Dear contributors,

I would like to find out what is your opinion on the flange connection with the specific size, ASME B16.5 - DN200-150#, using spiral wound gasket and material pairs A105/A193B7 or A182F5/A193B16. The given flange and bolt material pairs are very common in the industry and the piping design code is ASME B31.3.

In the flange connections we investigate the compliance of flange and bolt stresses with allowable in accordance with ASME Sect VIII Div 1 under the operating and gasket seating conditions.

When I investigate the flange connection with operating condition considering the external loads, the flange and bolt stresses are adequate. However, under the gasket seating condition (which requires large gasket seating stress) the bolt stresses are larger than the allowable although the flange stresses are adequate.

I did the calculation by a spreadsheet and the Flange Analysis option of Caesar II, in both cases the results are the same. The required bolt area is always greater than the available.

In the calculation, the effective gasket seating area is considered for the bolt calculation rather than the full seating area. Bolts are checked with allowable stress at the ambient temperature against the gasket seating force. I come up with around a ratio of 0.72 which is the allowable forces of bolts to the force introduced by the gasket seating for this size of flange connection.

Is there any source I can reach that explains the background of using effective gasket area and the allowable stress of the bolts in the flange calculations?
Why do not we consider the full gasket seating area for gasket (instead of effective area) and 0.6 times the yield stress of the bolts at ambient temperature for the gasket seating condition?

I have done similar calculations with other sizes and the ratio of allowable forces to the gasket seating force is around 0.97 and accepted adequate. But DN200-150# flange connection with spiral wound gasket looks very suspicious.

Have you been experienced this kind of problem with spiral wound gasket?
By considering the piping code B31.3, would you accept the flange connection DN200-150# with spiral wound gasket adequate from your experience?

I would like to hear from you and thanks in advance.

Ibrahim Demir