The stern shaft sealing device plays a critical role in protecting the marine environment.

At present, stern shaft sealing devices are mainly of two types: oil seals and air seals. The working principle of oil-type seals is relatively simple, so I will focus on explaining the more advanced air-type stern shaft sealing device. The air-sealing type is particularly important in reducing marine environmental pollution. Another significant feature is its ability to automatically regulate air pressure according to the vessel’s draft. For example, when the draft increases, the seawater pressure acting on the outside of the aft seal also increases, which in turn raises the pressure in the compressed air sealing chamber. This pressure change is then fed back to the oil circuit, maintaining a balanced pressure differential at all times and ensuring the sealing effect.

The stern shaft sealing device belongs to the category of face seals. Its features include: using drive screws to connect the sealing assembly composed of a composite material dynamic ring, spring seat, spring, and dynamic ring seat with a pump-effect spiral ring, thereby achieving both radial and axial sealing. The pump-effect spiral ring and oil holes form an automatic circulation lubrication system. The aft sealing device is equipped with a sand-prevention sealing ring with double lips, as well as forward and aft seal glands, a hollow piston, and a cooling water jacket. This design ensures excellent sealing performance, resistance to fishing line entanglement, extremely low oil leakage rate, and ease of installation.