Draft Survey

Service Background

In maritime bulk cargo transportation, the accurate determination of cargo weight loaded or discharged is a critical factor for payment, contract settlement, and dispute resolution.

Draft Survey is a technical method used to determine the weight of cargo by calculating the vessel's displacement change before and after loading or discharging. This is a highly specialized marine survey technique, primarily applied to:

• Dry Bulk Cargo: Coal, ore, clinker, cement, grain, etc.
• High-volume shipments where direct weighing is impractical.
• Import-export transactions under FOB/CFR/CIF terms.
• Payments based on actual weight received/delivered.

Vinacontrol’s Draft Survey services empower businesses to:

✔ Accurately determine the quantity of cargo delivered or received.
✔ Establish a reliable basis for payment and contract settlement.
✔ Mitigate dispute risks between Shippers, Shipowners, and Buyers.
✔ Enhance transparency in international trade transactions.

When should a Draft Survey be performed?

Businesses should engage Draft Survey services in the following cases:

• During the export or import of bulk cargo via sea vessels.
• When payment is based on actual delivered weight.
• When direct weighing of the entire cargo is not feasible.
• When required by commercial contracts or Letters of Credit (L/C).
• When there are suspicions of quantity discrepancies.
• When an independent inspection certificate is required for insurance or legal claims.

Survey Locations:

• Loading Ports / Discharge Ports
• Anchorages
• Barges, coastal vessels, and inland waterway craft.

Scope of Services

Vinacontrol’s Draft Survey process includes:

1. Six-Point Draft Reading

• Forward (Port & Starboard)
• Midships (Port & Starboard)
• Aft (Port & Starboard)
• Calculating the mean draft at each position and the vessel's overall mean draft based on technical principles (Mean of Means).

2. Measurement & Correction of Influencing Factors

• Measuring water density using a hydrometer.
• Checking and calculating ballast water volume.
• Determining fuel (FO, DO) and lubricating oil quantities.
• Measuring fresh water and domestic water reserves.
• Accounting for vessel stores and constant weights.

3. Hydrostatic Table Reference

• Determining total displacement.
• Correcting for actual water density.
• Calculating Trim and List corrections (if applicable).

4. Cargo Weight Calculation Cargo Weight = (Post-loading/discharge Displacement – Pre-loading/discharge Displacement) ± Necessary Corrections.

5. Issuance of Inspection Certificate

• Detailed reporting of all measurements.
• Clear explanation of calculation methodologies.
• Final conclusion on cargo weight.
• Issuance of certificates for payment and legal purposes.

Applicable Standards

Draft surveys are performed in accordance with:

• ISO/IEC 17020:2012 (Requirements for the operation of inspection bodies).
• International Maritime Inspection Practices.
• Commercial Contract Regulations and Incoterms.
• Technical guidelines from the International Federation of Inspection Agencies (IFIA) or equivalent maritime associations.