ML20135E597

Forwards Comments on Proposed Rev 1 to Nmac Application Guide for motor-operated Butterfly Valves in NPPs

ML20135E597
Person / Time
Issue date:	03/05/1997
From:	Wessman R NRC (Affiliation Not Assigned)
To:	Varma V NUCLEAR MAINTENANCE APPLICATIONS CENTER
References
NUDOCS 9703070162
Download: ML20135E597 (14)

Text

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y & UNITED STATES s* j NUCLEAR REGULATORY COMMISSION 1

WASHINGTON, D.C. 20666-0001

• • • • • / March 5, 1997 Mr. Vic Varma Senior Project Manager Nuclear Maintenance Applications Center Electric Power Research Institute 1300 Harris Boulevard Charlotte, NC 28262 '

SUBJECT:

COMMENTS ON DRAFT APPLICATION GUIDE FOR MOTOR-0PERATED BUTTERFLY VALVES IN NUCLEAR POWER PLANTS-REVISION 1 (TAC M88898)

Dear Mr. Varma:

i According to your letter of November 4,1996, the Nuclear Maintenance  !

Applications Center (NMAC) is revising the NMAC Application Guide for Motor- 1 Operated Butterfly Valves. This revision is intended to update the methods for predicting butterfly valve toraue based on information obtained from the Electric Power Research Institute (EPRI) Motor-Operated Valve (MOV)

Performance Prediction Program (PPP). On January 13, 1997, the NRC staff provided comments regarding a similar effort for the NMAC application guide on motor-operated gate and globe valves.

i Staff members in the NRC Offices of Nuclear Reactor Regulation (llRR) and Nuclear Regulatory Research (RES), and an RES contractor, have reviewed the proposed revision to the NMAC Application Guide for Motor-0perated Butterfly Valves (Revision 1) as an extension of our review of the EPRI MOV PPP. Our review is being tracked under TAC M88898.

As we stated regarding the guide for gate and globe valves, we consider the proposed revision to the NMAC Application Guide for Butterfly Valves to provide important new guidance on M0V performance. The incorporation into the NMAC Application Guide of the lessons learned from the EPRI M0V PPP, NRC research conducted by the Idaho National Engineering Laboratory, and industry testing programs represents a significant improvement in the inform aion in the previous version of the NMAC Application Guide.

Enclosed are our comments on proposed Revision 1 to the NMAC Application Guide for Motor-Operated Butterfly Valves. For example, these comments incluc'e (1) alerting users of the NMAC Application Guide to the NRC Safety Evaluation (SE) on the EPRI MOV PPP (and the applicability of the SE to information in the NMAC Application Guide), (2) suggesting that the validation of methods in the r/

NMAC Application Guide other than those associated with the EPRI M0V PPP 5e discussed in more detail, (3) clarifying that some of the references in the 4

NMAC Application Guide have not undergone peer review, and (4) alerting users of the NMAC Application Guide to potential valve degradation. pf@ 2

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V. Varma 2 If you have any questions on the enclosed comments, please contact Thomas Scarbrough of my staff at 301-415-2794.

Sincerely, Richard H. Wessman, Chief Mechanical Engineering Franch Division of Engineering Office of Nuclear Reactor Regulation

Enclosure:

As stated Distribution: ~ ,

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j APPLICATION GUIDE FOR MOTOR-OPERATED BUTTERFLY VALVES j REVIEW AND COMtENTS 4

U.S. Nuclear Regulatory Commission Sheet 1 of 12 Centacts: T. Scarbrough and G. Weidenhauer March 1997 Telephone: 301-415-2794 and 301-415-6015 j Page, Para, Comments or Recommendations Disposition f Reference of Comments S O

l Cover Page To be consistent with Volume 1 for Gate and Globe valves, the title should be changed to:

" Application Guide for Motor-0perated Valves in Nuclear Power Plants - }

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, Volume 2: Butterfly Valves."

l l Cover Page Change "NP-66600" to "TR-106563" in the parentheses under the title.

General The Application Guide should indicate limitations and conditions on use of the EPRI MOV l

Performance Prediction Program (PPP) methodology. Specifically, appropriate limitations and conditions established by EPRI on its MOV PPP methodology and the additional limitations and conditions included in the NRC Safety Evaluation on the EPRI MOV PPP methodology should be indicated in the Application Guide at the applicable locations. ,

Also, insert the following new paragraph at the bottom of the page:

"When using the EPRI MOV PPP methodology, the users must review the NRC Safety Evaluation (SE) dated March 15,1996 (and its supplement) for limitations and conditions regarding the methodology. Users of this NNAC Application Guide must also review the SE and its supplement for applicable limitations and conditions."

