Teflon/Neoprene Gasket in Bolted Structural Connection

[rayb08]

I am looking into design of a CS/316SS connection. AISC Design Guide 27 mentions using a neoprene gasket to prevent dissimilar metal contact. Application would be in a highly corrosive environment. Typically I would avoid doing this altogether, but I wanted to pursue research in case I can't avoid it or for future reference.

I came across this detail of a bolted connection with a teflon pad at the interface but in a non-sliding connection. I don't think you can calculate shear capacity of this connection normally since the teflon is so soft compared to the steel. Is it possible to do it, reasonably?

AISC design guide doesn't elaborate on any differences in calculating connection strength while using a gasket. Am I correct in assuming that this is because if the gasket is thin enough, that it doesn't make a meaningful difference?

 

[RPMG]

For simple shear connections, I would say that the failure modes are all the same, whether or not there are insulating gaskets. I'm curious about the insulating bushing though. That seems a bit theoretical. In a practical sense, that probably means add tape, and let it wear because a SS bolt is not going to greatly increase corrosion in carbon steel.

 

[rayb08]

RPMG thanks for your reply.

I think I found what I was looking for in RCSC Spec. It seems that gaskets would only be prohibited for pretentioned connections. But the commentary also mentions that deformed surface slope should be limited to 1:20 to avoid inducing localized bending stress in the bolt. So technically, I think if the gasket is thin and compresses such that the slope at connected plies is small, then I can treat this like any bolted connection without gaskets.

Also, I know that it's common for isolation kits with stud insulating bushings to be used in process piping flange connections, but I don't know that direct shear is a large consideration on these studs or if ring gaskets would take that? I think in practice, tape would work just as well in some applications.

 

[HTURKAK]

I know insulating couplings and isolation kits with stud insulating bushings, washers used for piping to isolate the dissimilar pipes or , CP piping.

I will suggest either painting of the bolt shanks with epoxy or filling the remaining annular empty space with epoxy mortar.