API-620 Skirt, shell and bottom welding

[EngFax]

Hello,

we have an API-620 tank 18ft diameter, 25ft shell height, conical roof, conical bottom and skirt support.

What is the best way to weld the bottom and shell to the skirt?

Thanks

 

[chicopee]

I'll stick my neck on this one because eventho I have read a few books on tanks I don't with such tanks, so I'll say at the line of discontinuity between bottom head and tank shell. I can hardly wait for replies on this answer.

 

[JStephen]

It's really all a compression-ring issue, and you need to hold the minimum compression ring area and hold the centroid of that area relative to the intersection. But without checking into if closer, I'd probably look at a thickened section of shell extending above and below the junction, a thickened area of cone near the junction, and an additional horizontal bar outside if required.

 

[gr2vessels]

I would suggest a tori-conical junction of the bottom cone and the shell, perhaps an FE analysis for the junction. Attach the skirt to the tori section just like attaching to a dished end. The shell to roof is a straight forward compression ring design. Easy....
Cheers,
gr2vessels

 

[JStephen]

Unfortunately, API-620 does not always produce reasonable results in knuckle regions, so there are some drawbacks to that approach.

 

[gr2vessels]

Yep, precisely. That why I mentioned FEA for the joint/knuckle area. Normally, you should achieve the required strength with less material than the cone-cylinder junction.
Cheers,
gr2vessels