ASME 600# Raised Face Flange = 7mm &/or 6.4mm a requirement or recommendation?

[TEIGRAY]

Hi All,

Just a quick one,

Firstly is the 7mm (6.4mm on some other sources) raised face on the ASME 600# rated flange a requirement or just a recommendation?

I.e if I were to machine this down to 2mm would it then affect the sealing properties and therefore the rating of the flange itself, or is the rating mainly just down to the thickness (tf)?

On a side note, any reason why in some it's 7mm and others 6.4mm - maybe just the conversion from inch to mm?

Any help on the first point would be great as I'm limited in my overall face to face values for a new prototype assembly.

Cheers!

 

[KevinNZ]

The raised face is required so the sealing surface is limited to the area of the raised face.

 

[BJI]

Please refer to ASME B16.5.

This is not a requirement, just the nominal height from B16.5. It may optionally be ordered in a different height.

This does not affect the rating, the raised face may be re-machined as required as long as the minimum flange thickness is not reduced. Also, some raised face is recommended to ensure centering ring is not contacting the flange ring (and required for sheet gaskets as Kevin said). Consideration should also be given to pipe fitting if the arrangement was based on standard dimensions.

7mm is given in B16.5 with 0.25in in parentheses, which is 6.35mm, therefore both are correct. 2mm and 7mm are the more recent rounded metric version used in the code.