ML20212L307

Forwards Addl Info Re Facility safety-related motor-operated Valve Program,Per NRC 870219 request.Motor-operated Valve Program,Revised to Incorporate New Info & Response to IE Bulletin 85-003 Also Encl

ML20212L307
Person / Time
Site:	Callaway
Issue date:	03/05/1987
From:	Schnell D UNION ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-85-003, IEB-85-3, ULNRC-1456, NUDOCS 8703100348
Download: ML20212L307 (54)

Text

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n 1901 Gratiot Street. St. Louis Donald F. Schnell Vice President March 5, 1987 U.S.

Nuclear Regulatory Commission 1

' ATTN: Document Control Desk Washington, D.C.

20555 Gentlemen:

ULNRC-1456 DOCKET NUMBER 50-483 CALLAWAY PLANT SAFETY-RELATED MOTOR-OPERATED VALVE PROGRAM

References:

1)

NRC I & E Bulletin No. 85-03 dated November 15, 1985 2)

ULNRC-1309 dated May 14, 1986 3)

C.

E.

Norelius letter to D.

F. Schnell dated August 1, 1986 4)

ULNRC-1372 dated September 19, 1986 5)

ULNRC-1387 dated October 17, 1986 6)

C.

E.

Norelius letter to D.

F.

Schnell dated February 19, 1987 Reference 5 transmitted the Union Electric response to I & E Bulletin 85-03 which documented the MOVATS safety-related motor-operated valve (MOV) program.

The additional information concerning the MOVATS program, as requested by the NRC staff in reference 6, is provided herein as Enclosure 1. to this letter is the Union Electric MOV program which is being resubmitted in a revised form to incorporate the information found in Enclosure 1.

Revision bars in the margin annotate where changes to the program have been made.

If you have any additional questions, please contact me.

Very truly yours, m

8703100348 B70305 PDR ADOCK 05000483 O

PDR Donald F.

Schnell WEK/ dis g

Enclosures g

I l

Mailing Address: P.O. Box 149, St. Louis, MO 63166

STATE OF. MISSOURI-)'

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SS

~ CITY OF ST. LOUIS )

Donald F. Schnell, of-lawful age, being first duly sworn upon' oath says that he is Vice President-Nuclear and an-officer of Union Electric Company;'that he has read the. foregoing. document and knows the content thereof; that-he has executed the same for and on behalf of said company with full power and authority to do so; and that the facts therein stated are true and' correct to the best of1his

. knowledge, information and belief.

By Donald F.

Schnell-Vice~ President Nuclear SUBSCRIBED and sworn to before me this day of 198 f

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3 lu.

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ccs 1Geraldicharnoff, Esq..

Shaw,'Pittman,.Potts'& Trowbridge.

2300 N.. Street,JN.W.:

. Washington, D.C..

20037.

J. O. Cermak~

'. C FA, Inc.

3356 Tanterra circle:-

-Brookville,-MD 20833

-W.'L.

Forney Division of Projects and Resident Programs,-Chief,.Section lA U.S. Nuclear Regulatory Commission

-Region III

799 Roosevelt Road Glen Ellyn,-Illinois 60137 Bruce Little Callaway Resident Office U.S. Nuclear Regulatory Commission RR#1 Steedman, Misuouri-65077 Paul'O'Connor (2)

Office of-Nuclear Reactor Regulation U.S. Nuclear-Regulatory Commission Mail Stop 316 7920 Norfolk Avenue.

Bethesda, MD-20014 Manager,~ Electric Department:

Missouri Public Service Commission P.O.' Box 360 Jefferson City, MO 65102

/

Encic;ura 1 ULNRC - 1456 UNION ELECTRIC RESPONSE TO NRC QUESTIONS CONCERNING MOVATS MOTOR OPERATED VALVE PROGRAM 1)

How is the calculated delta P load listed in Table 2 of Attachment B of your response of 10-17-86 added to the stem thrust signature without delta P in order to obtain the unseating thrust for a given valve?

In particular, if a constant delta P load is used, at what point of the signature without delta P is the delta P adder applied in order to deter-mine the value of unseating thrust (Tu)?

NOTE: Please refer to the sketch on the next page for clarification of Question 1.

Response

The signatures during valve / operator testing without differential pressure are used to determine the approximate running load after unseating (Point A on the attached figure). The calculated thrust required for valve operation with differential pressure is added to the thrust at point (A) to establish the minimum thrust at torque switch trip. This is the methodology which was used in verifying MOVATS equations.

In our 10-17-86 submittal, the above calculation is used to ensure that the torque switch is above the unseating thrust that will occur with AP.

We had committed to doing one time AP testing in the open direction specifically for the purpose of verifying the actuators are of sufficient capacity to overcome this cracking thrust. Since our 10-17-86 submittal, MOVATS' research has been able to show that their equation for calculating opening thrust due to AP will also bound the actual cracking thrust with AP.

Due to the results of this research, we have revised our submittal to no longer require one time AP testing in the open direction.

The cracking thrust measured without AP as well as the calculated opening thrust with AP will be verified to be less than the MOV design thrust.

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- 2)f Is.Valvel27 of Table.'2 of-Attachment B of you response of110-17-86 meant.to' have a Size 1= operator? It appears to be grouped incorrectly with Size 00-

-operators.

~ Response:-

'The information for Valve 27 in Table 2.is. correct as shown.

_ he T

valve was equipped with Size 00 operator.~- -The MOVATS calculation

'shows that the valve, operating under the stated ~ differential pressure conditions could require'a thrust value greater'than the SMB-00 rating. However,~ the actual test data indicated that the valve opened at 13,584 pounds, which is less than the operator's rated output.

Valves which'have' calculated thrust values higher than design rating will be evaluated on a case by case basis (change operator, lower AP requirement, get extension of operator design rating, etc.) A state-ment addressing this situation will be-added to our submittal.

3)'

Why are valves'HV-5,

-7,

-9, and -11 of the AFW System excluded from the list.of valves for which bulletin actions are required, particularly in view of the observations that they are safety-related M0V's and that they-could be left closed inadvertently?

Per Page 1 of Enclosure 2 of your response of 10-17-86, these valves are taken to be exceptions to the WOG methodology because they are used for flow contro1' purposes at Callaway. The possible. problems that the system would be inoperable if these HOV's were left closed inadvertently should be addressed.

Response

These valves were excluded in our submittal because they were not included in our Section X1 Pump and Valve Program. Our Section XI Program has since been revised and these valves were added. These valves will be included in our response to this bulletin.

4)'

Is valve stem drag caused by the packing checked in accordance with mainte-nance procedures?-

Response

Thrust and motor load signatures will reflect valve stem drag as part of the running load. Running loads will be compared to Threshold values for determination of acceptability during our MCC testing to be performed once.per fuel cycle. 03/03/87

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S-J.Our submittal relies on ASME Section XI. retest requirements for fverification;of operability following minor maintenance on the valves.

l(i.e.fpreking' adjustment, adding lubrication, etc.).

Following major maintenance activities-(i.e. disassembly'of valve or actuator,

~

(replacement:of spring pack, etc.) a complete' MOVATS signature 1 analysis

.~will be' performed.

.We feel that this item addresses possible deficiencies in the ASME

~

Section XI Code testing requirements. LWe feel these possible deficiencies should be addressed by going through the appropriate code-committees and review processes 1to get the Code changed..This will ensure that the-proper reviews of additional cost to the industry, additional safety margin gained, etc., are completed.

5)

~ Is data available to-justify the.following-statement at the bottom of

-Page 4 of Enclosure 2 of your response of 10-17-867 "Since cracking thrustJpeak does'not occur.on the closing cycle, actuator thrust capacity will not be exceeded during this initial phase of valve travel'in the closed direction and need not be tested for this capability."

The following items should be addressed in considering the validity of the-

' foregoing statement:

a)

Has the effect of different torque switch settings for opening and

closing been taken into account?

b),

Has the effect of the torque switch bypass settings for opening been taken into account?

c)

Has the effect of en'd pressure on th'e valve stem (piston effect) been considered?

Response

" Cracking thrust" is defined as the force required to set the valve disk into motion.

Cracking thrust is affected by static friction coefficients and forces.between;the disk and the seat and guide surfaces.

When a valve is closed, forces develop between the disk and seating surfaces.- A cracking thrust is required to open a valve from'the fully closed position.

If a valve is in the open position, but is not backseated, there is essentially no perpendicular force between the disk and disk guide.

Static friction forces under these conditions are very small. As a result, cracking thrust is so small that it often cannot be observed or measured. 03/03/87

l Our submittal ~ utilizes different' equations for setting the open torque switch and close torque switch. Part of the difference in these equations is due to the piston effect.

