Weld encroachment

Date 08-21-2007 05:55

At my current location, I don't have a recent 650 but according to 3.5.5 of the 98 version it states: In lieu of annular plates, the entire bottom may be butt welded provided the requirements for annular plate thickness, welding, materials, and inspection are meet for the annular distance specified in 3.5.2.
To me this means that even though you don't have annular plates, the requirements would be the same for edge distance between an annular plate weld and the vertical shell weld, and therefore the floor plate weld would require the same distance as an annular plate weld.

Regards,
Gerald

By Shane Feder (****)

Date 08-21-2007 19:40

Thanks Gerald but I can't find anywhere that details the minimum distance between annular butt welds and vertical shell welds.
I have to have it in "black and white" before I approach the contractor,
Thanks and regards,
Shane

By CWI555

Date 08-21-2007 21:49

Shane,

API 650:05
3.1.5.5 "Three-plate joints in the tank bottom shall be at least 300 mm
(12 in.) from each other and from the tank shell."

Where three plates meet, no joint can be within 12" of one another. According to this your answer is 12 inches. If for instance, where a floor weld meets two plates on the vertical weld joint, then the distance between the floor weld and the vertical weld should be 12".

Regards,
Gerald

By dbigkahunna (****)

Date 08-22-2007 00:44

650 does not address the weld spacing between the verts and the floor welds. Butt or lap welded. The three plate lap deals with floor plates not shell welds. 653 does address weld spacing on floor patches and verts where the patch will be in the critical zone.
BABRT's

By CWI555

Date 08-22-2007 00:58 Edited 08-22-2007 01:05

Definitions from API 650
3.1.1.1 double-welded butt joint:
A joint between two abutting parts lying in approximately the same plane that is
welded from both sides.

3.1.1.2 single-welded butt joint with backing:
A joint between two abutting parts lying in approximately the
same plane that is welded from one side only with the use of a
strip bar or another suitable backing material.

3.1.5.5 Butt-Welded Bottom Joints
"Three-plate joints in the tank bottom shall be at least 300 mm
(12 in.) from each other and from the tank shell."

It specifically deals with floor plates. butt welded bottom joints, thats floor plates. it also throws in the words tank bottom, and tank shell in the same sentence for clarity.
I would have to respectfully disagree with your statement, I may be wrong, but I doubt it given the wording as printed in 650: 05 edition.

Regards,
Gerald

By Shane Feder (****)

Date 08-22-2007 03:36

Guys,
Thanks for your responses.
Gerald,
In regard to the statement in 3.1.5.5 I don't think that it is applicable to the situation I am describing.
It says 3 plate joints shall be at least 300 mm from each other and from the tank shell but it doesn't mention the vertical weld at all.
The butt weld intersects underneath the shell at all the positions where the annulars would have been but I am trying to establish how far the butt weld (or annular for that matter) must be from a vertical weld.
Figure 3-11 is the closest I can find but that is for a Flush Type Shell Connection and I don't think it is applicable,
Thanks and regards,
Shane

By CWI555

Date 08-22-2007 03:47

I see your point, but with the emphasis put on vertical welds and welding near them, I can't see it being allowed to weld directly over one, or near it. I believe an inquiry is in order on this one. It's a good question, one that needs a clearer answer.

Regards,
Gerald