ML20136H133
| ML20136H133 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 03/12/1997 |
| From: | Mccoy C GEORGIA POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-05, GL-96-5, LCV-0904-B, LCV-904-B, NUDOCS 9703190061 | |
| Download: ML20136H133 (21) | |
Text
. -
-.. - -.... -. ~. -- -.. ~.- -
4 l
.. Grorgia Powsr Comptny i
40 invzmass Centar Parkway I
Post Office Box 1295 j
' Birmingham, Alabama 35201 Tele' phone 205 992 7122 Georgia Pbwer-C.K.McCoy the southan doctric system 4
Vice President. Nuclear j.
Vogtle Project March 12,1997 LCV-0904-B 7
2 t
Docket Nos.: 50-424 l-50-425 1
U. S. Nuclear Regulatory Commission i
ATTN: Document Control Desk l
Washington, D. C. 20555 3
j Gentlemen:
j
{i VOGTLE ELECTRIC GENERATING PLANT I
GENERIC LETTER 96-05 MOV PERIODIC VERIFICATION PROGRAM -
i 180-DAY SUBMITTAL The U. S. Nuclear Regulatory Commission (NRC) issued Generic Letter 96-05, " Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated. Valves" on i
September 18,1996. The generic letter requests licensees "to establish a program, or to ensure the effectiveness ofits current program, to verify on a periodic basis that safety-related MOVs continue to be capable of performing their safety functions within the current licensing bases of the facility". In response to the generic letter, Georgia Power Company (GPC) has completed a review of the VEGP MOV periodic verification program which was established in conjunction with the implementation of Generic Letter 89-10. The attached document provides a summary of the VEGP periodic verification j
program and the reviews undertaken to ensure its effectiveness.
In addition, Vogtle Electric Generating Plant (VEGP) will participate in the differential pressure testing program which is being undertaken in conjunction with the Joint BWR and Westinghouse Owners' Group Program on Motor-Operated Valve Periodic
)
Verification. The objective of this program is to demonstrate that valve internals do not experience significant inservice degradation, which could lead to increased thrust / torque requirements.- VEGP will perform testing to support this program, and will evaluate the overall results of the test program to ensure that the VEGP periodic verification program i
adequately addresses inservice degradation.
- i,
9703190061 970312 U P"
^"
- W Mppuppppppp
4 J
U. S. Nuclear Regulatory Commission Page 2 1
Should you require any additional information regarding this response, please contact my J
office.
1 a.
Mr. C. K. McCoy states that he is a Vice President of Georgia Power Company and is 1
authorized to execute this oath on behalf of Georgia Power Company and that, to the best -
of his knowledge and belief, the facts set forth in this letter are true.
GEORGIA POWER COMPANY l
By:
.Mk C.K.Mc y
Sworn to and subscribed before me this l1. Day of GA
,1997.
%N l
' NotaryPublic
()
l My Commission Expires: fM. $ l 90 i
G J
i CKM/HET/het i
j Enclosure xc:
Georgia Power Company Mr. J. B. Beasley, Jr.
l Mr. M. Sheibani NORMS j
U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator Mr. L L. Wheeler, Licensing Project Manager, NRR Mr. C. R. Ogle, Senior Resident Inspector, Vogtle LCV-0904-B
1
-l i
I i
Vogtle Electric Generating Plant i
l Generic Letter 96-05 Submittal March 1997
1 TABLE OF CONTENTS
1.0 INTRODUCTION
2.0 STATIC TEST PROGRAM 2.1 Scope 2.2 Static Test Frequency 2.2 MOV Diagnostic Test Equipment 2.4 Periodic Differential Pressure Testing 3.0 POTENTIAL MOTOR-OPERATED VALVE INSERVICE DEGRADATION MECHANISMS 3.1 Motor Operator 3.2 Valves 3.2.1 Gate Valves 3.2.2 Globe Valves 3.2.3 Butterfly Valves 3.2.4 Summary 4.0 POTENTIAL SUSCEPTIBILITY TO INSERVICE DEGRADATION 4.1 Anchor-Darling Gate Valves 4.2 Westinghouse Gate Valves 4.3 Fisher Globe Valves 4.4 Velan Globe Valves 4.5 Fisher Butterfly Valves
1.0 INTRODUCTION
Generic Letter 96-05," Periodic Verification of Design-Basis Capability of Safety-Related Motor-Operated Valves" was issued September 18,1996. The generic letter requests licensees to review their existing motor-operated valve (MOV) periodic verification programs to ensure that safety-related MOVs will continue to be capable of performing their design-basis safety functions. Specifically, the generic letter requests that licensees ensure that their programs " address potential degradation that can result in (1) the increase in thrust or torque requirements to operate the valves and (2; the decrease in the output capability of the motor actuator".
