Reducing flange analysis using FEA or Div 1 1

[jt1234]

Dear all,
I have a Div. 1 vessel with top 36" nozzle, 600# B16.47 series A, connected to a forging flange with hub ( we call it reducing flange) and a 18" outlet pipe as shown.
Can this reducing flange be classified as custom made component, not fitting UG-34, UG-39, Appendix 2 or Div 2 Part 4, such that it meets Div. 1 46-4, "Design by Analysis", and using FEA only per Div. 2 Part 5 is acceptable ?

(Note, using UG-34, UG-39 or Appendix 2 will end up much thicker than standard 36" flange)

 

[SnTMan]

It looks to me that the reducing flange could be considered an Apx 2 integral hub flange, design would presumably be performed per Apx 2-5(2), flange pairs and subsequent rules. The operating and seating loads may not to be identical for each flange of the pair, due to the effect of Hp. Seems the B16.47 flange would govern.

Not clear to me whether you would be obligated to analyze the B 16.47 flange per Apx 2 if it is within its rating.

"Course this may not come out the way you want. Things don't always

Whether you can fit it into 46-4 I have no idea, might be a case of agreement among the parties.

Regards,

Mike

 

[TGS4]

Don't use the DBA rules to design flanges (unless you want to introduce the concept of "leakage" into your design - and you don't want to do that!). The DBA bolting rules tell you to go back to 4.16 (the VIII-2 equivalent of App. 2) anyway. How would this not qualify for App. 2 / 4.16?

 

[Si-bo]

As the others wrote, your reducing flange is an Appendix 2 integral flange and it needs to be calculated as per it. And there's not much you can do since most parametres are fixed by the 36" flange.

You can try making both custom designed flanges and calculate them as per appendix 2: maybe you can save some thickness and reduce the number and/or size of bolts.
Not sure it will be cheaper.

 

[r6155]

I agree with jt1234 about UG-39.
The thickness of the reducing flange must be at least equal to that of the 36" flange.