ML19276E687
| ML19276E687 | |
| Person / Time | |
|---|---|
| Issue date: | 03/15/1979 |
| From: | NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | |
| References | |
| REGGD-01.XXX, REGGD-1.XXX, NUDOCS 7903200261 | |
| Download: ML19276E687 (36) | |
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REGULATORY GUIDE 1.v.XX QUALIFICATION AND ACCEPTANCE TESTS FOR SAFETY-RELATED SNUBBERS A.
INTRODUCTION General Design Criterion 2, " Design Bases for P*otection Against Natural Phenomena," of Appendix A, " General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, " Licensing of Production and Utilization Facilities," requires, in part, that the design bases for structures, systems, and components important to safety reflect appropriate combina-tions of the effects of normal and accident conditions with the effects of natural phenomena such as earthquakes.
Section II, " Quality Assurance Program," and Section III, " Design Control," of Appendix B, " Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants,"
to 10 CFR Part 50, requires, in part, that the quality assurance program shall be applied to the design, fabrication, construction and testing of the structures, systems, and components of nuclear power plants.
Dynamic loadings developed by system transients or by earthquake or other natural phenomena in safety-related systems.are usually mitigated by snubbers.
This guide delineates minimum acceptable test requirements for design qualification and acceptance testing of safety-related snubbers.
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B.
DISCl'SSION I.
GENERAL Snubbers, both hydraulic and mechanical, are used extensively in nuclear power plants for the restraint of safety-related systems and com-ponents (snubbers, systems, and components) against seismic or other types of dynamic loadings.
Recent operating history of nuclear power plants indicates the existence of numerous inoperative snubber units.(1) This unsatisfactory performance can be attributed to many reasons (2) and the solution of insuring proper perfor.mance is multi phased.(3) One phase.
the fulfillment of minimum requirements for qualification tests and accept-ance tests for snubbers will increase the confidence level in the initial functional reliability of snubbers.
The purpose of qualification testing is to verify the functional capability of a specific snubber design as related to the design criteria and to demonstrate the, ability of the snubber as constructed to perform properly in the operating environment.
The purpose of acceptance testing is to monitor the adequacy of the manu-facturing process and quality assurance program such that each finished snubber will function as specified.
A functional specification for snubbers which specifies functional parameters and general performance requirements should provide a basis for both series of tests.
All snubber designs should be qualification tested, all snubber units should be acceptance tested.
However, because of the present limitation of test equipment capacity, test loading requirements for snubber units with rated capacity of more than 150,000 lbs should be considered on a case by case casis.
Snubbers used to restrain safety-related systems and ccmponents should be constructed according to the rules of Subsection NF of the ASME 1.XXX-2
Boiler and Pressure Vessel Code Section III. When materials exempted by Subsection NF are used in the construction of snubbers, tneir compatibil-ity with other materials used in the construction and the operating environ-ment during its designed service life should be established.
Furthermore, the ability of snubbers to perform within an acceptable range after they have been degraded normally under a simulated anticipated operating environ-ment should also be demonstrated.
II.
SNUBBER OPERATING CHARACTERISTICS' In nuclear power plants, snubbers are used to restrain dynamic system responses.
Ideally, under a steady or continuing force, the system or component supported by snubbers will move freely as if the snubbers are not existing.
However, when a force is applied suddenly, snubbers will eliminate the undesirable dynamic responses so the supported system will not be overstressed.
Five functional parameters are essential for the users to design their systems.
These are, the activation levei, the release rate, the drag, the dead band and the spring rate of snubbers.
1.
The activation level describes the magnitude of the character-istic that activates the snubber.
It could be based upon velocity or acceleration depending on the principle of the design.
2.
The release rate is the rate of snubber axial movement under a load after the snubber is activated.
It will allow slow axial movements under continuing force from the supported system after a dynamic event; e.g., the thermal growth of a system after SSE or LOCA.
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3.
The drag is the. frictional resistance in the snubber against an axial movement at certain velocity.
The force required for initial axial movement, or the breakaway load, is the maximum drag at zero velocity.
Since the force developed and accumulated in the system has to overcoce the snubber frictional force and other forces to move the snubber, the drag will help to determine the smoothness of the snubber movement under a steady loading. When the snubber drag force is appreciable the supported system with a thermal growth will build up force until the drag is overcome.
Then system movement may be so sudden that the snubber will be activated.
After the activation is released, normal snubber movement will resume.
4.
The dead band is the free axial movement of the snubber between the two activations of opposite directions.
It includes the manufacturer's mechanical tolerance and the distance traveled by the snubber under loadings before the activation takes place.
It is therefore a function of the manufacturing process and the interaction of the applied loading and the activation level.
5.
The load-displacement relationship is used u, designers for the modeling of snubbers in a system analysis, and in turn adds to the validity of the system analysis.
