Flange rigidity ASME VIII, Div.1

[wsmith22]

Does anyone have any background on why this was made mandatory in App 2? We design self energizing gasket flanges and have never had any issues with leaking. By the nature of o-ring sealing, these flanges can handle more deflection without leaking, however ASME gives no relief from the flange rigidity calculation.

 

[carthago]

1/-I believe that is because the old method as given in apendix 2, of ASME VIII did not take or tooke in acount the flange deformation and the flange leakage.

Some other Codes did, and define for instance the maximum acceptable flange rotation.

2-/ It is well known , the appendix 2 method is not 100% valid for large flanges * those used for heat exchangers for instance

3-/the PVRC is also busy with some other studies which will complement or even superseede the appendix 2 method.
And introduce other and better sort of gasket factors.
And one can even in some cases predict the leakage amount.


The appendix 2 method is from the thirties , it is a proven method to a certain extend, but has a lot of drawbacks, some are
- Effect of radial pressure diregarded.
- Gasket elasticity disregarded
- Flange deformation disregarded.
- Influence of bolt torquing also disregarded



Besides thoe gasket factors m and y are given for indication, are old ..out of date thus..but we have no choice