3 G:neral The reference documents in the Application Guide were not evaluated as part of this l review.

1 General In the EPRI MOV PPP for butterfly valves, equations and methodologies were compared with test results as part of a validation. The NRC staff has not evaluated other methods in this guide. The validation of those methods should be discussed in more detail.

General The document should identify those sections and equations which rely on unreviewed references and have not undergone peer review.

! General The Butterfly Valve Application Guide should indicate whether the 15 feet /second flow limit from the Gate and Globe Valve Application Guide is also a limit for butterfly

{ valves.

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U.S. NRC Sheet 2 of 12 I

l Page, Para, Comments or Recommendations Disposition Reference of Comments f Page 1-6 In the second bullet at the top of the page, replace " Operability" with " Capability" 4

Page 2-2 Revise the first full sentence to read: "It was concluded that most of the previous

problems with butterfly MOVs resulted from misapplication and inadequate design i qualification (including evaluation / sizing procedures) and maintenance."

l Page 2-3 Delete the last sentence of the first paragraph stating that all testing of the EPRI MOV 4

PPP was conducted in accordance with 10 CFR 50 requirements. See NRC Safety Evaluation.

! Page 2-3 At the end of the page, reference the NRC Safety Lvaluation dated March 15, 1996, on the

) EPRI MOV Performance Prediction Methodology (PPM) and NRC Information Notice 96-48 which

discusses lessons learned from the EPRI MOV PPM (including the need to update the EPRI 3 Butterfly Valve Application Guide).

4 Page 3-5 The self-closing aspect of the butterfly valve is not true in all designs and i Bullet 6 installations. Over-reliance on self-closing aspects of butterfly valve performance may cause problems. In any direction, the actuator must be capable of ,vercoming resistance to movement, including exceeding the friction on the self-locking gears even when the disc is self closing. Dependance on seating torque capability to overcome all resistive loads may be adequate if the seating torque is very large. However, one of the butterfly l valves in the EPRI progrhe did nct seat in the ir- situ tests. This bullet should be deleted or revised to reduce the emphasis on selr-closing aspects of butterfly valve

, performance.

Page 3-5 Revise the sentence beginning on line 9 from bottom of page to read as follows

! Line 9 "As discussed in Section 2, most problems with butterfly valves in nuclear power plant i from bottom systems result from misapplication, and inadequata design qualification (including j evaluation and sizing procedures) and maintenance."

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U.S. NRC Sh;st 3 of 12 Page, Para, Comments or Recommendations Disposition Reference of Comments Page 3-15 Lines 9 through 13 identify friction coefficients for bearings. References for these Para 3.1.4 coefficients should be included.

! Page 3-19 Insert the following paragraph at the bottom of the page:

i "The user is cautioned that the closing and opening thrust requirements will depend on the condition of the elastomer seals. Therefore, the effects of degradation on the elastomer must be considered to ensure proper valve function when required."

Page 3-22 At the end of line 2, insert the sentence: "The actuator should not be set such that the torque switch trips upon torque applied to the position-limiting stops."

l Page 3-22 At the third sentence in the first full paragraph, insert the following: " Care must be j taken to ensure proper connection of HBC operator to the valve stem."

Page 3-24 At the end of the third bullet, insert the sentence: "The torque switch should not be set to trip upon torque applied to the limit-position stops."

Page 3-29 The last paragraph should include the aspect ratios of the valves.

3 Page 3-30 Figure 3.10 should include the aspect ratios and diameters for the symmetric and the offset valves.

Page 3-33 Delete the word "somewhat" in the first line at top of page.

Page 3-33 Additional information should include the aspect ratios and the diameters of the valves identified in the second paragraph below Equation 3.6.6. Also, this information should be included in Figure 3.12.

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1 U.S. NRC Sheet 4 cf 12 Page, Para, Comments or Recommendations Disposition i

t Rsference of Comments l Page 3-36 In the last paragraph, it is stated that, for those valves where no testing was performed

by the manufacturer to determine the pressure drop ratio factor, the values on

Figure 3.14 can be used to calculate the pressure drop under choked flow conditions. '

Figure 3.14 shows that the pressure drop ratio factor can change by as much as 50%

l depending on the manufacturer. Justification for this statement should be included and

additional information on valve sizes and aspect ratios should be given on Figure 3.14.