6)

A continuing program for flow and pressure testing of at least some motor operated valves is needed in order to provide assurance that the method-ology and empirical formulas, as outlined, are acceptable. This program should be explicitly outlined by MOVATS, Inc. The lack of test data to support the MOVATS empirical formula concerning closure against flow is of particular concern.

Response

Since our original response, MOVATS has continued to compile flow and pressure testing results. Sufficient data is available to demonstrate the adequacy of MOVATS equations for opening gate valves against differential pressure. The data base also has been shown to be adequate for relatively small globe valves.

The data base does not include sufficient test results to validate MOVATS equations for closing flex and solid wedge gate valves or for operation of globe valves with orifice sizes less than 1.75 or greater than~2.0 inches.

Because of present data base limitations, the testing program at Callaway will include one-time differential pressure testing of representative valves in the closing direction.

In our revised submittal to be issued with these answers, we would like to propose that rather than have everyone test all their valves to verify the closing equations, the equations will be considered accurate for a particular valve if a certain number of valves with the same type and/or size have been tested. We propose that sufficient data to verify the equation is provided by four (4) valves of the same type and size or twenty (20) valves of the same type but various sizes.

7)

Recommendations should be made by MOVATS regarding the frequency for each test or verification.

If the MOVATS recommended schedule is not followed by a licensee, an explanation should be provided. Any conflicts with ASME Section XI testing should be addressed.

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Response:'

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.MOVATS. states that they are not in a position.to-determine the proper; frequency of. testing for each utility and circumstance. However, p.:

MOVATS'has advised us that the baseline test'on each valve.would not have to be repeated unless extensive maintenance is performed that couldiaffect.' operator thrust development. Examples.of actions requir-

,ing; retest. include torque switch replacement and mechanical disassem

bly of the operator.

MOVATS'also advises.that motor load testing from the Motor Control Center should be considered once per fuel cycle and after any mainte-nance that could affect operator performance. Examples of the latter L

case are packing adjustments, mechanical disassembly / reassembly of the valve, and obvious degradation of lubricants due to harsh environ-ments.

Union Electric's submittal on 10-17-86 committed to performing the

" baseline" test initially to set up the valve, following extensive maintenance that could affect operator thrust development, and once every four. refueling cycles. We committed to performing the motor load testing from the Motor Control Center once per fuel cycle. As addressed in question 4, retest following minor valve maintenance (packing adjustment, etc.) is covered by ASME Section XI.

The test frequencies specified above are longer than most of the Section XI, testing frequencies of quarterly but are about the same as the frequency generally accepted for relief requests. At this time.

'the testing for'this Bulletin is not intended to replace Section XI testing for these valves.

8)

In Table 2 of Attachment B to the October 17, 1986 letter from Union Electric Co. the notation "NC" is undefined. Also, an explanation should be provided for blank entries'..It is also noted'that several actual values are very close to calculated. Since the MOVATS formulas include a factor which, in the NRC discussions with MOVATS, was represented as being quite conservative, the closeness of the values should be explained.

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Response

"NC" was used to indicate that the thrust required for valve closure could not be computed (measured) because the value was less than the operator spring pack preload. Valve 35 on sheet 3 of Table 2 should have included a calculated open load of 6777 pounds.

The other blank entries indicate that no test data was obtained for the particular valve in one stroke direction. The above explanations will be added to the submittal.

An explanation of the development of the calculational method and its accuracy is presented with question 11.

9)

On page 4 of Attachment B to the October 17, 1986 Union Electric Co.

submittal, the formula for thrust against flow includes a differential pressure term. The precise definition of what is meant by differential pressure should be explained because differential pressure will vary until the valve closes.

Response

The equations for expected thrust use the maximum differential pres-sure that will be encountered during the opening or closing stroke.

The maximum differential pressure is generally developed with the valve in the fully closed position. This will be clarified in the submittal.

10) A plot which compares actual vs. computed thrusts for gate valves in the open direction is included in Attachment B to the October 17, 1986 Union Electric Co. submittal. No plot was submitted for the close direction.

This should be explained or the plot should be furnished.

Response

Plots of current data are attached.

Included are plots of test results.for thrusts to open and close standard solid and flexible wedge gate valves and standard globe valves. 03/03/87

11) The method used to arrive at the empirical formulas, including each of the numerical factors would be explained in detail.

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Response

Early in 1986, MOVATS Incorporated began to develop mathematical models and compile test data to compute valve thrust requirements.

They started by looking at the various equations people in the valve industry had been using for years for calculating total thrust. From these equations, they pulled out portions which were affected by differential pressure. Disk-to-seat friction forces (seat load) were calculated assuming standard friction coefficients for a variety of valve types.

A " wedging factor" accounts for disk distortion that can lead to increased friction forces under differential pressure conditions. The factors influencing " wedging" are differential pressure, valve orifice area, and a representative friction coefficient.

The sum of calculated seat and wedging forces closely matches the observed forces required to open typical gate valves (based on analy-sis of test data using linear regression techniques).

Even though the model matches the "best fit" of the test data, there is considerable variation in actual test results. Many valves re-quired more thrust than that computed from the " seat load plus wedging load" model.

As a result of the test data variation, MOVATS used a statistical approach to refine the mathematical model. The test data were ana-lyzed using regression and analysis of variance (ANOVA) techniques. A scaling constant was introduced to provide greater than 95 percent confidence that the model will produce conservative results for the thrust required to open gate valves.

For the closing direction, sufficient data is not available to allow use of a statistical approach. As an interim measure, the closing calculation employs the same scaling constant and seat load force that resulted from analysis of the opening stroke. A wedging load is believed not to exist for the closing direction. The model for closing forces appears to fit test results obtained to date.

The forces acting on globe valves are more easily modeled than those in gate valves. The dominant force in globe valves is the seat face load. This force is simply the produ:r of the differential pressure and the surface area of the valvo orifice.

The other force included in the MOVATS model is termed the " piston effect". This factor represents the force acting along the axis of the valve stem and tending to expel the stem from the valve. The piston effect is the product of the stem area and differential pres-sure or system pressure (depending on which is larger).

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The' piston effect tends to-assist the operator in opening-the valve,-

but the force' opposes valve closure. The piston effect is not includ 7 ed in the MOVATS equation for the opening stroke as a measure of added conservatism..

Available test data for the force required to open and close globe valves also support the MOVATS approach. A statistical analysis indicates that the present data base provides reasonable (90 percent) confidence for MOVATS calculations involving small globe valves.

Confidence diminishes for very small (less than 1.75 inch diameter orifice) and larger (greater.than 2.0 inch diameter orifice) valves due to insufficient test data in these size ranges.

Relatively little data is available for double disk and parallel disk gate valves. Test results to date indicate that existing MOVATS equations do not apply to these valve types, or to Westinghouse gate valves with disk-to-stem pins going in the closed direction only.

In addition to the 95% confidence that the torque switch will be set.

above the unseating thrust level, we have additional confidence provided by the torque switch bypass while the valve is unseating.

The following page is a summary of the MOVATS thrust calculation method:

A i

i 9-03/03/87 f

'I X:

- l 11

e THRUST CALCULATION EQUATIONS

. Solid and Flex-Wedge Gate Valves *-

Seat (Friction) Load (SL)=

0.3 x Delta P x Orifice Area

.i Wedging Load (WL)=-

0.75'x Seat Face Load Piston Effect' (PE)=

Delta P x Steam Cross Section Area Sca' ling Constant (SC)=

1.3 Opening Thrust against Delta P=

SC (SL+WL)

Closing Thrust against Delta P=

SC (SL+PE)

Standard Globe Valves

• Seat Face (Friction) Load (SL)= - Delta P x Orifice Area Piston Effect (PE)=

Delta P x Stem Cross Section Area Scaling Constant (SC)=

1.3 Opening Thrust against Delta P=

SC (SL)

Closing Thrust against Delta P=

SC (SL+PE)

P

• NOTE: These equations are not used if a careful review of valve drawings identifies unusual valve design features.

In particular, the equations do not apply to double disk or parallel disk gate valves, or Westinghouse gate valves with pinned (hinged) disks in the closing direction only.

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Enc 1ccura 2 ULNRC 1456 CALLAWAY PLANT SAFETY-RELATED MOTOR OPERATED

~'

VALVE PROGRAM The response to.IE Bulletin 85-03 is organized into four phases which correspond to Action Items a, b, c, and d from Bulletin 85-03. These phases provide for

1) identification of valves to be included and verification of design basis for the operation of each valve (Action Item a.); II) development of policies and procedures for establishing correct switch settings (Action Item b.); III) switch adjustment, demonstration that the settings defined in Phase II above have been properly implemented, and demonstration that-the valves will function properly under the maximum differential pressures expected on the valves during both normal and abnormal events within~the design basis (Action Item c.); IV) preparation or revision of procedures for periodic testing and inspections to ensure that correct switch settings are determined and maintained throughout the life of the plant (Action Item d.).

