3 families of shaft seals
On a boat with a propeller shaft, whether it is a motorboat or a sailboat, there is the problem of the sealing of this shaft. The famous "stuffing box". There are 3 families of seals to solve this problem.
Historically, the gland was developed. It consists of two metal pieces that press gland to ensure the sealing around the shaft. As the shaft rotates, the gland wears out and the seal is not perfect. A good sailor always has an eye on his stuffing box to fine tune it and limit leakage.
Then came the lip seals. Plastic lips are used to seal around the shaft. This works well if the seal is new, but over time, the seal wears out (or sometimes even the shaft). In addition, this type of seal tends to heat up with friction.
Mechanical seals, the most efficient
Finally, there is the third family: mechanical seals. The PSS manufactured by SeaView is the perfect example. This seal has no friction on the shaft. The seal is made between a rotor (a rotating part fixed on the propeller shaft) and a stator (a stationary part fixed on the stern). The rotor is made of stainless steel and the stator of carbon. The faces in contact are glazed (mirror polished).
The stator is held against the rotor by a bellows that maintains a slight compression. This bellows also absorbs the movements of the motor when maneuvering (forward and reverse, movement in waves...).
No maintenance required
Totally waterproof, this type of seal does not let the slightest drop of water through. After a break-in period of the first 3 hours of use, the seal ensures a self-glazing afterwards. The seal requires no maintenance. Only the bellows made of a kind of rubber may age and lose elasticity with time. The manufacturer advises to change it every 6 or 7 years. Otherwise, this seal, which does not wear out, can last even with heavy use of the engine.
Available for all tree sizes
The PSS seal is available for shafts from 20 to 150 mm diameter (a range with inch dimensions is also available). This type of joint is widely used on many boats in the professional world (SNSM, military...) or in the yachting world (Azimut, Ferreti, Monte-Carlo Yachts, Hanse, Dufour, Alubat...).
