ENS 42844
ENS Event | |
|---|---|
04:00 Sep 15, 2006 | |
| Title | Improper Valve Springs in Pressure Relief Valves |
| Event Description | LeBoeuf, Lamb, Green and MacRae LLP provided the following information on behalf of the licensee via facsimile:
Tyco Valves & Controls LP (TVC) manufactures, sells, and services Pressure Relief Valves (PRVs) to NRC licensees for use in NRC licensed facilities. There is a potential problem with one series of those PRVs, but TVC's analysis to date leads TVC to believe that there is not an imminent safety problem with the PRVs that would require the immediate shutdown of licensed nuclear facilities. Rather, TVC believes that there is adequate assurance that the public health and safety can and will be adequately protected until such time as it is possible to replace the spring(s) at issue. The background of this matter is as follows: The National Board of Boiler and Pressure Vessel Inspectors performed certification testing on PRVs manufactured by the TVC plant located in India (Tyco Sanmar Ltd). The valves tested by the National Board (NB) were the Crosby series JLT pressure relief valves. These valves are spring-loaded PRVs which are used to provide over-pressure protection for liquid applications. The Series JLT are certified to be in compliance with ASME Boiler and Pressure Vessel Code Sections III and VIII. The certification testing performed by the National Board indicated that these JLT valves did not meet ASME standards and so notified TVC. Thereafter, TVC performed its own testing on the JLT valves and confirmed the NB findings. TVC performed a root-cause analysis and determined that the Spring Selection Tables were inaccurate in that the Tables specified a spring with a spring rate which was too high for the adjusted set pressure. It was further determined that, in most cases, the Spring Selection Table specified the correct spring for the higher portion of the tabulated set pressure range; however, the Table specified a spring too strong for the lower portion of the range. The corrective action which has been taken by TVC is as follows: 1. The Spring Selection Tables are being revised and will take effect by 9/23/2006; 2. All of the safety-related PRVs which were affected by the Spring Selection Table have been identified; 3. A list of all nuclear facilities has been compiled; 4. A Product Safety Advisory is being drafted and will be forwarded to all nuclear facilities as identified in Exhibit A; and 5. The Product Safety Advisory recommends replacement of the spring. [TVC] believes that, while not in compliance with ASME, these PRVs do not pose a safety hazard inasmuch as there are many levels of conservatism built into the design of pressurized equipment and selection of PRVs such as: 1. These valves will open at the specified set pressure and will flow some capacity at the ASME specified overpressure of 10%. Further, based on our testing, these valves will flow the ASME certified capacity at an overpressure of not more than 20%. Most equipment will have been designed with a safety factor above the set pressure of at least 200%. 2. In sizing a PRV for an application, the 'required capacity' is determined by the user and the next largest PRV is selected to assure that the ASME certified capacity of the ARV is always greater than the 'required capacity' adding additional conservatism. 3. These valves have been supplied to the industry using these same spring selections for over 21 years without incident. TVC has notified the affected NRC licensees: Arkansas Nuclear One, Beaver Valley, Calvert Cliffs, Clinton Nuclear Station, Columbia Generating Station, Davis-Besse, Fort Calhoun, Millstone Nuclear Power Station, Nine Mile Point, Oconee Nuclear Station, Peach Bottom, Salem Station, Seabrook Station, Wolf Creek Generating Station. |
| Where | |
|---|---|
| Tyco Valves And Controls Lp Wrentham, Massachusetts (NRC Region 1) | |
| Organization: | Tyco Valves And Controls Lp |
| Reporting | |
| 10 CFR 21.21 | |
| Time - Person (Reporting Time:+15.63 h0.651 days <br />0.093 weeks <br />0.0214 months <br />) | |
| Opened: | David Thibault 19:38 Sep 15, 2006 |
| NRC Officer: | Bill Gott |
| Last Updated: | Sep 15, 2006 |
| 42844 - NRC Website | |
Tyco Valves And Controls Lp with 10 CFR 21.21 | |
WEEKMONTHYEARENS 428442006-09-15T04:00:00015 September 2006 04:00:00
[Table view]10 CFR 21.21 Improper Valve Springs in Pressure Relief Valves 2006-09-15T04:00:00 | |