Are there size limitations for use of WN & SO flanges?

[BigTank]

In Section VIII, are there any size limitations set for the use of slip-on flanges where one must switch from the SO to a weld-neck, i.e. with manways?

I thought I remembered something regarding either size or service of a nozzle, and if it exceeds the given size or is to be used for that particular type of access or nozzle service, it cannot be a slip-on flange...but I could be wrong.

Aside from the temperature/pressure ratings in B16.5 as mentioned in UG-44, I cannot find any other type of limitation such as those mentioned above. Can anyone confirm this for me?

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Fitter, happier, more productive

 

[TomBarsh]

Section VIII, Div 1 accepts "standard" ASME B16.5 and B16.47 flanges as standard pressure parts, no calculations needed. B16.5 defines several types of flanges, including slip-on. B16.47 defines only weld neck type, it does not define the slip-on type. Thus it would seem that 24" would be the largest "standard" sli-on flange you can use. Slip-on flanges produced to other standards (API, AWWA, etc) would have to be analyzed with Appendix 2.

 

[vesselfab]

not the code, but service conditions may limit use of SO flanges as well as PWHT with out vents.

 

[BigTank]

Tom: gotcha.

Vesselfab: I think I understand where you infer those limitations to be.

Thanks guys.

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Fitter, happier, more productive