Calling all Piping guys! Fracture Mechanics in ASME B31.3 piping welds (NFS)

[ASMEweldGuy]

Background. Piping welds in Normal Fluid Service made per ASME B31.3. For specifics, lets consider this to be a Carbon steel pipe to pipe groove weld. SA-106gr.B piping welded with GTAW open root with ER70S-6, then filled and capped with SMAW, using E7018-H4R, no PWHT.

Thoughts on how Incomplete Penetration (IP), which is only located at the root of the weld (found by RT), compares to Lack of Fusion (LOF), which can be located anywhere in the weld (between layers or on the side wall) but does not breach the surface. Look at the two discontinuities from purely a fracture mechanics stand point.

Compare the two both being of the same length (linear indication. I am interested in hearing your opinions. I would also like to hear your opinions on the two, regardless of fracture mechanics. Do you want to allow LOF in your piping systems? (Currently none is allowed per B31.3)

Reason being, ASME B31.3 is voting to allow the same amount of LOF as they currently do IP. I have my own very specific thoughts on the matter, but Fracture Mechanics is not one of my strong points.

 

[TGS4]

@ASMEweldGuy - what item number is this being proposed under?

 

[ASMEweldGuy]

@TGS4
It is record number 20-1760 under B31.3 if you have access to C&S Connect.

 

[DekDee]

Fracture mechanics is the mechanical analysis of materials containing one or more cracks to predict the conditions when failure is likely to occur.

Replace "one or more cracks" with "one or more examples of incomplete fusion".

When using fracture mechanics a subsurface flaw can be longer or larger than a flaw that is exposed to the surface.

So, 38 mm of incomplete penetration (exposed to surface) is more likely to fail than 38 mm of incomplete fusion (subsurface).

If the code currently allows 38 mm of IP it seems logical that 38 mm of IF is also acceptable.

 

[XL83NL]

What exactly is your point in bringing this up here? When there is you have something against the current voting and proposal of this record makes under B31.3, have you attended any of the code committee meetings to address your concerns? I think that should be a good,, first place to start off such a technical discussion.

Huub
- You never get what you expect, you only get what you inspect.