Dry bulk carriers carry unpackaged cargo such as coal, nickel ore, bauxite, clinker, fertiliser and grain loose in the holds. Their hold section is distinctive: lower hopper tanks and upper topside tanks help cargo settle to the centre and reduce the risk of shifting.
Because cargo comes from high-rate shiploaders, loading is done in several pours per hold and matched to deballasting. Each stage must keep shear force and bending moment within harbour limits, draft and trim safe at the berth, and air draft under the loader.
Beyond longitudinal strength, cargo properties drive safety. The IMSBC Code groups bulk cargoes, including Group A cargoes that may liquefy when moisture content exceeds the Transportable Moisture Limit (TML). In Indonesia, nickel ore and some other mined cargoes need particular care, including on bulk barges carrying similar cargo.
Typical sizes & characteristics
| Parameter | Typical range |
|---|---|
| Size classes (generic) | Handysize ~10,000–40,000 DWT; Handymax/Supramax ~40,000–60,000; Ultramax ~60,000–65,000; Panamax/Kamsarmax ~65,000–85,000; Capesize > ~100,000 DWT |
| Number of holds | Usually 5 (Handysize–Ultramax), 7 (Panamax), 9 (Capesize) |
| Gear | Handysize–Ultramax usually geared (~4 grab cranes); Panamax and Capesize usually gearless |
| Ballast tanks | Double bottom, hopper, topside, peaks and often one heavy-weather ballast hold |
| Cargo stowage factor | Ore ~0.3–0.5 m³/t; coal ~1.1–1.4 m³/t; grain ~1.2–1.5 m³/t |
| Related rules | SOLAS XII, IMSBC Code, International Grain Code, BLU Code |
Typical ranges for the vessel class, not data for any specific ship. For planning, use your vessel’s stability booklet and capacity plan.
Cargo spaces & how they are modelled
Cargo holds
Each hold is modelled with volume capacity, maximum cargo mass per hold and pile height for dense cargo. Per-hold limits differ between homogeneous and alternate conditions.
Ballast tanks
Ballast per tank and deballasting rate are recorded so the condition of every loading stage can be calculated.
Ballast hold
Some ships can flood one hold for heavy-weather ballast voyages; it must be empty and clean before loading.
Bulk barges
Coal or ore barges with side boards are modelled as deck areas with pile height and heap slope.
General stowage rules
Staged pour sequence
Cargo is loaded in several pours per hold according to a plan agreed between ship and terminal. SF/BM, draft and trim are calculated for each stage.
Matched to ballast
Deballasting must keep pace with the loading rate. If the pumps fall behind, the loader stops; the plan is not broken.
Permitted hold conditions
Alternate or block loading is used only where the ship’s loading manual permits it, with per-hold masses within their limits.
IMSBC cargo properties
The shipper’s declaration, moisture content vs TML for Group A cargoes and chemical hazards are checked before loading. Doubtful cargo is not loaded until verified.
Trimming and final draft
The cargo surface is trimmed reasonably level to reduce the risk of shifting. The final draft is confirmed with a draft survey.
Common mistakes & risks
- SF/BM exceeding harbour limits at an intermediate stage even though the final condition is safe.
- Deballasting lagging so the ship is too deep or trimmed excessively at the berth.
- Group A cargo with moisture above TML liquefying and shifting at sea.
- Per-hold mass over the limit because the final pour was not corrected.
- Large draft survey differences because trim, density or tank corrections were ignored.
- Insufficient air draft under the loader at high water while the ship is still light.
Frequently asked questions
Why is a safe final condition not enough?
Shear force and bending moment can peak mid-loading, for example when one hold is full and the surrounding ballast has not yet been discharged. That is why every stage is calculated, not just the departure condition.
What is the TML?
The Transportable Moisture Limit is the maximum moisture content considered safe for cargo that may liquefy. It is determined by laboratory tests under the IMSBC Code and compared with the declared actual moisture content.
Are STOWAGE.ID loading sequence calculations official?
No. The Bulk module is the third wave and is rolling out in stages. Its results are shore-side planning; the class-approved onboard loading computer and loading manual remain the official reference.
Shore-side planning & decision support. The class-approved onboard loading computer remains the official reference.