VEGP established a periodic verification program in conjunction with the implementation of the recommendations contained in Generic Letter 89-10. The existing program was reviewed relative to the recomn endations contained in GL 96-05 to ensure that the program adequately addresses the concerns associated with potential inservice degradation. The objective of this document is to summarize the review undertaken to support the implementation of the recommendations contained in GL 96-05 at VEGP, and to identify those activities which will be undertaken to provide additional assurance that the potential for inservice degradation has been adequately addressed.
In addition, it should be noted tha. the work undertaken to support the implementation of the GL 96-05 recommendations was performed based on the assumption that the VEGP GL 89-10 program is acceptable to the NRC. The VEGP GL 89-10 Close-Out Submittal was transmitted to the NRC for review by letter LCV-0136-K dated January 31,1996. This submittal provided a detailed description of the program undertaken to implement the recommendations contained in GL 89-10, and outlined the basis for justifying that each of the valves included in the program is capable of performing its design-basis function. VEGP understands that the NRC is currently reviewing this submittal, and the closure of the VEGP GL 89-10 program is contingent upon the completion of this review.
l 1
2.0 PERIODIC VERIFICATION PROGRAM i
The periodic verification program established in conjunction with GL 89-10 was reviewed relative to the requirements of GL 96-05. Based on this review it was determined that the periodic verification program currently in place at VEGP provides adequate assurance that safety-related MOVs will continue to be capable of performing their design-basis functions. However, the VEGP periodic verification program will be a living program which will be reviewed and adjusted periodically, based on valve performance and maintenance.
2.1 Smp.c The VEGP Generic Letter 89-10 (GL 89-10) program covers a total of 254 safety-related MOVs. The scope of valves covered by Generic Letter 96-05 is considered to be identical to that of GL 89-10.
2.2 Static Test Freauency The VEGP GL 89-10 program requires that valves be statically tested on a 5 year /3 cycle interval, as recommended in GL 89-10. This frequency has not been altered with respect to addressing GL 96-05. However, it is VEGPs intent to prioritize valve test activities based on a combination of risk significance and deterministic considerations. The Westinghouse Owners Group (WOG) is currently developing a generic methodology for use in risk ranking MOVs utilized in Westinghouse PWRs. When completed, this methodology will be evaluated for use in ranking MOVs at VEGP. VEGPs objective is to adjust the static test frequency for individual MOVs to reflect the relative risk significance and available margin while continuing to provide adequate assurance that the MOV will be capable of performing its safety function until the next scheduled test.
2.3 MOV Diagnostic Test Eauipment VEGP currently utilizes Liberty Technology supplied VOTES test equipment to perform MOV periodic testing. Rising stem valves are normally tested utilizing the VOTES Force Sensor, although a variety of additional sensors are available and may be utilized for measuring both thrust and torque. Rotating stem valves j
are normally tested utilizing Torque Plugs although, here again, a variety of additional sensors are available for use as required.
{
In addition, VEGP has procured a Motor Power Monitor (MPM) test system from J
Liberty Technology for use in performing MOV testing from the motor control center (MCC). This system is currently being evaluated for use at VEGP and this system may be integrated into the periodic verification program, as appropriate, l
based on each individual valves relative risk significance and available margin.
,2.4 Periodic Differential Pressure Testina A total of 83 in-situ differential pressure tests were performed in conjunction with the implementation of GL 89-10 at VEGP The objective of this testing was to validate the analytical methodology utilized in the engineering design review.
The results of this testing verified the methodology and provided a basis for establishing switch settings for the GL 89-10 MOVs. The periodic static test program ensures that the MOVs are maintained in an acceptable configuration for the life of the plant. There are no plans to perform long term periodic differential pressure testing at VEGP.
