ML20195D682
| ML20195D682 | |
| Person / Time | |
|---|---|
| Issue date: | 10/26/1988 |
| From: | Rothberg O NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Baer R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| NUDOCS 8811070109 | |
| Download: ML20195D682 (44) | |
Text
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00T 2 61988 T_po dd, e l MEMORANDUM FOR: Robert L. Baer, Chief Engineering issues Branch 77 v n'16M.
Division of Safety Issue Resolution Office of huclear Regulatory Research THRU:
Fiank Cherny, Section Leader A Engineering issues Branch Division of Safety Issue Resolution Office of Nuclear Regulatory Research FROM:
Owen Rothberg Engineering Issues Branch Division of Safety Issue Resolution Office of Nuclear Regulatory Research
,JBJECT:
SUMMARY
OF MEETING BETWEEN NRC STAFF AND INDUSTRY REPRESENTATIVES ON 10/19/88 TO DISCUSS IN SITU TESTING OF MOTOROPERATEDVALVES(MOVS)
On October 19, 1988, a public meeting was held at the NRC Offices in Nicholson Lane to discuss in situ testing of M0Vs. An ettendance list is enclosed (Attachment 1).
NUMARC acted as the lead spokesmen for the utility attendees. Copies of the slides from presentations by Tom Tipton of NUMARC and Bob Kershaw of Arizona Public Service Company are provided as Attachments 2 and 3.
Robert McPherson of Southern California Edison and Bill Ross of Texas Utilities Electric Company also made presentations. Attachment 4 was included at the request of Gerry Weidenhamer and indicates results of blowdown tests on several MOVs equipped with several commercial diagnostic test systems.
The discussion focused on the NRC's proposed generic letter to all nuclear plant owners regarding in situ testing of MOVs. In the generic letter, NRC would recommend that owners perform additional testing, including flow and pressure testing, if practical, of safety-related MOVs in order to assure design-basis operability. That proposed letter was presented to ACRS on October 7, 1988 and CRGR on October 12, 1988. The CRGR package dated 9/28/88 had also been placed in the NRC Public Document Room.
Most of the industry representatives appeared to agree with the need for a MOV testing program that went beyond the requirements of Section XI of the ASME Code and IE Bulletin 85-03. The industry coments centered around the cost and schedular aspects of implementing the program as proposed in the CRGR O
glatonh/Ri$gt
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4 OCT 161988 pe dage..
In general, the industry representatives disagreed with the NRC estimates of cost i.e., stated they were underestimated, and indicated that the schedule did not allow sufficient time to set up the proposed program or conduct periodic testirg.
Specific comments by the industry /NUMARC representatives can be characterized as follows:
a.
The nuclear industry has an ongoing programatic approach to MOV surveillance and maintenance.
Several INP0 and EPRl/HMAC documents and initiatives were discussed.
It was noted that there is no industry-wide comitment to this program to date.
b.
The industry representatives suggested that testing schedules should be prioritized based on the importance of the specific MOV's contribution to avoiding core melt. Several suggestions were made about how this might be done, although the general impression was that prioritization would be a difficult task and there was no current consensus on details of how to accomplish it.
The cost of imp (Coment:lementing the plan would be about 10 times what c.
had estimated Such a cost would be about equal to the benefit without considering improved safety),
d.
Problems in implementation of the HRC program due to shortages of trained personnel, spare parts, test equipment, and vendor support were discussed.
e.
Differential pressure testing in place was considered by the industry representatives to be difficult and expensive.
Periodic testing was also discussed along with trending, as well as industry's desire to adjust test frequency based trending re:,ults.
f.
Detailed test information on Butterfly valve operators and other specialized operators may be difficult to obtain. This will therefore make determination of design basis operability difficult for these components.
These components are less than 15%
of the MOV population.)(Coment:
1 NRC representatives outlined ongoing staff activities on MOVs including several changes that are being made to the proposed generic letter, based on ACRS coments, industry coments at the ACRS subcommittee meeting, and CRGR coments. The comments from this meeting also provided useful information to the staff, i
OCT 2 619B8 NUMARC and the NRC staff plan to discuss the results of this meeting in forthcoming meetings with the ACRS Subcommittee on Mechanical Con.ponents to be held October 23, 1988 and the full ACRS Committee in November, 1988.
/
Owen Rothberg Engineering issues Branch I
Division of Safety Issue Resolution Office of Nuclear Regulatory Research Attachments:
As stated
[MEETit'G NOTES /INSITU TSTNG MOV)
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- SIR :RES
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DATE:10/ p/88_...:.10/3(/.88. :
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4 00T 2 61989 Distribution:
RES Chr'667CTrc E. Sullivan EIB.r/f.
