e.eleulelsel f alo us.
F = T/k d Re[. ,yage.2.+6
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& = pi+ch di oin . =. J.1688 in. 13 e$. 3 , p ag e. /2-7/
d = nominal clroin. = 1. 2. s- in. . f=bo* Oe . 3 , p og e l'L.fo3 Y : t9n(In /rcI,,) def. 3 j p ege z.37
't' = fen(Ve /wO.l666)) , f( = /. f I
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[toni.9r* + o./ .5 e t 3 c '
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) + o. 6 t s- ( o. I) k = o./n case ( *. )= = 950bQ l(o.133XIts") = 6857/ lb.5 1
4o$e L *. F: 7 o o 0t /(.o.l.33X/, Is-) : Sor2.6 14.5
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})oke , s in c e k = ), c o In tke. qbove 'Jo e ds o ( s.
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i Pos 21036 3 (9 84) Babcock & WHcox GENERAL CALCULATlONS s Nuclear Power Division ooc. i.o
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7.0 h ESLREWLO A of F I.A) L T E ELENENT Mobe L S r 7/ /f X is vm m e lti c hade/ The sin in c k cbec ir tie lve. (cover to v g lve. bod y join t re-glon) 1.s m o d eleel e.s on oxisy nnsfelt s + ru e f u t e. a.s .s h o w n in / = i g u t e. 2 (See. App en din h far elemen f on d no de n um b ers . 7'b e f in i fe. Alem
- e. encode. t A nsy.s (R e.f. 7) )was used for tAis en ely s t s .
The valve b o dy an d c.o v e r w e t t. modeled u sing ? -b 5 is op o te n e f ri c. e.lem en f s , s rzt= +t. Ato a ttemp t I n o.1 m o d e. 1o m o del th e. e.ffect af bo/t Aales in the value. cover; however ' the. bolt holes w;// be. I m o de le.d in th e. 3-s cavec mode.l. since + A e.
.s tu d 1 ote tAreade d inio th e. v < /v e. 4/enge thi.:
will essen /; gity sIih{en tAe. Fleng e. and i t w ill ac+ simila r to a s o /i el fla ng e. The sinds w e te. modeled u sing the. t-s beem e lem en t' s rri= 2 . The. b e.a m e. lem en f w a a s: um e el to e.dend f rom 0 s' b infa the- . volv e. FI,ng e_ an d up +o a.s a in t o the n u f L wh e ce-b = n omino/ d i s m e -le r oF .s +~ d.s = /.2.s- in.) . Th e. beorn opeQ an m oni en Y c h in et hl , atR. Ingq f on Q fei rabian hasIS , from p og e. 21, A = 12 (i.000) =i,90 97 in?
.T = I2- (0 01758) ; o./52. in.V w
The gosket and tie. me.+al to mefel interface.s between tje. valve. cover Lod , and stud outs are m odele el using th e. in $ e rh a,ce. e em eer /, S T r F / 2.. Tbe. g e.s /re f an d l in fe r ha ce. $ fi fh n ess e.S m u s f b e. inp u f on a p er l redion bosis. l kg.s/ ret = 6 9 87s o o & = t n x io 6 n.s / i n N Ref. o o9 e_ 23 0 9cl PREPAtto SY oATE R ..... ., BN ... 4AAr ....~o. />
PDS-21036 3 (9-84) ' "Yd' ",,',ca= GENERAL CALCULATIONS Nuclear Power Division ooc. i.o. 32-1159425.-00 1 (
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r PDS-21036 3 (9-84) r Babcock & Wilcox GENERAL CALCULATIONS ' **"""~~"' Nuclear Power Division o o e. i.o. 32-1159425-00 t The. in ter f a ce. s fi ffne.ss e.s o rn. L e s t e e /ly arli} n t V o lu e s qs /aog q .t tbey att on o rcler e h m ag nlylu ele or no I vg er tien the a dj a e en + elemen l s +rf f n ess, A e /L (.R e [.7 , p age +.12. / ) . kInferhoee.=.z lo g- A E /L 4 :- -- X 71 - : T 453/3 ' (3 93 75Dd :- /6.7 7 8 in' N n ed e. n o. L= y,, - y ,, = e.. f o6 3 - +.6 a >r = o. u ss in . E: ?776x/o' psL R e f . p eg e. /0 , e. / 7 e */ ( kw ,,5,,, = ie Osm e%.n xic') / o.u e 8 a. t x ra' iulin.
- 2. rr res.
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/=o r elem en f no.s 't+, A3 ; /r = 3. o xia 9 L lin is used Dod
/~ot elem e,1+ no. ts 3
It= ).s sio 9 lbs/in i.s used paa Tbt htic.l ion c.o e h hi c.ien bS a sso ciole$ Lui i l thess in t erf a ce e. lem en ts u s t e- e .s s um e el +-o A s.
. u = o. I S-r lu bri c a le d s u r 5 a e n. s Lun d e r n v+ )
en J s = o. ) + e. l.s e u>b e c e. , 19 e f . peg e./I . ll 0U) R V e V , norr1EnQf hViC. 5On C.o 6 h ( C i ert h3 Q[L s u bj s c.+ fa o I a t g e. cleg ree oh un C e rhoinif y . In a eldi+1 on , tf e. in+etlace e.lem e,i fs uith w -p o.o are nonconsarvolive elem en Fs . 74 es e. elem en /s re the leeds to be app li e d v + ty e n d all i al.g uite.ng tAs o c+u Ia al d bis f a ry p a+A er d iny ,+ 4 8. poper s e p e<> c e. . This u mio It e. de s , rAe.
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p o ble ,n and c.o u /d r ey u t r e a la ty am a u n }- o h comp u he r fim < har 3-b o p p lI e. o -l-l on s Ih j frichron to o s cle+ttminsc$ fo b 9- 0 P rima ry l
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L POS 21036 3 (9 84) , smo.w a wn x GENERAL CALCULATIONS L Nuclear Power Division ooc. i.o. 32-1159425.-00 l con cern . .1^ n en efemp /- to resolve tai.s .forc}ron \ p ro blem ,o .sec.ond ANSys run was m o de with u =. o . o in p lo c e. o $ s =. o. ') + . Th us a e omp ort s on between th e. two runs s hou ld indeale t-b e - relofive. orlo n c e. s f f erc+ron ta ye.sfre.+ lan d and s imp +ud b eneling.
\ ~S t u d prelood =. 6 8. 6 hsU is opplieel for 1bc. u = c' . o c os (s (r,,, yb fbe. b e a n, e Itm en l on ini f1 q / Sfre in . Tl tis giniving ifr 9 / .s f ra in is seI by iteraling until the proper preload is al foin e e{.
For the a = o.24 c a.s e. the.. sone. +o tel s + roin i1 u s e I ; h owever, it is applie d in four laed s+e b y th e rmal d i H e r en +1 a f a ponston b e +w e en ibe.p1 beam o n el the. re:+ o f t l1e m a de /. E oun du;, ( on eh tion s
/ lodes I a n d 3 a r e. c.on s frein ed to o. o malion in th e. , 2., Y direc fi on.
Aloel es 2s, 93 a r e. cons freine.d to a.o mafion in tke.sxo, doice nd Son. c l-t 9
.Z~n addi} i on c.ons frein f ej u a lfon s a r e. used.
to +1e. tb e ' .s fud to th e. value. couec and valve bad y fleng e. . Th e va lv e. c.o v e r + o stu d j oin t is o.cs u m e d t-o act as a p in n e d' 3 o in f while. the- v alu e. bo17 fleng +o slu d j oint is os.s um e d t o b e. +;e.d toge ther for ro +9fia n as well es knslefi on .
,,,,,,,, ,, A5 ,,,, II/zs/BS~ ,,m-, o , OR o,,,/Vn/V ,,o,~. !&
[ { ,0..u m m ...., Babcock & WHcox GENERAL CALCULATlONS Nuclear r ivision occ. i.o. 32-1159425.-00 t
.S fu d bv m~ remo e refutes '
, / 4]h en t-lte p teloed is ked in + lo d sfers tAe
< hrst .s+
T . Tbe !itst /oad Step w lIl u s e. o. c a t. c e.s fle ini+;nI beam s f tgin . This leaves o. c o & 2r -o =nr = 0.co2 sr ini+>et s +r e. in +o be a c c oun f eel for b y fletmo/ Jiff eren fia / expen.5;on. , le. f 4, g y ,', =: o. o , sg,g = -1 0 x.i o in /in / *F A 7 :. o. o o3 sr//. x,o-r : 3 e r /=
- Thus,
- 2. n d La n d S tep : Tsrug = 170 'F 2 04 Lo J5tce ;
r,.fo J = 3 2.o */= ++h L o 9d Step . % j.= 3BT+20 = 4 S' 1'* */ = Tbe hiNfb lood Sfep teguires addif ton s/ clibt(enfie! I thermal eman sion to a c coun f -F o r +A e. siceJy S t o fe f em,o e ro fu t e. o f 17 o */= bdA ,,, ,J , / bd E A o c.fu o / l.gtc'T LT,,4,j = (8.6 9+ ~ S.o ??ho (i2o - 7o) Ar,,,, gel- z.r.95 e* Tlies, 5 th Lo a d S tep ' kg = rsr + 2 s'. 9 7 = 4 8 0 97 *F en,r4 ,o er b o , ///NBC ,,,,,,,o ., d)EL ,,,, /z /4 4 V , , , , , , _ n L _ { - POS-21036 3 (9 84) sancock a wucox GENERAL CALCULATIONS [ Nuclea o Division o o c. i.o. 32-1159425.-00 (
- 7. 2. 3-b C.over hodel
[ A teo* 3-b m a de./ o f rh e. v o lve. eaver an d Sfub5 OJo s con S hr4 C $ e b c.5 .S b o W A in fig wreS A-an d v (see. Apeenclin a Ft e.le m en t and node n um b e r z h . The finile. e.lem en + e. . d A us y.s l G e.+ . , ) us a .s used f or this an ayl sis. The volve. e-o v e r co n s m o dele d u s in a 3 -b isopara-mekic. s c h a e.lem en +.1, SirF 4.s . V h e. s +ud h oles are ap by t rap e s o i el s to $ o eili to Ie E in; f e.p roxim als 1e.lem en Th e.t d imen s t ans of m a d tl> e. froPehaicis e t e. ele- c twin s d a s f a //o u.>s : s la'ng+. \ \ ) - - Y h6 6-l - -> < R, ( Rt &=(ll'/s)/s = s. 93 7 7 in: R, :(./ %,) /t. : o. 6 r63 in. 8, = R - R, t S = s. 2. en. +- 6 /h: R F 4, - 6 = 4 573 s - 6 A3,/e = 7r (o.4 re sf = /. 3 s 3 iny A nop, = (8 -8,M sin e c.o s e A A./e.
