Appendix 2 Flange Thickness 2

[chaulklate]

Appendix 2, Figure 2-4, Note 4 reads in part, "Facing thickness greater than 1/16" shall be in excess of the required minimum flange thickness, t; those equal to or less than 1/16" may be included in the overall flange thickness." I interpret that (rightly or wrongly) as I may consider 1/16" of the raised face in my overall flange thickness, but no more than 1/16".

If I am trying to analyze a 8" Class 600 RFHB per Appendix 2, which has a flange thickness of 2.1875" and a raised face of 0.25", may I consider my flange thickness for Appendix 2 as 2.1875" + 0.0625" = 2.25"? If I am interpreting that wrong, can you offer the correct interpretation of Note 4?

 

[Cobra17]

"Facing thickness greater than 1/16" shall be in excess of the required minimum flange thickness".

flange required thickness = 2.1875"
raised face thickness = 0.25"

total thickness = 2.4375"

 

[jt1234]

Some many times in this forum and one more time for you: please stop analyze standard flange using Appendix 2. The only reference is pressure-temperature rating table. Nothing beyond that for standard flanges which have been in the world for more than 50 years. Don't waste your time and other people's time to argue with this.

 

[TGS4]

I'm with jt1234 on this one. Do NOT "analyze" a standard flange using the Appendix 2 approach. That approach is appropriate for designing robust, non-standard flanges. It was never intended to "analyze" standard flanges.

 

[chaulklate]

@jt1234 and @TGS4
I get it, and I have no intention of arguing or disrespecting your response. For further context...the vessel and nozzle were designed correct per the original stress data. Since completion of vessel fabrication, client would now like to remove a pipe support which passes considerably more load to the nozzle. The nozzle as currently designed and built cannot withstand the new load combination. I am just trying to come up with an option for clients consideration. It would be up to them if they wanted to accept the Appendix 2 rationale as a means of deleting a pipe support. I tried to design per Appendix 46, all works except it increases the fillet weld on the internal projection. We are trying to come up with an option that will not involve additional welding and a re-hydro. Designing nozzles per Appendix 2 or Appendix 46 is not my usual approach.

Back to my original question; is my interpretation of Note 4 correct and I can use 2.25" as flange thickness? Or must the flange thickness remain as 2.1875"?

 

[TGS4]

Does it fail Code Case 2901-1?

 

[chaulklate]

I will be looking into 2901-1 tomorrow, not yet familiar with it. Posted in another forum whether or not it could be toggled on in Compress? I may end up going through my output line by line to see if the new values will grant me some relief.

 

[jt1234]

Equation in UG 44(b) is the first place to do as it is already stipulated by code in lieu of the old code case 2901. DO that simple analysis by having your bending moment and pulling out axial force (if force is pushing into the flange, ignore the force). Also ignore shear force and torsional moment, which will produce insignificant stress.
I used to calculate equivalent pressure using equation in Dennis Moss, which is much conservative than UG-44(b). But, please do UG-44(b) first. Don't make simple thing complicate. As someone criticized me in the forum that I have too much ego. Yes I do and I want you to do things right and simple, as I have done this analysis many times.

 

[chaulklate]

Thanks, @jt1234. I started with UG-44(b) but was far from the result my client requires. Then I tried Appendix 46. Then I tried Appendix 2. Client just wants to divert more than what I think is a reasonable amount of load to the flange. I will keep working on it. End result may just be sticking with the pipe support. But I will do my part to present any options that may be out there. Or maybe they have to suck up the additional weld and extra hydro.

 

[KevinNZ]

What has "additional weld and extra hydro." got to do with flange loading?

 

[jt1234]

chaulklate,
Give me your MAWP, design temp, flange material, axial pulling out force (not pushing in force) and bending moment at the face of flange. The loading must be from CAESAR II pipe stress analysis for the loading at the FOF, not at the shell junction. You can give me the final "operating loading" (combination of sustained and thermal from CAESAR II, pipe stress engineer knows what I am talking about), and separate seismic / wind loading. I will run the analysis for you. If fails, you need to change the flange rating or out the support back. What did you do from Appendix 46 ? Your last sentence "additional weld and extra hydro" do not make sense to me. You are analyzing standard flange rating to see if it can take external loading without failing the code. Don't make simple things complicate.

 

[chaulklate]

Thank you, jt1234, a very kind offer, but not necessary. Truly. We do have several people exploring options internally, no need for your additional effort. Thank you. The comment for welding and hydro is because the vessel fabrication is complete; people on my team had suggestions incorporating additional welding, machining, replacing/increasing the flange rating, which would result in hydrotest again. I was looking to come up with a calculation that fit the as-built condition. Client is now showing more flexibility towards these other approaches. I genuinely do appreciate your offer.