The spring rate is a simplified expression of the load displacement relationship (linear approximation of the peak load-displacement ratio) of the snubber under the action of a cyclically applied load equal to the magnitude of the rated load of the snubber at both tension and compression.
The spring rate may vary as a function of the frequency and the magnitude of the applied load.
The designer should be aware of t e magnitude of this variation.
This relationsnip is used as a cencnmars.
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It should not be confused as a preferred way to model the snubber into a system analysis.
While hydraulic fluid leakage rate in hydraulic snubbers is not a functional parameter, it is of vital importance since hydraulic snubbers will not function without hydraulic fluid.
Limits for this rate should be speci.fied in the functional specification, and should not be exceeded dur-ing the testing.
The effects of system vibration in line with and ;;dependicular to the snubber load axis fatigue life and wear or fluid leakage should also be considered and verified in the pre-operational tests.
III. FUNCTIONAL SPECIFICATION To assure that all pertinent information and requirements are incorporated in the snubber design criteria, the owner or the manufacturer should provide a functional specification to define all the required. performance characteristics including the acceptable values and ranges of snubber functional parameters for anticipated environments. Typical contents of a functional specification are shown in Appendix A.
They should provide the criteria for all functional tests. Additional tests to assure capability of providing special functions or withstanding special conditions should also be defined in the functional specification.
If a snubber design has been qualified according to the requirements of a functional specification set by the manufacturer, its suitability to meet the requirements of the functional specification for a specific application by an owner should be documented in an Application Report certified by one or more registered professional engineers.
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IV.
QUALIFICATION TESTING The qualification of a snuboer design should be conducted by usi..g a minimum of two prototypical units or two units randomly selected from the production line of the same design and rating according to the sequence and requirements set forth by Appendix B so that the repeatability of the test results can be assured.
The design is qualified only when both units have passed the requirements.
In case one or both units fail the require-ments, an analysis should be made to determine the reason of failure. The design should be revised according to the results of the failure' analysis before it can be tested again for qualification.
Units used for testing purposes should not be used for safety-related purposes since they may have used a major part of their useful life (Fatigue).
Minimum testing require-ments should include the following:
1.
The determination of the drag can be accc7plished by a load cell measuring the breakaway force and the force required to move the snubber at a low velocity.
The drag chould be determined in both directions with the associated velocity clea j stated.
2.
The dead band is measured by the distance traveled by the snuober before it activates.
The dead band should be measured with the associated loadings at 5%, 10%, 25%, 50% and 100% of the rated load.
3.
The a-tivation of the snubber is triggered by the design character-istic (a velocity or an acceleration) reaching a predetermined value in each direction.
Only a small fraction of the rated load is required to activate a snubber.
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4.
The release rate is measured after the activation of the s.nubter.
Since its magnitude depends on the loading magnitude and is an indication of the recovery rate of the snubber back to the unactivated condition, as a minimum, it should be determined for 5%,10%, 25%, 50% and 100% of the rated load and also for the faulted load in both directions at a specified temperature.
5.
The spring rate, which is a function of the load direction, the location of the piston, the amplitude, and the frequency of the dynamic loading as well as other environmental conditions, should be determined by a dynamic cyclic test over a frequency range with the piston at a specified position under the action of the rated load (or other specified load) for both directions at the temperature extremes specified.
6.
The margin to failure due to overloading conditions should be furnished by the manufacturer as the ultimate load.
Ultimate load capa-bility may be determined analytically by the limit analysis procedures permitted by Subsection NF.
It should be determined whether the snubber movement will be frozen or free after an ultimate failure.
The acceptable value of these parameters should be specified in the functional specification.
V.
ENVIRONMENT QUALIFICATION The functional parameters of snubbers vary with working environment since temperature, humidity, irradiation dosace and other factors cause degradation of the materials, including hydraulic fluid and lubr cants, i
used for the construction of snubbers, e.g.,
the loss of hycraulic f'uid 1.XXX-7
through seals and the premature rust activation may both occur because of high temperature and humidity.
The aging process and test environment should be specified so that testing will be meaningful with respect to the anticipated environment, which may include the effects of salt. spray, sand and dust, extended humidity and special thermal transients, such as that of the LOCA, as b,eing specified in the functional specification.
The environment qualification should include the application of a low ampli-6 tude axial vibration to the snubbers for not less than 5x10 cycles.
The design limits should be established for all service conditions.
Functional parameters, therefore, should be determined for a service range of room temperature (or the lowest design service temperature) and 200 F (or the highest design service temperature).
Since hydraulic fluid leakage has been an operating problem, the measurement of hydraulic fluid leakage should be obtained during all tests on hydraulic snubbers.
VI.
