Smurf flanges are specially designed for filling and draining piping systems during a hydrotest.
Because the flanges have a fill/drain connection on one side, it is possible to leave the flange in place during filling or draining.
A Smurf flange is similar to a bleed flange, except that the Smurf flange does not have a full passage, but is closed except for a small hole.
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Smurf Flange Name
The name smurf flange is used in the Netherlands, and I don't know what the flange is called in another language.
Smurf Flange Standard
There are no industry guidelines (at least I have been unable to find anything) specifically named for the design and manufacture of Smurf flanges. Consequently, Smurf flanges are often designed, manufactured and sold as little more than a commodity product.
Because there is no standard available, the design may vary from manufacturer to manufacturer. I have found on the internet countless manufactures and suppliers, who refer to ASME and DIN standards, but in both standards I can't find anything about Smurf Flanges.
As for the T and A dimensions in the sketch above, the dimensions of a bleed flange can basically be applied. Before fabricating a Smurf flange, ask your client for approval.