ML20032C067
| ML20032C067 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 08/01/1981 |
| From: | SARGENT & LUNDY, INC. |
| To: | |
| Shared Package | |
| ML20032C061 | List: |
| References | |
| EMD-032463, EMD-32463, NUDOCS 8111060663 | |
| Download: ML20032C067 (8) | |
Text
T
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'//YbC SARGENT & LUNDY.
EN T4EERS COMMONWEALTH EDISON COMPANY.
-LASALLE COUNTY NUCLEAR STATION UNIT - 1 &.2
SUMMARY
REPORT L
ON l
VALVE FLEXIBILITY STUDY BY 5
. ENGINEERING MECHANICS DIVISION SARGENT & LUNDY ENGINEERS 8-1-81 i
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EMD # 032463
EMD-032463 VALVE FLEXIBILITY STUDY
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Client Commonv/ealth Edison Co.
Prepared by *
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- iroject LaSalle County Reviewed by Date Proj. fio.
4266-10 Equip. No.
Approved by Date I.
INTRODUCTION In the dynamic analysis of piping systems, in most cases a valve is modeled using rigid beam elements (Fig. 1).
These models represent the eccentricity of the center of gravity of the valve-operator assemblics correctly, but do not account for the valve flexibilities.
To account for the flexibility of the' valves, the computed accel-erations for the center of gravity of valve-operator assemblies, using the approach indicated above, are obtained and are multiplied by a factor of 1.5 using the basis of reference 1.
These accelera-tions thus obtained are used in the qualification of flexible valves.
The objective of this summary report is to describe a method that is used for assessing the accuracy and justification of the (1.5) amplification factor that is used in the qualification of flexible valves.
II.
ANALYSIS a)
Samples Selected for Analysis:
Three representative piping subsystems of LaSalle-1 Nuclear Power Plant were identified, each having a moderate to large size flexible valvo, for detailed dynamic analysis.
These subsystems and the respective flexible valves are as follows:
(1)
Subsystem: HP-03 Valve
- E22-F001, 14" gate valve, Motor Operated, Limitorque SAB00-25 Operator (2)
Subsystem: VP'-04 Valve
- VP-063B, 8" gate valve, Motor Operated, Limitorque SMB-000 Operator (3)
Subsystem: MS-69Z Valve
- lE-51-F076, 1" globe valve, l
Motor Operated, Limitorque SMB-000 Operator b)
Method of Analysis:
i l
Dynamic analysis of piping Jystems are generally performed using j
response spectra method.
Main reason for the selection of response spectra method is the economy it provides in the computer I
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Chent Commonwealth Edison Co.
Prepared by Date Prcject LaSalle County.
Reviewed by Date Praj.fio.
4266-10 Equip. No.
Approved by Date time used to obtain the results.
More accurate results for the same piping system is achieved by the use of time history analysis method for the dynamic behaviour of the system.
Two sets of dynamic analysis were planned for this study.
The first series of analyses consisted of dynamically analyzing each one of the piping subsystems mentioned before, by using the time history method of analysis.
The available finite element models, consisting of straight and curved pipe elements and other necessary beam elements, for each subsystem were studied.
The parts of these models corresponding to the valves, which are originally modelled as shown in Figure 1, were modified using 3-D beam elements in order to represent the mass and stiffness characteristics of the various valve components more realistically.
Thus the stiffness / flexibility of the valves were accurately accounted for in these coupled piping / valve models.
The improved finite element models for the three valves are shown on Figure 2.
The second series of analyses consisted of dynamically analyzing the original finite element models of the piping subsystems without any change of the valve representation (valves were modeled as shown in Figure 1), using response spectra approach, since all the piping subsystems analyses are currently being performed using this method.
For the time history analyses, the time history forcing functions (Reference 2) consisted of various seismic and hydrodynamic loads.
These were SSE, SRV, CHUGGING and Cp acceleration time history records.
