Is 841.1.2 Fracture Control and Arrest (B31.8 2010) written correctly? 1

[dtn6770]

Prior to the 2010 edition, in at least the 2003 and 2007 editions, the Brittle Fracture Control and Ductile Fracture Arrest paragraphs were nested in/under paragraph (c) which implies their applicability only when the Fracture Toughness Criterion is triggered. Interpretation 15-5 would seem to support that.

In the 2010 edition, post interpretation 15-5, the Fracture Toughness Criterion, Brittle Fracture Control, and Ductile Fracture Arrest paragraphs were moved out of 841.11 into newly created section 841.1.2 Fracture Control and Arrest. Now, however, the Brittle Fracture Control and Ductile Fracture Arrest paragraphs are NOT nested in/under the Fracture Toughness Criterion. Rather, they are on equal footing which implies autonomy from the Fracture Toughness Criterion trigger. That is, they would seem to be stand alone requirements exclusive of the 841.1.2(a).

I think this is where JRCARMEN was/is coming from in thread 378-303188. It was obviously a deliberate move by the Code Committee to carve our a specific Fracture Control and Arrest section but I’d like to think that they didn’t intend to make Brittle Fracture Control and Ductile Fracture Arrest, 841.1.2(b) and (c) effectively mandatory…without a trigger, but it reads that way. About the only “yeah but” argument is, what would the fracture toughness criterion be if not 841.1.2(b) and (c)?

What am I missing?

 

[SJones]

The 'trigger' is there: it's either hoop stress or temperature. Fracture is dependent upon stress, defect size and fracture toughness. Temperature affects fracture toughness. It now brings ASME into the world of other pipeline codes such as DNV-OS-F101, ISO 13623 and AS 2885 when addressing fracture control.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[dtn6770]

Steve,

The wording has been in B31.8 for some time so you must be referring to how that wording is now structured insofar as ASME joining the world of other pipeline codes.

So in the context of how the Code is now written, not necessarily the mechanics of fracture theory, you are of the opinion that 841.1.2(b) Brittle Fracture Control, 841.1.2(c) Ductile Fracture Arrest, and 841.1.2(d) Mechanical Crack Arrestors are standalone paragraphs with no dependency on 841.1.2(a)?

 

[SJones]

(b) is linked to (a) by virtue of the term 'adequate ductility' appearing in both.

(c) is linked to (a) by virtue of the term 'adequate toughness' appearing in both

(d) is linked to (a) if one is incapable of, or cannot be bothered to, develop the ductile fracture arrest toughness requirements brought about by (a)(1) or (a)(2).

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[dtn6770]

The same implications as in earlier editions...the dependency is there even though the new format doesn't necessarily make it as obvious as the earlier, nested format.

Thanks for confirming what I'd hoped is the case.