Draft / Deadweight Surveys
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Draft Surveys can improve your shipping accuracy with a wide range of commodities, including grains, cement, coal, iron ore, and fertilizers.
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Draft Surveys determine the weight of the cargo aboard the vessel. A draft survey can save substantial costs for the interested party. These surveys are done to ascertain the quantity of a bulk cargo loaded or discharged by reading the vessel's drafts, measuring the ballast water, fuel, diesel oil, and other liquids on board, and calculating the final quantity by using the vessel's approved dead-weight scales and tank tables.
Our global network of highly qualified draft surveyors operates to a defined draft survey protocol, resulting in accurate draft weights for you at load and discharge points. Dependable and consistent draft weights allow you to monitor and control shrinkage while limiting the financial risks associated with bulk cargo transactions.
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In principle, draft surveys require only a measurement of the water displaced by the vessel before and after the cargo is transferred, along with a measurement of the water’s density. Water displacement is measured through draft marks on the ship and converted to a volume using draft tables. The weight of displaced water is calculated by multiplying its volume (displacement) by its density.
The difference between the weights of water displaced before and after the cargo transfer will equal the weight of the fertilizer within measurement accuracy limits.
In practice, draft surveys are complicated procedures that require a highly qualified draft surveyor.
Overall accuracy will depend on the surveyor’s skill in dealing with:
The varying density of sea or river water
Accuracy of the ship’s draft tables
Changes in the quantity of ballast between initial and final draft readings
Condition of the vessel’s draft markings
Changes in consumables on the vessel between init,ial and final draft readings (fuel oil, potable water, etc.)
Weather and sea conditions at the time of reading (pitch and swell)
Allowance for trim, list and deformation corrections (IME uses data from the vessel’s draft tables)
Weight of the cargo loaded when compared to the total capacity of the vessel
Weather and day-light
IME has trained draft surveyors who work on a defined draft survey protocol. Raw data are filled 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 preserved for further review.
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We also perform Deadweight Surveys to determine the amount of cargo a vessel could have loaded if all the available space were utilized to determine the loss of freight due to the short shipment of cargo.