Roughness of the pressure rated flange 1

[alexafkh]

Quick and Easy!

How do you calculate the surface roughness of a flange while designing it for a pressure rated application to mate the companion flange?

Thanks in advance!

Alex Afkhami
Mechanical Designer
Siemens-Milltronics

 

[unclesyd]

Normally you callout a roughness value that will be suitable for the type gasket that will be used to make the connection.

We had an internal standard for all type flanges depending on the anticipated gasket. Rougher for elastomeric materials and smoother for metallic types, but very definite callouts.

Every gasket manufacturer will have a recommendation for the surface finish that is recommended for a particular gasket type or style.

 

[alexafkh]

Thanks Uncle!

The problem is that This is a flange for a level measurement instrument that can be used by different customers and of course with different gaskets, so, any recommendation for a general value that I can use (for the most critical situation) would be a great help.

Best regards,
Alex

 

[unclesyd]

What Class flange is it and what would be the most likely gasket.
Do you recommend a particular style gasket?

 

[alexafkh]

It is a series of 2",3",4",6" and 8" 150# flange. Interms of gasket, we can not recommend any type of gasket as it can be used for different worldwide applications.

 

[codeeng]

Per B16.5:

Tongue and groove: 3.2 microns max
Ringe joint: 1.6 microns max
Other faces: 3.2 to 6.3 microns

 

[arto]

Note that per Par 6.4.5:
"The finish of the gasket contact faces shall be judged by
visual comparison with Ra standards (see ASME B46.1)and not by instruments having stylus tracers and electronic amplification."