Page 3-40 The sentence beginning in line 4 states that hardening of the elastomeric seats increases 4

the seating torque but not the unseating torque. This statement should be further i

s explained and justified with a reference to. specific supporting test results.

Page 3-41 Section 3.7.1.2 states that the bearing torque can be calculated using " valve manufacturers' bearing torque coefficients." One of the lessons learned from the EPRI j

testing program was the need to update the bearing torque coefficients. The Application l Guide should refer to " justified" bearing torque coefficients in light of recent test results.

! Page 3-48 Delete "Recent" before " test data" in the tenth line from the bottom of the page because much of the data is not recent.

Page 3-49 Add "and should not be attempted." to the end of the last sentence in the first paragraph j S3.7.3.2 under Section 3.7.3.2.

l Page 3-62 In the fourth line, the word " negligible" should be replaced by "small" because the 10% r j factor indicated in the parentheses may not be negligible.

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! Page, Para,- Comments or Recommendations Disposition

. Reference of Comments

Page 3-63 At the top of the page, the discussion of the torque predictions for continuous pipe flow

! bounding the free discharge may be misleading. In the case of free discharge blowdown, i the differential pressure across the valve can be higher than the continuous pipe flow

case. The validation of this methodology is based on one small valve test at low l pressure. The conclusions in the Guide are not well founded. Pipe rupture calculations l should be based on the worst case scenario for the valve.

! Page 3-63 Insert "having discs of greater thickness" following the word " designs" in the fourth line from the bottom of the page.

4

Page 3-65 In the last paragraph on the page, the Application Guide relies on manufacturers' data to validate its model. NRC-sponsored and industry butterfly valve testing has shown, in a j large number of cases, that manufacturer's theoretical performance curves were not conservative.

j Page 3-68 The Application Guide should note that the EPRI Topical Report, the NRC Safety Evaluation, and the NRC Questions /EPRI Answers on the EPRI butterfly model include

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l j several conditions and limitations.

Page 3-68 Section 3 does not identify that the generalized model is limited (without adders) to Item 2 valves with an aspect ratio of 0.25 or less. Where applicable, limitations should be j clearly listed at the beginning of the discussions throughout the Guide.

Page 3-68 The guidance for shaft upstream valves with aspect ratios higher than 0.35 is not clear.

Item 3 The Application Guide should discuss the determination of whether the dynamic torque exceeds the seating torque. The Guide should indicate whether it has eliminated valves with greater than 0,35 aspect ratios from its scope.

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! U.S. NRC She:t 6 of 12 l

Page, Para, Comments or Recommendations Disposition

, R2ference of Comments

) Page 3-70 The additional features of the EPRI PPP that "are not included in this guide" appear to j Item 11 be limitations for the Application Guide. The NRC Safety Evaluation and NRC 1 i Questions /EPRI Answers also include limitations and conditions. These considerations l should be clarified.

Page 3-71 The Guide states that the "PPP model provides predictions for double offset disc valves Item (d) using detailed disc geometry. However, the double offset disc valve was not validated at j

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the time of releasing this Guide." The double offset disc model was not validated in the PPP at the time it was released. While there is information regarding double offset disc 4

valves, the methodology was not validated as part of the EPRI PPP.

l Page 3-74 In the second line of the first paragraph, change " Figure 3.23" to " Figure 3.24."

i l Page 3-74 In the third line of the second paragraph, correct the spelling of " indicated."

Page 4-3 Replace " operability" with " capability" in lines 2, 9 and 26.

1 l Page 4-3 The third paragraph states that, for hydraulic systems that have multiple flow paths,

advantage can be taken of lower pressure drops across the butterfly valve by using the i detail hydraulic network analysis procedures shown in Appendix C. The NRC Safety 4 Evaluation on the EPRI MOV PPP states that users should ensure that the model is

consistent with design-basis conditions. A provision should be included in the

Application Guide for a review of the design-basis requirements. The review of reduced .

differential-pressure analysis should be compared with the design-basis requirement.  !

~l Parallel paths included in the reduced pressure analysis may not be operational under the design basis requirement.

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Page 4-8 Section 4.7.5 on parallel branches should also reflect design-basis requirements.

