Pipe Stress Intensification Factor


Stress intensification factor is a multiplier on nominal stress for typically bend and intersection components so that the effect of geometry and welding can be considered in a beam analysis. It is the basis of most stress analysis of piping systems.

SIF is used in a pipe stress analysis as shown in the equation  below:

(Beam Stress)(SIF) < (Allowable Stress)

Expanding the terms gives the following equation using the SIF:

(M/Z)(SIF) < 6N-0.2

(1.25(Sc + Sh) – Sl)

SIFs are obtained from tests and equations written to extend the usefulness of the tests. The Markl machine is the standard machine used to develop SIFs.