extremely light duty flanges

[pesy]

Is there a standard for light duty flanges?
We only have about 1 psi pressure and we're using sheet metal parts to confine the fluid. We would like to find a standard size light duty flange to use for our connections. Specifically, we're looking for 5" & 6". Everything I've found so far is 125# and higher.
Please let me know if there's anything lighter.
Thank you.

pesy

 

[butelja]

There are class 75 flanges per ANSI B16.47, Series B (Old API-605). Unfortunately, this standard only covers sizes 26"-60".

I think the normal practice is to use a plate flange with full face rubber gasket that is 150# ANSI B16.5 drilling, but thinner. Determining the minimum required flange thickness is not a trivial matter.