- A+e. g .
j PR. PAR.D SY DA,, ........ ,, /2< ..../v4Ar P.o .. 18 \ POS 21036-3 (9 84) GENERAL CALCULATIONS r sm a wn x Nuclear Power Division ""'""'"**"""... o c c. i.o. 32-1159425.-00 I 1 \ L . 9 Y s I I _ l l l t ! Fr(ru R E A-3 ' b f4 c BEL OF VALVE cov&R k ........ ., DEC ,,,,A Mrf ., n i9 c P05 21036 3 (9-84) c aw a wne.x GENERAL CALCULATIONS L **"""-"""' Nuclear Power Division o o c. i.o. 32-1159425-00 r l sf L ""~" ' ,( \ \/I l s - < b/ , - / ' 1 .t - )( %w7I7g.5 ,u frim a,I +. n nl e op ele *,eds e/e-eds Fr6-U R E S T1 P.rC A L Bo' S E(7M ED Y Z A) 3-b h 0 C> G L OP VALVE Cov EK *Alale : The a o s he t gae eleasen +s u> ts i a, e .t t < e Hy I. ea led e+ tbe c.en $er o & t'be_ asfre.f g foov t to tb e r fl\ ers o f tb L c.enle r o f the- g o sire f. Th is Vecults in 9 sin *Il *m aun f of c.o nsetu 46 sa wITlrceord +o fhe- % *I oa'Ir*+ /==d. ,.,, . . ., - 8N o.r. /// o/8f ,,,,,,,, ,, Oft ,,,,/zdds' , , , , . . 20 l . ( POS-21036 3 (9 44) Babcock & WIlcox GENERAL CALCULATIONS { " ' ~ ' ~ ~ ' Nuclear Power Division ooc. i.o. 32-1159425.-00 ( /.353 : [( 6 593 8 - 6 [- (c.18n f 8[] 5 in e c.os s ( /=r o m -l-t'le/ a n d e tto r , f b e. Solu l ton fa f b e. above-e.g u a li on is G =. E.6168 { l=0.ons in. Then, I a , = r. S 3 >c - o.g ras * . o n r : s . 3 r o io. Ru = c. p ns + o.cra s - 0. o nc = s.ru 2 in. l The. studs were m o deleel u sing 4e. 3-b beam elemen + , s rz F + . Tb e. leng f af FA e. beonn is fb e. s o m e. 9 s, L< J o .s u .s e el fn tb e, a k i sy mni e h/ c ostolysiS. /ror / %" - s v 4/ studs /tg: /- 0 0 o d e f. '3 j fa o g e. /s7/ beg : (, A + e /7T) = (t. O o ob / 7r ) 'b : /./1 6 + in. E= n (I. n a +f = o. 0 7 958 in ,+ &+ T h e g 9 1 fr e. t and the m e I-eI l a mek( in ter faces b e+us e en the v a lve. eooet en d boel are. E m os eled the. c.om bin a +1 o n f fe
- c. rlem r el 6 e.
u.s ing ~b e S rr i= + o . r .s +r ffn ess as e.lem en t s are. c. ale u lde d on +As fo Ho u.s ing F N Ae e e s .e, (i eli o u t ele m e,, h (srz e awith a ver .>m.,y a r e o ) u)et e. u.S ecl in tbe. Supet elem en f g e n ero llyos of tl1 s v elv e c. o v e r in arber to h a v e. in e.s /e V cloglee s chhretbem to c. o n
- n e. e. l' fL beem e.lem enf5 to in th e u .s e ru n ,
PR, PAR,0 SY
- OAfg
, , , , , - , , ,, /)fr ,,,, /z/n/gr , , , , , . 2/ l PDS 21036 3 (9 84) IBabcock & Wilcox GENERAL CALCULATIONS [ * "' " ~ "' Nuclear Power Division ooc. i.e. 32-1159425.-00 ( G as tref Stiffn ess W ( The follooing in formolton on tfe chee.k valve. g o s /T e.$ LJ o 1 i'e.Cei V t. 0. hrom To e. O c. A tioy (VEPco) . From VaPco purclose acc e r s y/ t t.9 6 / c. ! luj e spiro / - w oun d maYer. :ials : steinless sfeel an d c e ram i c. Nille r mode / no. ', R -o o 7 - 7 3 -o/6 .L b : 7 IS//6 in , ob : 8 11ht. in . thic hness
- 6 12T in . e.x trud e d to 0 13 5~ in.
Ve Pco p u rcha s e d t h e. e o s Ire f.s f t'o m L/it'oinis Pro d u e f1 . pavid hal gee ssealisisalin)a Pro d y c +s ) in formed ,n e. (_befvtre 4 t/eseto i a s k e.l co c.< /d have been m o de- b tbe. /=/e ile/bc p(re s /ce t c.o. a r b y the. 6 re y lo c h C?. Lui + e-e as ir e + stiffn e s s is in dep enclen t of uba m an u fa c+wn d rh e- g a s /re.h as the mvsf meef +/>a .s a m e. s4 an do ed.s. //e f e//r{ d wii A b r e ls LJh He. G.reyfae/) t wAo Aad . coo g es kets en a de. lo tb e. p u rch o .S e order sp e c t' I' c o lt'on s c?nd f ben ran comp re s si o n +esl'.S. Tbe re.sulfs e 5 th e 5 9- tes ts a re es f allo w S: s 7 ofo/ Loel (_/S.5) 6*.sITef Tl/iclineSS (in) &ashe+ l (7 asIce.f t o./33 o o o /2.5- / 2.oo o /6 LSo
- c. I o S" (36 o o o 737So 0* / Co 8900o 9$000 0,0 i S" //6 90o 12.6 000
# See Aole on PORE- /. Pa,P,n,o av onge ,,- -,o ,, Ok o ,, WWaf . o o. 22- s PoS-21036-3 (9 84). f Babcock & WHeox GENERAL CALCULATlONS ' "' ~ '*"~' c Nuclear Power Division ooc. i.e. 32-1159425.-00 _. Tbe g r.s he +1 re co ve red to or ll rn i/S a fler l being ca mp De.ss e el fa 0o? in. . ( Tbe height af tbe gaske f g rove. in tfe value. body is o./ to o . / o s- in . ( /:t a u r e. 2. ) . T4e m a x /m c<<rt d im en s ton wi/l be used as tAis lea ds to I a low er g e s /rs t fo n d and thus ine t e as es fle possil;liiy o-f leeltog e. c.ab e n tAv in } e tn el p tessu re load 1 1. applied . 1%e load on tb e. g o.s fref tJben ca mp re ss e el to
- c. lo : in. is
/= = (6 6 00 o + ms o) /2. =. 6 9 8 77 f.l s (b e. g<<siret sfi f $n e.s 3 el u rin0 l +o fe.re.co cons u e rhan t L un la o e in'c ) is o .s.s u m e d b in if i.: li ke l? to ver althoubbd some realitlZ gas S +$e /ref is ooIy (say I mireg)uifeel to spring bach a few m;l: l tAis Qff ot xim q$1 on hor g es Ne$ s l E'h5n e.: S iS C on Sl Net e) offpo f tf a he. , 61 9 q a mode. I 6 3/rel- Force N' ,c,g / (genero/ s4.g e onl7 ) Origs) N 0 lo hoS/re f' Sp Vl Agbg C k (mll Ng-sket = ynogbuls :M .o I = OWoo ,,,,..,o ., JW o.,, // he/'#S- ,,,,.... ,, #2 ..,,/z 4'r B / , , . . . 23 L - [ PDS-21036 3 (9 841 r s.ncock a wiscox GENERAL CALCULATIONS ( Nuclear Power Division occ. : o. 32-1159425-00 ~ i~l) e .sfi Yne sSe,s of f e. jo e.lemen f.1 ref resen fing tb e g o.ske. f a ? e. c.alc ulo f e el l. a s e e{ on tk t. p offion o f the. t a te / / f eacA r ep res en f . Note, the elemen+ngo.as s rsb e /.us r e fe r + = + f e. 'ut un s es .' For e.lernen r,s l 2 an d 2. c : # = (A G /360) k8 : [7.363t. /d (67875e) = fo969 /4s 36o /4 /*or e.lern en f 5 3, 4, b, 7, 9, / 0,12.,13,15, I S , t 8, and / 7 : k = (a/2so) /cp = (20.ss se /d (srs >ro n = z oo m ibs 3Go en Sr e.lemen /s 5, 6,11, /+, an d / 7 '. / 8 1 7 b 7 __/d s . /[ = ( a G/3c o) /t0 :[f.3 360631. ) (6 7 875oo) in Gap E fe.,n e n ts A+ tie +,/-ne.[al surfaces T'be .sfi f fn ess es osso eic.4ed with f Asse e le m e n +.1 ore b.u e e//y a pli+ r e.ty a.s lang as en seder o f m ag ,,if u d e or +we la rg e r+1s> t y, n A .a t < t A e. a Q een + ele,n e ,f s +rffn e ss , A e/L ( a e F. 7, p ag e. A . s o.1 ) . A =(13 a 2. /.xo) ri-R+.9s 8st-(+.s.siaf] = 0.3 sis in? E = 2 7, 7 & x to ' esl L: 3 ./6 7 5 o.3/2.s 2. 8 ?r /n . ..., io .y Mb o.,,///2e[8f . . . . . . . . ,, A6 .. . aA'Ar .... ~ o. 2+ W s PDS 21036 3 (9 84) c s.ncock a wiscox *""~"-"' GENERAL CALCULATIONS L r Nuclear Power Division o o c. i.o. 32-1159425-00 lT % JoohElL. = 100 (o.35 96fL7 26 yso')l2 875~ /T % 3,2.8 y fo 8 ll3 /in ( Fat e.lem en +s 71,37,40, and s'5 u s e. k= s~ % to S lbs lin . (o ibi} l'a ty nu mberb ( /~ot e /em en fs 1 L, L1, 2.r,16,18, L 9, 3 /, 31, 3 4., 3 r, 3 7, 3 s, 41, 4 L, + +, 4 7, 4 2, 4 8, Sio, 5/, T 3, T +, SS, 5 7 k = (z o. sus /1.u n > rxia e = t. t 0 2- x io ' Ibs /in i=vi elem enis 2 +, 2,, s o, 22, u , + 3, s c, s 9, sz, s r k :: 2. ( T x/o S') /. o X /o 9 //s //n Boonbory f.' o ndH-i on s l Alodes / thou 2.o 367 thru 3?o and 3?z th(q 38o ere c. on .5 Iroin e. d. +o c. o c]isplecemenf in the Y el i t s e. +1 o n . En addifian c.onNtoinf epvafions fie tbe. f or of the- s fuels to TA e. f~* P
- S P A
- v e lv e.
