Spiral Wound Gasket -Proper Seating Width "N" Per ASME VIII Appendix 2

[beh188]

When designing a flange to ASME VIII Appendix 2 and using a spiral wound gasket containing an outer and inner ring in combination with a raised face, what is the proper seating width "N" to use for the determination of b?

It seems like you should use only the width of the actual spiral wound portion of the gasket and neglect the width of the outer and inner rings. Using the whole width of the gasket for N would artificially inflate the required seating load.

 

[MSarver]

From my understanding of use with spiral wound gaskets, the inner and outer metallic rings are used as compression stops and should not be used in calculations for proper seating width "N".

Which is N=(G_od-G_id)/2 where G_od and G_id are gasket dimensions that are being compressed(touched) from the flange pair. With that being said, refer to Sec 8 Div 1 Figure 2.5.2a (second column) for a visual representation of what I attempted to explain.

Regards,
-Mathew

 

[TGS4]

beh188 - from the perspective of performing design calculations in accordance with ASME Section VIII, Division 1, Appendix 2, you are correct - the design bolt loads are calculated using the width of the spiral windings only.

Now that you've obtained the same answer twice (thanks MSarver), I will also point out Appendix S and ASME PCC-1 for recommendations on ACTUAL bolt loads to use once this flange is in service. Actual in-service bolt loads should never be confused with bolt loads for the purposes of flange design.

 

[meatpuppet]

Hi,

I am interested in such spiral wound gaskets. As the inner and outer rings act as compression stops, shouldn't it be possible to perform flange stress calculations with two lever arms (one for the gasket itself, and one for the compression stop) instead of one?

Thx

 

[TGS4]

meatpuppet - see

http://www.asmedl.org/getabs/servle...7543000145000001&idtype=cvips&gifs=Yes&ref=no

and

http://www.asmedl.org/getabs/servle...819000059000001&idtype=cvips&gifs=Yes&ref=no.