RF FLANGE VS FF FLANGES

Is there a difference in the face to hub dimension of a RF weld neck flange and a FF weld neck flange. Is a FF flange a RF with the 1/16 face ground off?

I was asking if a FF flange was a RF with the RF ground off, or does the flange start as a FF then you remove the outer ring to make it a RF. We are only talking about a 1/16" in most cases but as you move up in pressure rating the Rf becomes 1/4".

OK guys, this is unclear to me!?? CCCENTER ...Are you asking "if" you machine off the 1/16" raise face does it change the "thru hub" dimension (See chart below this is the "Y" dim. listed) on a weld neck flange?

OK guys, this is unclear to me!?? CCCENTER ...Are you asking "if" you machine off the 1/16" raise face does it change the "thru hub" dimension (See chart below this is the "Y" dim. listed) on a weld neck flange?

yes, that is what i am asking

I would say YES! ...I don’t think there is much call for a flat face steel flanges in quantity, so there is no reason for flange manufactures to stock pile “flat face” steel flanges, when the operation to machine off a raise face into a flat face condition is too easy to do. So any manufacture would just fabricate(machine off the raised face) any flat faced flange orders as required. …My $0.02!

I thought I would resurrect this post and do my bit at flogging the dead horse...

The common question which has been asked is: "Are raised faced flanges standard and turned into a flat face or are flat face flanges standard and turned into raised face?"

ASME B16.5 States:



In essence, flanges are specified as standard raised face, as the B16.5 considers the additional raised portion an addition (or redundant) to the minimum required flange thickness (tf). If a designer happens across a flat face flange on site or in the shop; seemingly new and unblemished, the default is to assume that it already represents the minimum required thickness for the respective class #.