c.o v e r to f o rrn pin n e d joint.s. Tbe bo Wo m o f tb e. S f u ci s an d tb e- n on - c. o u e r n ocle s f a r The. combinollon e.lem en f s a re , c on Sf rei/> e d f- o o.o moblan in a// d ifec fi onS . en r,n,o av b o,,, //[to'[8f ,,,,,-, ,, ON ,,,, ghk' ,, o , ~ o . 2 5~ t i P05 21036-3 (9 84) f Babcock & Wilcox GENERAL CALCULATIONS ""'~'*"*'"' Nuclear Power Division ooe. : o. 32-1159425-00 [ 90 R Es u L TS 6.[ 2 - c> A y i s v m en e f r t c. Mode.l.s Compulet twn C3' P V applied tbe .s 44] p telo e d j fs o k -14 e. a s e b in A- Ioad s+ers while- +Ae. (herm t edi((eren I fiel e xr9nsion e. f fe c+ (.G.!)o*N) and the in+ec C?3es6 y lie d in th e. F-i S tln/a a ad I p tes +e s.s u A-ftielson re. ae.ore-Fe. a k t tc>ef n l u=o>+ we1 u se d e f +h e.p. ( Lead. Step />a. nax s+ud s+tess valve. eeve.r 6asir - 6L.ad o d[+ 3 o in + du0, Elemen f Al- (Ib/ red.), Element '2 3 Tm N+b Y 675 /o3 5 ffo/ f 7/.8 /o f. 7 7 8 t6 c omp ler run cbut applie d tAe s tud p relo a d (fro U-/L case) in one while tbe +bermal diff eren}ial s yp onload step}ec f sj on e} a n d + b e. in fern al p re ssu re. (7 3 p s d a rle. e. ty ol *r)l appiee in th e. Second l o od A f ric] ion c. o e thic i enl of w as used of+ .5 f ep ,b evolve- c ov er - b od <.1 = o. 0 y jo in t. Lo ad S+ep Aso. /1ax Stud S Hess 6aslie.+ Load his D, Elem en f A.t dk/ rad),Eleurenf 2-3 Im I m+.6 ) I 68.l /o6 8 78/G 7- 677 /07.o 7767 F>eure 6 show s tAe disphceci s hap e (exog erdet ch ibe. \)a lv e f o r lo g d 5 f ep / - The a b ove. res ulf s inficale /;Hle di {$e feric e b e+0 e en the a = o.) A- c o s e. ond t*b e- 4=00 c a s e. Tl1v 5, ...r . o ., db o,,, ///" [85~ ,,m..,, />& o... /z//* ...~o. 26 L e FOS 21036 3 (9 84) a m cua wucox GENERAL CALCULATIONS ' " ' ~ * - ~ ' r ( Nuclear Power Division occ. : o. 32-1159425-00 L ( . k ~ l . I f ~ { / / ./ \f t - l ) h7. 6- u R E A } l brs PL A C E M 607~ P L o 7' , PR E L o Ab o N l- Y , .-<J = 0 o MU ~ ,,,,.... ,, ..,, ///2o /es- _ < ,,,,,,,, ,, 8N o.r /I4df 4o, n o. 27 : I a- - 1 - ,c,- .n,m, secock a wiscox GENERAL CALCULATIONS ' " ' ~ ' " " " ' Nuclear Power Division ooc. to. 32-1159425-00 _ , tbe- 3-b m o de l will be hn en !y [ e r +de. 1 > f ri ch on /e si c c.s e. , m : c> e . . B.a 3 - 6 Goer mode / Conipu+e r kn L c t<> m i.c tk e. s .q> e t e.le m en ;b g en ernfi an f
- r th e. v alv e cove t. i%.sier clef f ec.s eE f reedom a r e. d e -fin e d af g/l .s f u el a n d' gap elemeo + &c,si.' sin i <
veli:n s in t e. u+s ocannec+tng;e e.d i p+oints. Ae +- r eri o.a Sps r eg/cm
- e. en f (A:c oo) to flt fwt .; cre v,i d to a cover i F n s u e .s .
4./e ce # e p W ole,.t sfu d f a d; tak:,r. .iy o s' lt,)f ' " s # s 1 * ---- n a d e n u m o e t.s .> s ux,,,=o.2.r(vg.,,+uxn + u x,, s ux7 .) i , U Y4 ao = o.Ls-lu Yn + 4 h , + 4 h.9 +uyrg) U %..=e.trlussetuss,tuk n t u n n '> , Th e .s o m e 1. y p e. c-p a lt aa .s cl 4- > r a ll t A c. , sfu h. end it's autroundinsv ap'Iv Va ey cauti nodaG. 'liff e\ l al p rop e t hl e s u t n o */= w e t t- Med. L= e- z ,,7 c xio ' p.si R s ;- p ag e lo . f .: 9. tb 9 xt o in fin / ~,'= zr =. o 4 e AttD SY DA,f ,, _ N L .... /z/W!f* ... ~o. 26 j eo, um.n, .., a.w.c* A de = ~ ~"~"" ~ ~ GENERAL CALCULATIONS Nuclear Power Division occ. i.o. 32-1159425-00 L !. in +e n t p ruz u re oF t pri was we,, Ne J ' [ to 1-h e hoff am o f th e. eever Cour +o +Ae. g 4.s Its t lo c a li on ) ,
- up e t s!emen 1 run s hrts th. f tdu c e I
\ 7*be
- fif fn e ms.s e -hi x and Iv e d v e t. + s t for '
th e swe et elem e n + n file 3. four compufet .% n 'u s e p o 2 s e.s ' u e t e. m -do. using the .to p er e le W en !* , $ fuds vro d g o l fs . flo f A. , f*Ae ScCon$ and } bits tan v s u /1cdc,l / : >lp ic/s. emtbe en fout+A r<<n uaes [ /vod e / a. (py e ch. I) (cmo fer tun CERh a<1 m o de wil b a// 'st,ds s ek ve . T4 i s as;)/ oc f er a ( Lose c o s e. fa compoft taitb tb v. 7 ~ t. n isv m n e ri<.. eass. Thce'e Ic od >fe s were m .cle a) te l Bso h - Il c as <e )b) , p rele.d ;t di f fer nital+ loa d dern,al e.xpsns>co 410*A,c.) prelo,el t diffet en li a / thermoi exp en sion r in tetnel P('SS"I'- L' 9 bt *
- D -
Lead Step A. stud Stres.s (%6 6esket Laod (t$sb E EL. , a.c n. z. 4e r z. 3 L 73.6 62.7 4 4 3 6 t-3 73.5 9 t. 7 6+229 * %,s = c, n Cp qR elenen t- u 1. i '6ashel Loe d = 2 ? 6 for clemeni G T. L i P8tP Att0 SY ac = O Af f . .... nw P... . n _ 1 \ s ) ,onimm...., l s.6<.<k a wnc.= GENERAL CALCULATIONS ***~'~~'
- Nuclear Power Division occ. i.o.
32-1159425-00 I 2.) (.omp ule i tun CDDS Mes mede WIfb & ah l the 11, S i 4 0.s o ro l Ten o.5 S b o tu n o n (> e y e. 6 . The s om e. three loed S+etu e s to o s used in tbe. q// o c liv e sfuds c. a s e was again useb hete. L o o d .5te p Ato. Sfud Stress (ksb 6-e s het La.d bb D Im I m+6 i > +. 3 83.2 6/43o 2 77 6 69.I 6/ / 2.L 3 71.6 89 1 So 9 / S~
- Qg : % + [Q; + q;)- , e. lem en f 6o
* &aske t L e a d = (3 60/s e) F +ot ele m es + t = (3 6 o / +.45/i) F - = 7 6 817 li der run CO3 E w e.s m a de for tb e. .t am e. .3)las(cmkn sen difion s os coas u se d in run C uo.s e.y ce p a t e /c o d (7 oo ff-/6s c osch wol vsc L on d lower on ad hilt on sloia d .s feio with ? = 2 A Bo p si w o s. <dled. L o od .S te r A>a. D uel Stress Oni) Ges/ ret Lo acl (.lbsb* C L1 I :s.') 4 /. + 42560 I t do.o 67.3 62.zs3 3 60.o 67.3 42ct6 + 6 c. o 68.9 s'+ /6 / r . , , , , , o . , .- Alfd ,,,,t//2sl97 .n.n.. , 4& o.,, /2hhr . . , . . . 20 POS-21036 3 (9 84) e s.a.c.cua wucox GENERAL CALCULATIONS l *--~"' Nuclear Power Division occ. i.o. 32-1159425.-00 I +) d omgv /e t run G N a r wa s m ,de for t / e. Some Jaeding e.on dH. ton s as was used in run n *. S e.y e.e p t N del 2 Ts used ln.s f e a d af hode/ / ( p y e. db, a L o ad Step Shd Stress (in6 6 a.s ke.+ La.d 06k Ala. elem. 59 elem . & 3 G %f6 % rl+6 i e12 s1.s se.s s r. 2. ss o 96 2- st.3 S S. + s76 62 7 C+ + +4-3 55,3 45,4 57.6 62.,7 .c.3 9 6 7 + 56.o 46.2. 58 5 4f/ 3782-6 * (g : ( t[q[ + ( )E rar f e lem en t p .. Io ** 6 n.s / ret = 6 6L .e a //o.3/at = 3 +. 88 7/ d = L u o /a e) G) 5 .. .so ., -d/d o.,, / IEN ...,.... ,, #k .... /eAh ....~o u e e P05 21036 3 (9 84) r s.ncock a wne x GENERAL CALCULATIONS 1, ***"'"*"""' 32-1159425-00 ) Nuclear Power Division occ i o. L nesults f r. n the. 3-D m o d el <ri u.s t l e. ad I to o e c.un f for the eHect a f d e. vo lve.bod jv.s y fed wh i c h e.c o .1 naf in c luded in ' fb e ( For p reloed L 9s c h - Ibb + diHeren/te/m t a ele /.A e e x p en si on (17e */c) t in f ern al o jle.s s ule. ( 91 to .t ih tl, e re s u lh w e t e. given on the- prsut o u t p ages ( hot the q)/ $ f u d :. g o od c on di4r on as : no del . stud Sites.s Chsh &alte f La ad (lb.D { G % [ 2-D 677 /of.o 6/366* 3-6 73,r 62.7 6 4 tM biftete nc e. - 3. 6 26.3 - - 2 BG / + dull u s e. -40 26.0 - 3 oa o *&l3&B :. LTr(97Cr$ T,eI ch k e t en c e.s a re )n genetal' as eypec+ . The velve fl'nge no +a hon in 1 A e.
