Ballast tank - AbsoluteAstronomy.com

A ballast tank is a compartment within a boat, ship or other floating structure that holds water.

History

The basic concept behind the ballast tank can be seen in many forms of aquatic life, such as the blowfish

Blowfish

The blowfish, or Tetraodontidae, is a fish in the Tetraodontidae family.Blowfish may also refer to:* The Blowfish, a satirical newspaper at Brandeis University* Blowfish , encryption algorithm...

or argonaut octopus, and the concept has been invented and reinvented many times by humans to serve a variety of purposes. For example, in 1849 Abraham Lincoln

Abraham Lincoln

Abraham Lincoln was the 16th President of the United States, serving from March 1861 until his assassination in April 1865. He successfully led his country through a great constitutional, military and moral crisis – the American Civil War – preserving the Union, while ending slavery, and...

, then an Illinois attorney, patented a ballast-tank system to enable cargo vessels to pass over shoal

Shoal

Shoal, shoals or shoaling may mean:* Shoal, a sandbank or reef creating shallow water, especially where it forms a hazard to shipping* Shoal draught , of a boat with shallow draught which can pass over some shoals: see Draft...

s in North American river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

Ships

A vessel may have a single ballast tank near its center or multiple ballast tanks typically on either side. A large vessel typically will have several ballast tanks including double bottom tanks, wing tanks as well as forepeak and aftpeak tanks. Adding ballast to a vessel lowers its center of gravity, and increases the draft

Draft (hull)

The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...

of the vessel. Increased draft may be required for proper propeller immersion.

A ballast tank can be filled or emptied in order to adjust the amount of ballast force. Ships designed for carrying large amounts of cargo must take on ballast water for proper stability

Metacentric height

The metacentric height is a measurement of the static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre . A larger metacentric height implies greater stability against overturning...

when travelling with light loads and discharge water when heavily laden with cargo. Small sailboats designed to be light weight for being pulled behind automobiles on trailers are often designed with ballast tanks that can be emptied when the boat is removed from the water.

Submarines

In submarines ballast tanks are used to allow the vessel to submerge, water being taken in to alter the vessel's buoyancy

Buoyancy

In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...

and allow the submarine to dive. When the submarine surfaces, water is blown out from the tanks using compressed air, and the vessel becomes positively buoyant again, allowing it to rise to the surface. A submarine may have several types of ballast tank: the main ballast tanks, which are the main tanks used for diving and surfacing, and trimming tanks, which are used to adjust the submarine's attitude (its 'trim') both on the surface and when underwater.

Floating structures

Ballast tanks are also integral to the stability and operation of deepwater offshore oil platforms and floating wind turbine

Floating wind turbine

A floating wind turbine is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where bottom-mounted towers are not feasible...

s.
The ballast facilitates "hydrodynamic stability

Hydrodynamic stability

In fluid dynamics, hydrodynamic stability is the field which analyses the stability and the onset of instability of fluid flows. Instabilities may develop further into turbulence....

by moving the center-of-mass

Center of mass

In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

as low as possible, placing [it] beneath the [air-filled] buoyancy tank."

Wakeboard boats

Most wakeboard

Wakeboarding

Wakeboarding is a surface water sport which involves riding a wakeboard over the surface of a body of water. It was developed from a combination of water skiing, snow boarding and surfing techniques....

-specific inboard-engine boats have multiple integrated ballast tanks that are filled with ballast pumps controlled from the helm with rocker switches. Typically the configuration is based on a three tank system with a tank in the center of the boat and two more in the rear of the boat on either side of the engine compartment. Just like larger ships when adding water ballast to smaller wakeboard boats the hull has a lower center of gravity, and increases the draft

Draft (hull)

of the boat. Most wakeboard boat factory ballast systems can be upgraded with larger capacities by adding soft structured ballast bags.

Environmental concerns

Ballast water taken in to a tank from one body of water

Body of water

A body of water or waterbody is any significant accumulation of water, usually covering the Earth or another planet. The term body of water most often refers to large accumulations of water, such as oceans, seas, and lakes, but it may also include smaller pools of water such as ponds, puddles or...

and discharged in another body of water can introduce invasive species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

of aquatic life. The taking in of water from ballast tanks has been responsible for the introduction of species that cause environmental and economic damage. For example, zebra mussel

Zebra mussel

The zebra mussel, Dreissena polymorpha, is a small freshwater mussel. This species was originally native to the lakes of southeast Russia being first described in 1769 by a German zoologist Peter Simon Pallas in the Ural, Volga and Dnieper rivers. They are still found nearby, as Pontic and Caspian...

s in the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...