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W. Schwink Document,Confro1~Seetion/
F. Cherny Public Document' Room R. Baer R. Barrett M. Vagins R. Bosnak H. Vandermolen N. Le F. Rosa A. Busiik R. Kirkwood W. Minners J. Page J. Vora E. Rossi W. Farmer E. McKenna G. Weidenhamer W. R. Houston S. Aggarwal T. Novak H. Woods R. Major A. Spano C. Bartlett,
l G. Hammer C. Berlinger S. Israel J. Richardson F. Hebdon G. Cwalina J. Huang W. Parler K. Murphy - RI E. Jordan E. Girard - RII F. Gillespie F. Jape - RII E. Jordan D. Danielson - RIII B. Grimes J. Boardman - RIV C. Calloway - NUMARC C. Clark - RV J. Kopeck i
W. Russell - RI C. Michaelson - ACRS J. N. Grace - RII A. Igne A. B. Davis - RIII R. D. Martin - RIV J. B. Martin - RV T. Murley J. Sniezek F. Miraglia S. Varga D. Crutchfield L. Shao J. Partlow J. Row E. Beckjord D. Ross J. Murphy B. Sheron l
M. W. Hodges T. Hartin G. Arlotto R. Kiessel E. Brown J. Jacobson L. Marsh r
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f.
f A tachecnt 1 ATTENDANCE LIST
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10/19/88 MEETING ON MOV IN SITU TESTING NRC/RES NAME ORGANIZATION PHONE Jerry Mazetis NRC/RES/RPSIB (303)492-3906 Owen Rothberg NRC/RES/ElB (301)492-3924 John J. Lance EPRI/NMAC (415)855-2018 Richard J. Kiessel NRC/NRR/0GCB (301)492-1154 Earl J. Brown NRC/AE00/R0AB (301)492-4491 Frank C. Cherny NRC/RES/EIB (301)492-3945 Warren Minners NRC/DSIR (301)492-3980 Robert Baer NRC/RES/ElB (301)492-3930 Robert C. Elfstrom Toledo Edison (419)249-5000x7692 Robert Kirkwood NRC/RES/ElB (301)492-3928 Joel D. Page NRC/RES/EIB (301)492-3941 Eve Fotopoulos SERCH Licensing, Bechtel (301)258-3094 Brian Curry Philadelphia Electric Co.
(215)327-1200x4497 Bob Kershaw AZ Public Service /PVNGS (602)371-4250 Ron Scherman Cleveland Elec. 111.
(216)259-3737x5300 Bill Ross TV Electric /CPSES (817)897-5734 Joseph Nadean M0 VATS (404)424-6343 Roger CARR MOVATS (404)424-6343 Robert McPherson SCE-SONGS (714)368-6987 R. Clive Callaway NUMARC (202)872-1285 Peter J. Kang NRC/ DEST /SELB (301)492-0812 David Lowry Liberty Technology (215)834-0330 Frederick Burros NRR/ DEST /SELB (301)492-0833 Gerald H. Weidenhamer NRC/RES/EMEB (301)492-3839 Roy Woods NRC/RES/RPS1B (301)492-3908 Nick Konstantinov CECO (312)294-8557 Bill Farmer NRC/RES/DE (301)492-3858
b NAME ORGANIZATION
_ PHONE John Huang NRC/RES/ DEST (301)492-0921 E. L. Igne NRC/ACRS (301)492-1892 Warren J. Hall NUMARC (202)872-1280 Tom Tipton NUMARC (202)872-1280 Randy Yantear Babcock & Wilcox (804)385-2789 j
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t l a NUCLEAR MANAGEMENT AND P
RESOURCES COUNCIL MEETING I
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NUCLEAR REGULATORY COMMISSION 4
N ON I
l DRAFT GENERIC LETTER ON MOVs i
l
M0V GENERIC LETTER CONCERNS o
STATIC TESTING vs DESIGN BASIS TESTING o
PERIODICITY o
IMPLEMENTATION SCHEDULE o
GENERIC LETTER SCOPE o
MOV PROGRAMMATIC APPROACH o
CURRENT EPRI ACTIVITIES o
COST IMPACT l
l F
STATIC TESTING vs DESIGN BASIS TESTING i
o CANNOT IMPLEMENT o
APPENDIX A i
o ALTERNATIVES o
PLANT IMPACT
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PERIODICITY o
FIXED o
ITERATIVE 1
IMPLEMENTATION SCHEDULE o
PRIORITIZATION t
o NUMBER OF VALVES / PLANT o
RESTRAINTS t
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1 i
i
RESTRAINTS 1
o EXTERNAL VALVE VENDOR DATA ACTUATOR DATA DIAGNOSTIC SUPPORT SPARE PARTS o
INTERNAL l
AVAILABILITY FIVE (5)
M0V'S/ WEEK i
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- - - _ ~ - - _ _ -, _ -. _.._.
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GENERI_C LETTER SCOPE o
MAJOR EXPANSION DESIGN REVIEW RETEST REQUIREMENTS o
LIMITED DIAGNOSTICS o
CRITICAL VALVES h
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M0V PROGRAMMATIC APPROACH o
CONTROL /0RGANIZATION o
DESIGN AND EQUIPMENT REVIEW AND VERIFICATION o
DESIGN CONTROL o
PROCEDURES o
TRAINING & QUALIFICATION o
IMPLEMENTATION / MAINTENANCE AND TESTING o
PREVENTIVE MAINTENANCE 1
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EPRI/NPD -
CURRENT EPRI ACTIVITIES I
RELATING TO MOTOR OPERATED VALVES (MOV)
RP2233-2 MOV IMPROVEMENTS RP2814-2 TECHNICAL REPAIR GUIDE-SMB-000 (NMAC)
RP2814-6 APPLICATION GUIDE-LINES FOR MOV's (NMAC)
RFP2233-9 MOV TEST PROGRAM i
Motor Operated Valves (MOV)
Brooks-AtOV 9/EB8
COST IMPACT o
BASELINE
$570,000,000 ESTIMATED COST BASED ON ACTUAL EXPENDITURES IMPLEMENTING IE BULLE. TIN 85-03
$ 39,500,000 ESTIMATED COST BASED ON BROOKHAVEN NATIONAL LAB ANALYSIS o
PERIODIC TESTS
$420,000,000 PER PERIOD l
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EPRl/NPD I
CURRENT EPRI ACTIVITIES I;
RELATING TO fl 4
MOTOR OPERATED VALVES J.MOV3
%5 RP2233-2 MOV
[9 IMPROVEMENTS RP2814-2 TECHNICAL REPAIR T
GUIDE-SMB-000 (NMAC)
RP2814-6 APPLICATION GUIDE-LINES FOR MOV's (NMAC)
RFP2233-9 MOV TEST PROGRAM Motor Operated Valves (MOV)
EPRl/lLPD b
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RP2233-2 MOV IMPROVEMENTS DEVELOPMENT TO EPRI'S "INTELLITOROUE" SYSTEM prom &6 CONTROL & DIAGNOSTIC J_ -
FUNCTIONS FOR MOV's PERMANENT INSTALLATION - nuo p6-)
[1;4 A J< s, DEMONSTRATION UNITS INSTALLED
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COMMERCIALLY AVAILABLE d~ cc.
