NG-75-1089, Revised AO 50-261/75-8:on 750429,RHR Suction Valve RHR-862A Failed.Caused by Torque Switch on Motor Operator Being Out of Adjustment,Causing Valve to Be Wedged Onto Seat & Preventing Motor from Opening Valve

Revised AO 50-261/75-8:on 750429,RHR Suction Valve RHR-862A Failed.Caused by Torque Switch on Motor Operator Being Out of Adjustment,Causing Valve to Be Wedged Onto Seat & Preventing Motor from Opening Valve

ML20086F636
Person / Time
Site:	Robinson
Issue date:	07/11/1975
From:	Utley E CAROLINA POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20086F643	List: ML20086F644 ML20086F647 NG-75-1089, Revised AO 50-261/75-8:on 750429,RHR Suction Valve RHR-862A Failed.Caused by Torque Switch on Motor Operator Being Out of Adjustment,Causing Valve to Be Wedged Onto Seat & Preventing Motor from Opening Valve
References
AO-50-261-75-8, NG-75-1089, NUDOCS 8401030448
Download: ML20086F636 (3)

Text

7 Carolina Power & Light Company July 11, 1975 File: 3513 (R) Serial: NG-75-1089 (o )f I  ?

Mr. Norman C. Moseley, Director a U. S. Nuclear Regulatory Commission Region II, Suite 818 Q)Q

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230 Peachtree Street, N.W. E ^

Atlanta, Georgia 30303 i

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Dear Mr. Moseley:

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'Q-A4, H. B. ROBINSON UNIT NO. 2 LICENSE NO. DPR-23 9//ql-a FAILURE OF RHR VALVE 862A TO OPERATE =

In accordance with Section 6.6.2.a of the Technical Specifications for H. B. Robinson Unit No. 2, the attached Abnormal Occurrence Report is submitted for your infomation. This report has been revised as requested to further define the analysis of the occurrence and corrective action taken, and supercedes our report of May 7, 1975.

Yours ver truly,

.W ,

. E. Utley Vice President Bulk Power Supply DBW:pdd Attachment cc: Messrs. N. B. Bessac P. W. Howe J. A. Jones R. E. Jones W. B. Kincaid J. B. McGirt D. B. Waters

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O O Abnormal Occurrence Report

1. Report No. 50-261/75-8 (Revised) 2a. Report Date July 3, 1975 2b. Occurrence Date April 29, 1975

3. Facility H. B. Robinson Unit No. 2 Hartsville, South Carolina 29550

4. Identification of Occurrence Failure of RHR pump suction valve RHR-862A, which constitutes an Abnormal Occurrence, as defined in Section 1.8.d. of the Technical Specifications.

5. Conditions Prior to Occurrence A plant heatup was in progress after a scheduled two week maintenance shutdown. The Reactor Coolant System was at 950 psi and 419 F, and the RHR System was being aligned for power operation.

6. Description of Occurrence At 1123 hours0.013 days <br />0.312 hours <br />0.00186 weeks <br />4.273015e-4 months <br /> while aligning the RHR System for normal power operation, valve RHR-862A failed co open when operated from the RTGB. At 1138 hours0.0132 days <br />0.316 hours <br />0.00188 weeks <br />4.33009e-4 months <br /> a reactor cooldown was commenced. At 1155 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.394775e-4 months <br /> the valve was started open using the manual operator. At 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br /> the valve was completely open and capable of performing its intended function, and the reactor heatup was recommenced. An investigation revealed that the operator torque switch was out of adjustment causing the valve to be jammed on the seat. The torque evitch was adjusted and the valve returned to service at 1338 hours0.0155 days <br />0.372 hours <br />0.00221 weeks <br />5.09109e-4 months <br />. The valve was cycled at this time with satisfactory results. Later, at 1757 hours0.0203 days <br />0.488 hours <br />0.00291 weeks <br />6.685385e-4 months <br />, the valve was test operated on two successive cycles, and operation was satisfactory.

7. Designation of Apparent Cause of Occurrence As previously stated the torque switch on the motor operator was out of adjustment. This caused the valve to be wedged onto the seat and prevented the motor from opening the valve. When the valve was moved off its seat with the manual operator, movement of the valve was free and subsequent motor operation of the valve with the reduced torque switch setting was satisfactory.

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8. Analysis of Occurrence Upon determir.ation that valve RHR-862A would not meet its intended function, a plant cooldown was commenced. The valve was opened manually and the plant heatup commenced after the valve was fully open and would meet its intended function. The torque switch setting was then lowered and the valve test operated satisfactorily. The valve was again tested twice while checking the motor current temperature, and visual observations of operation were made. The motor current tempera-ture, and valve operation time were normal and no unusual noises were detected. At 1011 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.846855e-4 months <br />, April 30, 1975, the motor operator was dia-assembled and completely inspected. No abnormal conditions or defective parts were found during this inspection, however, an excessive amount of grease was found in the Belleville Spring pack area. An initial deter-mination was that this grease could have created a hydraulic lock effect around the spring and not permit it to function properly. This grease was removed when the operator was re-assembled. The operator was tested and returned to service at 1418 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.39549e-4 months <br />. Further discussions with the vendor have been made regarding this failure. The initial determinations of the grease being a possible problem is not valid since this type oper-ator has a slot cut in the housing that relieves any excessive grease to the main body of the operator.

This occurrence has been thoroughly investigated to determine all possible reasons for the torque switch adjustment to cause the valve jamming. No evident reason has been determined. The operator has functioned properly every time since the occurrence of April 29, 1975.

During the time of this occurrence, plant safety was not jeopardized, a,nd no personnel injuries, undue exposures, releases of radioactive materials, or threat to the public health and safety resulted from this occurrence.

9. Corrective Action The torque switch on this operator was adjusted to prevent the valve from being forced on the seat. No further corrective action is planned at this time but we will continue to observe this valve as part of our normal routine operations.

10. Failure Data No failure of this nature has occurred on this type operator.

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