The IMC allows the use of "converte

[Eng-firm]

The IMC allows the use of "converter fittings" to separate dissimilar metals in lieu of dielectric fittings such as unions and flanges. An example the IMC gives is cast brass male and female threaded adapters between steel and copper for instance. I am wondering if a bronze ball valve with threaded ends is suitable for dielectric separation between steel and copper. Bronze is after all, an alloy of copper and tin while brass is an alloy of copper and zinc. Can anyone offer any advice? The application is natural gas piping.

 

[EdStainless]

Between brasses and bronzes there are only about 1,000 different alloys.
You have to be very careful with such generalizations.
It is important to select an alloy that will be more corrosion resistant than the other metals in the system.
The other problem with using a valve for this is that any corrosion of small parts in the valve can compromise its function.

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P.E. Metallurgy, consulting work welcomed

 

[Eng-firm]

Thank you. I guess i will search out the best dielectric fitting to transition from the steel to the appliance bronze shutoff valve. The factory piping downstream of the valve is copper. I was thinking the bronze valve would work. I really appreciate your quick reply!

 

[Eng-firm]

Do i even need to worry about electrolysis when the application is natural gas piping? There is no electrolyte, ie: - no water...

 

[GBTorpenhow]

No electrolyte, no galvanic cell. Rainwater, condensation, etc. can also complete the circuit externally depending on installation location.

Of relevance is the relative size of the steel and copper sections. If the carbon steel (anode) is much larger than the copper section (cathode) there is little risk of any problems. For example a carbon steel plug in a copper piping system is not a good idea, but a bronze plug in a carbon steel piping system is fine.

I wouldn't be concerned with a predominantly carbon steel dry natural gas piping system going directly to a brass or bronze valve (with SS trim) going to copper tube.

However, even if the thinking is really for water piping, if the relevant code says "thou shalt", your hand is forced.