Painolasti

Painolasti refers to ballast—the weight added to a vessel or structure to improve stability, trim, and buoyancy control. In maritime practice, ballast is usually water stored in ballast tanks, but solid ballast such as ore, gravel, sand, or concrete can be used either as permanent support or for temporary adjustment. The term is widely used in Finnish and related languages to denote ballast.

On ships, ballast water is taken on and discharged to adjust draft, stability, and list as cargo loads and fuel change; ballast tanks are integrated into hulls and operated with pumps, valves, and monitoring systems; modern ships may use ballast-water treatment systems to meet environmental standards.

Environmental and regulatory considerations are central to ballast use. Ballast water discharge can spread aquatic invasive species, threatening ecosystems and economies. The International Maritime Organization’s Ballast Water Management (BWM) Convention, adopted in 2004, requires ships to manage ballast water to reduce transfer of organisms, including treatment systems and/or ballast water exchange, with implementation phased in by flag states and port states.

Other contexts of ballast use include civil engineering, where ballast refers to material used under structures to distribute loads and improve drainage, such as railway track ballast. In submarines and some aircraft, ballast tanks or weight-distribution systems are used to adjust buoyancy or center of gravity during operation and testing.

See also: ballast water, ballast tank, stability, trim.