ACCEPTANCE TESTING The acceptance of completed snubber units from the production line should be determined by the successful demonstration of the following:
1.
The materials and production pr.ocesses selected are compatible with each other and the intended operating environment, and the design life period.
2.
The completed snubber unit conforms to all design requirements related to materials, production process, dimensions and general arrangement of a snubber of a qualified design.
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3.
The completed snubber unit should meet the specified require-ments for the crag, the dead band, tne activation level, anc tne release rate.
Individual test records, such as those obtained from the qualifica-tion test program of C.4 and the stucy of material and process compati-bility and quality assurance program in the manufacturing process, should be used to show the adequacy of items 1 and 2.
The adequacy of item 3 should be illustrated by testing according to the requirements as outlined in Appendix C.
VIII.
DEFINITIONS Activation level.
The axial motion rate or acceleration that causes the activation of the snubber.
Dead band.
The free axial movement of the snubber between the two activations of opposite directions.
Drag. The breakway load which overcomes the internal snubber friction or the load maintaining the snubber movement under a specific velocity.
Emergency load.
The design load capacity for the snubber based on the use of level C Service Limits defined by the ASME, B&PV Code Section III.
Faulted load.
The design load capacity for the snubber based on the use of level D Service Limits defined by the ASME B&PV Code Section III.
Rated load.
The design load capacity for the snubber based on the use of level A Service Limits defined by the ASME B&PV Code Section III.
Release rate.
The rate of the axial snutter covement after tre activation of the snubber took place under a scecifiec load.
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Sprino rate.
The linear approximation of the peak force-discla:etent including the dead band relationship cbtained by a dynamic cyclic test between the two load peaks equaling the rated load or emergency load out of opposite directions, and the total displacement.
C.
REGULATORY POSITION 1.
For all snubbers used to restrain safety-related components and systems in nuclear power plants (snubbers), a functional specification including items described in Appendix A of this guide should be used as the basis to determine the acceptebility of test results frca Positicns 4 and 5.
2.
Snubbers should be constructed according to the rules of Sub-section NF of the ASME Boiler and Pressure Vessel Code,Section III.
3.
When materials exempted from Subsection NF requirements, including hydraulic fluid and lubricant, are used in the construction of snuobers, their compatibility with other materials of construction and the working environment (including temperature, humidity and irradiation dose) should be established.
Quality assurance procedures should be establisned for these materials.
4.
Snubbers with rated.apacity of not more than 150,000 lbs should have their designs qualified according to the requirements of Appendix B of this guide.
The qualification test loading requirements of those with rated capacity greater than 150,000 lbs snould be determined on a case-by-case basis.
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5.
A completed snubber unit should be accepted from the production line only if it has successfully passed all the testing requirements described in Appendix C of this guide.
The acceptance test loading.equire-ment for those with rated capacity greater than 150,000 lbs should be d1ter-mined on a case-by-case basis.
6.
All files shall be kept in auditable form according to the requirements of Appendix B, " Quality Assurance Lriteria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CFR Part 50.
D.
IMPLEMENTATION The purpose of this section is to provide guidance to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.
Because of the significance of the safety issue addressed in this guide', except in those cases in which the applicant prcposes an acceptable
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alternative method for complying with the specified portions of the Com-mission's regulations, the method described herein will be used in the evaluation of applications for docketed after If an applicant wishes to use this guide in an application docketed prior to the implementation date, the pertinent portions of the application will be evaluated on the basis of this guide.
The method described herein also applies to 1.XXX-11
after issuance of the construction permit, manufacturing license, early site approval, or design approval when it does not involve addi-tion, elimination, or modification of structures, systems, or components of the facility.
REFERENCES 1.
J. H. Butler and F. M. O' Hare, Jr., " Analysis of Abnormalities of Snubbers in Nuclear Reactor Service," ORNL/NUREG/TM-53 (Oct. 14, 1976).
2.
J. H. Butler, " Analysis of Owner Design Specifications for Snubbers,"
ORNL/NUREG/TM-116 (August 5, 1977).
3.
ASME B&PV Code Section III, WG on Component Supports /TG on Snubbers Report " Snubber Design Criteria" (To be published).
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APPENDIX A FUNCTIONAL SPECIFICATION OF SAFETY-RELATED SNUBBERS 1.
SCOPE This document establishes requirements for functional specification for safety-related mechanical and hydraulic snubbers (snubbers) for appli-cations in nuclear power plants.
2.
DESIGN SPECIFICATION RELATIONSHIP This specification provides detailed definition of functional require-ments applicable to snubbers in safety-related components and piping systems.
The requirements of this specification may be provided as part of the Snubber Design Specification or as part of an equipment or purchase specifica-tion which also includes the Design Specification.
