A draft survey is a means of determining the weight of material loaded onto or discharged from a vessel. This measures the displacement in water prior and after loading or discharge. By recording the initial displacement of the vessel, prior to loading (or prior to discharge) and then after, the weight of the cargo can be determined.

Experienced and highly qualified SGS surveyors can produce accurate draft survey weights. During the draft readings, several other key factors are taken into account and measured before the weight of the cargo loaded or discharged can be determined. These include:

• The density of sea or river water
• Changes in quantity of ballast between initial and final draft readings
• Changes in consumables on the vessel between initial and final draft readings (fuel oil, potable water, etc.)
• Allowance for trim and deformation corrections (SGS uses data from the vessel’s draft tables)

The accuracy of a weight determined by draft survey depends upon sea conditions at the time of loading or discharge (pitch and swell) and the weight of the cargo loaded when compared to the total capacity of the vessel.

SGS has trained draft surveyors who work to a defined draft survey protocol. Raw data are fed into a spreadsheet format, which then calculates the weight loaded or discharged. This result is reviewed before being released to you and the raw data is retained for further review.