Each phase of the program and the overall program schedule are described in the following summary.

Phase I -

Identification of valves to be included and verification of design basis for the operation of each valve.

This phase of the program has been completed and the results have been transmitted to the Nuclear Regulatory Commission (NRC) via ULNRC-1309, dated May 14, 1986 (Reference 2).

For completeness of the program, the information will be included here.

The Union Electric response to Action Item a. is based on methodology devel-oped by the Westinghouse Owners Group (WOG) for member utilities (see WOC-86-168, Westinghouse Owners Group Safety-Related MOV Program Final Report, dated April 7, 1986). This methodology is based on the SNUPPS design for the high pressure injection system and auxiliary feedwater system. The fluid systems evaluation was used to determine the maximum operating differ-ential pressure for all system operating modes and design basis events. The maximum operating differential pressure represents the maximum pressure producing capability of the system equipment for the system operating modes.

Attachment A. IE Bulletin 85-03 Valve Information, provides a list of the valves to be included and design information for operation of each valve.

The information censists of t l

A) MOV as listed by Callaway valve number.

f B) Brief description of valve function.

I (1)

C) Design E specification differential pressure for opening and closing as specified in the design equipment specification.

D) Maximum operating differential pressure for opening and closing as determined by the fluid systems evaluation.

E) A brief justification statement for the maximum operating differen-tial pressures.

F) Results of a review to determine if Emergency Response Guidelines (ERGS) are consistent with the fluid systems operating assumptions.

Phase II -

Development of policies and procedures for establishing correct switch settings.

This phase of the program defines the technical basis for establishing torque and limit switch setpoints. The technical basis for many of the setpoint policies to be used at Callaway have been obtained from MOVATS Incorporated.

MOVATS utilized test results from many plants to establish and justify several alternate policies for torque, torque bypass, and limit switch setpoint adjustments. A description of the policies and technical basis which were supplied by MOVATS is included as Attachment B, Switch Adjustment Policies and Justifications.

Listed below are the switches for which Union Electric determined that setpoint policies were required for response to Bulletin 85-03.

Also, listed are the policies which were not included in Attachment B.

A) Open Torque Switch

- See Attachment B B) Open Limit Switch

- See Attachment B C) Close-to-Open Torque Bypass Limit Switch

- See Attachment B D) Open Indication Limit Switch

- The policy to be utilized at callaway for the open indication limit switch will be to have the open indication limit switch set at the same point as the open limit switch.

Each of the valves included in the Bulletin has an open limit switch and will be set per B) above.

E) Close Torque Switch

- See Attachment B F) Close Limit Switch

- See Attachment B (2)

G) Open-to-Close Torque Bypass Limit Switch

- See Attachment B H) Close Indication Limit Switch

- The policy to be utilized at Callaway will be to have the close indication limit switch set at the same point as the close limit switch, if a close limit switch exists for the valve. If the valve is designed to close on torque, i.e. no close limit switch, the close indication limit switch will be set within 3% of valve travel from the fully closed position.

In no case will the close indication limit switch be set at the same position as the c1rse-to-open torque bypass limit switch.

This is possible for all the valves in the bulletin since they all have four limit switch rotors instead of only two.

I) Control of Butterfly Valves

- See Attachment B To accomplish Phase II of the program, first a review of the torque and limit switch configuration of each valve will be performed.

If this review indi-cates that the current design cannot meet the switch setting policies stated above, an evaluation of current valve operability will be performed.

For this initial evaluation of operability, all switches which affect the safe-ty-related function of the valve will be assumed to be set properly, unless two or more switches which both affect safety-related functions, and are required to be set at different places, are on the same rotor, i.e. are set at the same position.

For valves which fall into this category, the valves will be declared inoperable until an evaluation verifying operability is performed or the design can be modified to allow all switches affecting safety-related functions to be set per the above policies.

When review of the design indicates switches not affecting safety-related functions, cannot be set properly, design modification packages will be developed and the new design implemented at the first available outage that the valve can be worked.

Review of the design for each valve will be complete March 15, 1987.

Procedures for setting torque and limit switches are scheduled to be revised in accordance with the above policies by July 1, 1987. This is to allow time for the purchase of test equipment (which will be required to perform the switch settings as will be discussed in Phase III) and to allow time for training of appropriate personnel.

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Phase-III -

Switch adjustment, demonstration that the settings defined in Phase II above have been properly implemented, and demonstration that the valves will function properly under the maximum differen-tial pressures expected on the valves during both normal and abnor-mal events within the design basis.

This phase of the program begins with the actual adjustment of the switches using the policies established in Phase II.

To facilitate measurement of such things as percent valve travel and thrust values of torque switch trip, which are needed in setting the switches, and to facilitate testing to prove operability, the M0 VATS Signature Analysis Process will be utilized. To aid in the evaluation of our program and due to the many advances in valve signature analysis over the last few years, Attachment C, Description of MOVATS' Signature Analysis Process, has been included. Additional informa-tion regarding the operation and principles of MOVATS may be found in the American Society of Mechanical Engineers paper 94-NE-16 "Early Diagnosis of Motor Operated Valve Mechanical ar.d Electrical Degradations", 12th Inter-Ram Conference for the Electric Power Industry report entitled " Update on Field Signature Testing of Motor Operated Valve Mechanical and Electrical Degrada-tions", or by contacting MOVATS Incorporated 2999 Johnson Ferry Road, Marietta, Georgia, 30062, telephone 404-998-3550.

Utilizing the Control Switch Signature discussed in Attachment C, all the limit switch setpoints discussed in Phase II can now be set and verified to be within the correct percent of valve travel by indication of actual switch trip setpoint in milliseconds of valve travel.

Utilizing the Stem Thrust Signature and Control Switch Signature discussed in Attachment C, the actual thrust values obtained at the open and close torque switch trip can be measured. These values are then compared to the policies specified in Phase II and adjusted appropriately.

Therefore, to perform the switch adjustments and demonstrate that the set-tings defined in Phase II have been properly implemented, MOVATS Signature Analysis will be performed locally at the valve in conjunction with switch adjustment. This initial MOVATS Signature Analysia will consist of as found stem thrust, motor load, and control switch signatures, stem thrust signature calibration, switch adjustments and as left stem thrust, motor load, and control switch signatures.

The final part of Phase III is to demonstrate that the valves will function properlyundeythemaximumdifferentialpressuresexpectedonthevalves during both normal and abnormal events within the design basis.

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Callaway will utilize a test method developed by MOVATS which verifies the valves will function against differential pressure. This method breaks down the total thrust encountered during valve operation into two parts:

thrust resulting from differential pressure, and thrust resulting from the valve itself (i.e. packing loads, friction, gear efficiency, etc.) The thrust resulting from the valve itself is easily measured and quantified using the MOVATS thrust signature. Then if the thrust resulting from differential pressure alone could be calcula id and added to the measured valve running thrust, and the total was less than the thrust value at torque switch trip, we could be assured that the valve would operate under maximum differential pressure.

To perform this calculation, MOVATS has developed equations for different types of valves.

Examples of these equations are shown in Attachment B under II-A and II-E.

These equations have been verified by actual test data (shown on Table 2 of Attachment B) to bound cracking, seating, and unseating thrusts. The calculated thrust values will be verified to be less than the maximum allowable loading condition specified by the operator and valve supplier. We do not feel that additional differential pressure testing is needed to verify these equations unless one of the following conditions exist:

1) The industry data does not encompass the particular size of valve being evaluated.

2) The valve is of a unique or unusual design, such that the data base information would not apply.

3)

Sufficient industry full or partial pressure test data is not available at the time of the plant test to validate the equation being used for thrust calculations.

Sufficient test data to validate a given open or closed stem thrust equation is assumed if at least four (4) sets of pressure data exist for the same type and size of valve or twenty (20) sets for the same type but various sizes.

As the valve degrades, the running thrust value (without differential pres-sure) will increase. As it increases, the total thrust value (after adding thrust resulting from differential pressure) also increases. To ensure that this total thrust does not get higher than the torque switch setting, we will periodically monitor the running thrust. To facilitate this monitoring, MOVATS has developed a method of monitoring from the motor control center (MCC).

" Motor load" signatures will be obtained as described in Attachment C.

Motor load is a measure of motor mechanical output power, and changes in motor load can be reinted directly to changes in stem thrust.

Motor load will be monitored during initial MOVATS testing and a motor load

" threshold" value will be established to aid in determination of valve j

operability.

