Are full penetration welds required on a double mitered elbow under B31.3?

[ehbadger]

I've hit a small snag in one of my current projects. I am fairly certain this project falls under B31.3 as process piping in a chemical plant in a code state (KY). A manufacturer is fabricating some tantalum lined steel pipe for me. One of the parts is a double-mitered elbow. Category D fluid service.

The questions posed to me for approval:
1) Is a partial penetration weld acceptable on the elbow miters (circumferential) welds?
2) Could they omit radiography on those partial pen welds (as it would obviously not pass)

Apologies for my unfamiliarity with B31.3 (I haven't dug into details much in the past) but I've searched through it over the last day and from what I can tell:
- Table 341.3.2 indicates partial penetration welds are NOT acceptable (or have very, very little tolerance)
- 341.4.1.(b)(1) States I need at least some radiography (which would fail as a partial pen weld): Not less than 5% of circumferential butt and miter groove welds shall be examined fully by random radiography in accordance with para. 344.5 or by random ultrasonic examination in accordance with para. 344.6. The welds to be examined shall be selected to ensure that the work product of each welder or welding operator doing the production welding is included
- However since there are other pieces of pipe on this project, I could definitely get 5% RT done and not even touch this piece. But that doesn't feel like complying with the spirit of the code since I KNOW there are partial pen welds...

So my question for the experts is can I use a partial penetration weld on those mitered elbows at all? And if that answer is YES or MAYBE, what inspections/qualifications need to be done to remain compliant with B31.3?

 

[powerbouy]

I do not have much knowledge about the welding but i assume by partial penetration you mean "incomplete penetrations" as per B31.3 Table 341.3.2. So for category D fluids and Girth and Miter Groove (circumferential) welds, table states that "C" is the acceptance criteria, then if you go to table Table 341.3.2 "C" has a measure "Cumulative length of lack of fusion and incomplete penetration" and its acceptable value limit is "≤ 38 mm (1.5 in.) in any 150 mm (6 in.) weld length or 25% of total weld length, whichever is less" & I guess if you tell the manufacturer to comply with this you are complying with the code.


Also important to note is the Extent of required examination for category D fluids, if you refer para "341.4.2 Examination — Category D Fluid Service" you can notice that there is no 5% RT requirement for category D.


P.S - experts please correct me if i am wrong.

 

[ehbadger]

"Cumulative length of lack of fusion and incomplete penetration" and its acceptable value limit is "≤ 38 mm (1.5 in.) in any 150 mm (6 in.) weld length or 25% of total weld length, whichever is less"

I read that to mean if any more than 1.5" of the weld length (per 6 linear inches) is partial/incomplete penetration it does not pass. As the entire weld is spec'd partial penetration this would not pass.

I've attached a picture of the weld detail if that helps anyone. The pipe material is 18" STD WT PIPE SA-106-B

 

[KevinNZ]

How does the Ti liner do it's job if there is no weld of the liner at the joint?

 

[ehbadger]

The tantalum (Ta, not Ti) liner can welded from the inside with a "standing edge weld".