Deadweight tonnage

Not to be confused with vessel displacement.

The more heavily loaded a ship is, the lower it sits in the water. Maximum DWT is the amount of weight a ship can carry without riding dangerously low in the water.
Scale for a 6,000 tonne DWT ship.

Deadweight tonnage (also known as deadweight; abbreviated to DWT, D.W.T., d.w.t., or dwt) is a measure of how much weight a ship is carrying or can safely carry.[1][2][3] It is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew.[1]

DWT is often used to specify a ship's maximum permissible deadweight (i.e. when it is fully loaded so that its Plimsoll line is at water level), although it may also denote the actual DWT of a ship not loaded to capacity.

Definition

Deadweight tonnage is a measure of a vessel's capacity in weight, and does not include the weight of the ship. It should not be confused with displacement, which includes the ship's weight measured in tons of water displaced, nor other volume or capacity measures such as gross tonnage or net tonnage (or their more archaic forms gross register tonnage or net register tonnage).

Deadweight tonnage was historically expressed in long tons[note 1] but is now usually given internationally in tonnes (metric tons).[4] In modern international shipping conventions such as the International Convention for the Safety of Life at Sea and the International Convention for the Prevention of Pollution From Ships, deadweight is explicitly defined as the difference in tonnes between the displacement of a ship in water of a specific gravity of 1.025 (corresponding to average density of sea water) at the draft corresponding to the assigned summer freeboard and the light displacement (lightweight) of the ship.[5][6]

Notes

  1. ↑ One long ton (LT) is 2,240 pounds (1,016 kg)

References

  1. ↑ 1.0 1.1 Turpin, Edward A.; William A. McEwen (1980). Merchant Marine Officers' Handbook (4th ed.). Centreville, Maryland: Cornell Maritime Press. pp. 14–21. ISBN 0-87033-056-X.
  2. ↑ Hayler, William B. (2003). American Merchant Seaman's Manual (7th ed.). Centreville, Maryland: Cornell Maritime Press. p. G-10. ISBN 0-87033-549-9.
  3. ↑ Gilmer, Thomas C. (1975). Modern Ship Design (2nd ed.). Naval Institute Press. p. 25. ISBN 0-87021-388-1.
  4. ↑ McNicholas, Michael (2011-08-29). Maritime Security: An Introduction. Butterworth-Heinemann. p. 30. Retrieved 2014-08-25.
  5. ↑ SOLAS Consolidated Edition 2009. London: International Maritime Organization. 2009. p. 33. ISBN 978-92-801-1505-5.
  6. ↑ MARPOL Consolidated Edition 2011. London: International Maritime Organization. 2011. p. 44. ISBN 978-92-801-1532-1.