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Plug Welded Stays

Plug Welded Stays

Plug Welded Stays

(OP)
I am a bit cofused on how to determine the amount of pressure (and/or number and quantity of welds) that can be held in a rectangular pressure vessel with stay weld design.  We are planning on using a 3/8" top plate with a baffled construction.  The baffles are 3/8" thick and perpendicular to the top and bottom plate.  We plan to join the plates with the baffles by drilling (& chamfering)  holes in the in the top plate and placing a plug weld to secure it.  This is the stay design indicated in UW-19.  UW-19(c)(1) indicates to calculate the strength based on the shearing along the perimeter area.  The tensile area of this weld will be 4 times smaller than the perimeter area indicated in the code.  How should I calculate the strength of this weld so I can determine the number of locations for the pressure we are using (15 psi)?  

RE: Plug Welded Stays

I see your point.
My first point is that you are not within the coverage of UW-19(c), more within the coverage of UW-19(b).
My second point is that you cannot fulfil UW-19(b) as you cannot make a fillet weld having a size equal to plate thickness.
I would calculate based on a fillet weld size of d/2, a minimum leg dimension of 0.7d/2, a weld length of πd, and a weld efficiency of 55%.
Not clear to me though, what kind of chamfering or beveling are you planning to do on the holes.
Anyway you should discuss this with the AI: a proof test might be required.

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RE: Plug Welded Stays

Suggest you go to Sec I,Part PFT and Appendix A.

For SecVIII use U-2(g) and talk to your AI.

RE: Plug Welded Stays

(OP)
Thanks for your input on this.  It sounds like we need to do some more investigation on this design.  I am waiting for my contact at the vessel shop to get back with me.  

FYI:  We were planning on making the actual holes 1/2" with a standard 37.5 degree bevel.  I modeled this using FEA and it shows very high stress in the plug weld area based on the current pitch spacing.

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