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The motor load threshold value is determined by conservatively calculating the stem thrust required to overcome differential pressure and measuring the I

corresponding motor load value (see Attachment C for a more complete de-scription of this process). The equations used for calculating the required stem thrust have been validated by many in plant tests (see Attachment B, Table 2).

Motor load values recorded during routine tests will be compared to the 0

established threshold values. As long as the running motor load is less than the threshold, the operator is capable of delivering enough additional thrust to overcome the differential pressure condition. If the running motor load increases to the threshold value, the valve will be declared inoperable until repair and testing activities are complete.

Phase IV -

Preparation or revision of procedures to ensure that correct switch settings are determined and maintained throughout the life of the plant.

As stated in the last paragraph of phase II, the procedures for setting torque and limit switches in accordance with Phase II policies are scheduled to be prepared or revised by March 15, 1987..

In addition, preventive maintenance proeedures will be developed to periodi-cally perform testing to ensure the switch settings are being maintained and that the valves are still capable of ov*rcoming accident differential pres-sureo to perform their functions.

This periodic testing will consist of the following:

A) Motor load and control switch signature traces.

This test verifies the followingt

- motor running load has not exceeded the previously determined

" Threshold" value.

- cycle time has not changed by more than 0.5 seconds from previous test.

- clone-to-open torque bypass limit switches are within original criteria (time of actuation and comparison to valve unseating).

- check for unusual geometry of motor power signature which could be indicative of developing degradations.

- check time difference between contactor drop-out time and control switch actuation and compare to previous data.

l

- compare final closing power value to previous test. A change of 20% may warrant further evaluation.

1 (6)

+

Frequency - Testing will'be conducted and motor load and control switch signatures recorded, trended and analyzed at least once each.

refueling cycle.

B) -Complete MOVATS-signature analysis including spring pack calibration, stem thrust, motor load, and control switch signature traces.

This test-verifies everything identified in B above plus the follow-ing:

- verifies spring pack calibration.

' identifies actual thrust values at torque switch trip.

- identifies various failure mechanisms which may not be identifiable in motor load signatures.

Frequency - This test will be performed initially to set up each valve, whenever an operator spring pack is replaced or adjusted, at least once every four refueling cycles.

The preventive maintenance tests and frequencies identified above are what

. Union Electric feels are currently justified. As test data is obtained and evaluated and as new technologies are developed, these tests and frequencies may be changed.

(7)

c Page 1 of.4:

ATTACHMENT A l

IE BULLETIN 85-03 VALVE INFORMATION Maximum ERG l

Design Operating Justification Confirmation l

Callaway Plant (E-SPEC) AP AP for Max Of' Operating j

Valve Number MOV Description Close Open Close Open Operating AP

-Assumptions l

l BN-HV-8806 A&B Safety Injection 200 200 200 50 Open - 2 Yes' l

Pump Suction Close -1 from RWST EM-HV-8923 ASB Safety Injection 200 200 200 50 Open - 2 Yes Pump Suction Close - 3 from RWST BN-LCV-112 D&E CVCS Pump Suction 100-200 200 50 Open - 4 Yes from RWST Close - 4 BC-LCV-Il2 B&C CVCS Pump Suction 100 200 100 100

_Open - 5 Yes from VCT Close - 5 EM-HV-8823 A&B SI Pump 1500 1500 1500 1500 Open - 15 Yes Cross-Connect Close - 14 EM-HV-8835 SI Pump Discharge 0

2750

,0 1750 Open - 7 Yes Isolation Close - 6 BG-HV-8105 CVCS Normal 2750 2750 2750 2750 Open - 8

.Yes BG-HV-8106 Discharge Close - 8 Isolation EM-HV-8803 A&B BIT Inlet 0

-2750 0

2750

.Open - 9 Yes Isolation Close - 6 (See Table 1 Footnote 1)

EM-HV-8801 A&B BIT Outlet 0

2750 0

2750 Open - 9 Yes Isolation Close - 6 (See Table 1 Footnote 1)

BN-HV-8813 SI Pump Miniflow 2750 2750 1750 1750 Open - 11 Yes EM-HV-8814 A&B Close - 10 BG-HV-8110 CVCS Pump 2750 2750 2750 2750 Open - 13 Yes BG-HV-8111 Miniflow Close - 12

u Page.2ff41

~-: ;

ATTACHMENT A lb IE BULLETIN 85-03 VALVE INFORMATION V;c i

l Maximum ERG Design Operating Justification

' Confirmation Callaway Plant (E-SPEC) AP AP for Max Of Operating.

Valve Number MOV Description Close Open Close Open Operating AP Asstssptions FC-HV-312 Mechanical Trip 1275 1275 1220 1220 Open - 16 Yes-and Throttle Close - 16 AL-HV-34, 35, 36 Suction from 150 150 17 17 Open - 17 Yes CST - All Pumps Close - 17 AL-HV-30, 31,32,33 Suction from 200 200 180 180-Open - 18

_ Yes' Essential Close - 18 Service Water AL-HV-5, 7,9,11 Motor-Driven 1800.

1800 1645 1645 Open - 1 Yes-Pump Discharge Close - 1 Flow Control k

+

2 W

A

g Att:chment-A.

P ga 3 of 4?

JUSTIFICATIONS -

k 1.

This valve must be able to close to' isolate the RWST'from'the~ discharge of' the RHR pumps.during the recirculating mode of-operation, as a precautionary measure in the, event of backleakage through check valve 8926A (or B).) For

.this scenario,-the AP across 8806A (or B) could be as high as the RHR pump

' discharge head 200 psig..

,2.

This. valve is normally open..and is closed only for stroke testing and/or pump isolation for maintenance. The valve must be able to open against a full RWST head of water. For Callaway, this is_=50.psig.

3.

This valve must be capable of isolating (closing) one high head safety

. injection pump, given a passive failure in that train of ECCS. ' For this scenario, the AP across 8923A,.B could be as high as the RHR pump discharge

' head m200 psig.

4.

Same_as 8806A, B (for both close and open), except these valves are'in the suction of the centrifugal charging pumps and not the high head safety injection pumps.

5.

These valves must close on an "S" signal; the maximum AP across the valve is defined by the volume control tank at its design pressure (relief valve-setpoint) of 75 psig plus elevation head of the VCT above the valves. This is estimated to be 2100 psig.

6.

Valve is only closed when pump is not operating; no flow - no AP.

7.

Pump testing on miniflow circuit, AP is determined by the miniflow head of

-high head safety injection pump 21750 psig.

8.

These valves must be able to isolate the RCS from the CVCS, with a maximum possible'AP of z'the shutoff head of the centrifugal charging pumps.

9.

Given a miniflow test of the centrifugal charging pumps, the BIT isolation valves must be able to open with a AP 2 equal to the charging pump shutoff head.

10. Valves must close to isolate miniflow so that high pressure injection switchover to recirculation may proceed.

In the worst case, the AP will be equal to the pump developed head on miniflow *1750 psig.

11. Similar to 10, except valve must be able to open during miniflow testing of the high head safety injection pump.

12. Valves must close te ensure adequate high pressure injection flow (on "S" signal) against miniflow AP #2750 psig.

'13.

Similar to 12, except valve must be able to open during miniflow testing.

14. Must be able to move to allow realignment to ECCS to recirculation mode, and i

for ECCS train separation. Delta-P could be as high as 1500 psig a equal to miniflow head of high head safety injection pump.

.~

LAttcchment A Pag 2-4 ef 4-

15. _ Must be able to open to allow train separation during the recirculotion phase of'ECCS operation. Delta-P same as' closing.

16. Lowest steam generator safety valve set-pressure plus 3 percent accumulation.

17.

Static elevation head of the condensate storage. tank..

'18.

Discharge head of the service water pumps at miniflor.

19. Motor driven pump discharge pressure at miniflow.

FOOTNOTE TO TABLE 1 1.

The ERG-guidelines to terminate safety injection (isolate the BIT), and return to norma 1Lcharging are performed with the centrifugal: charging pumps operating. This termination method reduces net RCS makeup in a controlled manner-and maintains continuous reactor coolant pump seal injection. Since the charging pumps are operating, the BIT' isolation valves must close against a AP.

This AP could be large for some'SI termination scenarios (RCS could be-as low as 200 psi - AP could be as high as 2500 psi).

=

7 Peg 2 1 cf 8 ATTACHMENT B Switch Adjustment Policies and Justifications This phase of the program defines the technical-basis for establishing torque c

and limit switch setpoints. A given control switch may be set to a number of possible positions. The most appropriate setting will be selected and switch setting procedures revised after a review of the valve function, operator and valve design, and overall plant policies. The following are the setpoint methods and technical justifications that will be considered for implementation during the control circuit review process.

In each case, the method to be used by Callaway on most valves will be identified.

