Procedure for Seismic Evaluation and Design of Small Bore Pipingby Warren Bilanin, Electric Power Research Inst, Palo Alto, United States,
Steve Sills, Electric Power Research Inst, Palo Alto, United States,
Abstract: Simplified methods for the seismic design for small bore piping in nuclear power plants have been used for many years. Various pipe designers have developed unique methods to treat the large number of class 2 and 3 small bore piping systems. This practice has led to a proliferation of methods which are not standardized in the industry. These methods are generally based on enveloping the results of rigorous dynamic or conservative static analysis and result in an excessive number of supports and unrealistically high support loadings. Experience and test data have become available which warranted taking another look at the present methods for analysis of small bore piping. A recently completed Electric Power Research Institute and NCIG (a utility group) activity developed a new procedure for the seismic design and evaluation of small bore piping which provides significant safety and cost benefits. The procedure streamlines the approach to inertial stresses, which is the main feature that achieves the new benefits. Criteria in the procedure for seismic anchor movement and support design are based on analysis and focus the designer on credible failure mechanisms. A walkdown of the as-constructed piping system to identify and eliminate undesirable piping features such as adverse spatial interaction is required.
Subject Headings: Seismic design | Pipes | Power plants | Seismic tests | Nuclear power | Electric power | Dynamic loads | Failure analysis
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