Generic Letter 96-05 raises concerns relative to the adequacy of a static test program to adequately assess potential degradation which may occur inservice.
To address this issue the potential degradation mechanisms which may affect the ability of an MOV to perform its safety-related function are identified and discussed in Section 3 of this document. In addition, the applicability of the valve related degradation mechanisms to the VEGP specific valve types is discussed in Section 4.
Finally, the BWR Owners' Group (BWROG) and the Westinghouse Owners' Group (WOG) have joined together to sponsor the Joint Owners' Group (JOG)
Periodic Verification Program. Included within the scope of this program is a differential pressure test program, the objective of which is to demonstrate that valve internals do not experience significant inservice degradation. The program will address gate valves, balanced disk globe valves, unbalanced disk globe valves and butterfly valves.
VEGP will participate in the JOG differential pressure test program and will perform differential pressure tests on a total of approximately four valves. Each valve will be tested a maximum of three times within a five year period and a preliminary evaluation of the test results will be performed on site. The test data will be forwarded to the JOG Periodic Verification Program for inclusion in the overall program.
l In addition, VEGP will monitor the analysis, evaluation and resolution of the data collected in conjunction with the JOG differential pressure test program. The results of this testing will be evaluated for applicability to VEGP and will be factored into the VEGP Periodic Verification Program as appropriate.
1 r
3.0 POTENTIAL MOTOR-OPERATED VALVE INSERVICE DEGRADATION MECHANISMS In order to ensure that the VEGP MOV program adequately addresses inservice degradation, both the valve and motor-operator were reviewed to identify potential sources of degradation. In addition to evaluating the various degradation mechanisms, a number of the uncertainties associated with the establislunent of MOV switch settings are also discussed, as these issues are also relevant with regard to achieving an acceptable valve setup.
3.1 Motor Operator l
There are a number of factors associated with the motor operator which must be considered in establishing an acceptable valve setup. Many of these factors simply represent random uncertainties which are well understood within the industry, and which are accounted for in the valve setup. However, certain factors do represent potential sources ofinservice degradation which must be evaluated
- ~
and understood to ensure an acceptable valve setup. The various factors which are associated with operator performance are discussed in detail in the VEGP Generic Letter 89-10 Close-Out Submittal, and are reviewed here briefly for completeness.
Toraue Switch Reneatability 4
The control scheme for many gate and globe valves utilize a torque switch to trip the operator in the closing direction. The operator manufacturer, Limitorque, has determined that the repeatability of the torque switch varies as a function of both the torque switch setting and the operator output torque at the torque switch trip j
point. The capability of the torque switch, relative to repeatability, has been quantified and is considered in the establishment of switch settings at VEGP.
Torque switch repeatability represents a random uncertainty associated with the motor operator and is not a degradation mechanism.
J Test Eauioment Accuraev Valve setups are initially established and subsequently verified utilizing diagnostic test equipment. As is the case with all such test equipment there is some finite inaccuracy associate with the data collected utilizing this equipment.
The test equipment manufacturer, Liberty Technologies, has performed extensive testing to quantify the accuracy of this equipment under field conditions and the ultimate accuracy is considered in the establishment of switch settings at VEGP.
l Test equipment accuracy represents a random uncertainty asociated with the test process and is not a degradation mechanism.
4 1
t.
Load Sensitive Behavior Load Sensitive Behavior is a phenomenon in which the thrust at torque switch trip tends to be higher under static conditions than under dynamic conditions. The cause of the phenomenon is not well understood but it is believed to be related to characteristics of the stem, stem nut and stem lubricant. Although extensive iridustry research has been performed to develop a better understanding of this phenomenon, it has not provided sufficient insight to enable a predictive methodology to be developed.
To address Load Sensitive Behavior, the VEGP differential pressure test data was analyzed to quantify the phenomenon. The data was scattered, and in many cases the thrust at torque switch trip actually increased under differential pressure conditions. The data obtained from the test sample was statistically evaluated to quantify the Load Sensitive Behavior phenomenon, and the results of this evaluation are considered in the establishment of switch settings at VEGP.
