Underwater Mechanical Seal 1

[beatmajesty]

Hi All,

I have searched the previous threads with some leads but no real luck.

I have an underwater shaft(1" diam) undergoing linear motion only (roughly 1' stroke) which needs to be sealed as it slides into and out of a submerged air cylinder. Consider it a double acting pneumatic piston acting underwater.

Minimum friction is needed, and the air water seal interface needs to be able to hold roughly 2atm pressure difference. I have considered lubricated packing etc, but i think there will be less friction with a bellows. I have looked at "bolloframs" but the stroke length is not long enough. Does anyone know a supplier of long-stroke bellows' or a better solution?

Thanks for the help.
Best regards
Scott

 

[BowTied]

It is tough to seal air without leaks no doubt. No expereince here, just a recollection that I saw in machine design magazine once a diaphragm seal that rolled back and forth - might have been used inside a cylinder.

A quick net search found this:

http://www.ceetak.com/seals_sites/rolling_diaphragm_seals.htm

I am sure there are others.... good luck.