Tonnes per Centimetre Immersion(TPC)

The tonne per centimetre (TPC) of a ship at any given draught is the mass required to increase the mean draught by 1cm.

If the vessel is loading in salt water and the freeboard checked it may be found that more cargo can be loaded to immerse the ship another few centimetres is useful to convert this to tonnes. This is the TPC.

TPC can be calculated by the formula:

TPC=A x ρ/100

Where A= area of water plane at a certain draught
ρ= density of water in which the ship floats

The TPC varies with the draught and with the water density. Changes in draught cause a change in displacement and the TPC assists in calculating the change.

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