Slip On Flanges

[BJaffa]

Why does the B31.1 limit S/O flanges to NPS 4 and Class 300 per Par(s) 104.5.1(A), 122.1.1 (F) and Fig 127.4.4(B)? Can or should one design around this restriction?

 

[prex]

The main reason should be the lower fatigue resistance of those flanges with respect to weld neck.
If you are bound to B31.1 as the code, I can't see how you could circumvent that rule: you should switch, if you can, to a less demanding code, such as B31.3.

prex

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