NATARAJABulk cargoes & the IMSBC Code
Learning outcomes & permitted supports
- Apply the moisture rule to a Group A cargo: TML = 0.9 × FMP, and refuse the cargo when the moisture content reaches it
- Run the can test as the screening it is — and say what it can and cannot prove
- Read the angle of repose into a trimming requirement, and the density into a stowage factor
- Decide whether a hold is limited by SPACE or by STRENGTH, and why heavy ores go in alternate holds
- Check a bulk loading plan against BOTH the tank-top limit and the hull's still-water shear force and bending moment limits
Supports in this lab: Calculator. The IMSBC Code, the cargo's schedule and the shipper's declaration govern aboard — these are the decision rules and the arithmetic behind them. Hull limits use ST-07's own strength engine on the same box hull. Golden 961/961.
Glossary: TML · liquefaction · the can test · angle of repose · stowage factor · bending moment
Moisture: the number that sinks ships
A Group A cargo — nickel ore, iron ore fines, bauxite, some concentrates — is a solid until it is wet enough to behave like a liquid. Vibration and rolling pack the particles, water fills the gaps, and the pile turns into a slurry that slides to one side and stays there. The line is the transportable moisture limit, defined as 90% of the laboratory's flow moisture point: a deliberate 10% margin between "wet" and "flows".
| TML = 0.9 × FMP | 18.00% |
|---|---|
| Margin (TML − MC) | +2.00 points |
| Decision | MAY LOAD |
| Water in the parcel as loaded | 1456 t of water in 9100 t — you are paying freight on the rain |
moisture 16.0% is 2.0 points under the TML of 18.0% — she may load
The can test — ten minutes, before the lawyers
The mate's screening: half-fill a can, strike it sharply 25 times, and look at the surface. Free water, or a surface that goes flat and glossy, means the cargo may be at or above its flow moisture point — stop loading and call for laboratory tests. It never replaces the certificate; it catches the certificate that is lying.
no free moisture and the surface holds its shape — the screening passes; the certificate still governs
Angle of repose, density and the tank top
Two more numbers decide the stow. The angle of repose sets the trimming requirement — under 30° a cargo behaves like grain and a shifting surface is the danger. The density decides whether you run out of space or out of strength: iron ore at 2.6 t/m³ has a stowage factor of 0.38 m³/t, so a hold is full of WEIGHT long before it is full of cargo.
| Repose band 30°–35° | trim so the surface is reasonably level and the height difference between peak and trough stays within the Code's limit |
|---|---|
| Stowage factor | 0.38 m³/t — a 4032 m³ hold holds 10483 t of it by volume… |
| …but the tank top allows | 6272 t per hold at 14.0 t/m² over 448 m² |
| So the hold is limited by | STRENGTH — this is why heavy ores go in alternate holds |
The plan, checked against the hull
Now the part that makes bulk loading a stability problem. Put the ore in alternate holds to keep the tank tops happy and you have built the classic hogging loading — heavy ends, light middle — and the bending moment climbs. Even the cargo out and the tank tops complain instead. The plan has to satisfy BOTH, and the curves on the bench are the same engine ST-07 uses, so what you learn there is what you are looking at here.
Try "Alternate holds" and watch the bending moment go red while every tank top stays legal; then "Even" and watch the tank tops fail while the hull is comfortable. The answer a real plan reaches is somewhere between the two — which is exactly what the loading computer is for, and why the Code puts a bulk carrier's loading sequence in writing before the first grab swings.
| Cargo loaded | 9100 t in 5 holds |
|---|---|
| Heaviest tank-top load | 4.69 t/m² of 14.0 allowed |
| Max shear force | 280 t of 4200 |
| Max bending moment | 11200 t·m of 32000 (hogging) |
| Verdict | PLAN ACCEPTED |