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INTERIM REPORT NP-4254 341 geygs FINAL REPORT NP-5696 PUBLICATION 4Q 1988 I
Motor Op rated Valves (MOV)
Brooks-MOV 9/8/88 l
l
EPRl/NPD J
RP2814-2 TECHNICAL REPAIR GUIDE SMB-000 LIMITORQUE (NMAC}
l COMPREHENSIVE MAINTENANCE DOCUMENT PREVENTIVE / PREDICTIVE l
FAILURE MODES SPARE PARTS IMPLEMENTATION AIDS PUBLICATION 40 1988 GUIDELINES FOR LARGER SIZF_ UNITS ANTICIPATED Motor Operated Valves (MOV)
EPRI/NPD RP2814-6 APPLICATION GUIDELINES FOR MOV's (NMACS as s ]to! h 0Gitc)4 49 1&9 retuur l
l MOV DESIGN AND FUNCTIONAL REQUIREMENTS MATCHING OF VALVE AND THE MOTOR OPERATOR SELECTION AND SET-UP OF CONTROL AND PROTECTION DEVICES PUBLICATION 101989 Motor Operated Valves (MOV)
i EPRl/NPD RFP2233-9 MOV TEST PROGRAM I
OBJECTIVES PREDICT PERFORMANCE OF MOV's SIMPLIFY IN-SITU TESTS I
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METHODOLOGY l
ACCUMLATE & EVALUATE EXISTING MOV TEST DATA i
CONDUCT ADDITIONALTESTS AS REQUIRED
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UP-BATE MOV SIZING CALCULATIONS
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N h0h kNT EARLY RESULTS OF GATE VALVE FLOW INTERRUPTION BLOWDOWN TESTSa Kevin fi. DeWa11 Idaho National Engineering Laboratory EG&G Idaho, Inc.
Idaho Falls, Idaho 83415 ABSTRACT b
The areliminary results of the USNRC/INEL high energy BWR line breat flow interruption testing are presented. Two representative nuclear valve assemblies were cycled under design basis Reactor Water Cleanup pipe break conditions to provide input for the tecnnical basis for resolving the Nuclear Regulatory Comission's Generic Issue 87. The effects of the blowdown hydraulic loadings on valve operability, especially valve closure stem forces, were studied. The blowdown tests showed that, given enough thrust, typical gate valves will close against the high flow resulting from a line break. The tests also showed that proper operator sizing depends on the correct identification of values for the sizing equation. Evidence exists that values used in the past may not be conservative for all valve applications. The tests showed that i
improper operator lock ring installation following test or maintenance can invalidate in-situ test results and prevent the valve from performing its design function.
i Introduction As part of the Nuclear Regulatory Comission's (NRC) Equipment Operability research program, the Idaho National Engineering Laboratory
~i (INEL) is performing research to provide input for the technical basis for t
resolving Generic Issue 87 (GI-87), "Failure of HPCI Steam Line Without Isolation." This INEL research program also provides information applicable to two additional regulatory items:
(1) Generic Issue II.E.6.1, "In Situ Testing of Valves" and (2) IE Bulletin 85-03, "Motor Operated Valve Comon Mode Failures During Plant Transients Oue To Improper Switch Settings."
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The objective of the INEL research program is to determine whether isolation valves in high energy BWR piping systems will close against high i
flows in the event'of a pipe break outside containment. GI-87 applies to r
those process lines that comunicate with the primary system, pass through Work supported by the U.S. Nucle:r Regulatory Comission, Office of e.
NJclear Regulatory Research, under DOE Contract No. OE AC07-761D01570, under t
the direction of Dr. G. H. Weidenhamer. Technical Monitor.
b.
United States Nuclear Regulatory Comission/ Idaho National Engineering Laboratory.
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l containment, and contain normally open isolation valves. Three process lines meet these criteria:
(1) the High Pressure Coolant Injection (HPCI) steam supply line, (2) the Reactor Core Isolation Cooling (RCIC) steam e
supply line, and (3) the Reactor Water Cleanup (RWCU) supply line. Of the three, an unisolated break in the RWCU supply line was determined to have the greatest safety impact. The design basis hot water blowdown testing was performed to provide information on valve operability questions associated with the RWCU environment (subcooled water flashing to steam). The majority of r,lCU containment isolation valves are 6-inch, 900-pound, flexible-wedge gate valves with limitorque electric motor operators.
