Ballast tanks fill by allowing seawater to enter as air is released from the tank. This is accomplished by opening valves that allow seawater to flow in, displacing the air within the tank.
Here's a breakdown of the process:
- Initial State: The ballast tank is initially filled with air at approximately the same pressure as the surrounding water pressure.
- Air Release: A valve (often at the top of the tank) is opened to allow the air inside to escape.
- Seawater Intake: Simultaneously, or immediately after, a valve at the bottom of the tank is opened to allow seawater to flow in.
- Displacement: As the seawater enters, it pushes the air out through the open air release valve. The pressure difference between the surrounding water and the air escaping facilitates this process.
- Full Tank: The process continues until the ballast tank is completely filled with seawater, displacing all the air.
The rate at which the tank fills is determined by the size of the valves and the pressure differential. This process is critical for controlling a submarine's buoyancy and depth.
