ML20238D565
| ML20238D565 | |
| Person / Time | |
|---|---|
| Issue date: | 08/12/1987 |
| From: | Jeffrey Jacobson, Potapovs U Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20238D553 | List: |
| References | |
| REF-QA-99900100 NUDOCS 8709110255 | |
| Download: ML20238D565 (9) | |
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..t i ORGANIZATION:B LIMITORQUE C0RPORATIOS,.
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N REPORT NO.: 99900!00/67-01 DATES: 6/24-7/1/67 20l
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CORRESPONDENCE AfEE53I~Limitorque Orporatlor? [
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'.T ATTIM Mr. F. Kc Denhan
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Executive Vice President
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(002),528-4400
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I IJUCLEAR INDUSTRY, ACTIVITY:. Manufacturer of motor operatt!d valve actuators.
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i APPROVED BY:
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Uldts Potapovs. Chief, L
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9 INSFEC110H BASES AND SCOPE:
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10CFRPart50,AppendixBand10CFRPart;$1.
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SCOPE:, This inspection was made to review operatiginal, quality assurance, and environmental qualifice' inn issues reported to the NRC c
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'concerninr, limitorque motor operated va 5e actuators.
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A review of Limitorque's quality assurance prograniyas not conducted during this inspection, t
' s' PEANT SITE APPLICABILITY: Limerick 50-352/353, Brunswick'>EG-325/324, Peach Bottbm 30>171/277/278, Trojen 50-344, Erowns' Ferry 50-259/it60/296, Rancho Seco 60-312. Arkansas Nuclear One' 50-313, San Onofre 50-206/M1/362, Watts Bar 50-3?O/391.
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ORGANIZATION: LIMIT 0kQUE CORPORATION LYNCHBURG, VIRGINIA REPORT-INSPECTION i
NO.: 99900100/67-01 RESULTS:
PAGE 2 of 8 4
A.
VIOLATIONS:
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None.
B.
NON';0_NFORMANCES:
Nont.
C.
STATUS OF PREVIOUS INSPECTION FINDINGS:
A review of previous inspection findings was not performed. Previous inspection items will be reviewed during a future inspection.
I D.
OTHER FINDINGS AND COMMENTS:
1.
Ac~tuator Sizing and Performance It was determined that motors used in Limitorque actuators are ~20%
rated duty motors. DC motors are rated to run at 20% of the motor's maximum rated torque output for five minutes while AC motors have a 15 minute rating. For exemple, a 10 ft-lb DC rated motor is designed to run for five minutes at 2 ft-lbs without exceeding temperature I
rise specifications.
It was also determined that a typical AC motor will put out approximately 10% more and a DC motor 50% more than I
rated maximum torque before reaching a stalled condition.
Recently a number of plants have reported they have found actuators that contained undersized motors. This problem appears to have been caused by the use of wrong differential pressures, the failure to account for degraded voltage conditions, or the use of incorrect stem factor coefficients during original sizing calculations. These calculations were usually performed by the valve manufacturer or the plant architect-engineer.
2.
Hydraulic Lock Testing Program A review was conducted of Limitorque's program to test actuators for d
the potential cf spring pack hydraulic lock. Spring pack hydraulic lock was shown to occur on an actuator removed from the Limerick Nucicar Power Plant during a specially conducted test. Hydraulic lock occurs when the spring pack is filled with grease and then forced to quickly compress during valve seating. The trapped grease cannot be relieved quickly, the torque switch does not open, and the actuator essentially becomes locked. This condition results in rapid motor overheating and subsequent motor burnout.
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ORGANIZATION: L1HITORQUE CORPORATION i
LYNCHBURG, VIRGINIA REPORT INSPECTION H0.: 99900100/87-01 RESULTS:
' AGE 3 of 8 i
Limitorque has set up a similar actuator to the one that failed at Limerick and has tried to obtain the hydraulic lock condition.
Testing had not been completed at the time of the review and no firm conclusions had been drawn.
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3.
Spring Pack Stress Relaxation c
Problems with spring pack relaxation on normally closed valves have recently been reported. At Peach Bottom, Limitorque traced the problem to the rebuilding of the spring 3acks with parts of slightly different dimension. Specifically, the 3 earing cartridge stems had been redesigned and had a difference of 1/16" in length. This difference was said to have caused the relaxation observed. A spring pack was recently returned to Limitorque from the Salem Nuclear Plant where it is to be analyzed. No reason for the relaxation of this spring pack had yet been determined. This aroblem was also reported to Limitorque by Trojan and Browns Ferry aut Limitorque has not received spring packs from these plants for j
analysis.
4.
Improper Spring Packs Insta11ed'in Brunswick Actuators On June 22, 1987 the Brunswick Steam Electric Plant issued LER 87-018 which described the discovery of two undersized spring packs that were thought to have been furnished with two actuators purchased from Limitorque some time ago. The actuators were part of a purchase order in which four actuators were procured for use in the RHR system of Units 1 and 2.
