Fatigue evaluation of piping connections under thermal transients

Abstract

Weldolet connections have been widely used in the design of Class 1 piping systems in typical PWR nuclear power stations. Under severe thermal transients, the resultant stresses in such connections can reach very high levels and sometimes the qualification of such connections according to ASME Code Section III is very difficult. Because of that there are situations where it is necessary to design a special fitting in order to obtain a better thermal stress distribution, reducing the values of stress to acceptable levels. The main goal of this paper is to perform a fatigue evaluation of a connection, using a special fitting, through two different methodologies, as described later in detail. An alternative to employing a standard weldolet will be investigated and the results calculated using two connections will be compared.