dielectric fittings for black with S/S

[mech4321]

Hi everybody,

We just installed a new stainless steel condensate return tank. Is it necessary to use dielectric fittings to connect black steel piping on it? Any danger of galvanic corrosion between stainless and black steel over the years?

Thanks
Alex

 

[gr2vessels]

Yes, there is a great chance of galvanic corrosion, particularly at the interface (flanged connection) of CS piping to the SS inlet flange. It is a good idea to use insulating flange kit to prevent the galvanic corrosion.
Cheers,
gr2vessels

 

[Duwe6]

Problem seems to be more theoretical than actual. In the many places I have seen with C/S flanged to s/s, there has never been an issue that we noticed. However, a dielectric flange kit on new joints appears to be a good idea to me.

I would not break an in-service, nonleaking flange to install one, though.

 

[moltenmetal]

I'd concur with Duwe6, especially for a well-deoxygenated condensate.

 

[vpl]

I agree with not breaking an existing flange for no reason. However, I have seen galvanic corrosion on a SS/CS heat exchanger flange, so I wouldn't call it theoretical.

Patricia Lougheed

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