The two actuators which were installed in Unit 1 were found to contain the incorrect spring packs whereas the two actuators in Unit 2 have not yet been inspected.
Brunswick had no record of ever changing the spring packs in these actuators so their installation was attributed to vendor error. The incorrect spring packs that had been installed had part numbers that differed by one digit from the correct spring packs (60-600-0010-1 vs. 60-600-0011-1).
Discussion with Limitorque revealed that no documented checks for proper spring pack installation were performed at the time these actuators were manufactured. Limitorque stated that large actuators such as those in question are normally manufactured in quantities of 4-8 and that they would investigate to see if similar actuators made during the same time frame may also have had incorrect spring packs installed.
ORGANIZATION: LIMITORQUE CORPORATION LYNCHBURG, VIRGINIA REPORT INSPECTION N0.: 99900100/87-01 RESULTS:
) AGE 4 of 8 6.
Warped Limit Switch Rotors Supplied to Rancho Seco On February 50, 1987 the NRC received a 10 CFR Part 21 Teport from the Sacramento Municipal Utility District (SMUD) concerning warped limit switch rotors that Limitorque had supplied to the Rancho Seco Nuclear Generating Station. The report described a shipnent of 50 rotors of which 7 were found to be warped sufficiently to prevent proper limit switch adjustment. Review of this issue with Limitorque determined that previously only samples of rotors were checked for straightness. Limitorque is now checking 100% of safety related rotors for straightness and is in the process of notifying all nuclear customers of the potential for warped rotors for those rotors previously supplied. Limitorque has not determir.ed the cause for the warped rotors however, they did acknowledge the fact that warped rotors had been discovered during the sample inspections that ha'd been previously performed.
7.
Criteria for Exceeding Published Actuator Thrust Limits A discussion was conducted with Limitorque concerning the criteria given to Arkansas Power and Light Company for exceeding published actuator thrust limits on Limitorque's installed in the Arkansas Nuclear One plant. Limitorque stated that published thrust limits could be exceeded by 10% as measured at torque switch actuation by MAC or H0 VATS type testing.
Actuators can then be operated for a maximum of 100 cycles at this condition. For actuators that have been found to have had thrust limits exceeded, Limitorque recommends performing NDE on the actuator housing, housing cover, and drive sleeve. Additionally they reconinend performing a visual examination on the upper bearing for Brinell marks. The actuator can then be operated safely at or below the published thrust ratings.
8.
Cracked Grease Seals on Motors Shipped to San Onofre During a recent NRC inspection at the San Onofre Nuclear Generating Station the inspector was shown a number of newly purchased Limitorque (Reliance) motors that had been shipped to San Onofre with cracked or improperly installed grease seals. Limitorque is currently investigating the cause of cracked seals with their supplier Reliance Electric and has indicated appropriate actions will be taken as required.
ORGANIZATION: LIMITORQUE CORPORATION LYNCHBURG, VIRGINIA REPORT INSPECTION PAGE 5 of 8 i
NO.: 99900100/87-01 RESULTS:
9.
Shaft-Keyway Failures in Actuators at Watts Bar On November 12, 1986 the NRC received a report from the. Tennessee Valley Authority concerning a failed motor pinion key and shaft in a '
Limitorque actuator installed in the Watts Bar Nuclear Plant. The failure was reported to be similar to the condition reported in IE
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Information Notice 81-08 which addressed failure of motor pinion keys in Limitorque SMb-4 actuators with motor torques in excess of 100 ft-lbs. A subsequent letter from Limitorque recomended replacing the original mild steel keys with high strength keys on actuator sizes three and four with motors of 150 ft-lb or greater.
The failure at Watts Bar occurred on a size three actuator with a 100 ft-1b motor not requiring key replacement.
Limitorque analysis has shown that the safety factor of the motor pinion key is 3.9 for sheer stress and S.26 for contact stress as calculated for the original mild steel key installed in a size three actuator equipped with a 100 f t-lb ractor. In a letter dated January 20, 1987 to TVA, Limitorque stated they believe the reported failure was due to the fact that the pinion key was found in a position where it only partially engaged the rotor pinion and shaft.
- 10. Environmental Qualification Issues A.
Loading of actuators during testing It was determined that actuator loading during most of the Limitorque Environmental Qualification Tests was by means of a thrust tube. This method of testing provides a load only at the end of the actuator closing cycle. The lead is achieved by driving a stem into a stationary thrust tube. The tube stops the stem travel and the actuator is loaded until motor The load current is interrupted by means of the torque switch.
achieved during testing is therefore directly related to the torque switch setting of the actuator. Review of Limiterque test report B0212 shows that the motor installed in the tested actuator was rated for 15 foot-lbs. Using average torque values obtained before the test, a motor torque output of 14 e
foot-lbs. was calculated to have been achieved durir.g the EQ test of this actuator.
