Seal for an underwater shaft, what can I use?

[alandlclark]

I'm having to design A propeller but am unable to think of a suitable seal to be used to seal the shaft of the propeller. I thought possibly an O-ring or lip seal but they could quite easily give way and water seap into the boat.

Anyone Help?

 

[sealguy]

Most people use a mechanical packing enclosed in an adjustable stuffing box to seal this type of shaft. Newer desigs use a spring loaded PTFE seal as they do not need adjustment and will last muxh longer than a rubber seal.

 

[FERNENG]

Most stuffing boxes leak slightly when operating. The film of water provides lubrication. The trick is to minimize the leakage 1 to 2 drops per minute is typical. One of the problems is that if the are too tight the packing can wear very quickly or even damage the shaft.

I have a British sailboat that uses grease forced into the stuffing box by a permanently installed resevoir. The leak path is fairly long and the grease fill seems to work pretty well. Periodically tightening the cap on the resevoir forces more grease into the stuffing box.

 

[longeron]

There are mechanical seals that can be used in this application. The only company that comes to mind is Wartsila.

http://www.wartsila.com

 

[tigar1]

A shaft log is what cruiser manufacturers use. What is the diameter of your shaft? A simple three ring stuffing box and gland nut would work for surface applications.

Regards, tg

 

[smckennz]

If you want no leak path, a magnetic coupling could be used, but you would need external water lubricated prop bearings.

Stuffing box does about 99% of applications.

Outboard motors use lip seals which often let water into the gearcase.

Cheers

Steve