Hi,

Pressure stiffening on bend is allowed to use In ASME B31.1.
As you know, pressure stiffening effect makes SIF decreased, piping flexibility as well.

Normally I implement stress analysis taking only P1 as a design pressure and consequently elbow stiffening pressure is applied Pmax, design pressure, in default option.

but in terms of SIF, applying Pmax brings less conservative results. Therefore, i think it would be reasonable to apply operating pressure only at elbow pressure stiffening. Moreover it would be good for piping flexibility considering nozzle load.

Ultimately which is more reasonable? taking design pressure or operating pressure in elbow pressure stiffening.

Please let me know your opinion.

thanks