A Study on the Failure of Partially Thinned Pipes under External Pressure

Abstract

It is very important to prevent a buckling of thin pipes, such as are in the heat-exchanger system of PWR (pressurized water reactor), which occurs by external pressure. The design code in ASME Sec. Ill NB considers this point. However, the thickness of the pipe is partially thinned down by the steam-liquid flow in service. In the design step, no consideration has been paid to such a partially thinned down pipe, though much attenion should be given to this matter. In this paper, we discuss the pressure at the failure of the partially thinned pipe under external pressure. Experimental results show that the failure occurs at an unexpectedly small pressure, if the thinned part has some expansion, such as area. Also, the pressure at the failure does not follow the buckling equation given by the elasticity for a thin cylinder.