overbolting- Appendix 2 1

[mona2]

Hi, I am new on this site and on the pressure vessel area, so I apologize for any silly questions(and english mistakes).

I was trying to use some standard ring flanges(no hub, class 150) for my project, those flanges have the same dimensions as a slip-on flange from the ASME B16.5 but no hub (well I guess you guys already know that)
As they don't actually belong to ASME B16.5 I have to calculate them per Appendix 2(division 1), the thing is that none of the flanges pass...

My surprise is that it doesn't matter the diameter there is always great overbolting. I have read here that some standard flanges pass the Appendix 2 calculation( I guess that the smaller ones)

Am I missing something? Misscalculating something? or is it normal that altough the pressure is very low(only 4.5 bars) none of the flange pass the calculation?

I would apreciate any tips, sorry for my rookie question

 

[TGS4]

Actually, many of the small B16.5 flanges fail the Appendix 2 calculations, especially in Class 150. You'll have to change the dimensions of your flange.

No rookie mistake, and good on you for coming here and asking questions.

 

[mona2]

Thanks for the answer TGS4

Would it be unwise to use a screw with a smaller maximum allowable stress. If so the screw would require a smaller torque and I wouldn't have overbolting.
May I ask if it's acceptable to use SA-307 to join flanges?