Flanges B16.5 x Flanges ASME VIII Requirements 1

[ASMS81]

Hello all

I needed to check the possibility to increase the working pressure of a flange above the pressure-rating given by asme b16.5.

The pressure rating is 15.8 bar. The demand is to work up to 18.6 bar.

In order to verify the possibility I used the ASME VIII code procedures and surprisingly the flange is not acceptable even if I use the b16.5 pressure-rating (15.8 bar) in the calculations.

I checked the calculations many times, and it seems that there is no problem.

Does anybody know if it is possible?

Thanks in advance.

 

[marty007]

Yup, that's pretty common. If you design a custom ASME VIII-1 flange using the exact same geometry as a B16.5 flange, you often get a lower pressure rating.

I was once told that this just falls to industry experience. B16.5 flanges have been proven through decades of experience, whereas ASME VIII-1 Appendix 2 flanges are new every time with potentially no comparable track record (picture a very strange geometry...).

Cheers.

 

[ASMS81]

Thanks very much marty007! A friend of mine said the same.

The strange aspect about this issue is that despite ASME VIII gives requirements to determine a working pressure, and normally it´s lower than b16.5 pressure-rating, the code allows us to project a pressure vessel with b16.5 flanges!!

It really seems to make no sense!! So, it´s better to change the flange class...

 

[marty007]

Yes, to increase the pressure rating, it sounds like your only choices are a custom Appendix 2 flange or the next higher flange class.