Radiographic requirements for Annular Plates

[KnaT]

Hey guys...

This is with reference to API 650 8.1.2.9

We have a tank with annular plates which are single sided in design but welded without backing strip. (i.e. GTAW Root + SMAW Filling Capping.)

Since the joint is neither a double welded joint nor a single welded joint with backing strip, how much radiographs shall I take for these type of joints? 10% or 50%?

Thanks in advance.

 

[Clareok]

Cant help you Knat, having a simlar problem in reading this section of API 650. It states radial joints, we dont know if these are the joints in the bottom end or the joint of the shell to the base.
Any help would be great
j

 

[fegenbush]

Clareok,

The joints discussed in 8.1.2.9 are those of annular plate to annular plate. These are required to be butt welded. It does not apply to the (generally) lap welded bottom plates to annular plates. This joint can be lap welded.

 

[KnaT]

I'd agree with Fegenbush. The term 'radial joints' refers to Annular plate (Bottom end) joints.

 

[Duwe6]

With a GTAW root on your annular plate-to-plate welds, I would treat them the same as a backing-bar weld. You have [almost certainly] achieved full pennetration, just like using a backing bar. Full-penn is full penn.

IMHO, the reason API-650 does not mention open-root welds is that "tanky" welders tend to not have the skill to make acceptable full-penn welds from one side, without the use of a backing bar.