- 2. ~ o m o d e l tu t il eause e idif t on e l s F u d b en d i,s e, -
s+tess and a lowe r g asker lo ad th en al,+ i is p re.s en f in +/re 3-b model Also the Siiffer 3-b m odeI w ill e ouse m.t r membrane. sites.s due io d1%e r e,ili o f ti; e rm o/ axponsion. Sie,de .s tre s s e s %c tl, hie l, p re l < d } (onbIbion With 4ll $fud5 occb bots i;of meef tbe 9llotJ Q blt. if'(tSSe.$ g& ar a Herm a { c. o n c/;'[j on (see pag an .JAU ~ ,....... ,, o.,, ///u/'e r .... /d 4 h/ . . . . . . . . , AZ .... ~ o. n \ . / PDS 21036 3 (9 84) sancock a wiscox GENERAL CALCULATlONS '"'""~*"~' Nuclear Power Division occ. i.o. 32-1159425.-00 i eppu st on 7~Aus,fe f in rne p re s s u r e. /f o r the c p relo n di+ ton rde e d + m d:f . f xim e,, ren , ti g / + 1A s + u el s tres s e s a t e. : Macie l I (see p < o e. s ) lligh Prefoo<l (?sa E+-Ibs) , P = 1 s esi C, : ? 9. 6 - 4, o = > s . 6 /rs i 0',,4 : 8 7 / + 24 o : // n / /rs's Fyosk, + = 6 o 7/r - 2 o o o = T 77/S- /41 Loa Preload (700 ft-ils) , P = 1.5 p s i Q, = & c.o - +.o = s's . o Irsi 7,,, ,4 6 2. 3 + 7 6.o = :P3 3 ts i Fp ge + = 6 20 4 6 - 3 o o o = T?o+6 /Ss. Lou Ptclosd O co -(+-Ibs) ' P = L 4 8 o p.s i Q = 60 0 - 4, o = rG.c fr.s i T,,, g 6 8 9 + 2.6. o 9+.9 /Ts 't Fge t = T+/6 / - h o o o = s //&/ ds. flodel 2- (see Low Ptelood (200 f~Ibs) , ege.G),P=?ae lcm en t 29 esi l Q : rd. 3 -+o = Sz,3 /r5{ G 4 =S T + + 2.G.o = 1/. +- kst I:g ,$/ce t =- C3 7 8 7 - S o a a = TO 7 8) /bs L oco Pte/oud (.200 4+-/bs) , P = t + e a p>.> i Q C6.o - 1, 0 : f 2. . o h3[ l Q4=467 + 2. 6 . o :- ft.7. N5c' Fgc,3 /re p : 3 7 B 2.(:, -3aco= 3 4-8 2.(:, ff.:,, PetPAtto BY DAff atviewto sY Daft PAos No. 33 .J POS-21036 3 (9 84) r ~ s.nc.c= awie.x GENERAL CALCULATIONS a McDermott company Nuclear Power Division occ. i.o. 31~!!EIb7 I ~0 # l The of the y a s ke-f /o o d' # (e t +p Aeerwars c enh ? e lo calt on ') c>.s r 1/1 le+in p reasleirt a hcr the .s +u ds are brolren is e g le ule feel b e /o ea . i hode/ / pry h Prelo,d , P = 9 3 p.s ; S O 9/T ~ 3 o 00 (to a') :. f f *o / 6 4ft) - 3a co 1 oea Prelo,1 , P = 9 s p.s i 4 2 o 46 - S ooo (j o o) ::. Pf % 4 4 r 2.3 - B o o o Ho oo" l.0k.) f(6fo Q , P=MSo esi r4./ A/ -3 o o o (s oo') = b 2 To 6 4. f l. ), - 3 oo o 4 / o oo " t Asdel z. Lou Prefac d , P = 93 p s i 53 987 - 3 oo o (jo o) : o,8 2 To . 6 4 T 2. S - 3 0 0 0 f- l o c o l Low Pr elo 9 e\ , P = ?-4 9 o p.ti 3 7 8 2 (.o - l o o o ( i o') =- o,5% % 64rth - 3 mo o +/ooo * # *The ga>ke] ford eld <. t > p reland (6 + T M -Ja a b ,' b i c. Ix-ul>ife. (6 teylocit ) .s+ d e A f l o f a g *s /re:f l o a cl o -(- , hoooo lbs usuld pt'abeb/ pru en t le aliy e . "no Lee c.os a wi+4 e// sNel.s ac fiv e a f fle loco p te louel wo.s m o de . The looo Ibs i :, on a yu,s k enf tu e. rte e } ths l> rg f (2 t elo o elca.:e.. ,,,,,,io ., A<'/U o.,, N Ob ........ ,, /ke o.,, /24@ ,,,, ,,. 3+ s / i PDS-21036-3 (9 44) r s.nc cu a mw= GENERAL CALCULATIONS " ' ~ ' * " * " Nuclear Power Division occ. i.o. 3 2 - 115 94 2 5~- 00
- 9. o ASMF CODE ALLOld A S L E- S TR GS S ES
/15 'l 5^%.~/ (.a) , R e 9. 2- in drca f es tle b olf e d j o in + m oy be desig n e el a cc or ding f a tle- p ro cedu res o r /J 6 -3 t o o . kn =- 33 8 3 k.s i Ref. page. 7 , a. i v o f Foi No t m a l o r Up.s e t Con clif t on S Q,jf : 2. m5 : 6 7,66 h! /7 e f, 2.j pa-3 t3 t./ [,,4,y, = 3 5,,, = /o/, t f /rsi A e f. 2 , Ai a - n 3 t, t. ', For ]=a ulh d Con difI on s q'jf*=o,7Sy = o.) (n.s-b : 6 7. S- /rsi R e.f. 2. , ps-37 3r /fef. I, r- /3t3,/ (4) * (g : /.5-(e 7 5d = /3 /,3 /r s i u se. n.s , o Ns i The clave Irmii s app ly for n o n- c ra c /t e d s f u l .s , A FroC49fe m e cben ics an e yl s i.s u.> o er I.l have to Le j e r f o rm e el to d e m oirs f ro fe a c c ejo feb i /i+y F*r e e rec / rect s+uel. *No-la. rhis aMene u>as o rigin dly d e v elop e d + r non - ho/+ing mufert gis M* s'ee A ppenk .D +o k m+jon ced ; % 5 ,t c / w t. Meefu,vic s t/verly fisr e ()ffs,ugl n, , ,,,,.... ., J/O ..,,/W5 W , , , , . . , , #3C o.,, hh 4/ ... ~o. .3 r I - k-ros.uou.m.c s*=cu a === 4 MCoermott company GENERAL CALCULATIONS Nuclear Power Division oo e. i.e. 31'//f f Y7$~-6d nodel A Preloael Presse,te. stuk Allaa, snesses (psc) ( * ([+-Ild (fs i) S+tess(Psi) Normal hvlhd Tm C, C., Tm+b %+s %4 / 95o 93 7s. fo V &7.66 87.7 //r. / * / o /. + 7 / 2. 5 . o { / 7o o 93 rd. o 93 3 l ?oo 2+80 T6 0 94 9
- 2. 7oo 93 s a.3
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[ar er A)orm a { con diVr o n . F-r m odef i thes e s +resse s y ta a 'g - o el S S u cI ' in fhe. c ree t Ic Sfuc! aplpl o c.e f / o n , S f u d. <1 o. fo ( 5 e e. p e g e C.) . ( te c lce e{ S + wel s, oh c o q('S e cio n ci { ; meef b S f15 C Vih e fiq . . . . . . . . , , __ J o . , , ,1,/, ^ --Y . . . . . . . , , /h ... Wade ....~o. 36 PDS-21036 3 (9 84) . Babcock & Wilcox a McDermett cornparty GENERAL CALCULATlONS Nuclear Power Division o o e. i.o. 3 7_ -//U+ 7 s - o d /0 C C AJ C L U SI o A),S Tb e mini niurn g aske-f loa c[ for +l e. b t'o lren S fvd j is oppfo >c im a fely 8 2- l4 , o (~ can[l>ig hag er,a7 wh f'on +be for +.be na b to fren s fu d c yneell s heflion /o ndtJben tbe in } ecn ol ress ure is n p,si. This res iek a l $onef. shou /d be a de p afe. +o p teuek e s k f lee ky e in Slow h ,L b e en in i + r a +e d +4r o ug i ( tA e c.f e c /c ' v a lue . = 4 t/> e in letn a/ p te .s s ure c) a s 2.+aaesi so m e. Jea kogle in ery lias,e O C C u re b i k tbe,. C V9 C /re .5 l y c s bo b VolTe n . Et Sboulcl be* nobed Yba f a n e o h Pke c ro c k ed' Sl~4cl5 ( }wcl no.Sb lJas tes/ed $en.slos and 591/ eel a f 9 tensile faa d s hn Gis c o /4 s' The e les } i c + /I Res. D s Mc A v a? L v GPCo') . +4e c ele n/9ie d / o 9 ds fro m 1 nile e /e5 en-f m aele is in d; ca le this la e el a)+a.s e.x e.e e d ed L e..m bina lio n o f .G a cr.e and n o,,, e n f.) . // c us e u e r fhis does n a-l n, e on +-f e c re c A e d .s f n d w a 'v/cl l b ree lc as e .s m e // am oun + a5 / / re strain w o u /J e //aa .s . - e o-F +4 p es Io e d +o be re lish th e u/+1mele Slrein ( is r e a cb e el.i bu+e d b e f o r e. The .shd s +re.ss e.s for tle low prelo ed condi+r on solis by both the Aiorm/ end Rv/ led sfre.s.s
- li is Ilow eve r, f c th e hry fse fis $ relo c on di% on, e el t$e +s+.
u e! s f r e.s .s e.s e.gn a Y +de. /=ew/+e el c n di}ron .s +re s.s ),m;Y+.s .n /crached .s +n ds , a F e .u t s e, d. n o t m ee + A .s n e C P / + e r / et . f i PREPAREo SY oATE u m w o Sv AC oAn M/2/#/ uo no. 37 ( - ( PDS 21036 3 (9 84) sancock a wucox GENERAL CALCULATIONS Nuclear Power Division occ. i.e. 32-1159425'-00 ll,o R GFER 2A>c2 S /. ASHE Soiler anel Press ure. \le s sel caele , S e c +i on M, bivision I , A pp ench ee.s , /183.
