Butterfly in sea water service

[stanier]

I am being offered butterfly valves for sea water and brine service. The manufacturer claims that the shaft is in dry service and can be made in 13% chrome steel rather than super duplex stainless. The dry seal is achieved by machining a spherical seal in the rubber seal. This matches the shape of the disc. The disc is driven by split shafts using splines.

I have doubts about the durability of such a system and the ability to operate for 25 years without salt water reaching the shaft and causing pitting corrosion . Such corrosion would soon damage the seal more. Then salt water would get to the unprotected ductile iron body. Rust would expand the seal and the disc would jam.

Has anyone any experience of this type of valve in RO , dsalination or sea water cooling systems?

 

[Nicksun]

who is the vendor of this B'fly vlv? Armri from KSB?

Heard about it but never use this. But we use a lot Gemue b'fly vlv. Good quality.

 

[stanier]

Nicksun,

I tried to describe the valve without naming the supplier. You get the prize for a very good assumption.

I do not know if the lack of response is because no one uses the valve or there have been no problems.

I know of Gemu diaphragm valves but have never been offered butterfly. Will check them out.

 

[gerhardl]

If you have a 25 year duarability requirement, the whole Offshore North Sea oil business does not agree with your supplier.

Stainless steel stem would never be approved for seawater, regardless of protection seals (the risk is too great).

Go for your original requirement, although some other branches / end users might say OK to protected stainless.