“Ballast” in Marine Glossary

“Ballast” in the context of marine refers to the weight or material placed in a ship’s hull to improve its stability, balance, and seagoing characteristics. Ballast is typically added or removed as necessary to maintain the ship’s optimal trim and stability.

The primary purposes of ballast are:

1. Stability: Ballast helps to stabilize a ship by lowering its center of gravity. By adding weight low in the hull, it counteracts the top-heavy nature of a ship and improves its resistance to rolling or listing in rough seas.
2. Trim: Ballast is used to adjust the ship’s trim, which refers to the evenness of the ship’s draft from bow to stern. By redistributing the weight, ballast ensures that the ship maintains the desired waterline and optimum hydrodynamic performance.
3. Draft Management: Ballast can be used to adjust a ship’s draft, which is the depth of the ship below the waterline. Adjusting the draft allows vessels to navigate in different water depths and ensures proper clearance under bridges or over shallow areas.
4. Structural Stress: Ballast also helps distribute the stresses and forces evenly across the hull, minimizing the risk of structural damage during heavy weather or when the ship is empty or lightly loaded.

The type of material used for ballast can vary depending on the ship’s size and purpose. Common ballast materials include water (in ballast tanks), solid materials like rocks or concrete, or even specialized systems that use pumps to transfer seawater for adjusting ballast.

It’s important to note that ballast water, a separate but related term, refers to the water taken on board and discharged by a ship for stability and trim purposes. Ballast water can contain organisms, such as marine life or pathogens, which can pose environmental and ecological risks if not managed properly.