- 2. A SMG. Soiler and Pressure. tiessel c. ele, s e edr an .i.it,
, b} vision I, L u b sec-li on NS,178 h. 3 Oberg b. HoIbro,olE rik ; " Ton es, Fron IclinHantusYork, t L. , nach in et v's den fits-f ",on b fo_;ok- d r=e!i+i on , I t e 2, zn du.s + r'r e l Press . r n c., A.>eu.5yor/r. I A. Shi g ley , To seph Eclwa tel, "n e c hon ic al Enp inee t liig y b esig n ", I783 , h e G t 9 ea.) -//ill Lb oo k L a mp e i,l r., c , we u> y. c k.
- 5. Thebnica{ rn -formo+;on for FELPRo A>-looo Ldttconf' Cheiin c q { Proch< c / s b'iv is ion _, (A ++ 9 eke d as A prenel tr~ C ).
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_ T. / _ I NV ' ~ \) l E V L E A V V / \ K L A \ C E \ / / H . H C C / N I L. I R 6 T =L A E D O C H o P E X W M V f S T . D t 8 x f> 0 W AE 5 2 E h ~ - P r> E i ~P - $L , 1 A z E t ' .{_ - a- : 2 3 ' I .b ab U9 T [8 1. ~ Nf E a - 0 N l z-f- 0 S T/ / - T N G N R 5 E I E) 2 1E E L L A C 5. 6 0 PL / 4 6 S 459 T Ok 1 97= = . 9 4PM O1 T34 .E U 5 9RN PE T=S=F= UVIF AZDXY N 1 1 2 3 1 9 4 _ 4 / 1 1 9 _ 3 g _8 3 4 g $ 1 1 8 ~ ^35 g 7 1 2 1 7 Md" 9 > E 3 3 '- 1 V 6 6 1 1 4 2 L > A 8 4 ' V 3 3 " va f~ n 5 0 X "A & 7 I 1 1 5 3 1 3 3' N 7 6 s H C 4 4 4 N I 6 C . C 8 9 . O C fP P - 5 4 4 E 2 _ S P V f e 0 3 Y b - 3 2 ? n 5 5 5 5 2 + u i gA l U 1 W + . 2 3 k k p d " 32-1159425.v0 (;* -i+' 1
- s. '
Ausys 85/11/ 1 g( 59 60 61 S2 63 64 65 66 67 pgI)ES AUTO SCALIM3 50 51 52 53 54 55 58 D =4.5 56 , 57 XF=3.56 v, . . 1' ' 43 44 A5 46 47 A8 ,,;: ;;;; NOT PERTINENT / [2_cj/2577 35 36 37 39 26 27 28 29 38 ['-.) 19 28 2122 68 23 24 ,0 ode co .19 6 M A/un7l 3etS 13 .17 .18 14 I 7 8 938 J1 .12 m (O 4 5 6 . A . M Y cn [,32-1 N25-00, VEPCO 6 INCH bCKhALM o C 4 ~ lIl { i l 0 T r- O0s C2 t iD WHCC& aO 'o-E Nu N l 5 2 S Ia T 8-4 T N G R - EI N 9 5 1 s/3 Y167 7 1E E L L A C S 4 8.6 730 e . . 1 }P 1 2 s19P n / .E a55R 81P O1T31 T=S== UVIFF AZDYZ '} 0 N N O I T A 3 F ' E E G T N 7 EE 1 L - ? E C R I E P E U S L - E E V L A V C K T C I i J E / C T. H F C N I - R 6 E O v C gC c> P E V g E 0 0 7 V 5 L - 9 A 2 4 g v c i - 9 5 g e - 1 1 g t> - g ~ c * ' 2 3 j3 a p (g .' s s $ ) N% p l f l ll ,)Il llll!l I l l T o 0 N5 E8 cf no o HetAt9.Oo v - N"/ I T/2-5 : 2 S T R/ / ?. - N i 4 M E E 9 5 8 E L I L A 4 8.6 1 PNT - 1 S/1 Y187 1E 1 C S 759 Tf i = 1 1 / 5. E P T=S== O A. - - M58RNO1T31 N. 0 P UvIFF AzDYZ - N O I 2 - T A 3 F E 9 E G -- ly T - 8 N n E M O E L r E . e R v E P o U C S E V e L l v A V 1 c K i s ,, ' ' _ V C t I ' .- , E H C e ! - S W _ P e H C b N I m 6 u O 1 U/ C P 1 E i V n f , i 7 n 0 0 i , e - = i 5 r r ' s i e m 2 4 i l 9 1 5 - 1 3 2 E 1 1 1 r 1 2 3 y!' s i 1k sM x u lll - #Y _ .I T 2N'HH . 'oO s N - 0 3 E79 I m 5 T - 49 2 S T N G R/ E/ / N E E I L 2 P 5 1 S/4 8 7E7 L 21 A C S 9.681 3579 T& Oj/ Y1 67= = = 1 S1 4PXM d1T311 - N/ . EAU A58RMN 8 PEE T=S=== UVIFFF AZDXY2 N N O I 2 T A 3 F M E G 8 T . 1 N 2 E 8 I p E L E n R 3 o E P 7 r U S i ' e - _ 6 u E V , o L A C V 2 4 5 e K 3 C 2 4 I v E H 1 a C U H , C 2 N r s I e 6 ' b O 2 e ' m C P 2 u r E l V A fo , c 0 f e 8 " n 5 5 rr e 2 4 i m 9 l e o 5 1 - E3 1 r_ r Y 2 R 3 F-i ? s s (ht m* h)bs . 1ll t __ - r--_ , , , 32-1159425.-00 grrme -inr- . g yg . j' 95/11/ 5 13.G178 PREP 7 ELDENTS EMAX=9 EMM=1 s AUTO SCALIM3 Q' YV=-1 DIST=3.92 XF=3.56 ~ O g YF=.58 y- ZFs 1. 59 8 7 3 4 5 6 , 1 2 - ;- kn NOT PERTINENT c / / sw sds, , g <v i g I Q W Val'u e Couer c /esrie n f p > u m /> ,r s j-9 w CTt CD A 32-1159425-00, VEPCO 6 INCH CECK VALVE N 1 C11 -h o i O 4 32-1159425.-00 e m E l c u.a WN ca *~ ( + g g,g g,, - e: -l smuR o g RAumaan-uu i Igd SEMEWWh E ca co 2 (\ = ( -\\
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- T- 48J >= e e3l~M oT. e s. - mann Asu o M i *s t!E E iltRiE**h E . co g af 2 1 M 2% \ S O g .t t3 2 s a . 22 s s yt - N\ h$,q W 5 gq f g 9 " a b
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p - " n v a g 'h Q + 1 S 2 -t : t. r _ m- $3 M j'gw y/ksler occ /&/l?/9f 47 weem>rx c . msorg wowrzo FoR PEL Pho 3 2 - } } 5 94 2 5.- QQ 1EiEU&c NOTPERTINENT D E DESCRIPTION N-1000 NUCLEAR GRADE ANTI-SElZE LUBRICANT is a high purity.100% controlled production anti-seize lubricant. N-1000 is formulated for use on nuclear mechanical components and high nickel alloy studs where the highest purity anti-seize lubricant is required. ~ N-1000 NUCLEAR GRADE ANTI-SElZE LUBRICANT is manufactured under 100% inspection. Each batch is tested and approved before packaging. N-1000 is recommended for high nickel alloy bolting (incoloy. Hastelloy. etc.) because of its low sulfide content (less than 100 ppm);N-1000 is recommended for long term critical stainless steel applications due to its low total chlorine content (less than 50 ppm). Copper and graphite flake in petroleum carrier. All ingredients selected for extreme purity. USES Bolts. stucs. valves, pipe fittings in and around steam turbines, nuclear reactors. gas turbines. pressure ve'ssels, and piping in chemical plants. OPERATIONAL BENEFITS Before Assembly Certifications and traceability. During Assembly Prevents high friction galling, and seizing. Promotes uniform and predictable clamping. During Operation High purity prevents stress corrosion.
- Disassembly .. Prevents seizing, galling. destruction of threads.
