FESIF (разработчик: Paulin (PRG)) — is a finite element based computer program that automatically calculates stress intensification factors (SIFs) and flexibility factors for a wide variety of piping intersections not covered by the B31 piping codes. There is a surprising number of common geometries (see below) not addressed by the B31 codes where the accuracy of the SIF is left entirely to the piping analyst, (ref. B31.3 Appendix D Note 12.) The flexibilities calculated by FESIF can be input directly into any pipe stress programs to reduce loads and produce more accurate stresses and displacements. SIFs from FESIF can also be directly input into any pipe stress program to calculate correct stresses for branch connections in hillsides, laterals, cones, and end caps. FESIF also produces SIFs for vessel and heat exchanger nozzles so that evaluation of these components can be included in the pipe stress analysis automatically.