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! Page, Para, Comments or Recommendations Disposition i

Reference of Comments Page 4-9 Add another bullet stating: " Installation and removal of diagnostic equipment" l Page 5-3 In the second paragraph, the Application Guide should state that every valve must be ,

analyzed for its dynamic torque under the actual system conditions that might exist. For 1 example, valves opening against voided downstream lines may have higher flows than will '

be experienced after the lines are full and normal conditions are established.

Page 5-3 In the third paragraph, the Application Guide should note that velocity limits

established by the manufacturer only apply to the valve and not the system in which it j was installed. Users should not assume that the valve was specified correctly for the

system conditions. Dynamic torque calculations should be made to ensure valve operation.

1 Page 5-4 A new sentence was added to Section 5.2 stating that in situ testing may be necessary to account for degradation in valve seats, bearings and packings. However, the next i sentence in Section 5.2 continues to reference procedures in later sections for

calculating these torque components. Section 5.2 should be revised to indicate that

those procedures might not account for degradation.

! Page 5-6 The EPRI PPP requires a static diagnostic test to determine actual seating / unseating loads. Following a diagnostic test, the discussion presented in this section could be used to understand aging degradation of the seat and the possible increase in load. The

Guide should require a diagnostic static test as a minimum because in many butterfly

} valve applications the seating / unseating load may be the design-basis load. The same

comment applies to Section 5.2.3 on packing torque and Section 5.3 on hub seal friction i torque.

1 Page 5-14 Table 3.1 should include the aspect ratio limitations.

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! Page 5-15 The validation of Equation 5.3.5 on compressible flow should be discussed including test

results. Further,-the use of differential pressure versus upstream pressure in the j equation should be explained.

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U.S. NRC Sh ct 8 cf 12 Page, Para, Comments or Recommendations Disposition R2ference of Comments Page 5-35 The example discussion should note that the line model must be consistent with the licensing basis of the facility including the single failure criterion.

Page 5-43 Section 5.5.2 provides an example of Containment Purge Valve analysis. After the TMI-2 accident, the NRC and industry analyzed containment purge and vent valves for closing against the design-basis accident conditions. Many of these valves were blocked at less than full open because of actuator limitations. Since then, the question of two valves in series and their effect on operational requirements has been raised. For most valve types, this is not a problem because pressure drop is the only consideration. However,

for butterfly valves, upstream disturbances can add to the torque required to operate the

, valve. The skewed flow from the upstream valve should be accounted for when both valves are closing in series. Many purge and vent valves are not motor operated. The Application Guide should include a caution to alert users that other types of operators may have to supply full motive power in both directions.

Page 6-4 Section 6.1.2 should reference NRC Information Notice (IN) 94-69, " Potential Inadequacies in the Prediction of Torque Requirements for and Torque Output of Motor-Operated Butterfly Valves," and IN 96-48, " Motor-0perated Valve Performance Issues." These information notices alert licensees to the potential for higher motor torque above ratings, lower actuator efficiencies than published values, and greater degraded voltage exponentials than typically assumed. High temperature can also reduce motor output.

These differences in standard assumptions can result in lower actuator output than predicted by typical calculations. Limitorque has stated that updated guidance on actuator sizing will be issued in the Spring of 1997. The information in the Application Guide might need to be revised (including the tables in Section 6) based on the new limitorque guidance.

Page 6-4 Section 6.1.2 should alert users that they are responsible for contractor studies, such as those predicting greater overstress capability of actuators. See pages 4 and 5 of Enclosure 1 of Supplement 6 to Generic letter 89-10.

l U.S. NRC Sheet 9 of 12 Page, Para, Comments or Recommendations Disposition

R2ference of Comments Page 6-13 Note 4 should be revised to delete the implication that pullout and run efficiencies are

guaranteed by Limitorque. In the last sentence of Note 4, the phrase "and the actuator j stall torque calculation" should be included after " stall efficiency" when indicating these should never be used to estimate actuator output thrust capability.

4 Page 6-15 The Application Guide should state that setting the torque switch to trip when striking the limit stops could lead to overstressing the operator.

! Page 6-16 The example calculation should include the cautions regarding actuator output capability i discussed in the previous sections.

Page 8-1 Reference 1.1 to the EPRI Application Guide should be changed to " Volume 1: Gate and

Globe Valves, TR-106563VI."

Page 8-3 Reference 1.25 should be updated to ASME QME-1.