DIRECTIONS Use as a wet paste. Before or dunng assembly. wipe or brush onto threads and other joint surfaces needing protection: Do not overuse. as excess will be pushed off Use full strength Do Not Thin. _ SPECIFICATIONS PROPERTIES (Description) TYPICAL VALUES Wt/ Gallon 10lbs Specific gravity . 1.2 Penetration ... 285 Dropping (Melting) Pt. 225'F _ Flash Point ... 440*F Oil Separation (158* F) 0 05 % Friction Coefficient 0.10 :C u on reve'se side - - connn ed F_ . Babcock & Wilcox u , ,. , oi....on a McDermott company 3315 Ola Forest Reaa PO Son 10935 Lyncheurg. VA 245000935 January 20, 1986 (804) 385-2000 VEPBW-86-005 Mr. J.M. McAvoy Virginia Electric and Power Company P.O. Box 26666 Richmond,-VA 23261
Subject:
. Structural Integrity of Valve 241 -
Reference:
- 1) Task 39 - Examination of Safety Injection System Studs
- 2) Task 43 - Structural Integrity of Valve 241
Dear Joe:
Virginia Power authorized B&W to perform laboratory analysis on studs from low head safety injection system valve 241. Prior to completion of the laboratory analysis, B&W was also authorized to perform a structural analysis of the valve to determine its structural integrity with a degraded bolt pattern. The integrity analysis was completed prior to the final results from the failure analysis of the studs. used in the integrity analysis wasThe based number of failed studs on preliminary results(5) of the failure analysis. Final results from the failure analysis showed that additional studs (up to 3) may have partial cracks. The purpose of this letter is to document B&W's engineering judgement that the structural integrity of valve 241 would not be breeched with only four (4) studs remaining in service. The model developed for the analysis performed under reference (2) assumed that there were no more than three consecutive cracked studs. The model also assumed symmetry, le the computer runs is made looking at only half of.the valve. The criteria for the analysis were that the gasket preload remain greater than 70% of the ~ no broken studs case and that the load in the remaining studs be less than yield strength of the stud material. For initial conditions of low stud preload and 93 psi system pressure, the gasket load is 82% with three broken studs and the load in the remaining studs is less than yield. This meets the criteria. The final results of the failure analysis indicated that there is the possibility that there may be a span of four consecutive broken studs. The model was rerun assuming a span of four broken studs. The results of this analysis showed that the gasket load is reduced to 70% and that the load in the remaining studs is less than yield. These results meet the criteria, but the gasket load is marginal and some, as yet unquantified, leakage may occur under these conditions.
one of the studs which exhibited potential cracks was tested under tensile load. The stud did not yield when subjected to loads greater than 104,000* pounds force. This indicated that the actual conditions are closer to those as originally modeled, le no worse than three consecutive missing studs. It is B&W's opinion that valve 241 would have maintained its structural integrity with no appreciable leakage in the event low head safety injection had been initiated. I trust this letter will meet your needs, but should you need any further information, please do not hesitate to call me. Very truly yours, D.J irth Senior Product Manager Nuclear Engineering Services DFJ/rlb cc: G.M. Olds - B&W F fer~ WCIC0 0 S e Q \3a LJ, }1) MC &c] Vshowf ll2'ffh ( w <e Ioed w ,ts i n ,aco to, whictt n,fmod +shu n;- pam ' o 2, uo ,nz. (fw A dwd 'r D l# 5' N'l pi e s k u:t u .u/pis ) nn
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s' f-l P \ . L. I-L k APPENDIX D FRACTURE MECHANICS ANALYSIS FOR STUDS IN VALVE SI-241
FRACTURE MECHANICS ANALYSIS FOR
, STUDS IN SI-241 Purpose Based on B&W analysis presented in Appendix C to this report the integrity of the studs in SI-241 which exhibit incipient IGSCC was to be determined by a fracture mechanics analysis.
It is the purpose of this analysis to establish:
- 1) The initial stress / torque level for failed studs based on the flaw size at failure.
- 2) The affect of small flaws on the ability of the 410 S/S studs to carry load, and thus the applicability of the B&W analysis to this problem.
Enown The following information was known at the time of this analysis.
- 1. Flaw size at failure stud #2 is .44" deep by 1" long
- 2. ' Flaw size at failure in (lab) for stud #6 is .315" deep by .866" long
- 3. Flaw size at failure (lab) for stud #8 is .094" deep by .555" long
- 4. Failure load for stud #6 was 61,600 lbs.
- 5. Failure load for stud #8 was 123,000 lbs.
- 6. Stud #6 showed a very large size indication by liquid penetrant test JMM/jlm/021/MCAVOY f:
F 7. Stud #8 showed an intermediate size indication by liquid penetrant test
- 8. Studs #12, #1, and #11 showed small size indications by liquid.
penetrant test i .
- 9. Charpy V-notch values at 70*F were 14 ft lbs for two studs
- 10. Area at root for SI-241 studs is .929"'
11, ' Reported torque for SI-241 studs is'700 foot lbs
'12. For B&W Model #1, the maximum stud stress m&b is obtained which
.is 94.9 Ksi (B&W analysis, Appendix C to the major report, page 36) for the 2480 psi case with preload of 700 ft ".bs
- 13. For B&W Model #1, the maximum stud stress Em&bforthetwocases at 93 psi is: 115.1 Ksi for 950 f t lbs preload, and 93.3 Ksi for 700 ft lbs preload. (Same reference as 12. above)
Problem Solution
- A. Problem #1, Initial Torque level.
' 1. From the B&W analysis it is known that with a high preload (950 ft lbs) on studs at low pressure the total stress [ m&b would be very high and in the range of 115 Ksi. Since stud #6 failed in the lab at 61,600 lbs, which is 66,308 psi, the preload was much less than 950 ft lbs
- 2. Stud #2 failed in service and is thought to have been the initial K
IC failure.- The flaw size is known to be .44" deep by 1.0" long From fracture mechanics techniques the torque plus pressure stress needed to produce this failure can be calculated: JMM/jlm/021/MCAVOY - _ ___ _ _- _ - _ _ _- . _ _ .
s k A Relationsnips:
- a. From Barsom and Rolfe (1), there are several approximations for K when IC CV-notch data are known to be at or near the lower energy shelf.
(1) K IC = (E) (A) (CVN) A=5 E = 30 x 10 6 (2) K IC = .45 Tys din
- b. For a cracked stud, R.C. Cipolla (2) has presented a method of determining the relationship between the crack depth "a", the stress intensity factor K g and the stress (net) 7. 3 In figures 4 and 5 of paper D 7/2 " Application of Fracture Mechanics In the Assessment of Threaded Fastener Integrity" (presented at SMIRT-8 Conference, Brussels Belgium, August 1985), this relation is shown as:
F = Ky y EsJTra Where F 1 is an non-dimensional stress intensity factor for a number of aspect ratios, a/l of 0, 1/4, 1/3 and 1/2. Calculations:
- a. Use tensile test of stud #6 from 51-241 as a check on the estimation procedure for determining values of toughness in 410 S/S studs in tension.
j JMM/jlm/021/MCAV0Y From actual test, load at failure = 61,600 lbs which is a rett.ote stress
.of 66,307 lbs/ine in a 11/4" diaireter stud.
- b. As. stated previously: K 2 = (E) (A) (CYN)
IC t 6 Kf2 y = (30 x 10 ) (5) (14) KIC = 45 Ksi din
- c. Also, as stated previously: K gg=.457ysyin K
IC = 56.25'ksi h ,
- d. From Cipolla for a 1 1/2" stud,12 U;iF for a crack depth of 0.315 (use value at 0.12" where curve goes flat), for crack -location cer.ter L and crack edge location , the values of F -for _ an aspect ratio of .315/.866 (0.364) are:
F-edge = 0.90
-F center = 0.70 For 8 UNF vs.12 UNF for 1 1/2" studs the K y ratio from Table C-4 and Table C-3 is 1.04 (1/2.790 vs.1/2.673).
l
~ ~ \
-j Thus K{6UNF}
- K(12VNF) (1.04) l l
JM*i/jlm/021/MCAV0Y -I
y __ - - - - _ _ p-- .p , e v I ($t should be noted that 1/K g =_be _ for the 10 mil case) 1 For 1 1/4" studs vs. I 1/2" stede for 8 UNF. 1/Kg (g gjgn) = 2.774 and 1/Kgg,;72n)=1.673 . The retto for going down from 1 1/2" to 1 1/4" is 2.67_3 = 0.9635 2.774 from Figure 4 ard Figure 5 using values of 0.90 and 0,70 for F; s can be estir ned as follows for SI-241 stud 46: F edge n 9 30 = Ky
.g _--
sg W (.3:5)
.Since K g is estimated at 45 Ks1 h for SI-241 studs the exp ress ion becomes:
0.90 = ,_,5 A
~
\)3 h.5.14f6) (c315) c-Oo=__ 4,5 _
__ ,= 50.26 Kei (0.90) (0.97478) f Cmm the above: 2 0.70 = g 4 cer.ter I l s 'N (,315) i s= 45 = 64.62 Kr.1 (0.70) (.99478) JMM/jlm/021/MCAVOY l 1
I
~
But from Cipolla: F7 = center F2 = edge F= 1/2 p F1 2 + 2 (F2)/3 g F= (.70),2 + 2 (.90)2 /3 II2
)
F'= (.49 + 1.62) /3 1/2 = (.70)1/2 = .8386 F= 0.8386 = 45 O's (.99478)
\.) s = 45 = 53 Ksi (0.8386) (.99478)
Also, for the case calculated earlier where K g = 56.25 Ksi b f
@= 56.25 = 67 Ksi.
(.8386) (.99478) -
, The failure stress is therefore estimated to be between 53 and 67 Ksi.
The actual failure stress measured in the lab was 66.5 Ksi, q The estfraation procedure is therefore considered valid. I' Determine the torque at failure in stud #2 which failed in service. Frcm calculations above K IC is determined to be 45 Ksi d in by one techniqueand56.25Ksidinbyasecondtechnique, t L From Cipolla, for a cract .44" deep by 1" long with an 1/a ratio of 2.27 and an a/l value of .44, Fy from Figure 4 is estimated at .49 for maximum crack depth case. For edge crack case from Figure 5, the F 2 value is estimated at ,65. These values are considered valid as the Jfm/jlm/021/MCAV0Y -
- - _ _ _ _ _- - - 1
-1 l.-
curves for an a/1 ratio of % .5 will remain flat up to o value of a/D 2 .5. i .. Feca Figure 4 F en er
= 0.49 = lt y I- Dag R(.44)
Kg = 45 or 56.25 Ksi N in 45 = 78.09 Kst s(g) = (0.49) (1.176) s Sn.25 = 97.61 Kai ' g) = (0.49) (1.170)
>From Figure 5 F edge =.0.65 = K 1
f-- a TT(.44) f' Ja 45 = 58.87 Kai gg) = (0.65) (1.176) t-
= 56.25 = 73.59 Ksf s( ~
(0.65) (1.176) But frem Cipolla
~~
1/2 F= i y1 F2+2(7 22)9 - u /3 1/2 F= .49)2 e 2 (.65) / 3 ( JMM/31m/021/McAVOY- -S-
( - F = .60 F = .'60 = K y Es W.44 f = 63.77 Ksi D s[1) = (.60) 45(1.176) 55.25 = 79.72 Ksi (2) = (.60) (1.176) The s[1) and D s(2) values are less thanm&b thevalues calculated by B&W for either the 950 or 700 ft lbs preload with either 93 psi pressure or 2420 psi pressure, therefere it can be concluded that the j actual preload on the valve studs was l'ower than that prcduced by a torque of 700 ft Ibs. The studs were actually under-torcucd rathar t!.cn f over-torqued. B. Problem 2, affect of small flaws on stud integrity: This question is answered directly from the laboratory tensile tests with stud #8. This stud had an intermediate size indication 0.094" deep by 0.555" long and failed at a load of 123,000 pcunds. This load results in i a stress of 132,400 psi. Since it is concluded that studs dl, dil, and
#12 had more shallow and shorter defects than stud *8 it is kncwn that these studs would have exhibited similar tensile / fracture characteristics.
