Weight Disputes in Bulk Imports: Survey, Weighbridge, B/L

Sep 20, 2026 · pihaifeng

The vessel is in port, the bill of lading says 5,000 tonnes, and after discharge the weighbridge reads 4,950 tonnes. Whose are the missing 50 tonnes? In bulk imports, a weight that does not match comes up on almost every shipment. Rather than arguing over who miscalculated, it pays to first pin down each party’s measurement basis and permitted error.

Mineral handling and weighing at the quay

1. First, Work Out Who Weighed It

One cargo of minerals can produce three different weight figures:

Bill of lading weight: in most cases the result of a draft survey or weighing at the loading port, and the default basis for settlement
Discharge port draft survey: the discharge weight calculated by an inspection body at the discharge port after re-measuring the vessel’s draft
Weighbridge weight at the plant: the figure from weighing on arrival at the plant, which includes losses in transit and moisture change

These three figures should never be identical. They measure different things, at different places, on different principles, so divergence is inevitable. What matters is knowing how much difference is normal and how to handle anything beyond that.

2. How a Draft Survey Calculates a Cargo

A draft survey rests on Archimedes’ principle: a vessel afloat displaces a weight of water equal to the combined weight of the ship and its cargo. Measure the vessel’s draft before and after loading (or discharge), read the displacement table and hydrostatic curves, deduct the changes in ballast water, fuel oil, fresh water and stores, and the difference between the two displacements is the cargo weight.

The Chinese procedure for this operation is SN/T 0187-1993, Rules for the Weight Survey of Import and Export Commodities — Draft Survey, issued in November 1993 and effective from January 1994, drafted by the then Shanghai Import and Export Commodity Inspection Bureau. The rules set several key requirements:

Accuracy: on the premise that the vessel’s tabulated accuracy is 1%, the accuracy of a draft survey can stay within 5‰
Observation conditions: list angle held within 0.5°, using the six-sided observation method; where the trim is excessive, adjust first or apply a trim correction
Dock water density: measured with a hydrometer graduated at 0.0005 g/cm³, sampling at half the draft amidships outside the hull

Note that SN/T 0187-1993 was abolished on 1 July 2013 and replaced by SN/T 3023.2-2012. When appointing an inspection body for a draft survey, confirm which version it applies.

The 5‰ figure matters. On a 5,000-tonne cargo, 25 tonnes either way falls within the accuracy the rules permit. In other words, if the gap between 4,950 and 5,000 tonnes stays inside that range, a claim built on “the draft survey was inaccurate” will not hold up.

3. Wet Tonnes and Dry Tonnes: What Moisture Takes Away

Most bulk minerals are priced on a dry basis, meaning the weight after deducting moisture. Two conversions are involved.

First, wet tonnes to dry tonnes. Dry weight = wet weight × (1 − moisture content). Take 5,000 tonnes of wet cargo with a tested moisture of 3%: the dry weight is 5,000 × 97% = 4,850 tonnes. Every extra percentage point of moisture cuts 50 tonnes off the dry weight.

Second, compare where the moisture figures come from. Moisture measured at the loading port often differs from moisture measured on arrival. During the voyage the surface layer of the cargo sheds or absorbs water, and moisture varies with depth in the hold. Contracts therefore usually specify which end’s moisture governs, or take a weighted value of the two.

Moisture determination has its own procedure. For bulk minerals in China it follows GB/T 2007.6-1987, General Rules for Sampling and Sample Preparation of Bulk Minerals — Method for Determination of Moisture (Heat Drying Method), and the sample must be weighed within the shortest possible time or the moisture figure will be distorted.

4. How Much Difference Is Normal

Laid out plainly, the weight gap on a cargo usually comes from three sources:

Measurement error: the 5‰ accuracy of a draft survey itself
Moisture change: dry weight differences caused by moisture fluctuation in transit
Loading, discharge and transport losses: spillage, cargo adhering to the hold, and losses during barge transfer

Common practice is to agree a permitted difference in the contract — no claim either way if the discharge weight is within 0.5% of the bill of lading weight, for example, with anything beyond settled on actual weight or negotiated separately. The exact percentage has to be negotiated around the mineral, the mode of transport and the route; there is no universal standard figure.

One more point: the choice of weight basis feeds straight into final cost accounting, and How to Calculate the Landed Cost of Imported Phosphate Rock works through a specific example.

Bulk cargo handling operation

5. A Change on the Regulatory Side

Imported bulk commodities used to be subject to weight survey batch by batch. Customs later adjusted its supervision approach: the Announcement on Adjusting the Supervision of Weight Survey for Imported Bulk Commodities changed batch-by-batch survey to survey by customs at the enterprise’s application, and where necessary by customs ex officio.

This means an enterprise can choose who performs the weight survey, including appointing a third-party inspection body, which improves clearance convenience. It also means the enterprise has to think through its own weight clauses and inspection arrangements instead of assuming that customs will verify the weight for it.

The relevant legal basis also includes the Law of the People’s Republic of China on Import and Export Commodity Inspection and its implementing regulations, the Customs Law of the People’s Republic of China, and the Measures for the Administration of Quantity and Weight Inspection and Appraisal of Import and Export Commodities.

6. How to Draft the Weight Clause

Whose weight governs: bill of lading weight, discharge port draft survey or plant weighbridge — state the order of precedence
Pricing basis: wet tonnes or dry tonnes, and whether moisture follows loading port or discharge port data
Permitted difference: agree the percentage range and how anything beyond it is handled
Surveyor: appoint the inspection body in advance so you are not scrambling when a dispute arises
Objection period: how many days after discharge an objection may be raised, and what happens to retained samples

FAQ

Q1: If the weighbridge weight is lower than the bill of lading, can I claim directly?

Not on that basis alone. The weighbridge figure includes transport losses and moisture change, and not every leg of the transport has third-party supervision of weighing. First check whether the difference exceeds the permitted range agreed in the contract, then judge whether it is the seller’s responsibility.

Q2: Which is more accurate, a draft survey or a weighbridge?

The two do not measure the same object. A draft survey measures the cargo weight at loading or discharge; a weighbridge measures it at the moment of weighing, with a leg of transport in between. Comparing their magnitudes tells you nothing — what matters is stating in the contract which one governs.

Q3: Why do two draft surveys of the same cargo differ?

Draft readings, dock water density, ballast condition and the vessel’s constant all affect the result, and 5‰ accuracy is itself a range. As long as two readings fall within the permitted range, that is normal fluctuation.

Container yard dispatch records

Conclusion

Weight disputes over bulk minerals mostly have nothing to do with who miscalculated; the problem is that the two sides are working from different assumptions. Writing three things into the contract — whose weight governs, what basis pricing uses, and how large a difference can be pursued — is far more useful than trading two different numbers after the fact.