Increased flange ratings
Increased flange ratings
(OP)
I work in the natural gas industry. We have 150, 300, and 600# ANSI flanges in our system. Some of our old documentation has the old maop for these flanges. I believe in 1988 ANSI raised the ratings for these three flange classes. Is there a directive anywhere in the ANSI standards, or elsewhere, that tells us if these "new" ratings are retroactive? In other words do our old 600# valves have to be limited to 1440 psi, or can they, like our newer valves, be subjected to 1480 psi? Thanks for any help you can give me on this.
RE: Increased flange ratings
A good question. There are also several changes to the ratings from the 1996 ed to the 2003 ed. For example, at 200 deg F the rating of a CL-600 flange in material group 1.1 was raised from 1350 psi to 1360 psi while at 300 deg F the rating dropped from 1315 psi to 1310 psi.
The direct answer to your question is in B16.5 2003 (and at least as far back as the 1977 ed) in the last sentence of 1.3:
Another reference is Interpretation 2-38:
Now, have I seen flange rating "cherry picked" by edition. Yes. Is it hazardous? Maybe. I guess the bottom line is that if the joint seals - no problem! But make sure you are in a ethically and legally defensible posture (e.g. you verified that the material spec didn't change, the manufacturing requirements didn't change...) if it leaks and causes a problem.
When referring to the Code, you have to recognize that the committee does not have infinite volunteer resources (material spec's change, B16.5 requirements change...), and is really not in a position to retroactively change flange ratings. You really wouldn't want to be told that your line at 300 deg F now has to be derated since the flange rating changed, would you? So, the same applies to increases in ratings.
jt
RE: Increased flange ratings
Thank you for the answer and those references. Those are very useful to me.
RE: Increased flange ratings
Thanx.
RE: Increased flange ratings
jt