API 650 and API 653 shell welding space

[jfacevedob]

Dear Seir

Anybody could tell me if welding space to the horizontal weleded joint indicated in fig. 5.6 (API 650) or fig. 9.1 (API 653) apply in zones or areas without contact with the product (without liquid pressure)

 

[JStephen]

As far as I know, yes, it does apply. Note that Annex A design removes many of the weld spacing requirements, though.
I think you could make a good case why the spacing requirements should not apply in the case mentioned, but that's not the way the standard is written.

 

[IFRs]

Is the liquid prevented from coming in contact with this area by overflows or just operational controls? Does the tank volume in permits, fire protection plans, overfill protection plans, emissions calculations, etc include this section? If this volume is not legally part of the tank volume you could make a case that you have a shorter tank with an extension for cosmetic or other non-structural purposes. If however liquid could be up there under some circumstance, you need to follow the code to minimize risk to the owner and the public.