Although the results of the Load Sensitive Behavior analysis indicate that the
(
]
phenomenon is biased, and therefore does not strictly represent a random uncertainty, there is no evidence to suggest that Load Sensitive Behavior is influenced by an inservice degradation mechanism. Load Sensitive Behavior appears to be primarily related to the stem factor, and so long as the static stem factor is maintained constant over the course of the stem lubrication interval, there is no reason to suspect that any characteristics of the valve which may be associated with Load Sensitive Behavior will change.
Stem Lubrication Degradntion Stem lubrication is important because it directly influences valve stem factors which are essentially a measure of the efliciency of the torque to thrust i
conversion. The lower the stem factor the more efficient the conversion of torque to thrust. Conversely, an increase in the stem factor will result in a corresponding decrease in the available thrust for a given operator output torque.
The stem factor varies as a function of the stem friction coefficient. The primary factor which could cause the stem friction coefficient to vary following the initial valve set-up is a change in stem lubrication. If the stem lubricant looses effectiveness over the course of a lubricant cycle then the stem friction coefficient may increase. If the stem friction coefficient increases there will be a corresponding increase in the stem factor which will result in lower thrust output at the previously established torque switch setting.
At VEGP the stems on safety-related rising stem valves are lubricated with Fel-Pro N-5000 on a 36 month interval. Fel-Pro N-5000 is an anti-seize compound l
l m
4r-
t q
l with a relatively high viscosity. The lubricant was selected due to its ability to provide effective lubrication, in this application, over an extended period of time.
?-
l EPRI performed testing on this stem lubricant in conjunction with the EPRI Performance Prediction Program. The results of this testing indicated that the
{
effectiveness of this lubricant actually improved with use. -To evaluate the lubricant under field conditions, VEGP performed testing on a total of 18 valves at the end of a 36 month lubricant cycle. Each valve was tested in the as-found condition prior to stem lubrication, and in the as-left condition following the application of stem lubricant. There was no measurable difference in the stem
)
factors in the as-found and as-left condition. Based on the results of this testing it was concluded that Fel-Pro N-5000 did not experience any significant degradation over a 36 month interval.
Considering the results of the EPRI testing and the VEGP specific testing, is was j
concluded that Fel-Pro N-5000 does not experience significant degradation over the lubricant interval. Therefore, it is not necessary to include margin for stem lubricant degradation. In addition, the stem factor is routinely monitored in conjunction with the static test program and any changes in the stem factor relative to lubrication degradation would be readily apparent.
Spring Pack Relaxation i
Spring pack relaxation is primarily associated with'normally closed valves in j
l which the spring pack remains compressed for extended periods of time. When l
the spring pack remains compressed there is the potential for the belleville washers to relax to some degree, thereby reducing the spring pack preload. Since i
the operation of the_ torque switch is directly effected by the preload, any.
reduction in preload can result in a reduction in operator output torque at a given i
torque switch setting.
i e
Limitorque performed testing to quantify spring pack relaxation as a function of 4
i spring compression and time. The study evaluated belleville washers at stresses i
up to 230 KSI for time periods up to 24 months. The results of this testing were then applied to various spring pack configurations to determine the n. ;ffect on operator output at various torque switch settings. The results of this study are outlined in Limitorque Technical Update 93-02.
1 i'
Several interesting conclusions can be reached based on a review of the Limitorque test data. First, the data indicates that the majority of the relaxation occurs in the first twelve months of operation. There is very little additional relaxation in the second twelve month period. Second, the total relaxation
[
experienced by the belleville washers has a relatively insignificant effect on the i
torque output of the operator at the maximum nominal torque switch setting. The average total relaxation experienced by the spring packs tested was less than 4%
i
m.
4 t
t which is much lower than the overall accuracy of the equipment utilized to set-up and test MOVs in the field.
Prior to the advent of diagnostic testing, spring pack relaxation would have been a relatively difficult problem to identify. However, with routine periodic testing utilizing diagnostic equipment, spring pack relaxation is easily identified and corrected. The VEGP periodic test program ensures that any significant spring pack relaxation will be identified and corrected before it can have a significant effect on operator output. Therefore, it is not necessary to include margin for spring pack' relaxation in torque switch settings for VEGP valves.
