mixed ratings: Flange and Body
mixed ratings: Flange and Body
(OP)
The subject has come up about placing a flange on a valve or fitting wherein the flange has a higher class rating than the valve or fitting body.
My position is simply that this is not to be done. However, I thought that I had once seen this published in a standard, but I do not see it in B16.34 or B16.5.
Does anyone know if this subject has been addressed in a standard?
Thanks
My position is simply that this is not to be done. However, I thought that I had once seen this published in a standard, but I do not see it in B16.34 or B16.5.
Does anyone know if this subject has been addressed in a standard?
Thanks





RE: mixed ratings: Flange and Body
OK, so no one has any experience about this (?).
Anyhow (also without any experience here), let me try to put down some points:
a) mechanically you could of course (within the possible measurement and mechanical/material limitations) do this.
b) you could also produce material certificates and test certificates for your mixed product (within limits).
c) you would (my opinion) not be able to refer to this as anything else than what you have: a product of components according to different specifications, with no common specification covering the total product. This will again lower the juridical strength of installer and end-user if any damage should occur, now or later, caused (or suspected caused) by the installation.
d) I can imagine situations where the 'product' could come up as a suggestion. Usually this type of suggestions is motivated by
economics: unwillingness to do what is technically correct.
e) If this is the reason: I agree fully with your reaction: do not accept.
f) On the other hand I would be sceptic, but willing to listen, if the whole installation is degraded to lowest pressure class (valve body and seat).
Good luck! Would be interesting to have the end of this story with more details!
RE: mixed ratings: Flange and Body
Of course there are instances where a valve (ie a PRV) will have differing rated flanges, but I am pressuming that this is not where your question comes from?
RE: mixed ratings: Flange and Body
Going the other way would be just plain wrong. Putting ANSI 300 flanges on a valve body rated for 280 psig would be misleading, incompetent, and probably actionable.
David
RE: mixed ratings: Flange and Body
RE: mixed ratings: Flange and Body
As to B16.34 2.1.1(g)this does agree with this what I have said, except it offers an "out" in para.4.3.3.
I would prefer a stronger statement, but I realize that there are legitimate applications. (In my case we do not have this situation.)
Thanks again for an interesting thread.