Ships Plimsoll Mark

A ships "Plimsoll Mark" and the ships deck line are permanently marked halfway along the ship's port and starboard side as shown in the picture. The lines and letters of the Plimsoll Mark,are to conform to the freeboard regulations laid down by the IMO (International Maritime Organisation) and the relevant local authorities. It is also known as the International Load Line or water line which indicates the draft of the ship and the legal limit to which a ship may be loaded for specific water types and temperatures in order to maintain safe buoyancy, particularly with regard to the hazard of waves that may arise.


A Plimsoll mark indicates the maximum depth to which the vessel may be safely loaded. The depth varies according to the season and the salinity of the water. There are separate load lines provided for different seasons and salinity of water, e.g. load lines for sailing in freshwater and seawater, respectively, with further divisions for tropical conditions and summer and winter sailing. According to the international freeboard rules, the summer freeboard draught for seawater is equal to the "Scantling draught", which is the term applied to the ship's draught when dimensioning the hull. The winter freeboard draught is less than that valid for summer because of the risk of bad weather whereas, on the other hand, the freeboard draught for tropical seas is somewhat higher than the summer freeboard draught.


The Plimsoll Mark has been named after a British MP, Samuel Plimsoll took up the load line cause. In the 1860s, after it was observed that there was a increase loss of ships due to overloading, a Royal Commission on unseaworthy ships was established in 1872, and in 1876 the United Kingdom Merchant Shipping Act made the load line mark compulsory, although the positioning of the mark was not fixed by law until 1894. In 1906, laws were passed requiring foreign ships visiting British ports to be marked with a load line. It was not until 1930 (The 1930 Load Line Convention) that there was international agreement for universal application of load line regulations.


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