05000293/LER-1979-030-03, /03L-0 on 790725:motor Control Ctr Breaker of Globe Valve MOV-1001-36B Tripped on Overload After Valve Given Signal to Open.Caused by Shear in Valve Stem Guide Key.Stem Clamps Drilled in Place & Tapped for Set Screws

/03L-0 on 790725:motor Control Ctr Breaker of Globe Valve MOV-1001-36B Tripped on Overload After Valve Given Signal to Open.Caused by Shear in Valve Stem Guide Key.Stem Clamps Drilled in Place & Tapped for Set Screws

ML19261E509
Person / Time
Site:	Pilgrim
Issue date:	08/16/1979
From:	Fulton J BOSTON EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19261E506	List: 05000293/LER-1979-030, Forwards LER 79-030/03L-0 05000293/LER-1979-030-03, /03L-0 on 790725:motor Control Ctr Breaker of Globe Valve MOV-1001-36B Tripped on Overload After Valve Given Signal to Open.Caused by Shear in Valve Stem Guide Key.Stem Clamps Drilled in Place & Tapped for Set Screws
References
LER-79-030-03L, LER-79-30-3L, NUDOCS 7908280533
Download: ML19261E509 (2)

LER-1979-030, /03L-0 on 790725:motor Control Ctr Breaker of Globe Valve MOV-1001-36B Tripped on Overload After Valve Given Signal to Open.Caused by Shear in Valve Stem Guide Key.Stem Clamps Drilled in Place & Tapped for Set Screws

Event date:
Report date:
2931979030R03 - NRC Website

text

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50-293 Attachment to LER 79-030/03L-0 The failure of the valve gufde stem key on MOV 1001-36B on July 25, 1979 was the fourth such failure sinct. July of 1974.

The three previous failures occurred to the key on MOV 1001-36A.

Date of Failure Report 7/31/74 U.0. 9 6/20/77 LER - 024/03L 7/27/79 LER - 028/03L An investigation was conducted to determine the cause of these failures.

Meetings

_ _wcre held with the manufacturer of the valves (Anchor / Darling) and the manufacturer

.of the operators (Limitorque)

MOV 1001-36A&B are 12"-300 lb. globe valves.

The stem is restrained from ro-tating by a stem clamp. The clamp is affixed to the stem by a \\" square steel key. The shear forces on the key were calculated and proved to be marginal for this application. The contention was verified by telephone conversations with a Field Service Engineer for Anchor / Darling.

A search of all Pilgrim's nuclear class valves was made to de'termine the extent of this problem. This search revealed two additional globe valves supplied by Anchor / Darling which have a similar design. These valves are MOV 1001-16A&B which are 18"-300 lb. globes. The stem clamp is affixed to the stem by two 5/8" set screws drilled 60 degrees apart. A check of the maintenance files indicated no failures on ~these valves.

Action has been initiated to implement corrective action. Alternative solutions were evaluated. It has been decided to drill the stem clamps in place and tap them for two set screws. This fix is the simplest and most cost effective of thoce evaluated. These modifications will be monitored to judge their effectiveness.

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