II-A Open Torque Switches The open torque switch acts to alert plant personnel of mechanical problems with the valve or operator. The torque switch also provides some element of protection if the open limit switch fails to open. Historical data has shown that open limit switch failures are extremely rare.

Typically, the open torque switch is set to actuate at a thrust value above the calculated unseating load (including maximum design differential pressure loads). During valve unseating, the initial load peak (cracking load) may be of a high enough level to cause the torque switch to trip. Because of this peak, the torque switch must be electrically bypassed during this phase of valve operation.

One acceptable approach (being evaluated by Callaway as a possible -.pproach) in to eliminate the open torque switch from the control circuit. From a hainte-nance point of view, the " alerting" function of the open torque switch trip is not necessary if valve / operator condition is monitored using some other means to provide adequate indication of developing mechanical degradations (i.e., MOVATS' MCC System).

As an alternative (also being evaluated by Callaway), the open torque, switch will be wired into the control circuit and set to trip at a value greater than the load calculated for valve unseating. To establish the torque switch setpolpf, the opening thrust value for full differential pressure conditions must be established accurately. The following is an example of the equations for the opening thruat.

The equations were developed by MOVATS and validated using full and partial pressure testing data.

s

'[

C v

- P g2 2 cf 8 l-Liing

.,c L:

- ':L

_J.

l-THRUST CALCULATION EQUATIONS p

Solid and Flex-Wedge Gate Valves

• Seat (Friction) Load (SL)=-

0.3 x Delta P x Orifice Area L

Wedging Load (WL) = -

0.75 x Seat.. Face Load

(\\L (SC)=

1.3

-Scaling Constant l.

Opening' Thrust against Delta P=

SC (SL+WL)

Standard Globe Valves

~

Seat Face (Friction) Load (SL)=

Delta P x Orifice Area l

Scaling Constant.

(SC)=

1.3 Opening 1 Thrust,against. Delta P=--

SC :(SL)'

• NOTE: These equations are not used if a careful review of valve drawings

. identifies unusual ~ valve" design features.

In particular, the

~

~

equations do.not. apply to double disk or parallel disk gate valves.

Unseating Thrust (Tu)= Running Load t Opening Thrust against Delta P l

' Running Load measured at point A'on Figure 1.

l l

i-i 1

L - _ __ _

Ptg2 3 cf 8 Y -

After the unseating thrustl(Tu) has been determined, it will be compared to the maximum allowable loading condition specified by the operator and valve suppliers. Valves which have the calculated unseating thrust (Tu) exceeding the maximum will be evaluated on'a. case by case basis. Corrective action may include-such things,as. operator replacement, full pressure testing, lowering of the AP requirement', or a vendor approved extension of :the operator rating.

After an acceptable unseating thrust has been determined, the torque switch setting will be adjusted to some valve above (Tu). Typically,-the minimum accept-able value is 1.05 (Tu) af ter all expected instrumentation and equipment variation are taken into account. These variations are as follows:

Operator / Torque Switch

- !10% (Thrust loads less than 4000 lbs)

Repeatability

- !5% (Thrust loads greater than 4000 lbs)

MOVATS Instrumentation Accuracy 50K Load Cell

!2% of load 0.4% linearity 200K Load Cell

!1.9% of full scale Nicolet Scope 10.2% of Voltage Range (10V)

TMD Linearity

!0.6% of 10 Volt Scale Combining these tolerances, torque switch trip points established as follows:

For stem thrust loads less than 4,000 lbs, Tu (1.05 + 0.15) = 1.20(Tu) minimum setpoint setting For stem thrust loads greater than 4,000 lbs, Tu (1.05 + 0.10) = 1.15(Tu) minimum setpoint setting In general, a target band of 1.20 - 1.30 Tu (loads less than 4,000 lbs) and 1.15 - 1.25 Tu (loads greater than 4,000 lbs) will be used to allow for field setting of the switches (See Figure 4).

After the open torque switch has been set, the thrust at the actual trip setpoint will be verified to be less than the maximum allowable loading condition specified by the operator and valve suppliers.

II-B Open Limit Switches The open limit switch must be adjusted to prevent inadvertent backseating of the valve.

(Conditions and precautions to be observed when intentionally backseating a valve electrically are addressed in the discussion of open torque switch settings.)

Paga 4 of 8 Typically, the open limit switch will be set at approximately 90% of stroke from the close-to-open position.

It is recognized that the amount of stem travel after limit switch trip is influenced by the inertia of the MOV assembly, valve design, and delay in motor contactor drop out after actuation of the open limit switch. Therefore, a specific setpoint for the open limit switch cannot be established.

Instead, the following process will be used:

The limit switch will be set initially for 90-92% of the full open stroke.

The valve will then be cycled open e.nd allowed to trip electrically, Plant personnel will then place the operator in manual and continue to open the valve using the handwheel. If the valve can be opened an additional amount past the trip and coast down position, the switch is set correctly. If the valve cannot be opened past the coast down position, it can be assumed that the valve has hit the backseat.

In the unlikely event that the valve has inadvertently backseated, a MOVATS signature analysis test will be conducted and the stem loading and subse-quent stem stress levels will be evaluated. The limit switch setting will then be reduced in 2% increments and the valve will be cycled and checked until it is verified that the disc is not coasting into the backseat.

II-C Close-to-Open Torque-Bypass Limit ~ Switch The close-to-open torque bypass limit switch prevents torque switch actuation during the high loading condition normally experienced when the valve disc is

" cracked" from its seat (Tc - see Figure 2).

From a operational standpoint, many switch settings are acceptable, denending on utility operating and maintenance policies. Operator loading conditions during the opening cycle must be examined to understand technical justifications for each acceptable setting.

Figure (1) shows a typical stem thrust and control switch actuation signature for a valve going from the close-to-open position with zero differential pressure across the valve. Figure (2) is the same basic signature modified to show bypass switch actuation at 5-10% of valve stroke'(based on stem movement). Historically, it is believed that the 5-10% switch setting would encompass the initial valve unseating. After the valve began to pass fluid, the high loading conditions would decrease rapidly. This theory was generally accepted even though full pressure and flow data were not available to validate such an assumption.

Figure (3) depicts a thrust signature from the same valve shown in Fig-ure (2). The changes in the signature characteristics result from differential pressure across the valve. With the typical bypass switch setting of 5-10% of stroke, it is clear that the torque switch may not be bypassed during the full unseating process. However, Figure 3 demonstrates that the " cracking load" (Tc) occurs early enough in the open cycle that the 5-10% bypass encompasses this loading condition.

Data from tests with full and partial differential pressure conditions (Table 1) indicates that the cracking load condition occurs at less than 1% of valve stroke for globe and gate valves, even though the loading condition during unseating does not begin to decrease until as much as 15% of stroke.

^

~

..\\-:.

-Paga 5 of 8

~

e Based on analysis of test, data, the following are acceptable settings for the close-to-open torque bypass limit switch.

1)

Three (3) percent'ofitotal valve stroke as measured from the point of stem motion. The three percent value. ensures that cracking has occurred at the time.of switch actuation though unseating may not be complete.

To use the three percent setting, the open-torque switch must be set in accordance with recommendations contained in Section II-A.

2) 5-10% of stroke will provide some additional margin for added stem loads due to' buildup of foreign materials on the valve seat, etc.

Bypass switch actuation will occur during or at the completion of valve unseat-ing under differential pressure conditions.

3)

The approach to generally be used by Callaway will be to use 20-25% of stroke to ensure that the entire unseating is bypassed. The advantages of this approach are the same as 1) and 2) above.

In addition, the valve will most likely perform its intended function even if the torque switch is set improperly. If this option is selected, it should be recognized that the closed light will illuminate when the valve is 20-25% open on operators equipped with two-rotor limit switches.

Operationally, this condition can be justified for many applications.

Of course, the 20-25% setting will not affect position indicating lights if operators are equipped with four-rotor limit switches and the indi-cating light limit switches are on different rotors than the close-to-open torque bypass limit switch (which will be the case at Callaway).

4) 90-98% of stroke will have the same advantages as 1) through 3) above and will preclude stoppage of valve travel if large mechanical loads are encountered anytime during the opening stroke.

90 - 98% of stroke will still provide back up for the open limit switch.

5) 100% Bypass - With this option, the open torque switch is wired com-pletely out of the opening circuit, thereby negating the need for the bypass switch (see II-A, Open Torque Switches, for guidance on this condition).

II-D Open Indication Limit Switch See Phase II in body of this enclosure.

II-E Close Torque Switch The closing torque switch ensures that sufficient loads are delivered to the valve stem to provide leak tight closure of the valve. Although certain types of valves and/or unusual closing requirements may dictate use of a limit switch for valve closure, the torque switch is the most common method for control during the closing stroke.