If this specification is prepared by the snubber manufacturer, an Application Report prepared for the owner by one or more licensed professional engineers certifying the compliance of the functional parameters required by the Design Specifica-tion to those in this specification prepared by the manufacturer shall be accepted as part of the Design Specification.
Compliance with the requirements of this specification is intended to assure that the operating conditions and safety-related functions of the sntbber have been adequately defined, permitting the snubber manufacturer to demonstrate the adequacy of the snubber design and materials used in its construction for the intendsd service.
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3.
DEFINITIONS Activation level.
Tne axial m tion rate or acceleratien tr.a c 25es the activation of the snubber.
Dead band.
The free axial movement of the snubber between the two activations of opposite. directions.
Drag. The breakaway load which overcomes the internal snubber fric-tion or the load maintaining the snubber movement under a specific velocity.
Emergency load.
The design load capacity for the snubber based on the use of level C Service Limits defind by the ASME, B&P.V Code Section III.
Faulted load.
The design load capacity for the snubber based on the use of level 0 Service Limits defined by the ASME B&PV Code'Section III.
Rated load.
The design load c'pacity for the snubber based on the use of level A Service Limits defined by the ASME B&PV Code Section III.
Release rate.
The rate of the axial' snubber movefuent after the activation of the Snubber took place under a specified load.
Spring rate.
The linear approximation of the peak force-displacement including the dead band relationship obtained by a dynamic cyclic test between the two load peaks equaling the rated load or emergency load but of opposite directions, and the total displacement.
4.
FUNCTIONAL SPECIFICATION It is the responsibility of the Owner or his agent to identify the safety-related functional requirements of the snubber and provide for the delineation of the following.
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d.
Application Characteristics, see Section 4.1 b.
Design Requirements, see Section 4.2 c.
Operational Requirements, see Section 4.3 d.
Functional Parameters, see Section 4.4 e.
Spec.ial Material Requirements, see Section 4.5 f.
Installation Requirements, see Section 4.6 g.
Maintenance Requirements, see Section 4.7 h.
Other Requirements, see Section 4.8 4.1 Application Characteristics The application characteristics of each snubber shall be identified
' by listing whichever of the following descriptive terms are appropriate.
a.
Seismic restraint
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.b.
Dynamic force restraint c.
Pipe whip restraint d.
Relief valve restraint e.
Others such as combination (s) of the above 4.2 Design Requirements The following information shall be specified.
a.
The design operating temperature.
b.
Time-temperature data for design thermal transients, with number of cycles indicated.
c.
The seismic acceleration and dynamic loadings that the snubbers shall be capable of withstanding transverse to the snucber line of action without loss of functional capability.
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r d.
The seismic acceleration and dynamic loadings that the snubbers shall be capable of withstanoing along the snubber line of action witnout.
loss of functional capability.
e.
Limits on acceptable range of fundamental frequency of snubber assembly.
f.
Limits on acceptable angular offset from the line of action of the load.
4.3 Operational Requirements Anticipated modes of snubber operation including safety-related function (i.e., dynamic events, seismic, etc.) shall be specified.
The operating conditions and environmental conditions shall be identified.
' ~.
4.3.1 Operating Conditions.
The number of operational cycles, imposed loading or movement (number, amplitude and direction), and environment including temperature, for each of the following operational categories shall be specified.
a.
Installation Testing b.
System Hydrostatic Testing c.
Preoperational Testing d.
Start-up Testing e.
Normal and Abnormal Plant Operations, including postulated accident conditions, shock or pulsating loads f.
In-service Testing A-4
o g.
Vibration h.
Otners 4.3.2 Environmental Conditions.
A histogram of the environmental conditions which are postulated to exist shall be identified and specified.
The need of snubbers to survive normal and abnormal environmental conditions, with or without maintenance, shall be stated.
Since the attaching hardware can influence the survival of the snubber, it shall also be considered.
The following factors are considered relevant.
a.
The atmosphere including chemistry, temperature, humidity and radioactivity in which the snubbers will be installed and must cperate under normal plant conditions.
b.
The atmosphere including chemistry, temperature, humidity and radioactivity in which the snubbers must operate under upset, emergency and faulted plant conditions.
The duration of these conditions shall be specified.
c.
The application of an axial vibration with an amplitude of not less than 120% of the dead band of the applied frequency of not less than 6
5x10 cycles.
4.4 FUNCTIONAL PARAMETERS The following functional parameters shall be specified as a minimum a.
Acceptable limits for both the break away drag force and the drag force associated with moving ur. der a specified velocity at the maximum and minimum working temperatures.
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b.
Acceptable limits for dead band at the maximum and minimum working temperatures for :ne range of worxing icad and pisten ic:ati c.
Activation level and tolerance at the maximum and minimum working temperatures.