'Backaround The gate valve, Figure 1, is designed for use in a.ystem where a positive shut off is required with minimal pressure drop when the valve is open.
It is ideally suited to those situations where isolation of one part of a system from another is required and control of the dynamic properties i
is unnecessary. With the disc (or gate) in the of the fluid (throttling) f the valve is free of any obstruction with raised position, the run o j
approximately the same head loss as in the adjacent piping. When the disc j
is lowered into the seat, the upstream pressure forces it against the seat, l
j creating a seal and isolating the downstream system from the fluid.
I Most of the valve and operator manufacturers use the same equation to determine valve closure forces, with only minor variations in coefficients.
1 In this equation, the required force to cycle the valve is equated to the sum of the disc drag load due to differential pressure, the stem rejection low (stem end pressure load), and the packing drag load, as detailed below.
F
= p(Aq)(AP)
A (P) + F (1) t 3
p Where F
= Total stem force
(
t
= Disc friction factor l
Ad
= Dise area AP
= Differential pressure 1
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- Stem cross-sectional ar=&
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i P
= System pressure F
= Packing drag load (a constant).
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The disc load is determined by multiplying the exposed disc area by the differer.tial pressure and a disc factor to account for seating surface and I
guide sliding friction. The disc factor normally used for wedge type gate valves in Equation (1) is 0.3.
The stem rejection load is.found by. taking the.
stem cross-sectional area and multiplying it by the system pressure. Note J
that in this equation the stem rejection load can be either positive or negative depending on whether the valve is closing or opening. This is
~
because the stem rejection load is always in a direction out of the valve I
body; the stem rejection load resists valve closure and assitts in valve l
opening.
The service conditions used in the force equation are supplied by each individual plant, t
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Figure 1.
Typical motor-operated gate valye.
Test Desian in the blowdewn test research program two full-scale, representative nuclear valve assemblies were cycled under design basis RWCU pipe break conditions. Both valves were modified to incor) orate extended yokes (4 inches longer than normal) and stems cut in half and tireaded to allow installation of the special stem force instrumentation. Flanges were attached to both i
sides of eacti valve for mating with the test system piping.
The first test specimen, Valve A, was a 6-inch, 900 pound standard rated.
cast steel, flexible wedge gate valve with a pressure seal bonnet and butt
' weld ends. The valve seats were hard faced with Stellite and seal welded to the valve body. The one-piece flexible wedge (disc) was also hard faced with Stellite on the seating fa:es, and the disc guides were carbon steel. The valve was manufactured for this test prograc by Anchor / Darling Valve Company using a nuclear grade body ca: ting, nuclear design and materials, without third party inspections. The valve was powered by a Limitorque SMB 2-40 electric motor operator. The valve design was representative of valves installed in early nuclear power plants, i
The second test specimen, Valve B, was a 6-inch, 900 pound standard rated, forged steel, flexible-wedge gate valve with a bolted bonnet and butt weld ends. The valve seats were hard faced with Stellite and seal welded to the valve body. The one piece flexible wedge (disc) was also hard faced with
)
Stellite on the seating faces. The valve was manufactured for this test program by Velan incorporated using nuclear design and materials, without third party inspections. The valve was powered by a Limitorque SMB 0 25 electric motor operator. Representing one of the newer valve assemblies delivered since 1970, the Valve B design incorporated hard-faced disc guide wear surfaces.
Both valves utilized 460 Vac, 3 phase, 60 Hz electric motor operators. To ensure valve closure and data collection at the anticipated greater-than normal loadings, Valve A utilized a larger, greater-capacity 1
motor operator than would normally be used. The motor operator used with Valve B was sized in accordance with curr6nt practices to represent a typical valve used in nuclear power plants today. With their differences in internal and friction bearing surface design, the two valve assemblies represented a large number of motor-operated valves used in nuclear plants today.
The test system used for the subcooled water blowdown testing featured a large water tank, heated and pressurized so that various system water conditions could be established and regulated, replicating actual BWR conditions. The water was propelled by high-pressure gaseous nitrogen. The water heating system consisted of a heating section and a high-pressure, high-temperature water pump. The heating section contained an electrical heater in an 8-iach pipe and heated tha water as the pump recirculated water from the pressure vessel, through the test section ar.d heating section, and 4
back to the pressure vessel. The test section was a 6-inch pipe with the test specimen mounting flanges and appropriate fittings for obtaining temperature and pressure measurements. The system is shown schematically in Figure 2.
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Bleed n
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=
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Mechanism ig 3
Pump Heater p
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- g Flowmeter Vent Valve 4
BMCOO176 l
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Test system schematic showing instrumentation locations.
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m r-r--
To acceiplish the functional testing, the system contained bleed valves which provioed the means to reduce systcm pressure on both sides (upstream and downstream) of the test specimen.
In this manner, differential pressure conditions could be established across the test valve's disc. The test system also featured a fast acting (approximately 300 msee opening stroke),
hydraulically operated valve, positioned so that when the valve was actuated, the system's fluid was abruptly dumped to the atmosphere, resulting in high-flow (blowdown) conditions through the test specimen.
The test system was instrumented to monitor flow, pressure, and temperature at various locations, including test valve upstream and downstream positions. Motor operator electrical characteristics were also recorded. Valve stem force was monitored using a special high temperature load cell installed between the two halves of the specially designed valve stems. The test parameters measured are listed in Table 1.
