You will have to include more detail in your question before you can get a good answer. And remember this: we don't know the work you do, and many of us don't even know what an "orifice flange" is.
Well...assuming you are talking about flanges to retain square-edged orifices, to conduct flow measurments per ISO 5761 or one of the other such standards...extra machining might include:
You need to add centering devices. Flatness requirements, finish requirements. Corner taps, tap pockets. Machinining after welding to square/true the flanges relative to pipe centerline.
Probably missed a few.
Maybe buy a copy of the standard and read up on it?
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
Um, no, you don't bevel the flange, you bevel the orifice...well, per the standard anyway. But I'm ASSuming the flange is not an integral orifice, i.e. seperate orifice plates are to be installed between the flanges...and disagreeing with David about flow and piping stuff is not usually a winner.
LOL, tell that to BigInch, he does it all the time.
From a gas measurement perspective, an "orifice flange" really should be called an "orifice-holding flange" (basically a standard flange with pressure sensing ports on both flanges). The actual flanges are just raised-face flanges with ports drilled and tapped. I've been assuming that this discussion was about the paddle plates that go between the flanges. Just about every answer above has taken that path. If he is really asking about the flanges then they get drilled and tapped.
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