Release rate and tolerance at 5%,10%, 25%, 50%, and 100% rated load, and that at emergency load, for the maximum and minimum working temperatures.
Acceptable range of spring rate and the maximum and minimum e.
working temperatures, the frequency and the range and the classifica-tion of the load at which the spring rate is to be determined, with piston locations at 1/4, 1/2 and 3/4 stroke locations.
4.5 SPECIAL MATERIAL REQUIREMENTS Special material requirements of the snubber shall be specified.
Items to be considered shall include, but not be limited to the following.
a.
Hydraulic fluid b.
Seals c.
Springs d.
Special surface preparations or coatings required e.
Lubricantt 4.6 INSTALLATION REQUIREMENTS Requirements for the installation of the snubber shall be specified.
Orientation of the hydraulic snubber and relative position c' :ne a.
hydraulic reservoir to the snubber shall be defined if any limitatiori exist.
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b.
Orientation of the mechanical snubber installation shall be defined if limitation exists.
c.
The available space for installation and removal shall be defined if any limitations exist.
d.
Piston location in the snubber as installed shall be defined.
e.
The range of transverse movement provided shall be defined.
f.
Another special mounting providad shall le defined.
4.7 MAINTENANCE AND INSPECTION REQUIREMENTS Acceptable hydraulic fluid leakage rate shall be specified for hydraulic snubbers.
Other special provision for snubber maintenance shat 1 be specified.
Where requirements are established for in-situ in-service testing, this may include requirements for the demonstration of the feasibility for the required in-service drag test, activation level test and release rate test of snubbers with specific test equipment.
4.8 SPECIAL PERFORMANCE REQUIREMENTS
~ 0ther requirements for special performance or loading conditions, as applicable, shall be specified.
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APPENDIX B QUALIFICATION OF FUNCTIONAL PARAMETERS FOR SAFETY RELATED SNUB 8ERS IN NUCLEAR POWER PLANTS 1.
SCOPE This document describes the basic requirements for the qualification of a design for snubbers used in safety-related systems in nuclear pcwer plants (snubbers).
2.
PURPOSE The purpose of this document is to provide guidance for ' demonstrating the capability of a snubber design to satisfy the functional requirements.
Testing is required for the demonstration of capability to satisfy all specified functional requirements except for the ability to withstand ultimate load for which an analysis may be used instead of testing.
3.
QUALIFICATION PLAN A qualification plan shall be developed for each snubber design and rating and this plan shall be submitted to the Owner or his agent to be reviewed for consistency with the Design Specification and for approval or acceptance as the basis for an Application Report.
The qualifica-tion plan for functional parameters for Snubbers shall, as a minimum, contain the following information:
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I Snubber descriptions and specifications, see Section-3.1 e.
b.
Snuober sampling requirements, see Section 3.2 Material data requ rements, see Section 3.3 i
c.
d.
Mounting requirement', see Section 3.3 e.
The aging simulation requirements, see Section 3.5 f.
The service condition simulation requirements, see Section 3.6 g.
Functional parameters and environmental variables to be measured, see Section 3.7 h.
Test and monitor equipment requirements, see Section 3.8 i.
The test sequence, see Section 3.9 f
j.
Special Tests, see Section 3.10 t
j k.
Limits or failure definition for the test, see Section 3.11 l
1.
Ultimate Load Capacity, Section 3.12 3.1 Snubber Descriptions And Specifications The snubber design to be qualified shall be described in full by its model number, drawing numbers and total weight.
Serial numbers of tested snubbers shall be recorded.
The qualification requirements shall be specified in the Function Specification which covers the functional parameters as described by Appendix A.
3.2 Snubber Sampling Requirements Two snubbers shall be used to qualify a specified design and rating.
They shall be either two prototypical urits manufactured for qualification purpose or two production units selected randomly from a population of not less than four.
This includes the use of same materials, parts, and B-2
general arrangement.
Snubbers used for qualification testing shall not be used for safety-related functions in nuclear power plants.
3.3 Material Data Requirements Material data shall be included as follows to assure that the snubber was manufactured according to the specification.
a.
The data or reference from tests conducted to prove the adequacy of the basic design, this should include, for example, the compatibility test between seal material and the hydraulic fluid and the working environment with special consideration giver to the combined effects of temperature and radiation on material pertermance.
b.
The data of material and process traceability of the snubber.
These data shall be included to demonstrate that the snubber has suces-sfully met the construction requirements.
- 3. 4 Mounting Requirements The qualification plan shall spec'.fy the way in which the snubber shall be mounted for testing.
The pla1 shall require that the snubber uni? shall be mounted in a manner and positions that simulate its expected installation with attachments for service application when in actual use unless an..,alysis can be performed and justified to show that its performance would not be altered by otaer means of mounting.
By manner is meant the means to be used such as pins, bolts, welds, clamps, etc.
