Dear All,

Can Hillside nozzle be modeled in Caesar and if yes than how?

Also i want to know if Hillside nozzle are modeled the way Radial nozzles are on vessel than stiffness-es calculated by WRC be realistic or not?

Modeled file + Snapshot attached for further clarification.

Regards,
Salz

You've built the model, so the answer to the first question is "yes".

As to WRC, the 297 bulletin is for cylinder-cylinder intersections at 90 deg.

Thanks Richard.

Just one doubt I have:
Indeed WRC mentions cylinder-cylinder intersections at 90 degrees but it may only be applicable if line of axis of nozzle and vessel coincides at some point.
As per my understanding Radial bending stress & stiffness equations in WRC seems not to include the offset distance of nozzle axis with vessel axis (for Hillside nozzles)while calculating bending stresses. If anyone has some deep insight into the equations of WRC then he/she can comment on this. Can this point be confirmed from WRC group if anyone can contact? I need to be sure if i'm using WRC the way it was intended to be used.

Ofcourse i've other options for stiffness calculations as Nozzle Pro etc and I havn't done any comparison of calculated stiffness from an FEA to WRC so far.

The reason for being in doubt is as Hillside nozzle make an ellipse opening in the vessel and that ellipse having Major and Minor dia. The stiffness calculated will always be for Nozzle dia in WRC i.e approx Minor dia of that ellipse nozzle makes during connection. Hence values of Longitudnal stiffness(Ls) versus Circumferential stiffness(Cs) SHOULD differ from Ls and Cs compared to Radial nozzle attached at the same location.

The more appropriate method which is suggested is to calculate Longitudnal stiffness with Major dia of nozzle and Circumferential Stiffness using Minor dia of nozzle. Assigning these stiffness as User defined to the same nozzle will give a more accurate value (Atleast thats what I understand at this moment).

Any comments/suggestions will highly be appreciated on this type of method. I just want to assure you all that I have no intention to reject WRC or methods utilize all over the world but I need to be sure of what best could I do with the situation I have....and...situation is that my Boiler creates alot of stress at Tee points of Nozzle vessel intersections (3x to 4x Allow.Sy)when I don't use nozzle flexibility and after application of WRC297 all stresses have gone away .

Many regards,
Salz

As far as I know, WRC 107/297 do not address hillside nozzles.

Dear Richard,

For hillside nozzles I would rather prefer for this situations to consider FEA analysis and those stifness values (with Nozzle-Pro is quite easy). But I would like to know how to consider axis for these stifness values and allowable loads from vendor drawings, because they mention P/axial stif., Fl, Fc, Mt/torsional rot.stif., Mc/outplane rot.stif. and Ml/inplane rot.stif.

P (Axial Force) wolud be align with:
1. Nozzle axis?
2. Equipment radial axis?

I would say 1, but just want to be sure. Thanks for your help.

Stiffness input into CAESAR II (using restraints w/ CNODES) is made in the global coordinate system.

Dear Richard,

I am aware of that, but for a hillside nozzle, when I do input the stiffness in Caesar (using the cnodes), should I consider the axial stiffness align with the radial axis (case 2) or with the nozzle axis (case 1)???
Because usually on a normal nozzle, the nozzle axis will be align with the radial axis, so there is no doubt.

Thanks

Restraints are defined in the global coordinate system. So axial stiffness must be associated with either X, Y, or Z depending on the orientation of the nozzle.

In your example above (normal nozzle where the axial stiffness aligns with the radial direction), that could be Kx of the nozzle is in the X direction, or Kz if the nozzle is in the Z direction.