In order to facilitate a direct comparison of results of the two series of analyses, exact corresponding response spectra values for each of the acceleration time history records were obtained using the RSG Computer ' Program.
Both the time history and response spectra analyses were performed using Eargent & Lundy PIPSYS computer program.
In the first series of analyses, each piping subsystem model were analyzed using the appropriate directional components of the acceleration time history forcing functions individually for each load case (namely for SSE, SRV, CHUGGING & Cp events).
30 modes were considered for all the analyses, and maximum transient accelera-tien responses for each node were obtained individually for different load cases.
Similarly, the original finito element models (without valve modification) were dynamically analyzed using the response spectra obtained as explained before.
Again 30 modes were considered for all the corresponding analyses and SRSS of X, Y and Z excitation responses for each node were
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Safety-Helated Non-Safety-Related Page
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Prepared by Date Project LaSalle County Hefewed by Date Proj. No.
4266-10 Equip. No.
Approved by Date obtained.
(Thesc X, Y and Z responses are based on SRDS of first 30 modal responses).
III.
METHOD OF COMPARISON Results from both series of analyses, namely from time history analyses of improved models and response spectra analyses of the original models were done as follows:
a)
The node representing the center of gravity of the valve-operator assembly was identified on the original model (as shown in Figure 1).
For each load case, acceleration responses at this particular node as a result of response spectra analysis for each direction were obtained, b)
Two load combinations were postulated, i)
Accelerations obtained for each load case as indicated in III-a, were combined as indicated by (i) and (ii) above, for X, Y and Z directions separately, resulting in absolutely summed total directional response for response spectra analyses at the center of gravity of valve-operator assembly.
c)
Results of the time history analyses were inspected, and the nodes which have the largest acceleration responses of the improved valve models were identified.
These nodes were at or near tha center of gravity of the operator.
Acceleration. responses along each direction, for each load case were recorded.
d)
For the two postulated load combinations, along X, Y and Z directions, absolutely summed total directional responses for time history analyses were obtained at or in the vicinity of the center of gravity of the operators (nodes having largest acceleration responses).
e)
For each valve, and for each load combination, the total acceleration response obtained from time history analysis (at the extreme nodes of the improved valve models) was divided by the total acceleration response obtained from response spectra analysis (at the center of gravity of valve-operator assemblies) for X, Y and Z directions
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4266-10 Equip. No.
Approved by Date respectively.
These ratios represent the actual amplifica-tion factors.
i IV.
PRESENTATION OF RESULTS Total acceleration response from both series ou analysis.for both load combinations and the ratios are shown in Table 1 for the i
three valves.
i V.
CONCLUSION i
1 As seen from the Table 1 for all the three valves, the i
effective amplification ratios are all below the practiced value of 1.5 for all directions and for the resultants also.
In light i
of these results it can be concluded that the current practice i
of using a factor of 1.5 to increase the acceleration calculated i
at the center of gravity of tb-assembly by the response spectra method and of using this increased value to account for the valve flexibility is valid.
VI.
REFERENCES 1.
IEEE Std. 344-1975 - IEEE Recommended Practices for Seismic Qualification of Class lE Equipment for Nuclear Power Generating Stations 2.
Memo from Y. A.
Patel
" Time History Files for Valve Flexibility Study" - EMD File #032708.
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Prepared by Date Project LaSalle County Reviewed by Date Proj. N o.
4266-10 Equip. No.
Approved by Date TABLE 1:
TOTAL ACCELERATION RESPONSES AND RATIOS FOR VALVES:
E22-F001, VP-0633 and lE-51-F076 LOAD COMB!rvA7/oN (1)'
LOAD COME>lNATioN (2) l L
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4266-10 Equip. No.
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of Valve-Operator Assembly RY t
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14" GATE VALVE: E22-F001 8" GATE VALVE:
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Finite Element Models for 14", 8" and 4" Va'lves
.