Gasket type and material in natural gas piping systems

[cluelessinohio]

In a natural gas medium pressure aboveground piping system, what type and material of gaskets have others used between a 125# cast iron valve flange and 150# steel pipe flange with the raised portion machined down?

Has anyone successfully used a spiral wound metal gasket?

 

[unclesyd]

I would get with your gasket supplier and see what in has for natural gas lines with Cast Iron Valves. There are quite a few materials for your application.

I would not try to use a spiral wound gasket in your situation.

Do you think there is some need for the spiral wound, ie fire?

 

[11echo]

Historically, I've used a 1/16" thk. nitrile ring full face gasket on 125# gas, and a 1/8 thk. Flexitallic type "CG" for the 150# gas service. The Flexitallic gasket is a spiral wound S.S. gasket. Good Luck! ...Mark

 

[cluelessinohio]

11echo:
Thanks for your response.

Have you ever used the Flexitallic type CG when connecting the 150# steel pipe flange to the 125# cast iron valve flange?
If you have did you have any problem with stressing the cast iron?

 

[TBP]

It's not a fuel code, but the ASME B31.1 Power Piping Code requires that the when flanging 125# cast iron to 150# steel, the raised face on the steel be removed (as you have done), and a full face gasket be used so you're not springing the relatively thin & bittle cast iron flange into a gap when tightening the bolts. By the time you get done taking the raised face off the 150 flange, and playing with gaskets, I'll bet it's not much more money to just go with 150 cast steel valves right from the start.

 

[11echo]

cluelessinohio ...NO! The Flexitallic type "CG" is for a raised face application. IF you are going to mate up a 125# FF flange to a 150# flange you need to verify two things: 1st that the raise face on the 150# has been machine off so what you have is a flat face flange, and 2nd you need to use a flat face gasket! This type of connection is fairly common on cast iron pumps, so it's not "odd" as you might think. GOOD LUCK! ...Mark

 

[tothepoint]

Style CG or RW spiral wound gaskets are typically used on raised face flanges. In order to use this gasket style on flat face flanges- especially cast iron, you'll need to specify a full-face outer guide ring.