Steel Coils, a Rain Squall and a Marginal GM
Your 8,500 dwt general cargo ship is loading 24 steel coils at Rijeka. Each coil weighs 9.5 t and rests on a footprint of 1.1 m × 1.4 m. The tank top allowable load is 12 t/m². The loading plan shows two coils stacked vertically, separated by 100 mm timber dunnage, with chain lashings to the tank top. The calculated GM is 0.38 m; two double-bottom ballast tanks are slack and the loading computer shows an effective GM of 0.26 m. A rain squall is passing and the charterer wants loading to continue because the coils are 'only surface wet'. The forecast is for 35 kn winds and 4 m seas on the passage. The vessel has a single hold, no cargo ventilation, and dry bilges. The master must decide whether to accept the stowage plan and the charterer's instruction.
1. Check the point loading of the two-high coil stack and determine what stowage changes are needed.
Read the worked answer
Contact pressure. One coil footprint = 1.1 × 1.4 = 1.54 m². The pressure from one coil = 9.5 / 1.54 = 6.17 t/m². A two-high stack therefore imposes about 12.34 t/m² on the tank top, which exceeds the allowable 12 t/m² even before dynamic loads from the forecast weather.
Options. Either load the coils in a single tier, or spread the load. For example, two 200 mm × 200 mm timber skids of at least 2.0 m length under each coil give a contact area of 2.0 × 1.4 = 2.8 m². The two-high load then becomes 19 / 2.8 = 6.8 t/m², within the limit. The skids must bear on tank-top framing or stools, not on unsupported plate, and the coil axis should be fore-and-aft with wedges to prevent rolling. Lashings must be sized for the calculated transverse and longitudinal accelerations, not merely by habit.
Decision. Reject the plan as presented. Require a revised stowage plan with single-tier stow or proper load-spreading dunnage, verified against the tank-top strength and the loading computer. Record the change and inform the charterer and terminal. A point load that exceeds the tank-top limit can cause permanent deformation or cracking, even if the average hold load is acceptable.
2. Assess the stability condition for the forecast weather and state the actions you would take before departure.
Read the worked answer
The calculated GM of 0.38 m is positive, but the free-surface correction from two slack double-bottom tanks reduces the effective GM to 0.26 m. That is only 0.11 m above the IMO intact-stability minimum GM of 0.15 m for this size of ship, and GM alone is not the full criterion: the GZ curve, angle of maximum GZ, area under the curve and weather criterion must also be checked.
A low effective GM gives a long roll period, large roll angles and high accelerations at the cargo. That increases lashing loads and the risk of a coil shifting, especially with a two-high stack. Free surface also reduces the righting energy.
Actions before departure. Press up or fill the slack ballast tanks to eliminate free surface, or at least reduce it to one tank at a time. Add ballast low down to raise GM to a comfortable value, then recalculate the final condition. Lower the heavier coils, avoid two-high stow if possible, and verify lashings against the expected accelerations. Check the IS Code criteria and the loading computer's output, not just GM. If the forecast is 35 kn and 4 m seas, consider a weather route, reduced speed or delaying departure. Document the final condition and inform the master and charterer.
3. How would you handle the charterer's instruction to load in rain, and what cargo-care measures apply?
Read the worked answer
The master has authority over the safety of the ship and the care of the cargo; a charterer's instruction does not override that. Steel coils are not hygroscopic like grain, but free water in the hold promotes rust, reduces friction under the coils and can support a cargo claim. The hold has no ventilation, so any moisture that enters will remain.
Practical measures. Keep hatch covers closed except when a lift is actually being loaded. Use hatch tents or temporary covers. Stop loading during heavy rain and reject coils with standing water or ice. Measure the dew point: do not ventilate when the outside dew point is higher than the hold or cargo temperature, and in this case ventilation is not available anyway. Ensure bilges are dry and covered so water cannot splash onto the cargo.
Documentation. If the charterer insists on continuing, load under protest, photograph the wet coils, note 'loaded wet' on the mate's receipt and in the cargo log, and notify the charterer and P&I correspondent. Do not issue a clean bill of lading for wet cargo. If the coils are already rusted or deformed, reject them or record the condition. The aim is to protect the cargo as far as practicable while preserving clear evidence of the charterer's instruction and the actual condition.