Summary The determination and verification of operator capability is relatively straight forward as opposed to the evaluation of valve thrust / torque requirements. The diagnostic test equipment which is utilized in conjunction with the periodic static test program is capable of providing an in-depth assessment of the condition of the motor-operator. The performance of differential pressure testing does not provide any additional information regarding the condition of the operator beyond that which is obtainable from routine static testing.
Table 3-1 Factors Associated with Operator Performance Factor Susceptible to Detectable in Inservice Degradation Static Test Torque Switch Repeatability No N/A Test Equipment Accuracy No N/A Load Sensitive Behavior No N/A Stem Factor Yes Yes Spring Pack Relaxation Yes-Yes 3.2 Valves The determination of valve thrust / torque requirements is a largely empirical process which in many cases is unique to the specific valve type being evaluated.
The EPRI Performance Prediction Program (PPP) developed a bounding methodology to predict torque / thrust requirements for most of the valve types utilized in nuclear power plants. This methodology was utilized in certain cases to determine valve torque / thrust requirements in conjunction with the VEGP GL 89-10 program.
w m.
=
-w
-s
r In order to assess the potential for valve torque / thrust requirements to change as a result ofinservice degradation, the EPRI methodology was qualitatively reviewed to identify those valve loads which may be susceptible to inservice degradation.
The objective of this review was to identify those parameters associated with determining valve torque / thrust requirements which are not necessarily constant, and which may change inservice. The methodology derived in conjunction with the EPRI PPP program provided a basis frr performing this review because it addresses each of the relevant loads associated with operating the various valve types.
3.2.1 Gate Valves In determining the thrust requirements necessary to operate gate valves, there are three major loads which must be considered.
Packing Friction Force The packing friction force is the force required to overcome the frictional loads encountered when moving the valve stem through the packing. The packing friction load is primarily a function of the stem diameter, packing height, packing preload and the packing to stem coefficient of friction. The packing load is usually small relative to the other loads associated with operating the valve. Therefore, any variat!<ns in the friction coefficient which may occur inservice are generally not significant relative to the overall loads required to operate the valve. In addition, the packing preload tends to decrease over time which results in a reduction in packing loads. Changes in packing load can be identified in conjunction with a static test.
Piston Effect Force The piston effect force is the force caused by the internal line pressure acting on the area of the valve stern. The piston effect force is a function of the valve stem area and the line pressure. The piston effect force does not vary relative to any type ofinservice degradation.
Disk Differential Pressure Force The differential pressure force is the force required to overcome the frictional loads encountered when moving the valve disk against a differential pressure.
The differential pressure force is a function of the disk area, differential pressure and a coefficient of friction. The coefficient of friction may be either the coefficient of friction between the disc and seat or the coefficient of friction between the disc and body guide depending on the position of the valve disc relative to the open and close position. The coefficient of friction may vary in service, therefore, the potential for changes in differential pressure force does
- -.. ~
~~_- - -.
c j
.i..
d exist. A differential pressure test is required to evaluate changes in the differential l
pressure force, a
}
3.2.2 Globe Valves
[
The loads associated with operating a globe valve are very similar to those j
associated with the gate valve. The packing friction force and the piston effect I
force were discussed with regard to gate valves and will not be discussed further here. The primary difference in the determination of globe valve thrust j
requirement is with regard to the differential pressure loads. In addition, the
[-
determination of this load varies between balanced and unbalanced disk designs.
Disk Differential Pressure Force (Unbalanced Disk Design) j.
The disk differential pressure force is the force acting on the disk due to the variation in pressure from the upstream to the downstream side of the disk. The differential pressure force is a function of the disk area for seat-based valves and the differential pressure. The differential pressure force does not vary relative to any type ofinservice degradation.
I j
Disk Guide to Body Friction Force (Balanced Disk Design)
I g
The disk guide to body friction force is the force required to overcome the l
frictional loads between the disk guide and body. The disk guide to body friction force is primarily a function of the disk guide to body friction coefficient, the disc t
guide to bearing load factor, the differential pressure and the guide area. The coefficient of friction may vary in service therefore, the potential for changes in the disk guide to body friction force does exist. A differential pressure test is
{.
required to evaluate changes in the disk guide to body friction force.
