The vessel draft survey measures the displacement of the water both before and after the loading or unloading, with the resulting difference between the two displacements representing the weight of the cargo. Our surveyors work to international guidelines when determining the weight of the cargo and consider several key factors while making their surveys. These factors include:
- Water density of the sea, river or other waterway;
- Changes in the ballast quantity between initial and final draft readings;
- Changes in the vessel’s consumables (e.g. fuel oil, drinking water) between initial and final draft readings;
- Trim and deformation corrections (we use data from the vessel’s draft tables).
The accuracy of a weight determined by draft survey also depends upon the sea conditions (pitch and swell) at the time of loading or discharge. Draft Survey could be offered with or without the loading/discharge supervision.
Our draft surveyors carry out various measurements and input them into Ruswal’s unique draft survey reporting system. This report calculates the weight loaded (or discharged) using the internationally standardised draft survey protocol. All our calculations are cross-checked manually. We then compile the resulting findings into a draft survey report containing all of the details obtained during the survey. The client can use this report as the basis for quantity certification of the cargo, a copy will also be issued to the vessel and/or the client.