ML19270G091

Significant Deficiency Rept 8:limitorque Locknut Installation Deficiency

ML19270G091
Person / Time
Site:	Limerick
Issue date:	04/30/1979
From:	PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML19270G084	List: ML19270G088 ML19270G091
References
SDR-8, NUDOCS 7906020213
Download: ML19270G091 (4)

Text

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FINAL REPORT ON LIMITORQUE LOCKNUT INSTALLATION DEFICIENCY AT LIMERICK GENF2ATING STATION UNITS 1 AND 2 2268 302 PHILADELPHIA ELECTRIC COMPAhT April ,1979 SDR-8-1 7 00602 0gt3

TABLE OF CONTENTS 1.0 Introduction 2.0 Description of Problen 30 Analysis of Safety Implications 4.0 Corrective Action Taken 50 Conclusions 2208 303 SDR-8-2

.1. 0 Introduction 1.1 The Limerick Pro' ject uses Limitorque operators on certain motor operated valves, some of which perform a nuclear safety related function.

1.2 It has been determined that these operators could calfunction if the stem locknuts are not secured by crimping or staking. It had also been deter =ined that not all valve vendors have crimped or staked the locknuts on the operators they have supplied with their valves.

13 In compliance with 10CFR50 55(e), this Final Report is issued to describe the deficiencies, analyse the safety implications of the deficiencies and describe the action taken to correct the deficiencies and prevent their recurrence.

1.4 This significant deficiency was reported via telecon to the USNRC, Region I on March 23, 1979 2.0 Description of Problem 2.1 A potential problem with valves using Limitorque type SMB valve motor operators was identified by Bechtel Power Corporation during July, 1978.

2.2 During the assembly of the operator and its associated valve, the locknut which holds the stem nut in position must be crimped or staked. If this is not done, the locknut may back out of the threaded hole and permit the stem nut to move up the stem. This could render the valve inoperable.

23 Surveys of Limitorque SMB valve =otor operators delivered to the Limerick Project indicated that a substantial portion (about 25%) of the operators were delivered without the locknut being crimped or staked.

30 Analvsis of Safety Icelications 31 The failure to stake the locknut may cause the valve to become inoperable in any valve position.

32 Included among the Limerick valves which were found to have unstaked locknuts are valves classified as having to perform a safety related function.

33 Therefore, safe operation of Limerick could have been compromised had this condition gone undetected and uncerr ected.

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+.0 Corrective Action Taken 4.1 Following the initial identification of this potential proble=, valve suppliers were contacted to determine if they stake the locknuts. The vendors could not verify that locknuts are always staked.

4.2 Therefore, for the Limerick Project,Bechtel Power Corporation has notified their valve suppliers that the locknuts must be staked.

4.3 In order to correct the problem en valves already delivered and, in some cases, installed, cotor operated valves installed prior to October 12, 1978 are being inspected to verify locknut staking. Any unstaked locknuts found are being staked. Motor operated valves installed subsequent to October 12, 1978 have been and are being inspected at installation as part of the installation procedure requirements and the locknuts are staked if required.

50 Conclusions It is concluded that the corrective action described above will eli=inate the problem of unstaked locknuts on Li=itorque SMB valve operators at Limerick Generating Station. No further action is planned except that =otor operators will continue to be inspected for unstaked locknuts as part of the installation procedure requirements.

NOTE: It is recognited that the unstaked locknut problem can occur on both Limitorque type SMB and SMC operators. This report addresses only type SMB because no type SMC are used on the Limerick Project.

2268 105 SDR-8-4