Dry shaft shaft design

[yalkamer]

I am working on a project specs and it asks for butterfly valve with dry shaft design. Media is seawater. As I searched on the web, I saw that mostly concentric btv vendors are naming their product as dry shaft design. Is it so?
Personally I can not accept that shafts are can stay dry especially after a certain time of operation.
I would be grateful to receive comments of experts.Thanks!

 

[itascot]

Concentric butterfly valves are inherently "dry-shaft" as the seat itself should seal against shaft as well as disc.
of course, the possibility of a malfunction exists, but that is always the case regardless of valve design.
Ciao,

 

[hsbcn]

All butterfly valves are designed to be dry shaft, but depending on the application, the replacement frequency is higher than with other valves, to avoid leaks. Pressure/temperature also influences how long the valve will remain completely dry. Make sure you get to talk to plant engineers who have used the valve brand you consider buying!

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