Recommendation for studs for duplex SS flange

[KevinNZ]

We have a SS2205 flanged pipe spool bolting into carbon steel piping (class 300 CS to SS flange connection). What would be the recommended stud material for this application?

Thanks

 

[TugboatEng]

Is the corrosive condition internal or external to the flange? Internally corrosive means the bolts aren't likely exposed as the gasket protects the bolts from the process and your typical fasteners are acceptable. If it's corrosive from the outside you'll need to use corrosion resistant fasteners.

If flat faced is an option and there is potential for external corrosion, the gasket will protect all sides of the fastener provided the gaskets are low emissions.

 

[KevinNZ]

Thanks TugboatEng

External conditions are not very corrosive. The 2205 is for process inside the pipe. We are concerned with the dissimilar metals with carbon steel studs in a 2205 flange.

I have seen older posts here where galvanized CS studs were recommend.

 

[SJones]

And galvanised B7 studs are recommended again.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

I would use Xylan coated steel studs. I hate getting Zn on SS because someday someone may try to weld it.
Or if overkill is you goal just use 2205 studs and hardware, they are available.

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P.E. Metallurgy, consulting work welcomed

 

[david339933]

You can color the xylan/ptfe studs as well, indiating something different about that connection.

 

[SJones]

The problem with the polymeric coatings is that they can chew up exposing the steel. Then area ratio considerations come into play. If zinc is an issue, then go down the aluminium filled basecoat/fluoropolymer topcoat route, e.g. SermaGard.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.