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Weld stress calculation

Weld stress calculation

Weld stress calculation

(OP)
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?   

RE: Weld stress calculation

Ndondo2009,
           Use FEA.

RE: Weld stress calculation

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?)

RE: Weld stress calculation

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.

RE: Weld stress calculation

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.
  

RE: Weld stress calculation

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.

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