ML20044G531

Suppl to 921207 Part 21 Rept Re Declutch Sys Anomaly in Certain Types of Valve Actuators Supplied by Limitorque Corp.Limitorque Designed New Declutch Lever Which Will Be Available in First Quarter 1993

ML20044G531
Person / Time
Site:	Davis Besse, Oconee, Arkansas Nuclear, Three Mile Island, Columbia, Crystal River, Bellefonte
Issue date:	05/26/1993
From:	Taylor J BABCOCK & WILCOX OPERATING PLANTS OWNERS GROUP
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-93 JHT-93-128, NUDOCS 9306030257
Download: ML20044G531 (9)

Text

l BW B&WNUCLEAR TECHNOLOGIES 3315 Old Forest Road JHT/93-128 P.O. Box 10935 May 26, 1993 Lynchburg VA 24506-0935 Triephone: 804-385-2000 Telecopy 804-385-3663 Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Potential Safety Issue Regarding Limitorque Valve Actuator Declutch System Anomaly Gentlemen:

The purpose of this letter is to supplement a notification provided by Limitorque Corporation to the NRC dated December 7, 1992 concerning a Declutch System Anomaly in certain types of valve actuators.

The Limitorque letter (copy attached) advised that certain types of Limitorque valve actuators may not operate during a seismic event.

Following the end of the seismic vibration, the actuator will operate normally. As stated in that letter, Limitorque discovered through actuator testing that the possibility exists for malfunction of two types of actuators under certain conditions of seismic excitation. At certain excitation frequencies,'it was observed in tests that the actuators would not complete a stroke electrically during the dwell time when the actuator was vibrating. I After the excitation stops, the actuator will return to proper  ;

operation. The safety concern, therefore, is applicable to motor operated valves which are required to operate during a seismic event.

The basic cause of the problem is the declutch system. The system is imbalanced in the vertical axis, and at certain vibration frequencies, vibration of the declutch 3er.er causes disengagement of the motor. To correct this conditim , Limitorque has designed a new declutch lever which will be avc11able in the first quarter of 1993. In the interim, it is rec pamended that the levers be secured to prevent potential movement.

The affected actuators are the SMB/SF.-000 and SMB/SB/SBD-00 types.

It is likely that the B&W-designed plants were supplied with these types of actuators for the valves shown on the attached list (see Attachment B). These valves would have been in the initial scope of supply and were initially used in safety-related applications.

BWNT also supplied actuators of these types as spares or replacements to several utilities as listed on Attachment A.

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. 'l U. S. NRC JHT/93-128 May 26, 1993 Page 2 BWNT is advising the B&W-designed' plants of this concern for their evaluation of its potential effects on the operability of the affected valves and of the safety implications and reportability of the concern under Federal regulations. BWNT will' perform no further evaluation of the concern unless requested and authorized by the utilities.

-BWNT is advising the NRC of'this matter for information. This advisory is not a report under 10CFR21.

You may contact me at 804/385-2817 or Mr. David Mars at 804/385-2852 if you have any questions concerning'this matter.

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G . Tay r, Manager

/.Licensin Services JHT/bcc Attachment cc: C.R. Gaines, Entergy Operations, Inc.

Manager, Nuclear Safety Assurance, Duke Power Company 1 R. C. Widell, Florida Power Corporation R. S. Harbin, GPU Nuclear Corporation E. C. Caba, Toledo Edison Company R. D. Wells, Tennessee Valley Authority L. C. Oakes, Washington Public Power Supply System I. E. Wilkinson, Limitorque Corporation i

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'g Limitorque Corporation Aut:moted Vcive &c: voters oed J :ms 'of !nd6st'y 6,, 5114 Woodcli Road . P.O. Box 11318 Lynchburg, VA 24506-1318 Fo ,

Q Teepnene (804) 528-4400 . FAX (804) 845-9736 ,

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'" December 7,1992 d. N .