A secondary objective of the blowdown test program was to d*termine how normal utility in situ valve testing, using available diagnostic equipment, could be used to provide assurance of a valve's ability to isolate pipe break flows. By measuring actual stem forces and associated motor operator parameters, in-situ plant testing plans may be developed using available diagnostic equipment; the values of the functions measured by this equipment are then extrapolated to actual stem forces. Several motor-operated valve (HOV) diagnostic system manufacturers supported this objective by participating in the testing as listed in Table 2 in chronological order.
The manufacturer participation was not a competition but, rather, an attempt to determine what factors need to be considered to provide reasonable assurance of valve operability usino each device.
While general observations are made in this paper concerning the use of this diagnostic equipment, in depth analysis of the data taken and discussions of how the devices may best be utilized must await review of the digitized data, scheduled for early Fiscal Year-1989, as well as analysis coordination with the diagnostic equipment manufacturers.
Test ProcedEt Upon installation in the test system, each valve assembly was subjected 1
to a typical ANSI B16.41 functional qualification test, including the valve leakage test (Annex A), cold cyclic test (Annex B), and hot cyclic test (Annex C). These tests were accomplished to provide a baseline characterization of valve assembly operation for comparison with the later testing. The valve leakage test established the mainseat valve leakage. rate and the packing leakage rate of the test valves, while the cold cyclic test demonstrated the capability of the test valve assembly to open and close under adverse combinations of motive power and system cressure with the assembly at room temperature not exceeding 100*F. The i.st cyclic test sequence was performed to demonstrate the capability of the test valve assemblies to open and close under adverse combinations of motive power and system pressure with the assembly at design temperature, in excess of 100*F. Annex G, flow isolation, was the subject of this test program and thus was not performed as part of the qualification series.
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h TABLE 1.
TEST PARAMETERS MEASURED DURING BLOWDOWN TESTS Oscillo-Data X-Y Transducer Measurement FM Taoe oraoh Loooer Plotter Tl System Water Temp.
X Test Valve Inlet Water Temp.
X T2 T3 Test Valve Body Temp.
X T4 Heating Section Water Temp.
X T5 Load Cell Temp.
X P1 System Water Press.
X X
X X
P2 Test Valve Inlet Water Press.
X X
X P3 Test Valve Outlet Water Press.
X X
X P4 Discharge Section Water Press.
X X
X API Test Valve Differential Press.
X X
X AP2 Venturi Differential Press.
X X
X AP3 Pump Differential Press.
X X
11 Actuator Current X
X 12 Actuator Current X
13 Actuator Current X
El Actuator Voltage X
X E2 Actuator Voltage.
X X
LSI Open Limit Switch.
X X
LS2 Close Limit Switch TS Close Torque Switch X
X F
Yalve Stem Force X
X X
Al Actuator' Acceleration Y X
X A2 Actuator Acceleration X X
A3 Actuator Acceleration Z X
A4 Valve Body Acceleration Y X
X A5 Valve lody Acceleration X X
A6 Valve Body Acceleration Z X
Control room light. indicator only.
TABLE 2.
VALVE DIAGNOSTIC E0VIPMENT USED FOR SUBCOOLED BLOWDOWN TESTS Test Diagnostic Valve Serieg Description
_Eouinment A
1 Qualification Test MCSA A
3 Blowdown, 1000psig, 480'F MCSA A
2 Blowdown, 1000psig. 530'F None A
4 Blowdown, 1000psig, 400*F V MODS A
6 Blowdown, 1400psig, 530*F V MODS A
5 Blowdown, 1400psig, 580'F MOVATS A
7 Blowdown, 1400psig, 450*F MOVATS A
9 Blowdown, 600psig, 430'F None A
8 Blowdown, 600ps g, 480*F None A
10 Blowdown, 600ps g, 350'F MAC, VOTES A
11 Blowdown, 1000ps g, 530'F MCSA B
1 Qualification Test MCSA B
2 Blowdown, 1000psig, 530'F MCSA, MOVATS B
3 Blowdown,1400psig, 580* F V M005 B
4 Blovdown, 600psig, 480'F MAC B
5 Blowdown,1000psig, 530*F V MODS MAC Limitorque Motor actuator Characterizer MCSA ORNL Motor Current lignature Analysis MOVATS NOVATS, Inc. (BQY Anallsis and Iest System)
V MODS WYLE Labs Yalve Motor Operator Qiagnostic System V0TES Liberty Technology yalve Operator Iest & Evaluation System I
i Once baseline qualification testing of the test valve assemblies was completed, several test series were performed to address the questions of GI-87.
Each test series included leakage tests, cyclic tests without flow, cyclic tests at normal system flow, and cyclic tests at full blowdown conditions. A wide range of design upstream pressures and temperatures was maintained throughout the valve closures, with blowdown flow limited only by flashing and choked flow at the test valve or piping exit.
Each test series was structured to optimize the amount of useful data obtained. Required non flow data were collected during the preparation period for full-scale flow and post full-scale flow.
Fourteen blowdown tests were acccmplished, ten on Valve A and four on Valve B.
All tests were performed to evaluate the engineering parameters required to calculate closure loads for a typical valve.
In addition, the four tests with the Valve B and normally sized operator were performed to demonstrate expected in service performance with the motive power closer to normal.
l Test Results and Interoretation l
Valve A: A torque switch setting of 2.0 was selected for the motor operator so that the stem thrust capability was maximized without exceeding the valve and instrumentation capacity.
