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250# SS Flange ratings??

250# SS Flange ratings??

250# SS Flange ratings??


Is anyone experienced with 250# ANSI flanges in A182 material? B16.5 covers 150#, 300# etc in Carbon and other alloy materials; B16.1 cover 25#, 125# and 250# in CAST IRON.   Im trying to evaluate quotes for a pump with 250# RFSO flanges in 316 SS... to my knowledge, there is no ANSI/ASME document covering such fabrications.  

I also know you can't interpolate between ANSI class ratings, so how the heck do you qualify a flange of this material at such a rating?  I must be missing something, here...

Help would be greatly appreciated!


RE: 250# SS Flange ratings??

houseynukes, the normal approach for non-standard flanges is to design them per ASME Sec VIII or some other relevant Code.



RE: 250# SS Flange ratings??

If you approach this logically you will see the path to your answer.

Class 250 matches Class 300 in all dimensional aspects, except that Class 250 in Cast Iron normally has a Flat Face.

So if the pump vendor supplied a Stainless Steel Flange and labeled it Class 250 it is in reality a Class 300 Stainless Steel Flange (with or with-out a raised Face).  

RE: 250# SS Flange ratings??

Thanks for the quick responses!

SnT, if that was the course taken by the MFR (design to ASME), I assume it would be reasonable to request pressure-temp ratings of said flange?  And yet they quoted it as an 'ANSI 250# RFSO flange'... Im still waiting for their reply as to what ANSI standard they are referring to.

pennpiper, I can appreciate that logical breakdown, but if that is truly the case, why not just state it as a Class 300 flange?  Clearly there must be a reason for this intermediate classification, but what is that reason?  Having said that, I see what you're getting at - material grade is same, dimensions are same, thus integrity of structure must be the same.  But still, why mark it 250#?   

RE: 250# SS Flange ratings??

houseynukes, you can buy all kinds of flanges made to Standards patterns, including PVC flanges. They will bolt up but they DO NOT automatically meet the PT ratings of said standard.

As to your second question directed to pennpiper (who I am not speaking for), the vendor provides what the customer asks for, and don't always worry about the finer points.

If you have any doubts, get the vendor to provide the rating.



RE: 250# SS Flange ratings??

Just thought Id let you guys know what happened with this...

turns out the sales rep for the pump mistakenly quoted the flanges as 316SS... they are in fact Ductile Iron, and so B16.1 is applicable.  Were it not for the lady talkin to me like I was a tool, I wouldnt have questioned how I interpretted the codes.  Her emphatic and repetitive 'they're 250#, SS, and dimensions are the same as 300#' made me question whether I knew what I was talking about.  Once her senior sales rep got back from vacation, all was resolved in a short couple of hours.

Thanks for your help anyhow, folks!


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