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Sub DasGupta ,

Quality Assurance Manager SUB DASGUPTA B & W Nuclear Service Company 3315 Old Forest Road - P. O. Box 10935 DEC 151992 Lynchburg, VA 24506

Subject:

Potentially Reportable 10 CFR Part 21 Condition SMB/SB-000, SMB/SB/SBD-00 Declutch System Anomaly Please be advised that Limitorque Corporation has discovered througl actuator testing that the possibility exists for malfunction of the subject actuators under cenain conditions of seismic excitation. This situation could potentially be reponable depending on the operating practices of the licensee. Therefore, pursuant to the requirements of Title 10 CFR Part 21.

notification is herein provided of a potential malfunction of the subject actuators.

Identification of Basic Comoonent The affected components are the declu*.ching mechanisms in the SMB/SB-000 and SMB/SB/SBD-00 actuators.

Nature of the Defect A. The Basic Defect When the actuator is vibrated in the vertical axis with sufficient amplitude near the {

natural frequency of the declutch system, oscillations of the declutch system can cause the l motor to become disengaged. MOVs which are required to operate during such a seismic.

event may exhibit longer stroke times. The malfunction only occurs during tne seismic event. After the vibrations stop, the actuator will return to proper operation.

j The SMB/SB/SBD-00 and the SMB/SB-000 share the same basic design of declutch I

system which consists of the declutch lever, shaft, declutch fork, clutch ring, clutch keys.  ;

return spring, and tripper lever asambly. The system is imbalanced in the vertical axis because the declutch lever exerts more counter-clockwise torque on the shaft than the other )

parts exert in the clockwise direction. Thus, the lever can provide a driving force causing the d.c..rch system to oscillate with enough amplitude to disengage the motor.

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Page 2 i December 7,1992-Part 21 Notification 4

I B. Defect Observed in SMB/SB/SBD-00 j Limitorque has on two occasions experienced' malfunctions of the SMB/SB/SBD-00  !

declutch mechanism during seismic testing. The type of test performed was a seismic ~ dwell I test. In this' test the actuator was vibrated at frequencies from 2 hz' to 32 hz in 'one quaner octave intervals with a sinusoidal waveform in a single axis. The acceleration' level was 7.6-

- gs except at some of the lower frequencies where limitations of the shaker tables prevented .

reaching that level. At each frequency, the actuator was vibrated for fifteen seconds.

During each of these fifteen second' dwells, the actuator was electrically operated simulating a close and open valve stroke. This procedure was~ performed with vibrations in the vertical axis of the actuator and in two horizontal axes.

On the occasions in which the malfunction was observed,' the actuatois would not complete a stroke electrically in the expected amount of time during the seismic dwell. ,The problem was only found in the vertical axis, the units operated correctly.in the horizontal axes. Further, the problem.was only found at two specific vertical dwell frequencies: .11.3 - ,

and 13.5 hz. The problem was not seen at the 9.5 hz test and lower frequencies _nor was.it seen at the 16.0 hz test and higher frequencies. q 1

Limitorque has tested SMB 00 actuators in the manner described above on seven occasions. Refer to the table below for a summary. Of these seven tests, the declutch .

j problem was seen in two of the tests (numbered 4 and 6 below). Note that in test 6 the 1 amplitude of the fundamental frequency.did not reach 7.6 'gs at either 11.3 or 13.5 hz but 1 there were spikes of 15 gs present on the waveforms due to difficulties in controlling the -

seismic table. Due to these spikes,Ltest 6 may have been more severe with respect to ,

exciting the declutch system than the other tests which had cleaner waveforms.

SMB-00 Seismic Tests Pertinent to Declutch Problem l t

1. Doctutch Test Date Acceteration et Frequencies of Interest Pratten i Fremonsfes 1- none 12/19/s0 7.6 as et-11.4 ha and 13.6 ha i

none 4/14/s1 7.6 gs at 11.6 ha and 13.6 ha 2  !

3 none 2/3/Es 7.6 se et 11.4 ha and 13.6 ha 4 11.3 hr 9/2s/90 '7.6 se et 11.3 ha and 13.5 ha I 5 none 1/s/91 7.6 ss at'11.3 ha and 13.s ha 6 11.3,~ 13.5 ha 8/22/91 see mete 1

.7 none 1/23/92 7.6 se et.11.3 ha and 13.5 ha i

note 1 During teet 86 the fwedsmentet fremency reached en esplitude of 6.s es et 11.3 ha and 7.s pi at.131 ha. . neuever, et beta of these fragencies there were epikes of 1s es present en the nevefona ase to j difficuttles in centreLLlng the seismic teMe. j

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, - - - -_ , . . . . _ , , . . . , - . _ . - , _ , . . . . = .. _ - _ . ... , , - - , . , _ . .

