A234 WPB Elbow defects

[mizzoueng]

So I have an elbow on a 670 psig/700F steam line that has inclusions in the base metal.

We UT'd the welds and they all came out clean, but the actual elbow itself has these small (using UTSW) inclusions throughout the elbow that cause us to get thickness readings less than min wall. Using UTSW we know there is base metal under the inclusions, but we cannot determine what the thickness of said metal is.

This falls under B31.1 but under the admin of Sec VIII Div 1.

Does anyone know where I could find acceptance criteria for these inclusions? I looked up B31.1, E446, A960, A105, A234. None give true acceptance criteria for manufacturing, which I think this falls under.

I could use B31.1 criteria for welds, that would be overly conservative but it would be a criteria.

 

[metengr]

Since this is a steam line stacked inclusions should not pose a threat to failure. Why? Because the circumferential orientation of the inclusions are not in the hoop stress direction that would result in through wall crack propagation in service. Radial stacked inclusions would be harmful.

Stacked circumferential inclusions could be detrimental for ambient or low temperature service conditions where fracture toughness is a concerns or under corrosive conditions or in situations where attachments welded to the OD surface of the pipe could result in lamellar tearing of the pipe base material.

 

[SNORGY]

mizzoueng:

I have been down this path with badly pitted A234 WPB elbows sourced (after you follow the trail) from China. The pass / fail acceptance criteria followed were based on SA-960. Failure to meet these criteria was deemed by the local Regulator to be adequate cause for rejection, provided that the judgement was made by the engineer rather than the Regulator.

In other words, the Regulator would not make a ruling, but would support a judgement made by others (me) based on an accepted Code.

Regards,

SNORGY.