Draft Survey: cargo determination by draught

A Draft Survey, or draught survey, estimates the mass of cargo loaded or discharged based on the variation in the vessel’s displacement. It is an important tool in the transport of dry bulk cargoes: when properly documented, it provides the parties with an additional technical reference for checking the quantity handled and examining any discrepancies.

The work correlates draught readings with the vessel’s hydrostatic data and takes into account the density of the water in which it is floating. When comparing the initial and final conditions, changes in ballast, fuel, fresh water and other relevant weights must also be accounted for. Therefore, a variation that does not correspond to cargo should not be treated as cargo handled.

TWS plans the service according to the vessel, port and reported operational sequence. Cooperation with the ship’s officers and the availability of the necessary tables and records are essential. The survey must record the measurements and assumptions used, as well as any conditions that may affect the interpretation of the results.

Swell, visibility of draught marks, currents, vessel list, uncertainties in ballast or documentary inconsistencies may influence the determination. For this reason, the report does not present the result as a weighing without a margin of uncertainty. Material differences from other records must be analyzed in light of the method, observed conditions and movements occurring during the operation.

The client receives the calculation worksheet and observations relevant to the contracted scope, to support its technical and commercial verifications. TWS serves the interests of Brazilian and international clients at Brazilian ports, especially in the North and Northeast. Send the vessel data, cargo type, expected quantity, terminal and loading or discharge schedule so that we can define availability and service stages.