Hello.

For a nozzle to take advantage of the "F factor", is it necessary that it should be elliptical in shape. An elliptical nozzle will be oriented in the long axis parallel to the cir seam. And hence F = 0.5 in that direction.

Thanks

Sharjeel

The F factor is defined in UG-37, see Figure UG-37 for its values. The F factor is used to decrease the nozzle's required reinforcing area on cross-sections that are not parallel to the vessel axis; this accounts for the change in stress acting on the cross-section from circumferential stress (PR/t) to longitudinal stress (PR/2t) as angle theta in FIgure UG-37 varies from 0° to 90°.

F varies from 0.5 to 1.0. UG-37 specifies that values less than 1.0 can be used only when the nozzle is "integrally reinforced". See UW-16(c)(1) for definition of integrally reinforced. In general, this requires a full penetration weld of nozzle neck to the shell and no reinforcing pad.

The F factor can be applied to nozzles of any cross-section (circular, ellipsoidal, obround) as long as the nozzle is integrally reinforced.

The orientation of elliptical nozzle that you describe (opening's long chord axis is perpendicular to the cylindrical shell's axis) is a perfect example of how application of the F factor can be beneficial when you check the required area in the plane cut through the long chord.