ASME B16.5 versus AWWA C207 Flanges

[districtguy]

Application: Treated chlorinated water about 100 psi working pressure.

I would like to know the correct application of flanges when joining a 4 inch steel flanged nozzle to a flanged steel butterfly valve. The butterfly valve would probably have a raised face. Is a ASME B16.5 identical to a AWWA C207 flange or does one have a raised face and the other not? What is the difference? Is a raised face necessary or is a flat face more desireable? I would be using a EPDM gasket material. Previously a flat faced flange has been specified for the nozzle flange but I want to know if this is optimum. Is a serrated surface needed in both at flat face and raised face application. I realize a flat face should be used with a cast iron flange. Also, what type of serrations, concentric or spiral, is best for this application.

 

[JStephen]

Most waterworks stuff is flat-faced by default. If the BFV is an AWWA valve, it'll probably be flat-faced too.

The bolt patterns of the C207 Cl. B and D flanges are the same as the 150# B16.5 flanges, and you can bolt one to the other. The AWWA flanges are thinner (for Cl. B and Cl. D) and may require slightly shorter bolts. The AWWA flanges are commonly made as plate flanges, without a hub. The main motivation to use AWWA flanges is that they are cheaper in larger sizes. In 4" size, it may be easier to just use a forged flange. Either FF or RF should work there. I don't know about that gasket specifically, but with normal rubber gaskets, the flange finish is not critical under those conditions.

 

[districtguy]

Thanks for the information. I was just reading the AWWA C207 and apparently the pressure for water piping were fairly low and the temperatures are ambient so AWWA started out with a flat face flange and it has generally stayed that way in the following years. I read that AWWA flanges are preferred for mating with the cast iron flanges and I guess that is why - they are flat faced. Is there any problem with mating the raised face steel flange with a flat faced? The AWWA standard does talk about serrated facing so I assume all AWWA flanges are serrated except by special order.

 

[eliebl]

Mating between flat faced and raised face should not present a problem. You essentially have gasket contact at the raised face portion and the flat face contact outside of the bolt circle does not happen. This would present a problem if you are dealing with materials such as cast iron where the flat face reduces the stresses within the flange.

This is a generalization only. This is not always the case. It really depends upon the sizes and pressures.

Regards,
EJL