Since it has also been concluded from A. above that studs in valve SI-241 l had a low preload (torque) at failure it is concluded that the B&W JMM/jlm/021/MCAVOY 'I f ro calculations are valid. This work establishes that' studs #1, #8, #11 and
#12 would not have failed under loads as high as those calculated by B&W ) as I m&b. Stud #6 may not have failed under high pressure stress due to low preload, but this was considered to have occurred in B&W Model #2 and the results were acceptable with no affect upon valve safety.
l Prepared by: , f- J. M. McA7ef, NO /0&MS
// /
Checked by: D J ,[ , M.'B'. Shelton, Performance Services
. I '['[V, D
4 l JMM/jlm/021/MCAV0Y - 1
I, References (1) Barsom, J. M. and Rolfe, S . T. , " Correlations Betwen X V-Notch Test Results in the Transition-Temperature Range CI, in "and Charpy Impact i Testing of . Metals", ASTM STP 466, American Society for Testing and Materials, Philadelphia, 1970. pp. 281-302. (2) Cipolla, R C., " Applications of Fracture Mechanics In The Assessment of Threaded Fastener Integrity", Paper D7/2, SMIRT-8 Conference, Brussels, 1985. 0 6
?
l h l JMM/jlm/021/MCAVOY 11-
n.. .. . Attachment 1 to Appendix 0 V l Selected pages fromt Paper D7/2, " Applications of- Fracture -Mechanics In The
- Assessment of Threaded Fastener Integrity", by R. C. Cipolla. Presented at SMIRT-8 Conference, Brussels, Belgium, August 1985.
1. i i t ! e 1 i 4 (. JMM/jlm/021/MCAV0Y . .. .
) i ( 4.0 9 3.8 Net Section
, 1-1/2" - 12 UNF bolt H
3.4 - 3.2 '
; ol
[ . 3.0 -- w
" o = 0.012"
,, 2.8
{ (Kt = 4.5)
", 2.6 -
u 3 g 2.4 u
,$ 2.2 -
E l j 2.0 - . 1.8 - m a/t = 1/4 1.6 -
.$ 1.4 - a/t = 0 E
E 1.2 - e. j 1.0 - _.. 0.8 - a/t = 1/3 . bh_f* E"Id 0.6
/
a/t = 1/2 0.4 - 0.2 - 0 0 0.02 0.04 0.06 0.08 0.10 0.12 Cr.ck Depth, a (inches) Figure 4 - Estimated Stress Intensity Factor at Maximum Ce;tn (Crack , J Tip 1). ODTECM
l I 4.0
] " *"
3.8 ' ~\ a 1-1/2" - 12 UNF bolt H 3.6 ~\ 2 3.4 -
) . \
_ '= 3 . 2 . ( m
\ '
>2
.o ,
,, 3.0 - \
c = 0.012" f 2.8 {
. (K* = 4.5) b \ .
t 2.6 - c \
.? 2.4
\
8 \
- 3 2.2 -
3 \
$ 2.0 -
\
E 1.8 - k. a/t = 1/4 g \ o 1.6 - N e N E 1.4 -
% a/t = 0 5
N 1.2 - a/L = 1/2
'% ' ~
1.0 - h$ rep *lekeb a/t = 1l3 > 0.8 _ 0.6 - 0.4 - s . 0.2 - t I i i e i t 0 0.10 0.12 0 0.02 0.04 0.06 0.08 Crack Deptn, a (inenes) Ficure 5 - Esticated Stress Inter.sity Fa::or at Threaded Surf ace (Crack Tip 2).
-- ApTECH
Table C-3 TABULATED VALUES OF Ck FOR EXTERNAL EIGHT-THREA0 SERIES (8-UN/8-UNR) Minor Tensile Stress Reference-F1qw Primary Basic Major Diameter, O Diameter, d Area, A,p Factor, C Si:e (Inches ~IO k (Inches). (Inches) (Inches) (Inches') 1 1.0000 0.8466 0.606 2.929 1.1250 0.9716 0.790 2.842 1-1/8
~1-1/4 1.2500 1.0966 1.000 2.774
- 1.- 3 / 8 1.3750 -
1.2216 1.233 2.719 6 1-1/2 1.5000 1.3466 1.492 2.673 1-5/8 1.6250 1.4716 1.780 2.635 1-3/4 1.7500 1.5966 2.080 2.602 1-7/S 1.S750 1.7216 2.410 2.575 _2 2.0000 1.8466 2.770 2.550 - 2.510
?rl/4 2.2500. 2.0966 3.560 2-1/2 2.5000 2.3466 4.440- 2.479
~h-3/4 2.7500 2.5966 5.430 2.453 3 3.0000 2.8466 6.510 2.432 3-1/4 3.2500 3.0965 7.690 2.414 3-1/2 3.5000 3.3466 8.960 2.399 3-3/4 3.7500 3.5965 1C.340 2.386 4 4.0000 3.8466 11.810 2.375 4-1/4 4.2500 4.0966 13.380 2.355 4-1/2. 4.5000 4.3466 15.100 2.356 4-3/4 4.7500 4.5966 16.800 2.348 5 5.0000 4.8466 18.700 2.341 5-1/4 5.2500 5.0966 20.700 2.335 5-1/2 5.5000 5.3466 22.700 2.329 5-3/4 5.7500 5.5966 2a.900 2.324 6 , 6.0000 5.8466 27.100 2.319 Note: Reference flaw factor kC
- II I * = s/K. wnece K. is based or, a 10 mil semicircelar fiaw at a threac root.
e' TABLE C-4 TABULATED VALUES OF C FOR EXTERNAL 12-THREA0 SERIES b2,UN/12-UNR) L Primary Basic' Major Minor Tensile Stress Reference Flaw
' Size Diameter, D Oiameter, d Area, A Factor, C (Inches) (Inches) (Inches) (Inches 2 (IntnesIN i 7/8 0.8750 0.7728 0.495 3.050 1 1.0000 0.8978 0.663 '2.970 1-1/8 1.1250 1.0228 0.856 2.909 1-1/4 1.2500 -
1.1478 1.078 2.861 1-3/8 1.3750 1.2728 1.315 2.822 1-1/2 1.5000 1.3978 1.580 2.790 1-5/8 1.6250 1.5228 1.870 2.763 1-3/4. 1.7500 1.6478 2.190 2.740 1-7/8 1.8750 1.7728 2.530 2.720 2 2.0000 1.8978 2.890 2.703 2-1/4- 2.2500 2.1478 3.690 2.675
~
2-1/2 2.5000 2.3978 4.600 2.652 2-3/4 2.7500 2.6478 5.590 2.634 3 3.0000 2.8978 6.690 2.619 3-1/4 3.2500 3.1478 7.890 2.605 I 3-1/2 3.5000 3.3978 9.180 2.595 3-3/4 3.7500 3.6478 10.570 2.585 4 4.0000. 3.8978 12.050 2.577 4-1/4 4.2500 4.1478 13.650 2.570-4-1/2 4.5000 4.3978 15.300 2.564 4-3/4 4.7500 4.6478 17.100 2.555 - 5 5.0000 4.8978 19.000 2.553 5-1/4 5.2500 5.1478 21.000 2.548 5-1/2 5.5000 5.3978 23.100 2.54 5-3/4 5.7500 5.6478 25.200 2.540 6 6.0000 5.8978 27.500 2.E37 ) N0te: F.eference flaw factor k C
- I! * * =s/K' ""' KI is b se e r. I 10 mil semicircular flaw at a thread root.
Si:es less than 7/8 inch are n:t listed.
i I i i l i APPENDIX Z SURRY 410 S/S STUD BEND TESTS 6 O l JMM/jmj/0M4-69
SURRY 410 S/S STUD BEND TESTS f Test Method ! . Studs and . bolts of 410 stainless steel were subjected to a notched bar bend tests to: (1) determine the presence of stress corrosion cracks, and (2) )' serve as a qualitat;ve indicator of ductility. This test was employed because field hardness tests had initially demonstrated excessive scatter with large studs, and UT tests were determined to be incapable of finding small IGSCC flaws. Studs tested were in the size range of 3/8" diameter to 1 7/8" diameter. Bend tests were conducted with both unmodified studs, and with studs which were modified by milling to a thickness of 1/4" to 5/16" between thread root and flat surface. Normally, studs in the size range 3/8" diameter to 9/16" diameter were tested unmodified. Studs 5/8" diameter to 1 7/8" diameter were sawed or milled on one surface to ob'tain the test cross section. Test sample configuration is shown in Figure 1, and as-bent stud configuration is shown in Figure 2. Bends were conducted using a holding fixture with a 90 surface to the specimen long axis. This configuration produced'a cantilevered support. The bend test specimens were then subjected to several hamer blows perpendicular to the specimen long axis. Either a two (2) pound or an eight.(8) pound maul was employed depending on specimen cross sectional area. The force of the hammer blows deformed the bend specimen resulting in a crack or tear at the thread root adjacent to the holding fixture. Where stress corrosion cracks were present, the specimen could crack at any location above the holding fixture. Once cracked, the bend specimen failed by one of several modes depending upon ductility. JMM/jmj/0M4-69
1 l I Test Results The most brittle specimens failed by cleavage with no fiberous fracture and no shear lips and with a bend angle at failure of 0 to 4* as shown in Figure 3. These samples were indexed to a high tensile strength and very low notch l l
} toughness by Charpy V-notch tests (see Table 1). Specimens slightly more ductile failed by cleavage, but demonstrated incipient shear lips as shown in i
Figure 4. Such materials demonstrated slightly higher Charpy V-notch toughness than the preceding material, and bend angles at failure were in the range of 14* to 17 . These were the only materials found at Surry to demonstrate stress corrosion cracking.
