Minimum raised face height

[jonesey]

ASME B16.5 paragraph 6.4.1 states that 150# & 300# raised face flanges are 'regularly' furnished with 2mm raised face. I take it that there is no minimum value for the raised face height as paragraph 6.3.2 states you can actually remove the whole of the rasied face part as long as the minimum flange thickness tf is in accordance with the standard. We have a case on a 20" heater line where the existing raised face height is approx. 0.5mm and we are going to remove 1mm from the flange thickness, which will then give us a raised face of 1.5mm whilst still keeping a minimum flange thickness tf as stated in the standard. Anybody ever done anything similar ??

 

[codeeng]

As long as you stay within the minimum flange thickness you can use the B16.5 flange ratings. The raised face portion is basically optional. Not sure why you would want to remove 1mm from the flange.

 

[jonesey]

The flange is approx 0.5mm out of true and by maching the raised face we can make it parallel again thereby giving us a better gasket seating surface.

 

[unclesyd]

Be careful in machining a flange face. Just remember that the backside of the flange needs to be parallel to the opposite flange or in your case the raised face. Probably not a problem in you case as you aren't taking that much but it can cause a problem in some cases.