1st Shell Course Vert Weld Offset

[TankDude]

I can't find anything in API650 or 653 that discusses required offset between shell vert welds and bottom plate lap welds. Specifically, regarding a bottom replacement. I have always tried to use 12" when designing and detailing new construction, and this was just a rule-of-thumb that someone told me years ago. Does anyone know of any requirements by API, and if not what sort of "best practice" might you employ? Thanks.

 

[JoeTank]

Tank Dude,
There are no spacing requirements in API-650.
In API-653 it's addressed in 9.2.3.3 last sentence

Joe Tank

 

[TankDude]

Joe Tank,
Thanks for the response, however I can't say that I agree that 9.2.3.3 applies to this situation. That section is for replacement shell plates and the offset of such plates from bottom weld seams. In this case the shell is not being modified at all, only the bottom is being replaced. If it is the intent of API to convey that this section applies to situations such as mine, then it is not clear to me. In light of this, my opinion is that there is no requirement since it is somewhat similar to a new construction application (only backwards so to speak).
Your thoughts?

 

[JoeTank]

Tank Dude,
For bottom replacements, see 9.10.2.4 for spacing of bottom joints and existing verts. My apology for not reading you initial post carefully. If you are using tombstone insert plates, the "new vert" weld spacing also applies. It's also indicated on Fig 9-1.

Joe Tank