Page 8-4 The Application Guide should reference the NRC Safety Evaluation (dated March 15,1996) on the EPRI MOV Performance Prediction Program and upcoming supplement.

i Page 8-12 The title of Section 8.4 should include " Generic Letters"

. Page 8-12 Section 8.4 should include references to NRC Information Notice (IN) 93-74, "High

Temperatures Reduce Limitorque AC Motor Operator Torque," IN 94-67, " Problems with Henry Pratt Motor-Operated Butterfly Valves," IN 94-69, " Potential Inadequacies in the

Prediction of Torque Requirements for and Torque Output of Motor-Operated Butterfly

Valves," IN 96-30, " Inaccuracy of Diagnostic Equipment for Motor-Operated Butterfly Valves," and IN 96-48, " Motor-Operated Valve Performance Issues."

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U.S. NRC Sheet 10 of 12 4

4

, Page, Para, Comments or Necommendations Disposition Reference of Comments Page A-7 The second paragraph under Section A.3.1 states that the peak total dynamic torque for a large percentage of butterfly . valves occurs at small disc opening angles. For a large

number of low-flow, low-pressure butterfly valves, the statement may have merit, but j should not be assumed without evaluation.

1 4

Page A-7 The last sentence on page A-7 and first sentence on page A-8 are duplicates.

Appendix B The Application Guide should note that design-basis requirements must be considered in

! ar.d C modeling the butterfly valve fluid system.

! Page C-9 Correct " depend" in fourth line.

l Page D-9 The last sentence states that the EPRI testing showed this upstream elbow model to be i conservative. EPRI testing was conducted with water aad extrapolation of the model to j compressible flow is based on engineering judgment. It is not known whether the model is j conservative for gas flow. Further, NRC-sponsored testing at INEL did not move the elbow 4

in relation to the valve inlet.

i Page D-13 The -tatemeri that the Upstream Elbow Model is conservative should be justified with a l discussion of applicable validating material.

Page D-16 Section D.3.2 discusses pipe breaks at the valve and downstream of the valve. The EPRI i flow loop testing at low pressure and low flow with a 6-inch valve was not sufficient to fully validate the discussion. For the same differential pressure at the valve, the discussion may be valid. However, the differential pressure and the flow rate across the valve will not be the same and the torque must be computed on the differential pressure and the flow rate across the valve.

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U.S. NRC Sheet 11 of 12 Page, Para, Comments or Recommendations Disposition R3ference of Comments Page D-30 Item I states that the effect of upstream and downstream disturbances on the flow coefficient and hydrodynamic torque may be neglected in certain cases. This assertion should be justified with test information.

Page D-33 Item I of the Application Guide discussed a suggested factor of 1.5 for worst-case orientation for an elbow located at the valve inlet. The INEL testing involved air flow through purge and vent valves where, except for the containment penetration piping, most of the " piping" is sheet metal ducting, which is likely to be blown off under design-basis accident conditions. Also, many of these valves are blocked at some partial open position. The INEL testing did not move the elbow in and out from the valve to determine the extent of the elbow effects. The basis for the assumption in the Application Guide of 8 pipe diameters have an insignificant effect on compressible flow should be discussed. Further, the downstream conditions could be considerably different for compressible fluids.

Page D-34 In Item 3, the Application Guide should discuss whether the INEL critical flow results applicable to pumped flow incompressible conditions and the basis for this conclusion.

Page D-34 In Item 4, the broad base assumption that isolation valves do not have to open under postulated accident conditions may be true for purge and vent valves. Other isolation valves may be required to reopen after isolation. The design basis for each isolation valve should be verified.

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U.S. NRC Sheet 12 of 12 Page, Para, Comments or Recommendations Disposition Reference of Comments j Page F-1 EPRI established minimum in-situ flow and pressure requirements for extrapolation. The

Application Guide should also specify the minimum requirements and the basis for those i

requirements.

Page F-2 The sixth bullet on valve pressure drop should note that these measurements should be taken as close to the valve as feasible.

Page F-3 In line 13, the spelling of " elastomeric" should be corrected.

Page F-4 Delete comma from line 4.

I Page F-4 The last two sentences in the middle paragraph relate to high bearing friction and possible damage. Additional information on detecting this condition should be included.

Page F-6 Delete "a" at the end of the sixth line under Section F.3.

Page F-7 Delete comma from second line of Item 4.

Page F-9 The need for the factor of 12 should be verified in Equation F.4.1.

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