-All remaining bend samples failed at angles from 22 to 66 , and demonstrated fractures surfaces with varying degrees of cleavage and fiberous fracture, and showed shear lips of different sizes. This is shown in Figures 5 and 6. The least ductile of th'e materials, produced bend angles of 22 or 23*, nearly 100% cleavage fracture, but with defined shear lips. These few samples were considered temper embrittled (though to a lesser degree than material which was known to have cracked), and marginal in performance.
The best of the materials consistently produced bend angles of 30* or above with seine fiberous fracture and with shear lips. Materials tested on a vendor-by-vendor basis produced a similar cluster of test results as shown in Table 1. . Conclusion It was concluded from the bend tests that no studs in the size range from.3/8" through 3/4" exhibited stress corrosion cracking. Studs which did exhibit JMM/jmj/0M4-69
F i stress corrosion cracking by the bend test were 1 7/8" diameter, and from h valve SI-1890A. Studs from valve SI-241 were previously known to have cracked and no bend tests were conducted with the cracked studs. It was also concluded that the notched (threaded) bar bend test would provide a qualitative indication of ductility which was indexable to other test results such as hardness tests, tensile tests, and Charpy V-notch tests. Studs tested by this technique which were known to have shown stress corrosion cracking produced bend angles of 0* to 17 , and always failed in a cleavage fracture mode with no shear Tips or only incipient shear lips. This low degree of ductility was considered an indicator of temper embrittlement. Other 410. stainless steel studs, which were employed in similar corrosive environments at Surry, indicated greater ductility by the bend test and were free of stress corrosion cracks. Small diameter studs (<3/4" diameter) were considered acceptable; however, 5/8" diameter studs marked VB6-JC were only marginal in performance. Also some large studs, 1 7/8" diameter, marked VB6 - demonstrated only marginal ductility. For small diameter studs (<3/4") hardness test results were directly indexable to bend test results, and it is concluded that small diameter studs with hardness of HRC 29 or less will demonstrate adequate ductility. With adequate ductility it is concluded that the stud is free of temper embrittlement and should not be subject to IGSCC in environments encountered in bolted connections at Surry Power Station. J. M. McAvoy l JMM/jmj/0M4-69
,1 r
Reference Consulted - (1) ASTM Stan'dard'. A370-77,. Mechanical Testing of Steel Products, In Annual Book of ASTM Standards, Part-4, ASTM, Philadelphia,1982. I-t b 4 ( l JMM/jmj/0M4-69
. - , , - _ . = - . . . . . . _ , . - . -.. _ . . _ _ - _ , - _ _ . -.- . . _ , _ _ - _ - _ , ~ _ . . , . . _ _ - . . . _ . _ . _ , . _ - ,
l TABLE 1 SURRY 410 $/S FASTENER BEND TEST EVALUATION RESULTS Stud Bend Angles Mark Stud Type of Each IGSCC Type of Mechanical Valve No. of Size of Bend Test /Overall in Fracture Test MT Designation Studs Nominal Specimen Results Studs Surface Results Results 1-C5-12 JB6 3/8' Unmodi- 65*,54',40' No very None None (4) fied 27'/ ductile stud satisfactory fiberous, shear lip 1-BR-168 JB6 3/8" Unmodi- 38*,31*,30" No ductile, HRC 28.6 None (4) fied 25'/ fiberous -(30* bend) stud satisfactory with some shear lip 1.ER-182 JB6 3/8" Unmodi- 65",57.5", ho ductile, HRC 22.6 None (4) fied 41.5'.37.5'/ fiberous (65* bend) stud satisfactory with shear-lip 1-C5-65 JB6 3/8" Unmodi- 56.5".52" No ductile. None None (4) fled 50'/ fiberous stud satisfactory good shear lip 1-05-51 565 1/2" Unmodi- 50'.48.5', ho ductile, hane None (4) fied 47'/ fiberous stud satisfactory good shear lip 1-LW-99 JB6 1/2" Unmodi- 33".30" No fiberous None None (3) fied 27.5'/ with stud satisfactory possibly some cleavage, ductile HEQB6 1/2" Unmodi. 43"/ No fine grain hRC 25.0 None (1) fied satisfactory fiberous (33' bend) stud good shear lip 1-BR-FCV- VB6-JD 9/16" Unmodi- 49*.40*,40' No mixed HRC 26.1 None 149 (4) fied 40'/ fiberous (40' bend) stud satisfactory and cleavage, small shear lip generally ductile 2-CH-230 VB6-JD 9/16" Unmodi- 56",48*,44.5* ho fi berous HRC 27.0 None (7) fled 38.5'/ ductile (38.5' stud satisfactory with very bend) large shear lip JMM/jmj/0M4-69
ii Stud Bend Angles Mark Stud Type of Each IGSCC Type of Mechanical Valve No. of Size of Bend Test /Overall in Fracture Test MT . f gstonation Studs Nominal Specimen Results Studs Surface Results Results 1-BR-LCV- VB6-JC 5/8" Milled 38.5*.28*.23' No ' cleavage None 'None 115 (8) specimens 22*/ marginal fracture to 5/16" with small thickness shear lip MOV-RC- VB6(9) 3/4" Milled 63*.55*.41*/ No very HRC Yes 1535 B6C(3) specimens satisfactory fiberous 24.5 W to 1/4" and (bend thickness , ductile, angle only B6C 1arge 55*) tested shear' lip MOV-C5- B65 3/4" Milled 66*.49'.48.5" No very fine HRC Ves 100A (16) specimen 38'/ fiberous 25.3 F to 1/4" satisfactory with (bend thickness some angle cleavage. 48.5*)' small shear lip MOV-5I- VB6 1 1/8" Sawed 4 5tud #1 No very Mone All MT 1720A (16) edges 36*.31.5* 'fiberous CK(16) from 2 28*/ , ductile studs satisfactory with shear lip 1/4" 5tud 92 No cleavage None thick- 33*.32.5* fracture ness 22*/ marginal with small shear lip 51-241 J410 11/4" Sawed 2 14.5" lP / Yes. cleavage HRC 32.2 Ali (12) edges poor. IGSCC not in fracture T-145- 12 from 1 bend with very 147 Ksi MT stud specimen small Y-125- T shear lip 127 Ksi with 5/16" CV-14 indi-thick- ft/lbs cations. ness 51-1890A JB6 1 7/8" Sawed 4 0* to 4* Yes, cleavage NRC 29.7 All (16) edges (some O' none fracture T-140- 16 from 2 with IGSCC)/ in with no 145 ksi MT studs poor. IGSCC 4* bend shear'Tip V-120 T specimen 122 Ksi with 5/16" CV-5 indi-thick- ft/lbs cations ness JMM/jmj/0M4 69 I
~~
it a f
-Stud Bend Angles .
of Each . Type of Mark Stud Type -
- IGSCC Mechanical-Valve No. of Size - of Bend Test /0verall in Fracture Test NT Designation Studs Nominal Specimen Results Studs Surface Results Results Stock None 3/8" Unmodi- 92.5* No very HRC None
. material fied no break / fiberous 25.6 made to stud satisfactory large 77174 Ksi ASTM A193 shear lip Y-109 Kst Grade B6 on broken 1100*F specimens min. temp As None 5/16" Unmodi- 86.5" No As above HRC None above fied no break / 26.6 stock stud satisfactory 4
i I l i l JMM/jmj/0M4-69
l
@4Specknen !
Cross-Section Ham.mer Blow e Threads I This Surface : E Holding Fixture l l l FIGURE 1: BEND TEST SAMPLE AND BEND FIXTURE CONFIGURATION
l E l 1 1 y. E}t't Ef4 iM
;3 4 -
Figure 2: Unmodified Stud Bend Test Specieens: Left to right: 2-CH-230, 38.5 bend angle, 27.0 HRC; 1-BR-149, 40 bend angle, 26.1 HRC; 1-05-65, 50 bend angle; 1-BR-168, 30* bend angle, 28.6 HRC; 1-BR-182, 65' bend angle, 22.6 HRC. f ) JMM/jmj/0M4-69
l l l l i i ! l r i 1 i Figure 3: Bend' test specimen fracture by 100% cleavage; SI-1890A, 0* bend angle, 29.7 HRC. I e i JMfi/jmj/0M4-69 i
l l l ( - : n .e ' l '-_ y q :_g+~,.s e.s ,
+
l N i i 1 i i Figure 4: Bend test specimen failure by almost 100% i cleavage, but with incipient shear lip; /' SI-241, 14.5' bend angle, 32,2 HRC. t I 1 t JMM/jmj/0M4-69 l
~
i t I 1 I l t i f i 1 e e ,.. v_,;. .. , . , ,
-h'i'$q,b.'
- 7. . . . Ai ,- ;
b[*' ).:. : ' ..:...b,. t s ' , .; ),l. hg,1
- s. - . , i
" ,t
.:g:
1 l ?"!1
- l 2
4 a r" uY"_ ' . ._ : :: . " ~ ~ -_ '
- . y~ = ~ '
t i i
- i l r Figure 5
- Bend test specimen failure by mixed fiberous '
fracture and cleavage with small shear lip; CS-100A, bend angle 48.5*, 25.3 HRC. [ l l l t i I 1 I t l JMt1/jmj/0M4-69
I l
- l I i !
l 4 .i l i l l { , f
! .f -
,k-1 l
1
' }}~.
i* Y:W'M 5tQ~@ a g %..
~ ,' +
I
- pp' . ..y *
. t .
~
-- ~. l
-?yyT*W. ,i - -s 1
i - e 'l I s l l Figure 6: Bend test specimen failure by 100'. fiberous (ductile) fracture with large shear lip-RC-1535, bend angle 55', 24.5 HRC. i l l l l JMM/jmj/0M4-69 I 1 l 6}}