By position is meant the spatial orientation with respect to the gravitational field of the earth.
B-3
3.5 The Aging Simulation Requirements The qualificatica plan shall specify the aging siculation ':r the snubber design based on requirements in the functional specificaticn.
Aging simulation procedures to put the snubber units in a condition equivalent to the end of life condition, shall be conducted, including sand and dust simulation and/or salt spray test similar to mil-E-5272c if the specified working environment requires it.
3.6 The Service Condition Simalation Requirements The quali.fication plan shall specify a steam humidity simulation of 350 F saturated steam and 72-hour duration if the snubber service area is inside the containment.
It shall specify a submerge simulation of 200 F water and 72-ho.. duration of the snubber service is in submerged condition.
3.7 Functional Parameters And Environmental Variables To Be Measured The qualification plan shall specify the functional parameters anc environmental variables to be measured for the snubber test.
The func-tional parameters shall include, as a minimum:
the drag, the dead band, the activation level, the release rate, and the spring rate.
The environ-mental variables shall include:
temperature, humidity or steam-water con-dition, special thermal transients, etc.
For hydraulic snubbers, the hydrau-lic fit d leakage during tests shall be recorded.
The application of a low 6
amplitude, axial vibration to snubbers for not less than 5x10 cyc'es shall be included as an environmental requirement.
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3.8 Test And Monitor Equipment The test shall be conducted and monitored using equipment that provides resolution for detecting meaningful changes in the variables.
The quali-fication plan shall specify the test and monitor equipment used for the qualification of the snubber, and describe the accuracy within the range anticipated for use on the proposed tests.
The test equipment and monitor equipment shall be calibrated against auditable calibration standards and shall have documentation to support such calibration.
The data recording equipment shall have sufficient speed and capacity such that the time interval between recorded measurements will provide the time dependence of each variable.
3.9 The Test Sequence The qualification test shall include the following tests in the described sequential order as a minimum requirement.
a.
The determination of all five parameters described in Section 3.6 under recorded room temperature (or the specified lowest design service temperature, t10 F, whichever is lower).
Temperature shall be recorded at the beginning and the end of each of the following tests.
The snubber shall be at 1/2 stroke location unless otherwise required.
a.1 The drag shall be determined for both directions for both the break away condition and under the condition of moving under a specifie d velocity.
The values of the drag and the velocity shall be recorded.
a.2 The activation level shall be tested for both directions by rapid application of a force equal to 5%, 10%, 25%, 30% and 100% of tne B-5
rated load.
The acceleration and velocity of the piston motion shall De recorced as a function of time.
The activation level shall be determined by this recording.
a.3 The dead band shall be recorded during the activation level testing described in Section 3.8.a 1.
- a. 4 The release rate shali ;"
<.ted and recorded for both directions under 5%, 10%, 25%, 50%, and 100% ra o load and the emergency load.
- a. 5 The spring rate shall be tested by a dynamic cyclic loading equal to the rated load or the emergency load and at the 1/4, 1/2, and 3/4 stroke locations according to the requirement of the functional specifi-cation.
The testing frequency shall be from 3 Hz to 33 Hz at intervals of approximately 3 Hz.
Each frequency shall last not less than 10 seconds.
Response at each frequency shall be recorded as load-displacement traces.
- a. 6 A one cycle dynamic loading at each of the 1/4, 1/2, and 3/4 stroke locations equal to the faulted loading shall be applied to demon-strate adequacy of the response.
The force and displacement shall be recorced for this test.
- a. 7 Hydraulic fluid leakage during the testing shall be recorded.'
b.
Repeat tests described in a. but with snubber temperature at 200 F (or the specified highest design service temperature, whichever is higher).
c.
Aging simulation procedure described in Section 3.4 and 3.5 shall be conducted, including the application of an axial vibration with an amplitude not less than 120% of the dead band of the applied frecuency 6
for not less than 5x10 cycles.
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d.
Repeat tests describe in a. after the aging simulation and
~
service condition simulation procedures descrioed in c.
e.
The hydraulic fluid leakage during the test sequence shall be recorded and summarized.
3.10 Special Tests i
l The qualification plan.shall specify special tests for the snubber design according to the Design Specification requirements.
These are the tests demonstrating the ability of the snubbers to meet special specified requirements, such as an in-situ in-service activation test.
Test set-up and ecuipment used shall closely simulate the required condition so the feasibility can be illustrated and coorelation between results can be established.
3.11 Limits Or Fail'ure Definition For The Test The qualification on the snubber design shall be considered as failure if any one of the functional parameters failed to meet the following limits.
Drag:
Shall not exeed the specified limits, either direction.
Dead Band:
Shall not exceed the specified limit.
Activation Level:
Shall not exceed the specified range, eitt 't direction.
