Draft surveys are indeed a critical method for determining cargo quantity on various types of ships and with different types of cargoes. Here’s a breakdown of how draft surveys are applied in different scenarios:

1. Tankers and Liquid Cargoes:

   • For tankers carrying liquid cargoes with known densities (such as crude oil), calculating the loaded cargo weight is relatively straightforward. The density of the cargo and the volume loaded can directly provide the weight.
   • Measurement involves determining the ship’s draft before and after loading. The increase in draft corresponds to the weight of the cargo loaded, considering density.

2. Solid Bulk Cargoes (Coal, Urea, Phosphate, etc.):

   • Unlike liquids, solid cargoes do not conform to the shape of the hold, making direct volume-to-weight calculations inaccurate.
   • Draft surveys are crucial here. By measuring the ship’s draft before and after loading, the increase in draft represents the weight of the cargo loaded. This method is reliable for solid bulk cargoes where volume measurements alone are insufficient.

3. Special Case: Molasses (Liquid with Air Pockets):

   • Molasses presents a unique challenge due to its variable density caused by air pockets within the liquid.
   • Traditional methods of calculating cargo weight based solely on volume and density can lead to inaccuracies.
   • Draft surveys are essential for molasses and similar liquids with non-uniform densities. Measuring draft changes provides a more accurate assessment of the cargo weight loaded.

In all cases, the process involves:

• Measuring the vessel’s draft at different points (forward, middle, aft) before and after loading.
• Conducting soundings for all ballast, fresh water, sewage tanks, and other relevant spaces to account for changes in weight.
• Using internationally recognized methods and modern equipment to ensure precision in measurements.

This comprehensive approach ensures that the quantity of cargo loaded is accurately determined, adhering to industry standards and minimizing the risk of disputes or financial losses due to incorrect measurements. Draft surveys thus play a crucial role in maritime operations, particularly for ships carrying diverse cargoes with varying characteristics.