As with the open torque switch, the closed torque switch setting must be calculated accurately. To establish the torque switch setpoint, the closing thrust value for full differential pressure conditions must be established accurately. The following is an example of the equations for the closing thrust.

~.

Paga 6 of 8 The equations were developed by MOVATS and validated using full and partial-pressure testing data.. When the closing stem thrust (Tu) has been established, the margins for operator, valve, and instrumentation variations (previously described)'are applied to determine the target closed torque switch setting.

The following is an example of the equations for closing thrust.

THRUST CALCULATION EQUATIONS Solid and Flex-Wedge Gate Valves

• Seat (Friction) Load (SL)=

0.3 x Delta P x Orifice Area Wedging Load (WL)=

0.75 x Seat Face Load Piston Effect (PE)=

Delta P x Steam Cross Section Area Scaling Constant (SC)=

1.3 Closing Thrust against Delta P=

SC (SL+PE)

Standard Globe Valves Seat Face (Friction) Load (SL)=

Delta P x Orifice Area Piston Effect (PE)=

Delta P x Stem Cross Section Area Scaling Constant (SC)=

1.3 Closing Thrust against Delta P=

SC (SL+PE)

• NOTE: These equations are not used if a careful review of valve drawings identifies unusual valve design features.

In particular, the equations do not apply to Westinghouse gate valves with pinned (hinged) disks.

As will be discussed in Phase III, the equations will not be relied upon if sufficient industry full or partial pressure test data is not available at the time of the plant test to validate the equation being used for thrust calculations. The present MOVATS data base does not include sufficient test results to validate M0 VATS closing thrust equations for flex and solid wedge gates or globe valves with orifice diameters less than 1.75 inches or greater than 2.0 inches. Therefore, the testing program at Callaway will include differential pressure testing in the closing direction on representative valves. Utilizing this data specific equations will be developed. The equations will be considered accurate for a particular valve if pressure test data is provided by four valves

Pxga 7 of 8 i

of the same type and size or~ twenty (20) valves of the same type.

When closing a valve, the_ final loading condition may be significantly higher than the closed torque switch trip setp'oint. This difference is due to the inertia effects of the operator and valve assembly as well as variations in the

' motor contract drop-out time. Closing a valve without flow and pressure will result in the highest closure forces and the final forces must be evaluated against the operator and valve manufacturer's thrust limits.

II-F Closed Limit Switches For valves that are controlled using a limit switch during closure, the final closure forces must be examined closely. These forces can vary widely depending on inertia, contactor drop-out time and valve design. Signature analysis tech-niques will be used to verify that the closure forces are acceptable when compared with operator and valve manufacturer's limits.

In the long range program, any significant changes in contactor drop-out time will be noted and the impact on final stem loads will be monitored and evaluated.

II-H Closed Indication Limit Switch See Phase II in body of enclosure.

II-G Open-to-Close Torque Bypass Limit Switches Typically, the open-to-close torque bypass limit switch is of no operational concern because large hammerblow loading conditions do not occur during the initial phases of the closing cycle. For this reason, no specific requirements are placed on this switch setting relative to the valve stroke. Unless some other need is identified for positioning of this switch, the position that results from coast down of the motor after open limit switch actuation will be accepted.

II-I Control of Butterfly Valves The guidelines for setting butterfly valve limit switches (and torque switch-es, where applicable) will be basically the same as previously discussed for other types of valves. There is one notable exception.

Normally, butterfly valves do not employ torque bypass switches. Bypass switches for the open torque switch will be considered when all of the following conditions exist:

1)

Normal operating position of the valve is closed; 2)

The safety position of the valve is open;

^

Pega 8.cf 8 3)

The valve istin a. sea water or' water environment such that' foreign material build-up is of concern; 4)

The valve is not cycled frequently enough to ensure that thef oreign f

material build-up effects are negligible.

If all of-the above conditions exist, then the open torque switch will be wired out of the. control circuit or the close-to-open torque bypass limit switch.

will be set for approximately 98% of stroke.

Y

}

=

FIGURE 1 TYPICAL STEM THRUST AND CONTROL SWITCH ACTUATION SIGNATURES j

ma

\\

yu a

peak load delivered %

oc I&

I 2

/ running load i(valye hit l

i s backseat disc begins to unseat 8

i hammerblow.-stem is moving i

zero load on springpack j

switch turned to open i

i i-i i

I p-torque switch i

f

/c/o bypass switch opens opens limit switch opens 3

iR TIME (milliseconds)

[

a i

J

-..... m ~..

1%URE 2 hammerblow i

^

u u>3 actual valve unseating - Tc s

a) 3 g,

T A>

F A

/\\

- open limit switch actuation

..... - - - - ~.

5%-10% c/o bypass setting 4

O y

i TIME (SEC)

C/O STEM THRUST SIGNATURE W/O_ DIFFERENTIAL PRESSU.13E.,

y N a

=

e FIGURE 3 i

j i

valve cracking - Tc

^ 55 w

g valve unseating - Tu g

valve begins to pass fluid a-i I

i s

i

.,___ open limit switch actuation

~ 5%-10% c/o bypass setting i

~

i I

i w/o differential pressure w/ differential pressure r

TIME (SEC) 2!#

'a C 2a ul C/O STEM THRUST SIGNATURE a

FIGURE 4 3%

8' 10 %

t 3

98%

20%

25%

t-m n

D

[

I l-e

+-- open limit switch actuation ts setting = 1.25 Tu i

TIME (SEC) l l

C/O STEM THRUST SIGNATURE asc Si l

• C i

ca n

i Attachment S Figure 5

'~

FIGURE S

IDAD CEl.!. SilPPORT PLATE DIACRAM 4

I

,f.k C

(Y

)

Jd) l.dl

,1

\\

w>

LOAD CELL SUFFORT PLA' k.

MN 3h K

• P s

Nns CERTIFIED LOAD CELL

s 1$h.

h.

t

-lC, p.

,,j [

l hI w

,.x

":ij

';UPPORT RODS

[ --

. A,

• z-~~;

l.

s t

[

g I I l

l i i

}

l t

e t

A N

i.

Y'

/

f{

-/

\\

/

's,

e t

s l

\\

JPPER THRUST 3EARIL.

1 i

(

j

~~

!!C':S *::C

\\

\\-

- ~ s ol - ~__

\\

/l

/

V AI.'s*E STEM EXIENSION RCD

FIGURE 6

TYPICAL STEM THRUST AND CONTROL SWITCH ACTUATION SIGNATURES

.t

'eyc 1

a peak load delivered %

cc I

i 2

I 4

Lu j

p

)

I o

p;.

/ running load

/

I w

i vane hits backseat

/

disc begins to unseat i

8 hammerblow-stem is moving i

zero load on springpack switch turned to open i

i 4

I 8

i

,p' torque switch f

--d/o bypass switch opens limit switch opens iiE 7i.

m TIME (milliseconds) a

=

1

I FIGURE 7

' Attachment 8 Figure 7 DETERMINING DELAY TIME AND MOTOR LOAD THRESHOLD VALUE SWITCHES (A)

TORQUE SWITCH TRI7 W

I I

I V__

l CALCULATED i

i THRUST FOR DELTA P TORQUE (C)

}

sWITcu (B)

SETPOINT STEM THRUST I

I l

i I

l

.t X _._

l I

I I

I l

1 i

l I

g I

I l

4 P

& DELAY TIME j

g I

I l

lM I,

7'!

I DELAY TIME I

(D) l l

l

1. l ll RUNNING MOTOR LOAD i

(E) 1 l

l r

(F) l

__ 7 _ _ __.__. _ __,_

f-p MOTOR LOAD MAXIMUM MOTOR l

TIME

• LOAD " THRESHOLD" l

l l

j-

.Attachm:nt B Table 1 TABLE.,1 Sheet 1 of 1 CRACKING AND UNSEATING TIMES AS PERCENT OF VALVE STROKE (Arranged in Ascending Order)

UNSEATING w/ DIFFERENTIAL NUM.'5E.1 CRACKING PRESSURE

~1

.10

.25 2

.12

.26 3-

.13

.76 4

.13 1.05 5

.15 1.17 6

.15 1,32 7

.16 1.44 8

.19 2.21 9

.22 2.46 10

.22 4.78 11

.22 5.04 12

.27 5.22 13

.28 5.32 la

.29 5.7 15

.29 5.85 16

.33 7.5 17

.34 7.68 13

.36 7.89 19 42 9.46 20 46 9.53 21

.67 9.76 22

.68 10.8 23

.68 11.2

,c------

,,-n

~- - -r e-p e e - -, - - -,

w,w,--,,,-v.,-.-

e

L.

