IE Circular No. 80-12, Valve-Shaft-to-Actuator Key May Fall out of Place When Mounted below Horizontal Axis
SSINS No.: 6830 Accession No.: 8005050052 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 May 14, 1980 IE Circular No. 80-12 VALVE-SHAFT-TO-ACTUATOR KEY MAY FALL OUT OF PLACE WHEN MOUNTED BELOW HORIZONTAL AXIS Description of Circumstances: Tennessee Valley Authority has identified and reported to the NRC a nonconformance on a Bettis Robot-arm actuator installed on a Pratt Butterfly Valve at the Sequoyah nuclear plant. It is reported (ref. attached 10 CFR 50.55e report) that a valved became inoperable when the valve-shaft-to-actuator key fell out place. It is further noted that the orientation of this valve assembly was such that the operator was on the bottom of the valve (below the horizontal axis). The Pratt Butterfly Valve furnished with Bettis actuator is designed with a press-fit keyway connection valve/actuator. We believe other manufacturer's connections may be of similar construction and therefore subject to this failure mode. On May 1, 1980, Pratt Company sent letters to their customers who have these connections (enclosed list). They recommended that their customers review their installation of such connections, and if the keyway is oriented below horizontal, make one of the following field modifications: 1. Add a spacer bushing, or shim plate to fill the void between the top of the shaft and the indicating plate on the actuator. 2. Locally upset the end of the valve shaft in the area of the keyway using a hand punch in such a way that the key could not work loose. 3. Install new keys of longer length which extend above the end of the valve shaft whereby the key is up to the actuator plate and could not slip down if inverted. Recommended Action for Licensee Consideration: We request that all plants make the above recommended inspection of all connections similar to the above described Bettis/Pratt connection, whether or not supplied by those particular manufacturers. If connections are found that are susceptible to failure, on of the above recommended actions or other appropriate action should be taken to correct the potential problem. . IE Circular No. 80-12 May 14, 1980 Page 2 of 2 No written response to this Circular is required. If you desire additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
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