The direction vector for a nozzle is along the nozzle centerline pointing towards the vessel. For a cylinder or a cone, the direction vector is along the vessel centerline. The +/- direction does not matter, as it will only have the effect of switching the location of the A, B points.
For a spherical vessel the direction is tangent to the vessel at the nozzle-vessel junction. Since WRC-107 only addresses 90-degree nozzles, hence the nozzle and vessel direction vectors will not be collinear.
It helps to draw the vessel, axis, nozzle and the loads all on 1 page and then figure the direction vectors from there.
Program converts the global loads to the WRC system before doing the stress computations. A good check is to check the loads in WRC convention from the output.
Regards,
Mandeep
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Best Regards,
Mandeep Singh
CADWorx & Analysis Solutions
Hexagon PPM