(The torque switch was reset to 2.5 after test 10 to compensate for an observed torque out anomaly, discussed later.)
The valve closed satisfactorily for all tests; however, higher than predicted stem loads were observed during the blowdown flow isolation cycles.
Figure 3 is a reproduction of the stem force trace for the blowdown test with initial fluid conditions at 1000 psig and 530*F subcooled water.
The figure shows the stem compression (negative values) increasing as the valve closes until it reaches a peak where the flow path is finally blocked and the valve disc is riding against the full seat ring. At this point the stem compression decreases sharply to a value representing the force required to slide the disc on the seat to the fully seated position. Then the force rises sharply through final seat'ing and torque switch trip. The compressive force in the stem then continues to iacrease due to the time lag in the circuit dropout time and the momentum in the operator. The peak shown shortly before final seating of the valve is the force that must be overcome for successful closure. This peak is the flow isolation force referred to in comparisons and discussions throughout this paper.
Equation (1) was used to predict. stem forces during closur, at.high flow. Following typical industry practices, the parameters chosen for use in the equation were conservatively chosen to be maximum design pressure (P
& AP) and assumed worst case packing drag force. The Valve A closure thrust was predicted using nominal valve size (6 in.) to calculate disc area, maximum upstream pressure for P & AP, a packing drag force of 1500 pounds, and a 0.3 disc factor. The calculation was repeated using a 0.5 disc factor following recent industry recommendations for gate valves in high-flow applications.
e
Valve A,1000 psig, 530 'F 0
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Closure stroke begins
[seaung force _
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Flow isolated E
et G
r* itch sw trip
-30 I
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0 10 20 30 40 Time (s) sucoots:
Figure 3.
Load cell measurements show the effect of blowdown flows on valve closure stem loads.
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L Figure 4 shows a comparison between the predicted stem forces (using the above assumptions) using 0.3 and 0.5 disc factors and the actual stem forces measured during the blowdown isolation steps.
For Valve A testing, both the pressures and temperatures were varied to change the degree of subcooling and thus degree of flashing occurring at the valve during closure. This figure shows that at the lower pressures the actual stem forces were closely predicted by the sizing calculation, as were the forces that were at higher l
pressures but greatly subcooled. The sizing calculations did not bound stem forces for the tests at higher pressures with water closer to saturation i
temperatures. A disc factor of about 0.57 would be necessary to reach the 19,400 pound stem force measured during the 1000 psig, 10'F subcooled l
water test.
In order to investigate how well Equation (1) models the actual behavior of the valve, the conservatism needs to be removed from the calculation.
If the disc load is eliminated from Equation (1), such as would be the case without flow, what remains is a linear equation in slope intercept form (y = mx + b), namely:
Ft
- - A (P) i F (2) s p
Note that this equation has been written so that the stem rejection load is always negative (compression) while the packing load is either negative or positive depending on whether the valve is closing (compression) or opening (tension).
}
Figures 5 and 6 show the test data that are expected to apply to the above equation. The data plotted are the stem force measured at mid-stroke (running load) for tests at varying temperatures and pressures but without flow..The line fit through the data points has a slope equal to the stem cross-sectional l
area and provides an indication of the true packing load for each case.
For Valve A, data show a packing load of 835 pounds for opening and 430 pounds for
+
closing. Both values are well below the 1500 pounds used in the sizing i
equation, providing additional margin in the calculation. The difference i
between the two values can be partially accounted for by the weight of the disc ar.d lower half of the stem. This difference also provides evidence that the packing load is affected by direction of travel, possibly caused by water i
carried with the shaft changing the lubrication of the packing / stem surfaces l
or by other phenomena associated with stem travel through packing.
Based on the packing load and stem rejection load characteristics 1
determined from the running load evaluation, an evaluation of the total force equation (Equation (1)] was conducted. Here the conservatisms found.in-the, application of the equation were eliminated by using measured parameters in the equation. Figure 7 contains the results of this calculation for the l
blowdown test shown in Figure 3 and compares it to the measured stem force.
As might be expected, the calculated force bounds actual values during the first part of closure, when little of the disc area is exposed to the flow and differential pressure across the valve is small. As the disc drops further l
into the flow stream and differential pressure increases, the calculation ceases to bound measured values, where the actual flow isolation stem force i
l exceeds those calculated.
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i 0.5 0.7 0.9 1.1 1.3 1.5 t
(Thousands)
Up.=tream Pressure (psia) sucooise Figure 4.
Valve A measured stem forces exceeded those calculated for tests at high pressure and slightly subcooled conditions.
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1.4 14 (Thous ends) sritem Presswe (esio Figure 5.
Linear curve fit using industry equation closely approximates Valve A running stem forces for opening without flow.
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Figure 6.
Linear curve fit using industry equation closely approximates Valve A running stem forces for closing without flow.
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The valve assembly was disassembled after testing to evaluate the condition of valve internals exposed to the high flow testing. The disc (wedge) was removed and examined to determine how the blowdown forces had affected its condition. The disc was worn on the guides and sealing surfaces of the downstream face, indicating a cocking of the disc toward the i
downstream side. The upstream face was not damaged. An examination of the assembled position of the disc valve body revealed large clearances of about 1/4 inch between the disc and disc guide rails mounted to the valve body.