M) VATS DIFFERENTIAL PRESSURE TEST DATA 2

LOG TYPE OPER-DELTA STEM' ORIFICE-CALC.

ACTUAL CALC ACTUAL' CRACK NO.

SIZE

- - P-DIA._

AREA OPEN OPEN CLOSE CLOSE LOAD (PSIG)

(IN)

.(SQIN).

}

1-FWG 000 1050 1.000' 3.438 6652 4489 4873

'ND 3500 i

-2 FWG 00-54 1.887 13.250 5081

'3455 3100 ND 2580

-3 FWG 00 420 1.625 7.625 13089 11720 8612 ND' 10174 i

5 FWG 000 100 1.125 5.761 1779-1688 1145 1014 ND 6-FWG 000 100 1.125 5.761 1779 1100-1145 1062 ND 7

FWG 1-650 2.000 8.000 22299 21250 15396 ND ND 8

SWG 1

860 2.125 11'.750-63645 41837.

40333 ND ND 9

SWG-1 935

-2.125 11.750 69195 57702 43851 ND ND 10 SWG 0

852 1.875-7.875 28322 20809 19242 ND ND 11 SWG 1

850 2.125 11.750 62905 45199 39864 ND ND l

12 SWG 1

850 2.125 11.750 62905 36476 39864-ND ND l

13 SWG 00 900 1.625 6.000-17367 8015 12350 ND ND 14-SWG 00 900 1.625 6.000

-17367.

6100 12350 ND ND l

16 FWG 00 2400 1.125 2.000 5145 880 6042 ND 1255 17 FWG 1

300 2.000 17.000 46474 32800 27781 ND 32800-18 FWG 00 1050 1.500 5.761 18680 11257 13086 ND 11257 j

l 19 FWG 00 700 1.500 5.761 12453 7344 8724 ND 7344 20 FWG 00 1050 1.500 5.761 18680 10733 13086 ND 10733 f

21-FWG 4

1075 2.500 14.500 121153 90541 76090 ND 90541 22 FWG 1

1050-1.500 5.761 18680 15700 13086 ND 16200 23 FWG 1

750 1.500-5.761 13342 11820 9347 ND 14560*

ft 24 FWG 1

1050 1.500 5.761 18680 12959 13086 ND 12959 j

25 FWG 1

1100 1.500 5.761 19569 130 %

13709 ND 13096 26 FWG 00 900 1.500 5.761 16011 9656 11216 ND 9656 27 FWG 00 1050 1.500 5.761 18680 13584 13086 ND 13584 28.

FWG 00 1275 1.500 5.761 22682 14148 15890 ND 14148 l

[

FWG - Flexible Wedge Gate Valves

• Log. No. 23 and 162 are the l

SWG - Solid Wedge Gate Valves same valve at different AP's.

j ND - No Data Obtained This valve's operation is suspect due to conditions it I

has been operated under.

TABLE 2 Sheet 1 of 3

\\

LOG TYPE OPER DELTA STEM ORIFICE CALC ACTUAL CALC ACTUAL CRACK N0.

SIZE

~P DIA.

AREA OPEN OPEN CLOSE CLOSE LOAD (PSIG)

(IN)

(SQ IN) 29 FWG 0~

100 1.5 10 5360 4661 3293 ND 4661 31 FWG 000 105 2.25 8.021 3621 3002 2612 ND 3002 32 FWG 1

361 2.0 8.125 12774 11379 8774 ND 11379 34 FWG 000 100 1.25 5.761 1779 1600 1176 ND ND 43 FWG 00 2180 1.125 2

4674 3650 5488 ND 3650 70 FWG 000 151 1.25 10 8094 5126 4866 4450 4817 162 FWG 1

350

.5 5.761 6227 6040 4362 ND 10620

• 15 WFG 1

160 1.375 7.625 4986 3000 3158 5836 3025 91 WFG 00 2720 1.125 2.62 10008 7247 9234 11237 6833 92 WFG 00 2474 1.125 2.62 10100 6688 9319 10264 6688 96 WFG 000 2700 1.125 2.62 9935 8396 9166 ND 7577 97 WFG 00 2700 1.125 2.62 9935 10607 9166 ND 9100 98 WFG 00 2750 1.25 3.44 17444 5864 14355 10805 5540 99 WFG 00 2700 1.25 3.44 17127 4333 14094 6906 4267 100 WFG 00 2650 1.25 3.44 16810 4971 13833 ND 5116 103 WFG 00 2650 1.25 3.44 16810 7715 13833 11960 7715 104 WFG 00 2625 1.25 3.44 16651 4230 13703 10587 4230 105 WFG 00 1500 1.25 3.44 9515 4859 7830 10165 4859 106 WFG 00 1500 1.25 3.44 9515 7124 7830 7099 7124 109 WFG 00 1470 1.25 3.83 11559 6939 8950 12585 8750 110 WFG 00 1500 1.25 3.83 11795 6871 9133 14382 5699 111 WFG 00 1475 1.25 3.44 9536 4350 7700 7730 4350 35 GLB kkb0 1470 1.5 2.125 6777 5628 10154 6941 ND l

37 GLB 00 1470 0.81 1.625 3963 2825 4948 1705 ND 40 GLB 00 1350 1.25 2.75 10424 9161 1257A 10590 9030 50 GLB 000 1950 0.938 2

7964 1800 97I5 ND ND 51 GLB 00 1490 0.875 2

6085 3060 7250 ND ND 83 GLB 00 1360 1.25 2.75 10501 12671 11417 ND FWG - Flexible Wedge Gate Valves

• Log. No. 23 and 162 are the same valve at different AP's. This WFG - Westinghouse Gate Valves with pinned stem-to-disk TABLE 2 valve's operation is suspect due GLB - Globe valves Sheet 2 of 3 to conditions it has been operated

under, i

L

LLOG TYPE -OPER DELTA STEM ORIFICE CALC ACTUAL CALC ACTUAL CRACK NO.

SIZE

-P DIA.

AREA OPEN OPEN CLOSE CLOSE LOAD (PSIG)

-(IN)

(SQ IN) 93 GLB 00 2725

-1.125 1.875 9781 6000 13303 7845 6000 94 GLB 00 2750 1.125 1.875 9871 5420 13425 8241 5420 95 GLB-00 2560 1.125 1.875 9189 5000 12497 7580 5000 101 GLB 00 2750 1.125 1.875 9871 6861 13425 6891 6140 102 GLB 00 2710 1.125 1.875 9728 6184 13230 6636 6184 l

i 4

GLB - Globe valves TABLE 2 Sheet 3 of 3 l

l

TABLE 2 F.bru.ry 26; 1987 FIGURE 1 Attachment B TH Pl.lS, i' F 'fiil! il FRE 1 ) l!

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( ~, /s F E

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~

(.D.1 A F R MA D E.L1 s - P TE S1 '.

3 3 9 ---- -.-

Test Results Shown as Squares 120 -

110 -

100 -

.~s td 9 0 ---

p) 0 O'

2_.

80 --

to $

9c 7 0 --

.o 3 v>

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1 ~~-T~~

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0 20 40 60

.;0 10t>

1.;:i i I40 160 160

, T h aus nids

• Ul!TEREllll AL PRE' T UPL

'.EA T A k'[ A

F-bru ry 2:.;, 19~/

TABLE 2 Att:chment B FIGURE 2 I H RI r Ji Ht i I l F10 f

' (~ M E M l L

' Al ' 'F 'L-l i,,1 I p..t 1 L,[: [..;. - i '

M',l' 3.---_.-..

Test Results Shown as Squares 6--

7 r.

La 8._)

tr O

6 ft.m l9

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L3 C ZO E' - '

Calculated 7 _

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E'ruary z.,

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l Attachment B p

THRUST REQUIRED TO OPEN GLOBE VALVES DATA FROM DELTA--P TESTS 11 Test Results Shown as Squares 10 -

y

,./

/

O 9-

/

C 8-N 7-Calculated O

$gp Thrust bO 6-b O3 v0 1

O D

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3-O g

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i i

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5 7

9 (Thousands)

DIFFERENTIAL PRESSURE x SEAT AREA

TABLE 2 February 26, 1987 FIGURE 4 Attachment B THRUST REQUIRED TO CLOSE GLOBE VALVES DATA FROM DELTA-TESTS 14 Test Results Shown as Squares 13 -

/

12 -

/

f',/

D 11 -

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9

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i i

i i

i i

i 3

5 7

9 11 (T housands)

DELTA P x (SEAT + STEM AREAS)

• "* U TABLE 2 FIGURE 5 Attachment B THRUST TO OPEN WEST. GATE VALVES DATA FROM DELTA-P TESTS 18 Test Results Shown as Squares 17 -

16 -

15 -

3 O

k 12 -

m to $

11 -

/

k [O

/

3m Calculated O5 10 -

Thrust "5

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i i

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i i

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i i

i i

i 7

9 11 13 15 17 19 21 23 25 (Thousands)

DlFFEREtlTIAL PRESSURE x SEAT AREA i

Pcg2 1 cf 4 ATTACEMENT C To understand MOVATS' Signature Analysis Process, you must first understand the operation of a Motor Operated Valve. This first page gives a brief description of this operation. -The description given is for a general SMB Limitorque Operator and is taken from a Callaway Plant training manual on MOV's.

