Opening in B16.5 Blind Flange

[anolan23]

once you drill a hole into a B16.5 Blind Flange it removes the standard. This means that this bolted blind flange needs to be calculated as a flat plate. So I have a 1" hole in the flat plate (blind flange) and it is considered a small opening per UG-36 (c)(3)(-a).

UG-39(a) states that the opening not exceed 1/4 the head diameter or shortest span if I want to be exempt from the paragraph. My question: What is the head diameter dimension of the blind flange that I'm using? Is it the diameter of the whole blind flange itself, or just the effective diameter that see pressure, or........THANKS IN ADVANCE.

 

[pdiculous963]

Take a look at Figure UG-34. If the flange is raised face I would say that the head diameter would be the shell outside diameter based on sketched (j) and (k). If it is flat faced, it would be the bolt circle diameter based on sketch (p).

 

[SnTMan]

anolan23, see the figures in UG-34. It would usually be considered the mean gasket diameter.

The subjecct of holes in a B16.5 blind has been discussed numerous times, you might try a search.

Regards,

Mike

 

[loilfan]

Look at Table II-6 in B16.5 for openings in blind flanges.