Dry Bulk Cargo: Why Cargo Characteristics Matter

Dry bulk looks like the simplest cargo there is. It travels without packaging, it is handled in thousands of tonnes at a time, and the enquiry usually arrives as one line: commodity, quantity, ports, laycan. Yet more fixtures go wrong on cargo properties than on freight, and almost all of those problems were visible in the cargo declaration before the vessel was ever nominated.

The reason is that a bulk carrier is not a neutral container. Each commodity imposes its own conditions on the holds, on the loading rate, on ventilation during the passage and on the way the cargo can be discharged. Those conditions decide which ships can be offered at all — long before anyone discusses a rate.

Three groups, three different conversations

The IMSBC Code — the International Maritime Solid Bulk Cargoes Code — sorts every solid bulk cargo into one of three groups, and the group tells you immediately what kind of negotiation you are in.

• Group A — cargoes that may liquefy. Concentrates, many ores, certain bauxites and some coals. The commercial consequence is a moisture certificate and a master who is entitled to refuse the parcel at the berth;
• Group B — cargoes with a chemical hazard: self-heating, oxygen depletion, flammable gas, corrosion. Coal, direct reduced iron, seed cake, some fertilizers. The consequence is a ventilation and monitoring regime written into the fixture;
• Group C — cargoes that are neither. Grain, salt, cement, clinker, gypsum, aggregates. These are the straightforward ones, and even here hold condition and density decide the intake.

Some cargoes sit in two groups at once — coal is classified as both A and B — and that combination is exactly where owners ask the most questions before committing a ship.

Moisture: the property that stops a loading

Liquefaction is the one cargo characteristic that regularly turns into a stopped operation rather than a claim after the fact. A Group A cargo behaves as a solid while it is dry enough and begins to act as a fluid above a certain moisture content. In a seaway that fluid mass shifts, and the ship loses stability.

The Code handles this with two numbers. The flow moisture point is the moisture content at which the cargo starts to flow; the transportable moisture limit is set at ninety per cent of it. The shipper must declare the actual moisture content and the transportable moisture limit, supported by test certificates, and the cargo may only be loaded while the first figure sits below the second.

What this means commercially is simple: for a Group A cargo, the certificates are part of the enquiry. A parcel offered without a current moisture declaration will be quoted cautiously by every owner in the market, and it may not be quoted at all in a rainy season at an open stockpile. Rain between sampling and loading is enough to change the answer, which is why the sampling date matters as much as the result.

Self-heating, gas and corrosion

Group B is less dramatic but more persistent. Coal gives off methane and consumes oxygen, and depending on the grade it may heat by itself; the fixture therefore sets out surface ventilation, gas monitoring and a rule that holds are not entered without testing. Seed cake — sunflower meal, rapeseed meal and similar residues — is in the Code precisely because it self-heats when it is loaded warm or damp, and owners will ask for the production date and the oil content before they take it.

Direct reduced iron reacts with water and air and is carried under conditions strict enough that only part of the fleet is willing to handle it. Salt corrodes steel, so hold protection and a cleaning regime after discharge are usually agreed in advance rather than argued about afterwards. Sulphur is both abrasive and corrosive. None of this makes the cargo difficult to fix — it makes it a cargo that has to be described accurately, because the owner is pricing the condition the ship will be in at the end of the voyage.

Density decides how much you actually load

Every bulk carrier has two limits: the weight she may carry and the volume her holds contain. Which one applies depends entirely on the commodity. A dense cargo brings the vessel down to her marks with the holds part-empty; a light one fills the holds while deadweight is still available.

This is why the stowage factor belongs in the first message of an enquiry, and why two parcels of the same tonnage can need different ships. We keep a working reference of indicative figures, with a worked example of the same vessel loading wheat, barley and potash, in Stowage Factor and Cargo Reference for Dry Bulk Chartering.

Hold condition: a ladder, not a yes or no

"Clean holds" is not one standard. The trade works with a recognised ladder, and the rung named in the charter party decides how long the vessel needs between cargoes and what the previous cargo may have been:

• hospital clean — bare metal, paint intact, dry, ready for sensitive cargoes such as high-grade minerals and certain food products;
• grain clean — clean, dry, free of residue, odour and infestation, passed by a surveyor; the usual standard for agricultural cargoes;
• normal clean — swept and washed, no residues of the previous cargo;
• shovel clean — residues removed to the point where machinery can no longer pick them up;
• load on top — accepted when consecutive parcels of the same commodity are carried.

The previous cargo matters just as much as the standard. A ship that last carried cement or coal needs time and water to reach grain clean, and a failed hold inspection at the loading port is expensive in a way that is entirely predictable. When a cargo is sensitive to odour or contamination, the last two or three cargoes are worth asking about before the ship is fixed.

Ventilation and ship's sweat

Hygroscopic cargoes — grain, meals, some fertilizers — exchange moisture with the air around them. When a warm-loaded cargo sails into colder water, moisture condenses on the cold steel above it and rains back down: ship's sweat, and with it caking, mould and a discoloured top layer.

The practical rule applied at sea is to ventilate when the outside dew point is below the dew point of the air in the hold, and to keep the hatches shut when it is not. For a voyage from a warm loading area into northern winter, the ventilation regime is worth agreeing at the fixture stage, because it is one of the few cargo-care obligations that is easy to demonstrate and easy to dispute.

Discharge is part of the cargo description

How a cargo comes out shapes which vessel suits it. Grabs need hatch openings that reach the corners of the hold; a ship with narrow hatches will be discharged slowly no matter what rate the charter party states. Abrasive cargoes such as clinker and aggregates wear coatings and tank tops, and owners price that. Sticky or caked cargoes need trimming machines and manual work in the wings, which turns a nominal daily rate into a much lower real one.

Where the cargo is discharged by shore grab, the terminal's equipment is effectively part of the vessel selection: an owner will not accept a rate built on a productivity the berth has never achieved.

What to send with the enquiry

A dry bulk enquiry that lets a broker screen the market properly normally contains:

• the exact commodity, with grade or specification;
• quantity and tolerance, and in whose option;
• stowage factor, or test weight for grain;
• IMSBC group, and moisture content with the transportable moisture limit for Group A cargoes;
• loading and discharging ports, with draft and length restrictions;
• laycan;
• loading and discharging rates and terms;
• required hold cleanliness standard;
• gear requirements — geared or gearless, grab discharge or shore equipment.

Those nine lines are the difference between a freight indication that survives contact with the vessel and one that is withdrawn as soon as the details arrive. The distinction between a preliminary level and a binding quotation is set out in Freight Indication vs Firm Freight Offer.

Kiev Shipping Ltd charters grain, oilseed meals, fertilizers, coal, ores, cement, clinker, gypsum, salt, scrap and other dry bulk commodities, typically in parcels of 3,000 to 50,000 tonnes. We evaluate the cargo, the ports and the charter-party terms together, because that is the only order in which the numbers hold.

Service overview: Dry Bulk Cargo Chartering.

See also: Bulk Cargo Chartering: Vessel Selection, Stowage and Port Restrictions · Grain Cargo Chartering · How to submit a chartering enquiry · more in Dry Bulk Cargo.