Weld stress calculation

[Ndondo2009]

I have a 10" x 273 OD x 6 thk nozzle neck x 10 thk plate flange welded on a 48" manhole cover. This 10" must be connected to piping with the following external loads:

FX FY FZ MX MY MZ
Operating -2280 -9009 9480 16287 -12927 873
Sustained 13 -7477 141 -260 -334 173
Expansion -2292 -1532 9339 16547 -12593 700

I have tried PV Elite (WRC 297 nor 107) but it doen't cover nozzles welded on flat plates.

Can this be analyzed with WRC or how can I calculate or analyze these stresses?

 

[DSB123]

Ndondo2009,
Use FEA.

 

[TomBarsh]

WRC bulletin 107 considers attachments only to cylindrical and spherical shells (and by extension, to ellipsoidal heads). It does not consider attachments to flat plates (circular or otherwise).

WRC bulletin 297 provides a more sophisticated analysis than does bulletin 107 (it considers stresses in the nozzle neck and the interaction between the shell and nozzle) but is restricted to cylindrical shells.

This is why the program does not provide the option to analyze the nozzle loads by these two bulletins.

I'm not certain if there are other WRC bulletins that consider this condition. As mentioned, you can perform a finite element analysis. Or you can perform an analysis using methods from "Formulas for Stress and Strain" by Roark and Young.

(I partially retract the statement above about bulletin 297. This bulletin considers, as the title states "local stresses in cylindrical shells due to external loadings on nozzles". The analysis method considers the interaction between the shell and nozzle, and the flexibility of the nozzle but it does not report stresses along the nozzle neck or shell away from the junction. Prof. Steele's FAST2 fortran program and his shell theory on which the 297 bulletin is based do allow the designer to obtain stresses along the shell and nozzle surfaces at defined points. By the way, has ANYONE ever used FAST2? Is it still around?)

 

[TomBarsh]

Another clarification, your question's subject regards finding stresses in the welds. This is a pretty elementary calculation and you can find the solution in a number of texts or references on welding, structures, or machine design, develop your own based on fundamentals (bending stress Mc/I, axial stress F/A, etc).

The difficult part will be determining the stresses in the flat cover resulting from the applied loads.

 

[LSThill]

Techanical Reference:

ASME SHORT COURSE ON SECTION VIII, DIVISION 1 PRESSURE VESSELS, ASME EXAMPLE DESIGN PROBLEM J R FARR AUG 4 1987, Marriott Hotel Denver , CO.

 

[JStephen]

If the nozzle is centered in the plate, Roark's Forumulas for Stress and Strain will handle the axial load, but I don't believe he includes a load case for the moment loads. Torsion should be pretty simple, though.