This clearance plus the wear on the disc guides and guide rails allowed the disc to cock downstream far enough to come in contact with the seat ring during the last half of the closure stroke. This contact explains the wear i
pattern found on the disc face, and may also be the cause of the high i
closure forces noted just prior to ficw isolation during the higher energy blowdown tests (see Figure 3).
1 Judging by the wear patterns observed, it is unilkely that the valve could have produced a tight seal using the downstream face alone. A tight seal on the downstream face would have been required to isolate flow if the
[
valve torqued out prior to full travel but with the disc on the seat. The valve, however, maintained a tight seal throughout testing, indicating a tight seal on the upstream face of the disc-a benefit of using an oversized operator with a higher than-necessary torque switch setting.
Valve B: A torque switch setting of 1.75 was selected for the Valve B assembly to provide the needed closure thrust for the given test conditions. This setting, however, resulted in delivered stem thrust (as determined by the stem. mounted load cell) that was below the calculated l
magnitude. The torque switch setting was therefore raised to 2.0 prior to j
the first system blowdown test.
j The valve performed satisfactorily during the testing except for the 1400 psig test, where the operator torqued out before the disc reached the
[
fully closed position (1/4 inch travel remaining). Even during this test, however, the valve had closed far enough to produce a tight seal, with no leakage observed.
l i
in accordance with manufacturer procedures, the valve thrust was i
predicted using actual orifice area for disc area, upstream pressure for P &
j AP, a disc factor of 0.3, and a packing drag force of 5000 pounds (the j
maximum eroected for this packing configuration). Based on the initial j
results of the Valve A tests, all of the blowdown tests with Valve B were conducted at rear saturation temperatures for the various pressures. Figure 8 shows a comparison between the test measurements and the thrust,
i calculations for the Valve B tests. The estimated stem forces, shown as the i
solid line, provide reasonable predictions of actual forces for lower pressure cases. Maximum flow isolation forces could not be measured I
. for the 1400 psig test because the torque switch tripped prior to full
[
closure. Figure 8 therefore shows the extrapolated stem force ct 1300 psig (pressure at flow isolation) based on actual stem force characteristics prior to torque switch trip for two closure cycles. Here, as with Valve A, r'
predicted stem forces are not conservative at higher pressures.
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a Extrapolated closwo forces A
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.s 1.1 1.3 1.5 (Thousands) l Upstream Pressure (psig) omoeono
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figure 8.
Valve B extrapolated stem forces exceeded those calculated for tests at high pressure and slightly subcooled conditions.
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Figures 9 and 10 shov the Valve B test data that are expected to apply to Equation (2). Here ag0in, the data plotted are the stem forces measured at mid stroke for tests at varying temperaturas and pressures but without flow. The line fit through the data points has a slope equal to the stem cross-sectional area and provides an indication of the true packing load for both the opening and closing strokes. The increase in packing forces over those found for Valve A is believed to result from the different packing design and greater stem diameter of this valve.
The line fit through the data points for this valve shows a packing load
.of 1610 pounds opening and 1632 pounds closing. The force calculation for this case included a 5000 pound packing load, again providing conservatism.
The difference between the opening and closing values is less than expected, given the weight of the disc and lower stem half (over 50 pounds). This may indicate a directional relationship for packing load, believed to be a characteristic of the packing type used and its orientation.
Based on the packing load and stem rejection load characteristics determined from the running load evaluation, an evaluation of the total force equation was conducted. Here again the conservatisms found in the application of the equation were eliminated by using measured parameter:. in the equation.
For the Valve B assembly, stem force calculations under predicted actual measurements. Figure 11 shows the maximum stem forces for closure during the blowdown testing at 1400 psig and 580*F.
As with the previous valve, the calculated force bounds actual values during most of the closure cycle. As the valve isolates flow and differential pressure approaches full system pressure, the stem force exceeds that calculated.
No wear patterns were noted on the Valve B disc after testing. The inspection of the valve internals noted tight clearances in the disc guide / guide rail interface and eachined, hard faced disc guide surfaces.
Ocerator Toroue Switch Trio Anomaly: During the blowdown testing of Valve A, there were three incidences of anomalous operator torque switch trip
- behavior, it is believed these incidences occurred in conjunction with installation and removal of the MOV diagnostic test equipment. The valve stem forces associated with torque switch trip were normal in the numerous tests performed with diagnostic devices installed. The anomaly appeared in the form of abnormally low valve torque-out stem forces during the tests imediately af ter removal of two types of diagnostic equipment. The investigation that followed the discovery of the low stem forces showed that incorrect installation of the motor operator spring pack lock ring was the problem. The removal of the diagnostic test equipment and the subsequent incorrect installation of the lock ring invalidated the findings of the diagnostic test A recent problem investi atton at Brunswick (LER 87 023 01)2 has identified a similar ock ring installation problem and illustrates the potential for invalidated diagnostic testing elsewhere.
The point at which the torque switch contacts open is dependent only on the setting of the torque switch, rate of tne torque spring, and spring pack
.e e-o 3
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= Com. rettettle t
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e es e4 es se is i.
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Figure 9.
Linear curve fit using industry equation closely approximates Valve B running stem forces for opening without, flow.
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i Figure 10. Linear curve fit using industry equation closely approximates Valve B running stem forces for closing without flow.
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s, Valve B,1400 psig, 580 'F to g
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20 de so 80 1co Percent Closed suceover Figure 11. Caleviations using 0.3 disc factor and removing typical
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conservatises do not model final flow isolation forces.