3.2.3 Butter 0y Valves j
In determining the torque requirements necessary to operate butterfly valves, there i
are four loads which must be considered.
Bearing Toraue i
The stem bearings oppose the differential pressure load which is transmitted into the stem by the butterfly valve disc. The bearing torque for a given valve size is a I
function of the differential pressure as well as the coefficient of friction between the butterfly stem and bearings. The coefficient,of friction may vary in service, j
therefore, the potential for changes in bearing load does exist. A differential j
pressure test is required to evaluate changes in bearing torque.
i 4
i.
a Seat Toraue The seating torque is the torque required to drive the butterfly disc into the seat rings thereby providing a tight shut-off. For interference type seat designs the seat torque for a given valve size is a function of the seat torque coefficient. The seat torque coefTicient is an empirical factor and may vary, primarily as a function of the condition of the valve seat. The seat torque can be evaluated in conjunction with a static test.
l Packing Toraue The packing torque is the torque required to rotate the valve stem through the valve packing. The packing torque for a given stem size is a function of the packing contact area, the radial packing load and a friction coefficient. The packing load is generally small relative to the other loads associated with operating the valve. Therefore, variations in the friction coefficient are generally not significant relative to the overall loads required to operate the valve. In addition, the radial packing load tends to decrease over time which results in a 1
reduction in packing load. Changes in packing load can be identified in conjunction with a static test.
Hydrostatic Toraue The hydrostatic torque results from differences in the static head of the process i
fluid acting on the valve disc above and below the disc centerline, when the valve stem is horizontal and the downstream piping is empty. The hydrostatic torque is a function of the disk size and the process fluid density. The hydrostatic torque does not vary relative to any type ofinservice degradation.
4 3.2.4 Summary i
The determination and verification of valve thrust / torque requirements are considerably more complex than dealing with motor-operator capabilities.
However, the methodology utilized at VEGP to determine thrust / torque requirements has been validated based on an extensive differential pressure test program. This testing was conducted on a variety of valves in a wide range of i
applications with various operational and maintenance histories. Although the valves were statically tested prior to differential pressure testing to ensure that the operators were setup correctly, in most cases the valves themselves were in the as-found condition and had not been disassembled since plant start-up. Therefore, any internal valve degradation which may have occurred inservice was captured in the differential pressure test results.
j i.
Table 3-2 i
Valve Loads Evaluated for Susceptibility to Inservice Degradation Valve Loads Suscentible Detectable to Inservice in Static Degradation Ic11 Packing Friction (Gate and Globe)
Yes Yes Piston Effect (Gate and Globe)
-No N/A Differential Pressure (Gate)
Yes No Differential Pressure (Unbalanced Globe)
No N/A DitTerential Pressure (Balanced Globe)
Yes No Bearing Torque (Butterfly)
Yes No Seat Torque (Butterfly)
Yes Yes Packing Torque (Butterfly)
Yes Yes Hydrostatic Torque (Butterfly)
No N/A There are a number of parameters associated with valve perfoonance which can not be readily evaluated based on static test data alone. To quai.titatively evaluate changes in these parameters requires in-situ differential pressure test data. In addition, the test data would need to be extremely precise to accurately reflect the relatively minor changes which may occur due to inservice degradation. This precision is not readily obtainable utilizing conventional diagnostic test equipment, in the less than ideal conditions associated with an operating nuclear power plant. Therefore, periodic differential pressure testing does not represent a reasonable and effective alternative for evaluating inservice degradation.
.. _. _ _ _ _ ~ -. _ _ _
i t.
4 1
4.0' POTENTIAL SUSCEPTIBILITY TO INSERVICE DEGRADATION l
In conjunction with the development of the VEGP Generic Letter 89-10 program, the safety-related MOVs were divided into 29 groups. The valves within each group are the same with respect to manufacturer, type, size and pressure class. In certain cases the valve stems and /or operators may be different; however, the internal construction of all of the valves within a specific valve group are essentially identical.
l The valves in the 29 groups represent five major families of valves. With respect to gate valves there are a total of 20 Anchor-Darling valves comprising four of the valve groups and there are a total of 106 Westinghouse valves comprising 13 of the valve groups. With respect to globe valves there are a total of 22 Fisher valves comprising three valve groups and a total of 36 Velan valves comprising i
three valve groups. Finally, there are a total of 70 Fisher butterfly valves j
comprising six of the valve groups.