Release Rate:
Shall not exceed the specified range, either direction, under the specified loadings.
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Spring Rate:
Shall not be less than the specified range, for all frequencies at the specified stroke location.
Hydraulic Fluid Leakage Rate:
Shall not exceed the specified limit.
3.12 Ultimate Lead Capacity The ultimate load capacity of a snubber design shall be determined by analysis.
The analysis shall follow the stress report requirement described by the ASME B&PV Code Section III.
The made failure, whether the snubber movement will be frozen or free after an ultimate failure, sh&il be deter-mined by the analysis.
4.
DOCUMENTATION 4.1 General The qualification documentation shall verify that the snubber design is qualified for ifs application and meets its specified performance requirements.
The basis of qualification shall be explained to show the relationship of all facets of proof needed to support adequacy of the snubber design.
Data used to qualify the snubber design shall be pertinent to the application and organized in an auditable form.
4.2 Documentation Files The manufacturer shall maintain a file of the qualification plan and data of each specific snubber design tested.
The file shall contain the information listed in Section 3.
Test data shall be recorded as described in Section 4.3.
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4.3 Test Data The test data shall contain:
(1) The snubber functional specifications.
(2) Identification of the specific functional parameter (s) to be demonstrated by the test.
(3) The relative position of the test in the test sequence.
(4) Report of test results.
The report shall include:
(a) Objective of the test (b) The snubber tested (c) Description of test equipment (test setup) and instrumenta-tion used including calibration records reference (d) Deviations from the qualification plan, if any (e) Test procedures (f) Test results (g) Summary,-conclusions, and recommendations (h) Approval signature and date (certification by a Professional Engineer competent in the field of functional and environment testing) 4.4 Post Test Analysis Data After the snubbers have successfully passed or failed the qualifica-tion tests, a post-test analysis shall be conducted.
The results of this analysis shall be a part of the report and shall contain the following information:
(1) Identification of the snubber tested B-9
(2) The last test conducted on the snubber in the test sequer.ce (3) Analysis of the post test snubber condition (4) Summary, conclusions, and recommendations (5) Approval signature and date (certification by a Professional Engineer competent in the field of functional and environment testing)
(6) Disposition of snubber 4.5 Other Information Following information, as applicable, shall be included in the report:
(1) A statement of nonapplicable portions of the specification.
(2) A description of any conditions peculiar to the snubber test which are not covered above, but which would probably affect the performance of the snubber durin.g testing.
- 4. 6 Failures
- Any failures, except those caused by testing equipment or procedure abnormalities, shall disqualify the design.
Revisions to the design must be made before the new design can be qualified in accordance with this Appendix.
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APPENDIX C ACCEPTANCE TESTING CRITERIA FOR THE PRODUCTION OF SAFETY-RELATED SNUBBERS FOR NUCLEAR POWER PLANTS 1
SCOPE This document describes the basic requirements for the acceptance test for the production of snubbers used in safety-related systems in nuclear power plants (snubbers).
These requirements shall apply to all safety-related snubbers in nuclear power plants.
2.
PURPOSE The purpose of this document is to provide guidance for demonstrating the adequacy of fabrication in light of functional requirements for the acceptance of snubbers from the production line.
Acceptance testing is required for all snubbers.
3.
PRODUCTION ACCEPTANCE TEST PLAN A production acceptance test plan (test plan) shall be developed for each model and size of snubber by the snubber manufacturer and shall be submitted to the Owner or his agent to be reviewed for consistency with the Design Specification and for approval.
The production acceptance test plan for c. bbr.rs shall contain the following information:
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a.
Snubber descriptions and specifications, see Section 3.1 b.
Material data, see Section 3.2 c.
Mounting requirements, see Section 3.3 d.
Functional parameters to be measured, see Section 3.4 e.
Test.and monitor equipment requirements, see Section 3.5 f.
The test sequence, see Section 3.6 g.
Limits or failure definition for the test, see Section 3.7 3.1 Snubber Descriptions And Specifications The snubber shall be described in full by its model number, serial number, drawing numbers and total weight.
3.2 Material Data Material data shall be included as follows to assure that the snubber was manufactured according to the specification, and that materials and processes were similar to those used in the qualification tests (Appendix B).
a.
The data or reference from tests conducted to prove the adequacy of the basic design, this should include, for example, the compatibility test between seal material and the hydraulic fluid and the working environment with special consideration given to the c~ombined effects of temperature and radiation on material performance.
A master file of material properties can be referred to.
b.
The data of material and process traceability of the snubber.
These data shall be included to demonstrate that the snubber has successfully met the fabrication requirements.
A material or process traceback will be C-2
possible in case some flaw in material or process and workmanship shess up.
