Sealing mechanism:
1) Radial shaft seals:
Radial shaft seals, also known as lip seals, are used to seal rotary elements, such as a shaft or rotating bore. It is widely used for in applications of full submersion of seal and shaft.

Advantages:
- Aviods leakage sufficientally
- Prevent contamination which can harm components of the system.

Operating conditions ( pressurized conditions) :
Pressure ≤ 10 bar
Temp -30 to 140oc

Design:
Lip ring with spiral spring for radial preloading
Short but pressure stiff flexible, spring- preloaded sealing lip.

2) Stuffing box ( Gland seal) :
The stuffing box prevents sea water from entering the UV hull. In many cases the stuffing box is mounted inboard near the point the shaft exits the hull.
Design:
The "box" is a cylindrical assembly, typically of bronze, comprising a sleeve threaded on one end to accept adjusting and locking nuts. A sound stuffing box installation is critical to safety because failure can admit a catastrophic volume of water into the UV
Advantages:
In a common type of stuffing box, rings of braided fiber, known as shaft packing or gland packing, form a seal between the shaft and the stuffing box. Ideally, the compression is just enough to make the seal both watertight when the shaft is stationary and drip slightly when the shaft is turning.
3) End face mechanical seal:
An end face mechanical seal uses both rigid and flexible elements that maintain contact at a sealing interface and slide on each other, allowing a rotating element to pass through a sealed case.
Types of face seals:
O rings
E rings
C rings
Gaskets

- O rings:
The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring.
Advantages:
The seal is designed to have a point contact between the O-ring and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the O-ring body.
Design:
The flexible nature of O-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly crystalline.