Refer to Figure 1 of this attachment.

The electric motor has.a helical pinion mounted on its shaft extension. This pinion drives the worm shaft clutch gear which is engaged with the worm shaft clutch. This piece is splined to the worm shaft. The worm is splined to the worm shaft and when it is rotated it turns the worm gear. The vorm gear has two lugs cast onto the top portion which engages the two lugs on the drive sleeve. These lugs are spaced so that when the worm gear begins to turn during motor operation there is a certain amount of lost motion before the lugs engage and cause the hammer blow effect within the operator.

As soon as the worts gear lugs engage, the drive sleeve being splined internally with the stem nut, causes the stem nut to rotate and open or close the threaded stem of the valve. The stem-nut is threaded to fit the thread of any rising stem valve. In the case of non-rising stem valves or where the electric operator is mounted in tandem with an additional gear drive, the stem nut is merely bored and keyed to fit the shaft.

Sequence of typical gate valve closing (Refer to Figure 2):

1.

Motor A transmits rotary torque through helical gearing B and then through second reduction worm C and worm gear D.

2.

Worm gear drives stem nut E.

3.

Rotation of threaded nut E creates linear motion of velve stem F and resul-tant movement of valve.

4.

When valve closes, disc G is pressed into valve seat H; thus seating valve.

S.

Since the valve is seated, disc G no longer can move in a downward direction.

However, the motor drive still continues to rotate under increased load conditions.

6.

Instead of the vorm gear continuing to rotate, the worm C actually threads itself along the worm gear as the spring pack J is compressed. The worm rides on a precision spline which permits this axial movement.

7.

Movement of worm C trips Torque Switch K which breaks electrical motor circuit. The mechanical self-locking feature, inherent to the worm gear design, maintains valve seating force and assures a tight valve until Limitorque is energized in "Open" direction.

1 i

i

Pega 2 of 4 With a basic understanding of the operation of a Motor Operated Valve (MOV) the operating principles of MOVATS' Signature Analysis Process can now be explained.

There are three signature traces which are utilized the most in setting up and testing the MOV. These are a stem thrust signature, control switch signature, and motor load signature. Each of these signatures is described below.

STEM THRUST SIGNATURE The basis for the MOVATS stem thrust signature is the concept that the greater the load being delivered to the valve stem, the greater the movement of the worm within the operator itself. Therefore, if one could monitor accurately this movement, and correlate or calibrate this movement to actual stem load throughout a valve cycle, a dynamic measurement of the stem thrust load would be the result.

To obtain this parameter, a linear variable differential transformer is installed in a device called the " Thrust Measuring Device" (TMD). To install the TMD on the motor operator, the spring pack dust cover is removed and the TMD mounted such that its plunger comes in contact with any part of the spring pack preload nut.

With the TMD now installed and its conditioned output connected to the recording system, any subsequent movement of the spring pack or worm, which is reflective of the stem load, will be translated into a voltage output of the TMD. Although knowledge of the dynamic movement of the spring pack throughout the valve cycle is sufficient to provide adequate information regarding the valve and operator mechanical condition, the movement of the spring pack can further be correlated to actual stem thrust.

In order to " calibrate" the spring pack movement on a Limitorque type of operator, to actual stem thrust, the first step is to position the valve in tha mid stroke.

Next, the npper bearing thrust cover bolts are removed, and a threaded rod in-stalled in its place. Nuts on the threaded rod are then tightened on the housing cover to retain the cover plate. Once all of the upper housing bolts have been replaced with the threaded rods, a National Bureau of Standards (NBS) certified load cell is mounted such that it is within close proximity of the valve stem (see Attachment B, Figure 5).

For those valves in which the stem does not rise completely out of the operator body, an extension piece is used. With the TMD installed and monitoring spring pack position, and the load cell output likewise connected to the portable two channel digital recording oscilloscope, the valve is opened electrically from either the motor control center or the control room. As the valve stem contacts the load cell, the stem load rises dramatically with a corresponding spring pack movement. The spring pack movement signature can now be directly correlated to the actual load signature. The resultant curve has a definite slope which is referred to as the K-factor of the spring pack and is represented in terms of pounds of stem thrust per inch of spring pack deflection.

In the analysis of MOVATS signatures it has proven to be more helpful to express the K-factor as pounds of stem thrust per volt of TMD output.

Knowing the K-factor now allows the user to determine the actual magnitude of the load being delivered to the valve stem at any time during the valve cycle.

Similar techniques can also be used to determine stem load at various torque switch settings.

]

Pzg2 3 ef 4 CONTROL SWITCH SIGNATURE Actual field testing has shown that having the capability to determine the exact time and loading condition at which the control switches actuate is of paramount importance. This sub-system provides a single signature, simultaneously superim-posed on the thrust signature, which reflects the exact point and loading condi-tion, within the valve cycle, at which the various switches actuate.

To install the switch sensing circuit, operator control circuit leads are lifted from two of the motor operator terminals and MOVATS signal leads attached in series with the control circuit. After the leads have been connected and control power restored, the valve is still fully operational upon receipt of a Safety Features Actuation Signal, actuation from the control room or motor control cubicle. A schematic of the thrust and switch signatures is shown in Figure 6 of Attachment B.

Although field testing has shown that, for safety-related valves, quality control involvement is required and can be accommodated quite easily, an alternate tech-nique was developed for monitoring of' control switch positions without lifting of any control circuit leads. This is performed using the same circuit, however, voltage sensing downstream of selected switches is implemented instead of current sensing. Although using the voltage techniques precludes observation of the torque switch actuation during the initial valve loading condition, all other control switch actuation, including torque switch trip later during the valve cycle after the respective bypass switch has dropped out, is still readily avail-able.

MOTOR LOAD SIGNATURES Motor load is a measure of motor input power that has been adjusted to compensate for efficiency losses in the motor. Changes in motor load values can be related directly to changes in operator output torque and stem thrust.

Motor load signatures are generally obtained by attaching voltage sensing leads to each phase of the power feed to the operator motor. A clamp on ammeter is also attached to one power phase. The measuring equipment can be installed at the operator or at the Motor Control Center.

Motor load signatures are generally obtained and displayed with switch and/or stem thrust signatures. A typical set of these signatures are shown in Figure 7 of Attachment B.

Motor load signatures are used as follows:

1.

The operator torque switch is set to produce the required stem thrust at torque switch trip (Point A in Figure 7 of Attachment B).

2.

The stem thrust required to overcome differential pressure forces is calculated using empirically verified equations (see Attachment B), and the calculated thrust value is subtracted from the thrust at torque switch trip to obtain the " threshold" thrust value (Point B).

i

n-Pcg2 4 cf 4-L3.

Motor load lags behind the_ associated mechanical load changes.due to electrical characteristics of the motor, transmission time through the gearing, and ' delay time -in the measurement circuitry. The lag (" delay

-time") is measured by comparing the unseating spike on the stem thrust signature'(Point C) and.the corresponding spike in the motor load

~

signature (Point D).

4.

The measured delay time is added to the time associated with the thresh-old thrust value (Point B) and the resulting time is applied to the motor load signature to determine the " motor load threshold" (Point E).

During periodic and/or post-maintenance testing, the motor running load (Point F) will be monitored by maintenance personnel. The average running load value will.

be recorded and trended. As long as the average motor load value remains less than the threshold (Point E), the operator is capable of-supplying enough addi-tional stem thrust above running load to overcome maximum differential pressure conditions.

... ~.

_m.

ATTACHMENT C FIGURE 1 Figure 1 pper Bearing Thrust Cover Bolts Helical Pinfon Gear Valve Stem Drive Sleeve Uom Gear Morm Gear Lugs f ?

A f

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e e

Ca 4

b a

I 3

yl

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c y

k

A H

3

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s Clutch Gear r

f K

' ff Worm Shaft N-

~'

/

Clutch

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e

/

l e

~, w SMD 0 LIMITORQUE VALVE CONTROL (

CUTAWAY VIEW OF

^

Limit Switch Spring Pace, Drive Gear Dust Cover Spring Pack Worm Torque Switch Drive G.

Worm Shaft i

l I

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Attachment C Figure 2 FIGURE 2 t

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