ASME VIII Div 1: Floating Head Minimum and Maximum Flange Stresses

[BanditKeith]

Hi, I have a question regarding mandatory Appendix 2 in the back of ASME VIII for bolted flange connections.

I've used this appendix when calculating the minimum bolt stress required and maximum bolt stress allowed on girth flanges for shell and tube heat exchangers. However, I was recently asked about these stresses for the floating head flange. Most of the designs of the floating heads I've seen are in mandatory Appendix 1 section 6 if I remember correctly (spherically dished covers?). Is Appendix 2 applicable for these types of flanges? I'm asking because none of the flange types in Figure 2-4 seem to represent these types of flanges, although some could be approximated as such. The maximum allowable stresses I'm getting are quite large (up to 100 ksi) and don't "feel" right to me. Is it correct to compute the minimum bolt stress and maximum flange stress as per Appendix 2 approximating the flange to a type in figure 2-4, or is there something else in here that I'm missing to deal with these kind of flanges?

Thanks

 

[SnTMan]

BanditKeith, carefully read Appendix 1-6. Specific direction as to the applicability of Appendix 2 are within.

I would point out that your statement "minimum bolt stress required and maximum bolt stress allowed" is not a correct statement. Code provides an allowable bolt stress to be usd for flange design only. Applied bolt strresses in service may be higher, or (not often) lower. This difference has been discussed numerous times in these fora, a search should turn up many threads on the subject. Also see Non-Mandatory Appendix S, and ASME PCC-1 for fuller discussion.

Regards,

Mike