Taylor Forge gasket crushing formula

[hippocrocopig]

Taylor Forge's 'Modern Flange Design' used to have a formula to find the minimum gasket width which was based on the idea that gaskets would crush as a stress equivalent to twice the seating stress 'y' (I'm doing this from memory!). If I apply it to large medium pressure heat exchanger girth flanges I wind up with SW gaskets 30 or 40 mm wide which, of course, totally banjaxes the whole flange. Does anyone know if that formula has any credit in the real world?

 

[SnTMan]

hippocrocopig, it is common to use a gage ring on SW gaskets, in which case I would not worry aboout the min width calulation. You won't crush it.

Regards,

Mike

 

[hippocrocopig]

Exactly right, SnTMan, and thanks.

However, same thing with DJ for example . My point was more out of general interest - does anybody (owner or fabricator) use that formula? I use Finglow program which invokes it, but I usually ignore it because it's not in App 2. But is that formula justified? If not, is there any other way to prevent (say) DJ or SW w/out ring crushing (empirical or otherwise)? Or to put it another way - is there any way to know that a gasket is too narrow?

 

[SnTMan]

hippocrocopig, I have never been too concerned about metallic gaskets being narrower than the Nmin calculation. The are a few standards for gasket width vs. diameter (maybe TEMA has one?) which I have followed with good results. It seems to me that something like a bare DJ gasket must rely on very high surface pressures to seal in the first place. If there was a really large discrepancy, the width or even type of gasket should maybe get another look.

Composition gaskets are another matter, and I think more attention should be paid to this issue than with metallic gaskets.

Regards,

Mike