Compatibility of Flat Face vs.Raised Face flanges
Compatibility of Flat Face vs.Raised Face flanges
(OP)
In a technical paper of DIPRA they say that ASME B16.1 flat face class 125 flanges are compatible with ASME B16.5 raised face class 150 flanges if the raise is 0.06inches.
Previously, I was told that steel raised face flanges are not recomended with cast iron flat face flanges, since there is a risk of breaking the iron flange.
Does somebody know more about the subject?.
I want to use flat face cast iron flanges conected with raised face steel flanges for a fire protection system and want to know if there is an important consideration I should take on account (about the bolt torques, tipe of gaskets, etc) or if I can follow the same requirements as if I were using steel flanges).
Thanks.
Previously, I was told that steel raised face flanges are not recomended with cast iron flat face flanges, since there is a risk of breaking the iron flange.
Does somebody know more about the subject?.
I want to use flat face cast iron flanges conected with raised face steel flanges for a fire protection system and want to know if there is an important consideration I should take on account (about the bolt torques, tipe of gaskets, etc) or if I can follow the same requirements as if I were using steel flanges).
Thanks.





RE: Compatibility of Flat Face vs.Raised Face flanges
I really don't like 125 CI, and my experience is that by the time you fool around getting the raised face machined off the 150 flange, and rounding up the correct grade of nuts & bolts (and ensuring that they get used), you've probably incurred pretty much the same cost as if you'd just bought the more expensive 150 mating flange to begin with. And with a pair of 150's, you're left with a MUCH stronger joint.
RE: Compatibility of Flat Face vs.Raised Face flanges
RE: Compatibility of Flat Face vs.Raised Face flanges
RE: Compatibility of Flat Face vs.Raised Face flanges
Chris Foley
Midland, TX
RE: Compatibility of Flat Face vs.Raised Face flanges
Based on my experience:
- The "Pump Handbook" (Karassik et al) contains a cautionary statement about never configuring the piping system with cast iron flat-faced flanges mated with raised-face piping flanges
- Several in-house process chemical compay guidelines I have read state that pumps shall always be purchased with raised face flanges. ( They seem to agree with the point made above that FF flanges are not worth the trouble)
MJC
MJC
RE: Compatibility of Flat Face vs.Raised Face flanges
Edward L. Klein
Pipe Stress Engineer
Houston, Texas
"All the world is a Spring"
All opinions expressed here are my own and not my company's.
RE: Compatibility of Flat Face vs.Raised Face flanges
Sorry.... I should be more specific..
I purchase most of my pumps with cast steel casings and RF flange faces.
If a cast iron pump was a client or practical requirement, I would ensure that there were FF Flanges on both the pump casing and the piping.....This is as much insurance as reasonably could be expected to prevent cracked flanges.....
However, there may be some big gorrila fitter out there that could crack these also
My opinion only
MJC
RE: Compatibility of Flat Face vs.Raised Face flanges
RE: Compatibility of Flat Face vs.Raised Face flanges
If there's a chance that your flanges will be bolted up to CI flanges, a mating steel flange should be purchased flat-faced.
For steel flanges, you can order them to ANSI B16.1 (CI) dimensions. Or, if they are 24 inches in size or less, ANSI B16.5 flanges will bolt right up. On sizes greater than 24, ANSI B16.47 governs for steel flanges, and one of the types there will bolt up to CI flanges, but they are thicker.