When to Use Appendix 2?
When to Use Appendix 2?
(OP)
I was told here that any flange over 24" has to be calculated using appendix 2. I just accepted this as a rule to the code, but now I'm wondering where this 'rule' is located.
In UG-44 it states that the following ASME standards are acceptable and in these standards (UG-44(h)) it lists B16.47-Large Diameter Steel Flanges NPS 26-60...
So my question is, when is it required that Appendix 2 is used instead of one of these standards?
In UG-44 it states that the following ASME standards are acceptable and in these standards (UG-44(h)) it lists B16.47-Large Diameter Steel Flanges NPS 26-60...
So my question is, when is it required that Appendix 2 is used instead of one of these standards?





RE: When to Use Appendix 2?
RE: When to Use Appendix 2?
RE: When to Use Appendix 2?
RE: When to Use Appendix 2?
rmw
RE: When to Use Appendix 2?
It's my understanding that even with B16.5 or 16.47 flanges, if you want to calculate minimum bolt load, you would use Appendix 2. Can someone please verify this?
RE: When to Use Appendix 2?
The bolt loads in Appendix 2 are for designing the flange ONLY.
RE: When to Use Appendix 2?
RE: When to Use Appendix 2?
So, unless you have high temperature (which 2.5.2 describes as temperatures in the creep range) or low temperature (which 2.5.3 describes as below the ductile-to-brittle transition temperature), the Standards seem to imply that there is a margin inherent for external loads. There are papers out there (don't make me spoon-feed them to you, please) that indicate that for some standard flanges, external loads, as measured by the equivalent pressure method, could be as high as the design pressure itself, again.
Whatever you do, do NOT take Appendix 2 as a measure of "risk of leakage". I'll say it again, Appendix 2 is for designing flanges, not ensuring that they won't leak. Do not use the bolt loads calculated in Appendix 2 in actual operation. See Appendix S for guidance on this matter.
RE: When to Use Appendix 2?
RE: When to Use Appendix 2?
And, how do flanges "fail"? They leak. Have you ever seen an over-stressed flange? I haven't. Would you know what one looks like? Probably excessive deflection. But you want to know how it failed - it leaked!
For a good primer on this specific topic, check out this paper h
RE: When to Use Appendix 2?
Take a 300lb 24in std B16.5 flange with standard B15.20 spiral wound gasket. The required flange thickness is about 4in something for these design conditions.
Then use a 600lb 24in flange, the required flange thickness jumps to 8.3in. The longitudinal hub stress becomes twice of the 300lb flange.
Next, analyze a 900lb 24in flange, the flange required thickness is reduced back to 4.282 in.
The design conditions are 200F and 350 psi, 0.0625in internal corrosion. The material is SA234WPB.
The culprit is the 'f' factor. This shows that a 600lb flange is worst than a 300 lb flange in this particular case per App. 2.
What we think is that some factors are going off the edge when computing the 'f' factor.
Has anybody seen this before?
best regards,
Mandeep Singh
RE: When to Use Appendix 2?
BTW - note that the pressure/temperature ratings in B16.5 have NO consideration for corrosion allowance. I know - it's scary, isn't it.