Page ')

- Dece.mber 7,1992 Part 21 Notification C. Defect Observen t.. SMB/SB-000 1

Limitorque is aware of a similar malfunction in the SMB/SB-000 declutch mechanism during a utility sponsored seismic test. . De type of test performed was a sine beat test. In this test the actuator was vibrated at frequencies from 2 hz to 35 hz in one third octave .

intervals with sine beat excitation of 15 cycles per beat in a single axis. Each sine beat test at each frequency. consisted of a continuous train of sine beats with no pause between beats.

The acceleration level was 4_.5 gs except at some of the lower frequencies where limitations of the shaker table prevented reaching that level. At each frequency, the actuator was vibrated for a minimum of fifteen seconds. - During each fifteen second test, the actuator was electrically operated simulating a close and open valve stroke. ' This procedure was .  ;

performed with vibrations in the vertical axis of the actuator and in two horizontal axes. l The SMB-000 tested was reported as operating intermittently during the 12.5 hz and 7 i

16.0 hz tests in the vertical axis. ,The acceleration level reached 4.6 and 4.8 gs respectively  !

during these tests. . After the first 16.0 hz test, the declutch lever was prevented from j

vibrating in further tests by being taped to the handwheel. Dus, it is unknown whether the problem would have occurred at the next highest frequency (20.0 hz). It is known that the problem was not seen at the 10.0 hz test and lower frequencies. And, in the horizontal axe the unit operated correctly (the lever was not taped during these axes)'  ;

D. Critical Frequencies Based on the above tests, the potential exists for this malfunction to occur in the SMB/SB/SBD-00 at frequencies between 9.5 and 16.0 hz. This represents a maximum range 1

of critical frequencies of three quarters of an octave. The SMB/SB-000 declutch system should have a similar frequency range due to its' similarity with the SMB/SB/SBD-00 system.  :

1 For a conservative estimate of the highest potential problem frequency in the SMB/SB-000 iti is calculated that three quarters of an octave above 12.5 hz is 21.0 hz. Thus, the potential exists for this malfunction to occur in the SMB/SB-000 at frequencies between 10.0 and hz. .<

Limitorque does not have adequate data to determine the minimum acceleratio; ,

which could potentially cause the malfunction. Note that the malfunction only occur the scismic event. After the vibrations stop, the actuator will return to proper operation.

E. Actuator Output Torque Can Prevent Malfunction In the observed cases of this malfunction, the actuators had minimal torque load; present. .When torque load is present, side loads are applied to the clu l loads in turn generate frictional forces. These frictional forces oppose clutch key and thus movement of the declutch system.' This is observed, for example, when' a is declutched while under valve seaung load Much more force must be applied.to

declutch lever than when the valve is~in an unloaded condition. The driving f oscillations of the declutch system is due to the imbalance of the system a 1

.. .. pag g December 7,1992 -

. Part 21 Notification accelerated vertically. If sufficient torque load is present, the frictional forces on the clutch keys will be high enough to oppose the driving force due to the imbalanced lever and oscillations of the system will be prevented. ' At higher acceleration levels _more driving. force is generated and thus higher torque load is required to prevent oscillation.

Limitorque has performed calculations comparing the frictional key forces to the driving force to determine how much torque load is required to prevent shaft oscillations at a given acceleration level. In order to provide a conservative margin of safety 'and allow for uncertainties in the calculations, a factor of safety of approximately 4 is included in the resulting formulas. Torque is measured in ft Ibs and Acceleration is measured in gs.

SMB/SB-000.

Torque = 4 x Acceleration i

SMB/SB/SBD-00 Torque = 7'x Acceleration ,

i Example: For an SMB-000 undergoing a seismic event of 7.6 gs maximum acceleration the ~

l torque calculated is 30 ft lbs. For an SMB-00 at the'same acceleration level the torque-calculated is 53 ft lbs.

