Bulk Cargo Chartering: Vessel Sizes, Draft and Port Restrictions

"We need a bulk carrier" is the start of the question, not the answer to it. The fleet spans vessels of three thousand tonnes and vessels of two hundred thousand, and the right one for a given parcel is usually decided by the shallowest berth on the voyage rather than by the size of the cargo.

This article works through the choice in the order it is actually made: what the size classes are for, whether the ship needs her own gear, how draft converts into tonnes, and where the parcel size stops matching the vessel size.

The size classes and what they are for

The boundaries are conventions rather than rules, and each class shades into the next. What matters commercially is the pattern: as ships get larger they lose their own cranes and gain draft, and both changes narrow the list of ports that can work them.

Kiev Shipping fixes most of its dry bulk in the range from about 3,000 to 50,000 tonnes — the part of the fleet that can still reach restricted berths and handle its own cargo.

Geared or gearless: the berth decides

A gearless ship is cheaper to build and cheaper to run, and the saving shows up in the freight. It is only a saving if the terminal has the equipment to work her.

Ask three questions about the discharging port before accepting a gearless offer: what shore equipment exists, what productivity it actually achieves on this commodity, and what it costs to hire if it is not included. Where the answer to the first is "two mobile cranes if they are free", the vessel with four of her own is normally the cheaper voyage even at a higher rate — a comparison worked through in full in Why the Freight Rate Is Not Enough.

Gear also matters for the shape of the cargo. Bagged goods, big bags, steel and anything lifted rather than grabbed need hooks; homogeneous bulk into a silo berth does not.

From draft to tonnes

Deadweight is what the vessel can carry in total, not what she can load. The cargo is what remains after everything else on board:

Cargo intake = deadweight at the applicable draft − bunkers − fresh water − stores and constants

Take a 32,000 dwt handysize on summer marks, carrying 700 tonnes of bunkers, 150 of fresh water and 350 of stores and constants. Cargo intake is about 30,800 tonnes.

Now suppose the loading port allows 9.5 metres against her summer draft of 10.2. The conversion is made through tonnes per centimetre immersion, which for a ship of this size is roughly 40. Seventy centimetres of draft is therefore about 2,800 tonnes, and the intake falls to around 28,000 tonnes — a twelve per cent reduction that has nothing to do with the ship's deadweight and everything to do with the berth.

This is why the permissible draft, in fresh or salt water and at what stage of tide, belongs in the first message of an enquiry. Quoted without it, a freight rate is being calculated on a quantity the ship may not be able to load.

The other limit: volume

The second constraint is the cubic capacity of the holds. A dense cargo brings the ship to her marks with space to spare; a light one fills the holds while deadweight is still available, and the unused deadweight is simply lost.

Which limit binds depends on the stowage factor of the commodity, and the arithmetic is quick once the figure is known. Indicative stowage factors for the cargoes we handle, with a worked example of one vessel loading wheat, barley and potash, are collected in Stowage Factor and Cargo Reference for Dry Bulk Chartering.

Port restrictions beyond draft

• Length and beam — a berth that takes 190 metres will not take 199, and the difference removes an entire size band;
• Air draft — bridges and overhead lines on river approaches, and hatch-crane clearance under a gantry;
• Depth at the berth against depth in the channel — they are frequently different, and it is the smaller one that binds;
• Tidal windows — where arrival and departure are tide-dependent, the schedule is set by the tide table and not by the cargo operation;
• Seasonal draft — load line zones change the permissible draft with the season and the area of the voyage;
• Fresh water allowance — a vessel loading in a river sails deeper than she floats at the berth, and the allowance has to be built into the intake.

Matching the parcel to the ship

A 6,000 tonne cargo offered to a 30,000 tonne vessel is not a cheap fixture. The owner is pricing a voyage, and the freight has to cover it whether the holds are full or not — so the rate per tonne rises sharply as the parcel falls below the vessel's capacity.

There are three ways out, and they are worth considering before the enquiry goes out rather than after the offers come back:

• Fix the right size. Small parcels belong on small ships, even though those ships are fewer and their positions matter more;
• Combine. Two or three compatible parcels from the same area, moving in the same window, can fill a vessel between them — with segregation and the order of discharge agreed in advance;
• Take part cargo. Book space on a vessel already carrying a compatible cargo. Less control over dates, materially better freight per tonne.

Conversely, a parcel slightly larger than a size class handles awkwardly: 34,000 tonnes is an uncomfortable quantity, sitting above a comfortable handysize intake and well below a Supramax's. Where the tolerance permits, adjusting the quantity to fit the fleet is often worth more than negotiating the rate.

What decides the choice, in order

1. Draft and length at the most restricted berth on the voyage;
2. Whether the terminals can work a gearless ship at the rate the charter party will state;
3. Stowage factor, and therefore whether the fixture is limited by weight or by volume;
4. Parcel size against the capacity of the classes that survive the first three;
5. Vessel positions in the laycan window;
6. Freight.

Price comes last because everything above it changes what the price is being quoted for.

Kiev Shipping Ltd charters dry bulk cargoes — grain, oilseed meals, fertilizers, coal, ores, cement, clinker, gypsum, salt and scrap — in parcels from roughly 3,000 to 50,000 tonnes, from Asian, Black Sea, Mediterranean, Baltic and Persian Gulf loading areas.

Service overview: Dry Bulk Cargo Chartering.

See also: Dry Bulk Cargo: Why Cargo Characteristics Matter · Grain Cargo Chartering · How to submit a chartering enquiry · more in Dry Bulk Cargo.