316L S/S FCAW LOF @ Root

[MichaelV]

Evening BP

Well, I'm coming at it from a structural steel design point of view, then taking it through to fabrication under the framework of BS EN 1090. Eurocode 3 (BS EN 1993) is one of the main codes for designing steel structures. Part 8 of the code addresses connection design, including welded joints. Provision is made for increased throat thicknesses associated with deep penetration fillets. The only stipulation in the code is that this can be done "provided that preliminary tests show that the required penetration can consistently be achieved."

Now, turning to BS EN 1090-2 (and I'm referring to the final draft of the new version set to appear shortly), my reading is that the following requirements prevail when dealing with material of grade S460 or higher:

"For the first pass of a single or multi pass deep penetration fillet welding using a fully mechanized process, a welding procedure test according to EN ISO 15614-1 shall be performed and examined for the range of nominal throat thickness which occurs during production. The examination shall include three macro-sections, one from the beginning, one from the middle and one from the end of one test piece. The minimum value of deep penetration shall be determined by measuring the actual values in the macro sections."

More generally, in terms of production tests for welding, the following stipulation is made:

"...if the deep penetration of a welding process is used for fillet welds, the penetration of the welds shall be checked. The results of the actual penetration shall be documented."

Hopefully this gives some insight into what's required, and I think it's fair to note that destructive testing is required in this context to robustly demonstrate the extent and consistency of deep penetration. From my point of view as a designer, this requires a proper dialogue with the fabricator at an early stage to ensure that the desired (deeper) throat can readily be achieved.

Thanks
Michael

 

[backpurge]

Michael, cheers for that, very interesting. I see the "deep penetration" provision only appears to apply to fully mechanised welding which make sense to me as it will be easier to ensure consistent depth of penetration when using a mechanised processed as opposed to a manual one.

Cheers Bob

 

[MichaelV]

Grand, Bob

I rather share your interpretation re. mechanised processes. However, in the best tradition of codes and standards, it’s still a wee bit unclear. The first clause I quoted, making reference to mechanised processes, appears to be in the context of S460 grade or above. However, the second quoted clause comes later in the standard and doesn’t spell out that it refers only to mechanised processes.

So I think it’s still open to manual, or more likely semi-automatic processes.

Either way, as long as it’s physically tested and suitable documented, the path is open, in my reading, for practical adoption of deep penetration fillet welding in the context of EC3 and EN 1090.

For interest sake I looked in EEMUA 158 but see that it’s not covered in there. It’s focused on jackets and primary structures right enough; must check 192.

As ever, it’s healthy for designers to consider the details of manufacture

Michael