Fatigue evaluation of piping connections under thermal transients

Weldolet connections have been broadly used in the design of class 1 piping systems in a typical PWR nuclear power station. Nevertheless, under severe thermal transients, the resultant stresses 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 employing standard weldolet will be investigated and the results calculated using two connections compared