Impact Test Exemptions - Flanges

[pperlich]

If a standard B16.5 or B16.47 carbon steel flange is used in a vessel, does the UCS-66(c) impact test exemptions apply if the designer chooses to calculate the flange per App.2?

My position is: Yes and here is why.

Flanges evaluated per Appendix 2 must have their MDMT and impact test requirements determined per the appropriate material type Subsection-Part (UCS, UHA, etc.) as Appendix 2 does not address specific material requirements or Minimum Design Metal Temperature or impact test requirements. Therefore, for CS flanges (standard or app.2) the MDMT/impact-testing rules of UCS-66 apply in all cases. As such, UCS-66(c) applies whether the standard pressure-temperature rating is used or Appendix 2 is used to evaluate the flange. The key word in UCS-66(c)(1)(-a) and (-b) is “supplied.” There is no distinction between the method of evaluation in the text of the Code.

For example, an Appendix 2 design can be applied to an SA-105 B16.5 flange supplied in the as-forged condition. This flange would have an MDMT of 0°F without impact testing per UCS-66(c)(1)(-b).


Phil

http://www.quicktanks.com

 

[Krausen]

I would agree. So long as the SA-105 as-forged flange is made to B16.5, the code allows you to bypass Fig UCS-66 to rate to 0F MDMT without impact testing for both standard & App 2 designed flanges. Which is kinda ironic, since wasn't it the alleged brittle fracture issues with B16.5 SA-105 as-forged flanges that influenced the committee to change them to Curve A in Fig UCS-66 to begin with?

 

[pperlich]

Yes, I believe that was the reason, which is ironic. I use COMPRESS for my design work and it doesn't give the designer the correct MDMT for flanges like my example. I contacted their support center and the assigned support person disagrees with using the UCS-66(c) exemption as I have described it. He is taking the position that it's either App. 2 or B16.5/47, and cannot be both.

Phil

http://www.quicktanks.com

 

[Krausen]

I’m not very familiar with latest COMPRESS, but even if their position is the flange has to be designed to B16.5/47 or App 2, I’d think you could still use the UCS-66(c) exemption to rate the flange to 0F MDMT, no?

Tolerance is the virtue of the man without convictions -GK Chesterton