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A ballast tank is a compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to correct trim or list, to provide a more even load distribution along the hull to reduce structural hogging or sagging ...
Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, submarine, or other floating structure that holds water is called a ballast tank. Water should be moved in and out from the ballast tank to balance the ship.
Pumps can also be used to empty the leeward ballast tank and fill the windward tank as the boat tacks, and the quantity of ballast can be varied to keep the boat at the optimum angle of heel. A disadvantage of water ballast is that water is not very dense and therefore the tanks required take up more space than other forms of ballast.
The lower tanks are connected to these ballast tanks by non-return valves. The United States Coast Guard does not allow this design to enter US waters, effectively preventing it from being built. [citation needed] When a lower tank is damaged, the incoming sea water pushes the oil in the damaged tank up into the ballast tank.
USS Columbus (SSN 762) performing an emergency ballast blow. An emergency main ballast tank blow is a procedure used aboard a submarine that forces high-pressure air into its main ballast tanks. The high-pressure air forces ballast water from the tanks, quickly lightening the ship so it can rapidly rise to the surface.
The saddle tank was formed by moving the ballast tanks outside the pressure hull. [1] Early designs raised the weather deck and casing above the pressure hull, producing a ballast tank that wrapped around the upper part of the pressure hull (diagrams A & B). Following the terminology of steam railway locomotives, this was termed a "saddle tank".
A ballast tank has three distinct sections: 1) upper, 2) mid or "boottop" area and, 3) the "double bottom" or lower wing sections. The upper regions are constantly affected by weather. This area experiences a high degree of thermal cycling and mechanical damage through vibration.
The lower tanks are connected to these ballast tanks by non-return valves. When a lower tank is damaged, the incoming sea water pushes the oil in the damaged tank up into the ballast tank. Because of the hydrostatic pressure , there is an automatic transfer out of the damaged tank.