In Limitorque test B0009, a 25 foot-lb.
rated motor was loaded to 13.4 foot-1bs. The ability of the Limitorque motors to put out full rated torque was therefore not proven during these EQ tests. Rated thrust outputs of the actuators were however achieved during both B0212 and B0009 tests.
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ORGANIZATION: LIMITORQUE CORPORATION LYNCHBURG, VIRGINIA REPORT INSPECTION NO.: 99900100/87-01 RESULTS:
PAGE 6 of 8 B.
Degraded voltage testing of actuator It was determined that Limitorque Report B0212 is the only report that describes testing of an actuator during degraded voltage conditions. The applied voltage in all other tests d
1 was the nominal rated motor voltage. Calculations show that at a 90% nominal voltage condition motor torque output will decrease by some 19%. Limitorque Report B0212 is for an AC Reliance motor. DC motor performance under degraded voltage conditions would be considerably different.
The statement concerning degraded voltage in Limitorque Report B0058 was discussed.
It was determined that the motors installed in the tested actuators were sized based upon calcula-tions done using nominal motor voltage. Had degraded voltage been taken into account larger motors would have then been required on some of the tested actuators. To take credit for the Limitorque tests licensees therefore need to show their actuator motors were properly sized for the applicabic voltage conditions.
C.
Similarity analysis between Class B AC Peerless, DC Peerless, UC Reliance, and AC Reliance Motors A similarity analysis contained in a Wyle letter dated August 10, 1982 to Stone and Webster was revicwed. This letter contained a material analysis of the materials used in Class B AC Peerless, AC Reliance, DC Reliance and DC Peerless motors.
The analysis showed that the materials used in the manufacture of the Class B DC Peerless, DC Reliance and AC Peerless motors were equal to or better than those used in the manufacture of the Class B AC Reliance motor tested in Limitorque report i
B0003. No deficiencies in the Wyle material analysis were noted.
D.
Qualification of Nylon Insulation Wire Joints y
Actuators equipped with dual voltage motors have been found to contain nylon insulation wire joints. These wire joints were used at Limitorque to make connections on dual voltage motors. Actuators tested in Limitorque reports B0003, 600376A, and 600198 contained dual voltage motors that likely contained some type of insulate. wire joint. No documentation
J ORGANIZATION: LIMITORQUE CORPORATION i
LYNCHBURG, VIRGINIA
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REPORT INSPECTION l
NO.: 99900100/87-01 RESULTS:
' AGE 7 of 8 as to the exact type or as to the joint manufacturer exists at Limitorque. Additionally, no configuration control exists that would ensure that wire joints are kept away'from conducting materials. There is therefore no documentation that exists at Limitorque that would support environmental qualification of these nylon insulation wire joints.
E.
Limitorque Test B0119 Limitorque test bO119 describes at test in which a Marathon 300 type type terminal board was used to power a motor to a Limitorque actuator. The terminal board was subjected to an inside containment type environment and was shown to adequately transmit power to the subject motor at selected periods through-out the LOCA simulated portion of the testing. Resistance readings of the terminal board (terminal to terminal and l
terminal to ground) were then taken by disconnecting the motor immediately after energization.
The lowest reading obtained during the testing for the Marathon 300 termir.a1 board was 900 ohms. Since the motor performed adequately with the 900 ohms measured insulation resistance this value was set as the acceptance criteria for insulation resistance.
Upon review by the NRC inspector, it was determined that the measured 900 ohms insulation resistance was taken using a Biddle 21159 megger.
Inspection of this megger revealed that readings in the 900 ohms range could only have been read on the meggers ohms scele. This megger has four scales with four associated open circuit output voltages. With the ohms scale used in obtaining the 900 ohm reading, the output voltage applied to the terminal board would have been very low. From discussions I
with the manufacturer of the megger, Biddle Instruments, it has been determined that the meggers output voltage under the above conditions would have been approximately 2.2 volts.
Although the other tested boards exhibited insulation resistance 9
readings better than 900 ohms, some of these readings were also j
obtained using the meggers ohms scale. Consequently, the ability
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of the other terminal boards tested in B0119 to adequately supply a 480 volt or 120 volt circuit is indeterminate. Under the test conditions, all terminal boards would have indicated 0 ohms on the Biddle megger using the 500 volt or 250 voit scale.
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ORGANIZATION: LIMITORQUE CORPORATION LYNCHBURG, VIRGINIA REPORT INSPECTION l
NO.: 99900100/87-01 RESULTS:
PAGE 8 of 8 Additionally, a data transcription error was discovered in the review. The values obtained at event 5 for the Curtis "L" type board were really 800 ohms, 700 ohms, and 1K, not 800K, 700K, and 1K as indicated in test report B0119. These values are therefore below the 900 ohm Limitorque acceptance criteria.
o In conclusion, the ability of the Curtis "L," Marathon 1600, Buchanan 0222. Buchanan 0524 and GE-EB-5 type terminal boards to adequately supply 480 or 120 volt power to notor or control circuits can not be determined from Limitorque Report B0119.
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