The methodology utilized to determine the opening and closing thrust / torque requirements for these valves varies from valve family to valve family. The analytical methodology utilized for emh valve family was reviewed individually, with respect to the degradation meci aisms discussed in the previous section, to assess the potential for increases in the calculated torque / thrust requirements i
inservice.
I 1
1 I
i l
l
r.
4.'l Anchor-Darline Gate Valves There are a total of 20 Anchor-Darling gate valves included in the VEGP GL 89-10 program. The valves are all of the flex-wedge design and utilize carbcn steel discs and valve bodies. The disc guide slot and body guides are also carbon steel and the disc face and body seats are hardfaced with Stellite. These valves have been divided into four groups of essentially identical valves as outlined in Table 4-1.
Table 4-1 Anchor-Darling Valve Groups Group Manufacturer Valve Valse ANSI Total Iyne
_ Size Rating Valves AD-1 Anchor-Darling Gate 2.5 Inch 1500 lb 8
AD-2 Anchor-Darling Gate 3.0 Inch 1500 lb 2
AD-3 Anchor-Darling Gate 4.0 Inch 150 lb 4
AD-4 Anchor-Darling Gate 4.0 Inch 900 lb 6
The thrust requirements for the valves in groups AD-1, AD-2 and AD-4 were calculated with the EPRI Performance Prediction Program (PPP) methodology utilizing the default friction coefficients. The EPRI methodology was validated based on an extensive differential pressure test program which included the preconditioning of gate valves to stabilize friction coefficients prior to testing.
The use of this methodology in conjunction with the default friction coefficients ensures that the calculated thrust requirements determined with the EPRI PPP methodology are inherently conservative, and bound any potential inservice degradation.
The thrust requirements for the valves in group AD-3 were calculated with the Industry Standard Equation utilizing a 0.5 valve factor, since the EPRI PPP methodology does not apply to air systems. These valves are located in a service air system and operate against relatively low differential pressures. The industry standard equation is adequate for predicting thrust requirements for valves operating in relatively mild applications of this type.
r.'.
4.2 Westinehouse Gate Valves There are a total of 106 Westinghouse gate valves included in the VEGP GL 89-10 program. The valves are of the flex-wedge design and utilize stainless steel discs and valve bodies. The disc guide slot and the disc face and body seats are hardfaced with Stellite. These valves have been divided into 13 groups of essentially identical valves as outlined in Table 4-2.
i Table 4-2 Valve Groups Group Manufacturer Valve Valve ANSI Total
.Nm Iyne
_ Size Ratmg Valves j
l l
W-2A Westinghouse Gate 3.0 inch 2035 lb 8
W-2B Westinghouse Gate 3.0 Inch 2035 lb 8
W-3 Westinghouse Gate 4.0 Inch 150 lb 4
W-4 Westinghouse Gate 4.0 Inch 900 lb 4
W-5 Westinghouse Gate 4.0 Inch 1525 lb 16 W-6 Westinghouse Gate 6.0 Inch 150 lb 14 W-7 Westinghouse Gate 8.0 Inch 150 lb 6
W-8 Westinghouse Gate 8.0 Inch 316 lb 12 W-9 Westinghouse Gate 8.0 Inch 1525 lb 4
i W-10 Westinghouse Gate 10.0 Inch 150 lb 12 W-11 Westinghouse Gate 12.0 Inch 316 lb 4
W-12 Westinghouse Gate 12.0 Inch 1525 lb 10 W-13 Westinghouse Gate 14.0 Inch 316 lb 4
The thrust requirements for these valves were calculated with the EPRI NMAC equation utilizing a 0.55 friction coefficient for valves in steam service and a 0.60 friction coefficient for valves in water service. The EPRI Performance Prediction Program (PPP) methodology for Westinghouse gate valves was not available when these calculations were performed.
