What is the purpose of the shaft seal in a ship?

The purpose of the shaft seal in a ship is to prevent water from entering the hull. The shaft seal serves a critical function by creating a watertight barrier at the point where the propeller shaft exits the hull. This is essential for maintaining the integrity of the vessel's structure and ensuring that it remains buoyant and seaworthy.

When a ship is operating in water, there is always a risk of water intrusion due to the pressure difference between the exterior and the interior of the hull. The shaft seal is designed to withstand this pressure and keep the internal compartments dry, thereby protecting machinery and electrical systems located within the hull. This is vital for the overall safety of the ship and its crew. By effectively sealing the area around the rotating shaft, the seal enables effective propulsion while minimizing the risk of leaks.

The other choices pertain to different systems and functionalities that are not related to the primary role of the shaft seal. The adjustment of engine speed is typically managed by other components of the propulsion system, fuel flow regulation is handled by the fuel system, and steering control is primarily achieved through the rudder and associated mechanisms.