Bottom tombstone repairs clost to shell butt welds
Bottom tombstone repairs clost to shell butt welds
(OP)
Does a tombstone bottom patch (in the critical zone) have to be 3" or 5t away from a shell vertival butt joint? I know bottom/annular plate joints have to be 3" or 5t, but does a tombstone bottom patch? API 653 seems to be silent on this, or I can't find it. Thanks!!





RE: Bottom tombstone repairs clost to shell butt welds
In figure 9.1, use "V" for that distance. The reason i say this is because the tombstone is going to be the same thickness as a lap patch, and it's going to have the same the same radius corners as a lap patch. That being said, for a lap patch, you would use "V" for the spacing.
Hope this helps.
RE: Bottom tombstone repairs clost to shell butt welds
RE: Bottom tombstone repairs clost to shell butt welds
The reason I would go with that is because that distance is acceptable when putting a lap patch on the shell that crosses a vertical weld seam. For all lap patches on the shell that cross a vertical weld seam, the distance of the new weld from the existing seam shall be "V".
So... when i look at the tombstone on the floor. If the shell-to-tombstone weld is going to cross a vertical weld seam, i would treat it as i would any other shell lap patch weld that crosses a vertical weld seam.
I may be completely wrong, but that's just my theory. Yeah it's more conservative, but I have a better shot of being right that if i were to go with "C" in figure 9-9.
I've run into this before, but cant seem to remember what we did.
Let me know if you agree with my theory, or if you have something else.