Marine Surveyors Lexicon

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Load Line


A mark on a vessel's side indicating the maximum depth to which it may be safely immersed when loaded with cargo.

This depth is variable and depends on the waters of operation, time of year, and type of cargo; e.g. winter, North Atlantic, timber will have a special depth.

Laws regulate the amount of cargo a vessel can carry and still maintain enough reserve buoyancy and a low enough center of gravity to ensure its safety in adverse weather and dangerous seas.

While there are other load lines, the most common is the Plimsoll Mark, which was established by the British Parliament in 1876 to prevent overloading of vessels. It was named after Samuel Plimsoll, a member of British Parliament, who was interested in maritime safety. The letters signify:

  • TF - Tropical Fresh Water Load Line
  • F - Fresh Water Load Line
  • T - Tropical Load Line
  • S - Summer Load Line
  • W - Winter Load Line
  • WNA - Winter North Atlantic Load Line

The white areas in the pictures below are empty spaces for paying cargo, and the remaining space houses a vessel’s main and auxiliary machinery, living quarters and supply lockers.

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