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f be t'am force to increase, whether i
preload and gap. No matter what r e i
flow loads, valve reaching full s 'er a w n an obstacle in the disc path, the switch will always open 4.m # Nrque spring compresses to the I
j predetermined point. The force at t eq x switch trip was used to trace the I
function of the operator from one test to another through various diagnostic
- l compression at torque switch trip for each of the 11 tests performed on equipment installations and removals. Figure 12 shows the average stem t
1 Valve A, arranged in chronological order. The force measurements were made i
using the INEL load cell installed as an integral part of the valve stem, i
During tests 1 through 7 the valve operator functioned consistently, i
'with a stem compression at torque switch trip of approxi:aately 33,000 pounds. Tests 9 and 8, accomplished without operator diagnostic monitoring, showed consistent torque out forces, but at a significantly reduced level.
Here a drup of approximately 10,000 pounds appeared in the torque out stem compression.
i s
Two different sets of valve operator diagnostic equipment were installed i
1 j
to monitor test 10, and the valve stem torque out compressir.n returned to about the same level as tests 1 through 7 (re lubricatior of the valve stem threads increased loads slightly). The diagnostic eriopment was removed i
after test 10, and the results of test 11 show a similar reduction in force, j
even after the torque switch setting was increased from 2.0 to 2.5.
i After the completion of testing for Valve A, the Limitorque motor j
operator was removed and partially disassembled by Limitorque j
representatives with INEL personnel attending. The spring pack cover was removed and the internal configuration inspected. The lock ring that retains the torque spring and its locking set screw appeared to be properly i
installed. The set screw was removed and a special tool was used to attempt to further tighten the lock ring. The ring was tightened almost one full l
j turn before it reached its proper position.
f Limitorque design records were used to correlate the loosening of the i
lock ring to torque switch setting and torque out thrust. One full turn of
}
the lock ring is equivalent to 19 degrees' rotation of the torque switch.
i One full torque switch setting is about 21 degrees. This loosening of the i
j lock ring had the effect of backing off the torque switch from 2.0 (the i
actual setting) to 1.1 (the equivalent setting). From the torque spring l
J) curve the loss of thrust was estimated at 10,600 pounds, very close to the
]
discrepancy in the measured data.
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t i
i leproper positioning of the lock ring sometime after test 7 but before j
the next test would explain the reduction in stem force after test 7.
How s
it happened is not completely understood. None of the diagnostic devices installed artor to test 9 require the removal or adjustment of the torque spring loc ( ring; in fact, several of the devices are designed to diagnose i
spring pack gap, the result of improper lock ring installation. Review of i
the data taken by the various diagnostic devices shows no indication of i
spring pack gap. Also, none of the devices are designed such that their installation would correct for this problem, with the exception of the Limitorque motor actuator characterizer (MAC) device.
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Installation of the MAC device requires the removal of the torque spring lock ring to facilitate the installation of its spring pack load cell device. According to the Limitorque technician, the position of the lock ring was marked prior to removal and the number of turns during removal was noted. The load cell device was installed and tightened to the
> roper position to provide the design spring preload. After testing, tie load cell was removed and the lock ring installed the appropriate number of turns to the oreviousiv marked oosition. We believe this explains the similar reduction in stem force before and after test 10.
A correlated event was determined from a review of the Brunswick LER.
In this case, the HPCI steam line isolation valve (a GI 87 valve) had successfully undergone several diagnostic tests using the MC system.
Later, the valve motor failed on opening for an unrelated reason. During the subsequent motor operator chec(, greatly reduced torque out forces were observed.
Investigating personnel discovered that a burr on the threads of the spring pack bousing cover had prevented the lock ring from being fully installed after diagnostic testing and had caused the lower-than expected torque readings.
Both instances of improper lock ring positioning could have been easily diagnosed. A simple measurement of the lock ring position can be compared with both the position of torque spring transducer during testing and the manufacturer design position in order to validate post-test valve operation. Apparently this procedure was not completed for the above described tests, fanclusions The design basis hot water blowdown testing has shown that, given enough thrust, typical gate valves will close against the high flow resulting from a line break. Proper operator sizing depends on correct identification of the values for the sizing equation.
Evidence exists that values used in the past may not be conservative for all valve applications. The following items need to be considered during sizing,of gate valve operators.
1.
Gate valve internal and friction bearing surface design can have a significant effect on the operator force requirements for pipe break flow isolation.
l 2.
The degree of subcooling at the valve inlet can greatly influence valve closure forces. Valve operator force requirements increase as inlet fluid conditions approach saturation temperatures..
3.
Industry trends toward using 100 percent system pressure for all I
pressure terms'in the sizing calculation are justified for l
high flow applications.
1 leproper operator lock ring installation following test or maintenance I
l can invalidate in situ test results and render the valve unable to perform l
its design function. This is irportcnt in light of the present trend by i
l
[
+*
utilities to perform diagnostic testing of safety related valve assemblies to answer regulatory concerns such as IE Bulletin 85 03. A final quality i
check following diagnostic testing and maintenance must be made to ensure j
correct lock ring installation.
t References 1.
ANSI B16.41, Functional Qualification Reauirements for Power Ooerated Active Valve Assemblies for Nuclear Power Plants,1983.
I 2.
Brunswick Steam Electric Plant Unit 1, Inocerabilito of Hinh Pressure
- n_fection (HPCI) System (E41) Due to Failure of HPC : "urbine Steam inlet
- solation Valve E41-1:001, t.ER 87 023-01, June 27, 1988.
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