The following is a summary of information provided via facsimile:
Based on recent testing conducted on a 24 inch Class 150 TRICENTRIC [triple offset butterfly valve] to evaluate bearing coefficients of friction (COF), it has been determined that there exists an unseating load that has not been accounted for on our TRICENTRIC Triple Offset Product Line.
Weir has not experienced a field failure of the product, but recent testing by a customer indicated anomalies that required review by Weir. The review of the unseating anomaly relates to two inputs; the inputted seating torque and increases in differential pressure across the disc after initial closure. Weir has developed a conservative approach for calculating this additional loading.
Weir has reviewed data from customers for several recent orders, and has determined that there is a minimal risk of failure of an item to perform its safety function. However, based on the safety related functions of these items, Weir cannot provide absolute assurance of operability on items in service without confirming with the end user. Weir will be releasing an industry notice that will address our initial findings, continue with the detailed investigation, and advise customers concerning the recommended corrective actions.
Known customer -
PSEG