Light Displacement Tonnage

When a port agent is appointed it is that agent’s responsibility to act at all times in the best interest of the vessel. Shipowner will need to keep the Agent advised as to a ship’s movements and Expected Time of Arrival (ETA). Agent will know from the schedule when the next vessel is due at his port. The owner and agent will be in constant communication by telephone, fax or e-mail regarding changes to schedule and all the other anticipated requirements for the ship. Ship’s Master will also contact the Agent in order to advise the ship’s requirements. It is obviously necessary to give the Agent as much advance warning as possible, although this is not always feasible, as with and emergency due to damage or illness, for example. Agent will contact the ship with any information of which the Master should be aware. Equally, Agents will contact their opposite numbers in the next port of call, as a ship leaves, to advise the Agent there of any requirements about which there is not the time or the need to contact the Principal.

It is important to understand the different ways of describing a ships size and dimensions so that one vessel may be compared against another or the suitability of a vessel for a particular trade may be assessed. Light Displacement Tonnage is the actual weight of the vessel as constructed and afloat excluding fuel, stores, crew etc. Light Displacement Tonnage is of little commercial significance except when a vessel is finally being sold for scrapping, then it represents the weight of metal that the shipbreaker is acquiring. Light Displacement Tonnage is also used in draft survey calculations.

Total Displacement Tonnage is the light displacement tonnage plus the weight of all fuel, stores, lubricants, crews effects and everything else that makes the ship ready to go to sea. These are known collectively as “constants” and would total on an average size vessel of about 40,000 DWAT about 3,000 tons. Total Displacement Tonnage is used for describing the size of military vessels.