These calculations may be used to provide' assurance that an actuator will be able to open a valve from the torque seated condition to a point at which the opening torque drops to the level calculated.

Affected Eauioment The equipment affected are SMB/SB/SBD-00 and SMB/SB-000 actuators.

Limitoroue Comordan Corr =Mve Action To correct this problem, Limitorque has designed a declutch lever which balances the ,

torque of the other components in tb declutch system. With this lever installed, there is nol' imbalance in the' system and thus no driving force to cause oscillations. Levers have been designed for the SMB/SB/SBD-00 and for the SMB/SB 000. ' Such a lever was installed during the course of the SMB 00 test 6 mentioned above. This cured the declutch problem l in that test. ' Also, one of these levers was present in a test of an SB-00 and no declutch problem was observed.  ;

Limitorque will make the new levers standard for future orders of SMB/SB/SBD-0 l

ad SMB/SB-000 units for nuclear service. I.ever availability is scheduled during the first quarter of 1993.

f Page5 December 7,1992 Part 21 Notification Licensee Corrective Action 1 Limit 6rque recommends that each licensee evaluate this situation based on the l

potential of actuator malfunction at the frequencies mentioned above. If a specified valve stroke time is required, it must be assumed that valve motion ceases during a seismic event which includes these frequencies in a vertical orientation relative to the actuators. Herefore, the actual valve stroke time will be increased by the duration of the seismic event. An exception to this is a situation in which the torque load on the actuator is sufficient to create enough frictional forces to prevent declutch shaft oscillations as described in section E.

above. In this case the actuator will function as long as the torque load remains above the ,

critical value.

i Balanced levers may be purchased from Limitorque. For the SMB/SB/SBD-00 the .

new lever is part 0301-059 and fot the SMB/SB-000 the new lever is part 0101-081. In the interim it is tw.ommended that levers be secured to prevent potential movement.

Any questions regarding the above notification may be directed to P. McQuillan, Nuclear /Special Projects Manager at (804) 528-4400 Ext. 714.

Si ned:

Q, M y _

I. E. Wilkinson Vice President of Engineering LIMITORQUE CORPORATION pc: Mr. Mignogna Mr. Kornsey Mr. R. Segen Mr. M. Logan Part 21 Notification File

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ATTACHMENT A i

Soares or ReDlacements SuoDlied to Utilities

.i 1

i CUSTOMER CUSTOMER QZX CONTRACT 8 CUSTOMER B21 i

F./l SHIP DATE 2 788-400327 ANO 07736 S/Ns: 632-1

• 04/06/84 633-1  :

i 1 788-400346 ANO 23703 635-1 S/N: 12/07/84 [

1 788-7473024 ANO 188059 S/N: 891-1 10/27/88

_______________________________________________________q____________  ;

1 788-400297 ANO 84447 S/N: C507-1 3/22/83 1- 788-221131 TED 082-Q-72145A-M1 S/N: 889-1 8/31/82 1 788-400244 ANO- 76811 5007176 10/28/82 -

.____________________________________________________________________ 1 l

1 788-400444 ANO 14713 S/N: 661 1

12/26/86* l 1 788-7472044 FPC F740090D 0065380373 3/09/89 S/N: 668 i

1

• Our records indicate that this item was re-sold by ANO to TED (TED PO# C602218D90). 1

1 ATTACHMENT'B B&W-Desianed Plants (Oceratina'or Under Construction) I i

Ut111tv ' Plant-Duke Power Company. .Oconee Units"1,.2', 3 Arkansas Nuclear One-Unit.1 ~

~

Entergy Operations Florida Power Corp.- ' Crystal River-3 i

General Public Utilities -

Nuclear' Three Mile Island-Unit 1 Tennessee Valley Authority Bellefonte Units 1, 2.(1).

Toledo Edison' Company Davis-Besse l l

- Washington Public Power ' , l Washington Nuclear Power-Unit 1 Supply system -i (2)- l

,j l

(1) TVA intends to re-activate construction -

(2) WNP-1 is 'in a deferred status of construction l

1

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