1 The friction coefficients utilized in the calculations were developed from separate effects testing performed in conjunction with the EPRI Performance Prediction Program. The friction coefficients selected for use in evaluating the Westinghouse gate valves represent conservative values for Stellite on Stellite contact as determined by the EPRI PPP. The results of the JOG differential pressure test program will be monitored to ensure that the current friction coefficients provide a conservative prediction of thrust requirements for the Westinghouse gate valves.
c.
4.3 Fisher Globe Valves There are a total of 22 Fisher globe valves included in the VEGP GL 89-10 program. The valves have been divided into three groups of essentially identical valves as outlined in Table 4-3. The valves in groups FG-1 and FG-2 are of the unbalanced disk design and the valves in group FG-3 are of the balanced disk design.
Table 4-3 Valve Groups Group Manufacturer Valve Valve ANSI Inlal
.ML Iyps
_ Size Rating Valves FG-1 Fisher Globe 0.5 Inch 1710 lb 2
FG-2 Fisher Globe 2.0 Inch 900 lb 4
FG-3 Fisher Globe 4.0 Inch 900 lb 16 The thrust requirements for these valves were determined by Fisher utilizing proprietary methodology.
4 The balanced disk design globe valves in groups FG-1 and FG-2 are of a conventional design in which the differential pressure thrust requirements are not influenced by a friction coefficient. The results of the JOG differential pressure -
test program will be monitored to verify that the balanced disk globe valve design is not susceptible to inservice degradation.
The differential pressure thrust requirements for the unbalanced disk globe valves i
in group FG-3 may be influenced by changes in the disk guide to body friction j
force inservice. The results of the JOG differential pressure test program will be monitored to easure that the Fisher methodology provides a conservative prediction of thrust requirements for the balanced disk globe valve design.
i a
l
4.4 Velan Globe Valves There are a total of 36 Velan globe valves included in the VEGP GL 89-10 program. The valves are all of the unbalanced disc, seat-based design. The valves have been divided into three groups of essentially identical valves as outlined in i
Table 4-4.
4 Table 4-4 Valve Groups Group Manufacturer Valve Valve ANSI Total lh Type
_ Size Rating Valves V-1 Velan Globe 1.0 Inch 1500 lb 2
4 V-2 Velan Globe 1.5 Inch 1500 lb 12 V-3 Velan Globe 2.0 Inch 1500 lb 22 4
The thrust requirements for these valves were calculated with the EPRI Perfonnance Prediction Program (PPP) methodology for seat based globe valves.
The EPRI methodology addresses the relevant forces which act upon the valve stem at the point of seating and unseating. The loads associated with operating valves of this type under dynamic conditions are primarily a function of the differential pressure and the seat area. The major dynamic loads are not associated with a friction coefficient, and as such, would not be expected to 4
increase inservice. In addition, valves which are setup based on thrust requirements determined with the EPRI PPP methodology are inherently conservative and bound any potential inservice degradation.
i 4
4 1
A b
4
o-4.'5 Fisher Butterfiv Valves There are a total of 70 Fisher butterfly valves in the VEGP GL 89-10 progrem.
The valves are of the non-symmetrical disc, single oiTset design. These valves have been divided into six groups of essentially identical valves as outlined in Table 4-5.
Table 4-5 Valve Groups Group Manufacturer Valve Valve ANSI
'lotal
.Ma Inc
. Size Rating Valves FB-1 Fisher Butterfly 4.0 Inch 150 lb 4
FB-2 Fisher Butterfly 8.0 Inch 150 lb 28 FB-3 Fisher Butterfly 10.0 Inch 150 lb 10 FB-4 Fisher Butterfly 18.0 Inch 150 lb 16 FB-5A Fisher Butterfly 24.0 Inch 150 lb 8
FB-5B Fisher Butterfly 24.0 Inch 150 lb 4
The torque requirements for these valves were calculated utilizing a combination of Fisher and EPRI NMAC methodology. The dynamic torque requirements were calculated utilizing the Fisher methodology while the packing loads were calculated utilizing the EPRI NMAC methodology.
The loads associated with operating a butterfly valve under differential pressure conditions may' vary due to changes in the coefficient of friction between the valve stem and bearings. The results of the JOG differential pressure test program will be monitored to ensure that the Fisher methodology provides a conservative prediction of torque requirements for butterfly valves.
j