Question 1

During a North Atlantic passage in Force 9, your vessel rolls heavily. The loading computer shows the vessel listing 8 degrees to starboard and not recovering fully upright. What do you suspect, and what actions do you take?

Accepted Answer

Suspect cargo shift — particularly likely with bulk cargoes (grain, ore, coal), unsecured general cargo, or containers with incorrect stack weights. Immediate actions: inform master; reduce speed to ease vessel motion; assess whether the list is fixed (permanent shift) or rolling asymmetrically (G still on centreline but reduced GM); check cargo hold access for any signs of shift (do NOT enter in heavy weather); ballast double-bottom tanks on the starboard side to correct list without raising G. Longer term: assess whether the vessel can continue safely; consider diverting to a port of refuge; notify company/DPA. A list combined with heavy rolling and reduced righting ability is a serious stability concern — do not dismiss as normal rolling in heavy weather. Cargo shift in heavy weather is a leading cause of bulk carrier and cargo ship capsizing. Grain shift: grain behaves like a fluid and settles under vibration — a void space forms at the top of the full hold as the grain compacts, then the grain slides laterally in heavy rolling. This is why the International Grain Code requires calculated permissible heeling moment at departure. Coal and concentrate cargoes that liquefy under vibration and moisture (Group A cargoes under the IMSBC Code) can also shift catastrophically. The 8-degree fixed list (not rolling back to upright) indicates G has shifted off the centreline — very different from heavy rolling about the upright. Ballasting double-bottom tanks (adding weight low) lowers G and improves GM while also providing a small righting moment if on the low side. Critically, do NOT ballast wing tanks at deck level — this raises G. The master's decision to seek a port of refuge must be made before the list becomes unmanageable — waiting for further deterioration removes options.

Question 2

Your examiner asks: "State the nine classes of dangerous goods under the IMDG Code and give one example of each." Give a complete answer.

Accepted Answer

Class 1: Explosives (e.g. detonators, fireworks). Class 2: Gases — 2.1 Flammable (LPG), 2.2 Non-flammable/non-toxic (compressed air), 2.3 Toxic (chlorine). Class 3: Flammable liquids (petrol, acetone). Class 4: Flammable solids — 4.1 Flammable solids (matches), 4.2 Spontaneously combustible (wet fishmeal), 4.3 Dangerous when wet (sodium, calcium carbide). Class 5: Oxidising substances — 5.1 Oxidisers (ammonium nitrate), 5.2 Organic peroxides. Class 6: Toxic and infectious — 6.1 Toxic (pesticides), 6.2 Infectious substances. Class 7: Radioactive. Class 8: Corrosives (battery acid, caustic soda). Class 9: Miscellaneous dangerous goods (lithium batteries, dry ice). The IMDG Code (International Maritime Dangerous Goods Code, made mandatory under SOLAS VII/3) uses UN-based classifications. Key points for OOW orals: Class 4 has three subdivisions — 4.2 (spontaneously combustible materials including wet fishmeal which has caused numerous bulk carrier fires) and 4.3 (dangerous when wet — water reacts to produce flammable gases) are the most hazardous from a watchkeeping perspective. Class 9 (lithium batteries) has become increasingly significant — lithium battery fires in containers and car carriers have caused major incidents (e.g. Felicity Ace). The IMDG Code is updated biennially; the 2022 edition (Amendment 41-22) is the current edition. Segregation requirements between classes are specified in IMDG Chapter 7 — an OOW must understand that certain classes cannot be stowed in the same space (e.g. oxidisers and flammables).

Question 3

You are loading a general cargo consignment. The cargo plan shows ammonium nitrate (Class 5.1) in Hold 2 and petroleum products in drums (Class 3) in Hold 3, which is adjacent. Is this acceptable under the IMDG Code?

Accepted Answer

Ammonium nitrate (Class 5.1, oxidiser) and petroleum products (Class 3, flammable liquids) require segregation of "away from" (separated by an intervening space or hold) at minimum. Adjacent holds sharing a common bulkhead do not satisfy "away from" — the cargoes must be in non-adjacent holds with at least one hold separation. Check the IMDG Segregation Table (Chapter 7.2): oxidisers and flammable liquids require at minimum "away from" and in some cases "separated from." This loading plan requires amendment. IMDG Code Chapter 7.2: segregation categories: "away from" (minimum separation of 3m horizontally in the same space, or in different compartments/holds); "separated from" (separated by a complete compartment or hold — i.e. at least one intervening space); "separated by a complete compartment or hold" and "separated longitudinally by an intervening complete compartment or hold." Ammonium nitrate as an oxidiser can cause catastrophic decomposition if contaminated with fuel oil (the Beirut Port explosion 2020, Texas City 1947 were both ammonium nitrate events). The segregation requirement between Class 5.1 and Class 3 is "away from" at minimum — adjacent holds sharing a bulkhead do not satisfy this. An OOW discovering an incorrect cargo plan before loading must stop operations and refer to the Chief Officer and master. The IMDG Segregation Table in Chapter 7.2.4 provides the complete matrix of segregation requirements between all classes.