3.3 Test Mounting Requirements The test plan shall specify the way in which the snubber shall be mounted for testing.
The plan shall require that the snubber shall bs mounted in a manner and positions that simulate its expected service installation through standard interface when in actual use unless an analysic can be performed and justified to show that the snubber's per-fermance would not be altered by other means of' mounting.
By manner is meant the means to be used such as pins, bolts, welds, clamps, etc.
By position is meant tne spatial orientation with respect to the gravita-tional field of the earth.
3.4 Functional Parameters To Be Measured The test plan shall specify the method of testing for all functional parameters as specified in the Functional Specification.
As a minimum, the following four functional parameters shall be measured for the snubber test under a recorded temperature ambient.
They shall include: the drag, the dead band, the activation level, and the release rate.
The plan shall also specify that for hydraulic snubbers, the hydraulic fluid leakage during tests shall be measured and recorded.
- 3. 5 Test And Monitor Equipment The test plan shall indicate the equipment and types of sensors Jsed to measure the parameters for the test, and describe the accuracy witnin C-3
the range anticipated for use on the tests.
They should provide rescletion for detecting meaningful changes in the variables.
The test equipment and monitor equipment shall be calibrated against auditable calibration standards and shall have documentation to support such calibration.
The time interval between measurements shall be specified in the test plan so that the time dependence of each variable can be determined.
3.6 The Test Sequence The testing shall include the following tests in the described sequential order as a minimum requirement unless the Design Specification requires otherwi se.
Inservice test behavior shall be considered if it is a requirement.
a.
A free exercising of not less than 30 full stroke cycles shall be made to demonstrate that the snubber unit is in working order.
b.
The determination of all four parameters d.escribed in Section 4.4 under a recorded ambient and snubber temperature with the snubber at 1/2 stroke position.
b.1 The drag shall be determined both for the b Jak away condition and the condition of moving under a specified velocity.
Tests shall be made for both directions.
b.2 The activation level shall be tested for 5%, 10%, 25%, 50% and 100% of the rated load rated load for both directions.
b.3 The dead band of the snubber shall be measured and recorded during the tests as described in Section 3.6.b.2.
b.4 The release rate shall be tested at 5%, 10%, 25%, 50%, and-100%
rated load.
Tests shall be made for both directions.
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b.5 A one-cycle of specified faulted load shall be aoplied at the end of testing to assure the integrity of the snubber under that loading.
b.6 Hydraulic fluid leakage during the testing shall be recorded.
3.7 Limits Or. Fail'ure Definition For The Test a.
The test plan shall specify the limits for the following param-eters as a minimum.
The snubber unit shall not be accepted from the production line if any one of the functional parameters failed to meet the specified limits.
Drao:
Shall not exeed the specified limits, either direction.
Dead Band:
Shall not exceed the specified limit value for the associated loading.
Activation Level:
Shall not ' exceed the specified range, either direction.
Release Rate:
Shall not exceed the specified ranges, either direction, under the specified, loadings.
b.
The test plan shall specify a hydrualic fluid leakage limit for the test of hydraulic snubbers based on the Design Specification requirements.
Inability to meet the leakage limit constitutes a failure and the unit shall not be accepted from the production line.
Hydraulic Fluid Leakaoe Rate:
Shall not exceed the specified limit.
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c.
A post-test analysis shall be made for those snubber units t.'.at failed the test.
Rework to correct the deficiency identified by this analysis is allowed only if the deficiency is not caused by the basic casign.
The reworked snubber unit may be re-tested and accepted if it meets the test requirement.
4.
DOCUMENTATION 4.1 General The documentation of the testing results shall verify that e'ach snubber accepted from the production line has met its specified perform-ance recuirements.
4.2 Documentation Files The manufacturer shall maintain a file of production acceptance test
~
plan and dat; of each specific snubber tested.
The file shall contain the information listed in Section 3.
Test and analysis data shall be recorded as described in Section 4.3.
If a snubber failed to pass the test require-ments, a post-test analysis shall be conducted.
The results of this analysis shall be a part of the documentation as described in Section 4.4.
4.3 Test Data and Records The test data shall contain:
(1) The reference production acceptance plan.
(2)
Report of test results.
The report shall include:
(a) Objective of tests (b) Identification of the saubber tested C-6
(c) Description of test equipment (test setup) and instrumenta-tion used including calioration records reference (d) Ocviations from the test plan, if any (e) Test procedures (f) Test results (g) Summary, conclusions, and recommendations (h) Approval signature and date indicating acceptance or non-acceptance 4.4 Post Test Analysis and Records The post test analysis data shall contain:
(1)
Identification of the snubber tested (2) Tasts in which the Snubber failed to meet the requirement
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(3) Analysis of the post test Snubber condition (4) Summary, conclusions, and recommendations (5) Approval signature and date C-7