Evaluating Dynamic Loads in Piping Systems （评估在管道系统动态载荷）.pdfVIP

Evaluating Dynamic Loads in Piping Systems Caused by Waterhammer Jim Wilcox, CodeCAD Inc. And Trey Walters, Applied Flow Technology February 2012 Summary Waterhammer in piping systems results in unbalanced forces , particularly between changes in direction such as elbow pairs, and changes in area such as valves, reducers and other inline components . It is not uncommon for these forces to cause damage when a system is not properly designed to accommodate them, resulting in failed restraints, overloaded equipment, large displacements and overstressing or even failure, of pipe and fittings as illustrated in these photographs. High transient forces fail reducer connection. Unsupported pipe fails from transient pressure plus the bending caused by initial failure at reducer. In some cases, hand calculations and conservative assumptions can be used to predict the magnitude, direction, location and timing of these dynamic loads. In many cases however, the complexity of waterhammer loading renders manual methods useless, requiring computer analysis to properly predict the loading seen by a piping system. Once these loads are determined, pipe stress software can be used to evaluate the piping system response, such as deflections, restraint loads, equipment load s and stresses. This paper examines a waterhammer event caused by the partial closing of a valve in a relatively simple system. The hydraulic transient analysis is performed using AFT Impulse , and the mechanical system response is then evaluated using Intergraphs CAESAR II ® pipe stress analysis software. One direct benefit of using t