Plug Welded Stays

[earnsdorff]

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)?

 

[prex]

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 [π]d, 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.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[deanc]

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

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

 

[earnsdorff]

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.