Tanker Types: Classification by Cargo, Containment and Hazard
This domain tests whether you can classify tankers by cargo, containment and size, and explain why the design changes with the hazard. Exam questions often ask you to match a cargo to a ship type rather than recall a definition.
Oil tankers
Crude carriers move unrefined oil; product tankers carry refined grades and need more tank segregation and separate pipelines. Common size bands include VLCC/ULCC, Suezmax, Aframax, Panamax, MR and Handysize. Cargo tanks are usually integral, with cofferdams separating cargo from machinery and accommodation.
Chemical tankers
The IBC Code assigns IMO Type 1, 2 or 3 according to cargo hazard. Type 1 is for the most severe hazards and requires double-bottom and side protection plus the greatest separation from the shell. Tanks may be stainless steel or coated; piping segregation follows the cargo's reactivity and pollution category.
Gas carriers
Liquefied gas carriers use independent or membrane containment. LPG carriers range from fully pressurised to fully refrigerated; LNG is carried at about -162°C in membrane, Moss spherical or prismatic tanks. Combination carriers can carry oil or dry bulk but have specific structural restrictions.
Worked example
A charterer offers a toxic, water-reactive chemical requiring maximum segregation. You should reject a standard product tanker and specify an IMO Type 1 chemical tanker with independent stainless-steel tanks, dry certification and dedicated piping. Reasoning: Type 1 provides the required double-bottom and side protection and separation, while water reactivity demands moisture-free tanks and no shared lines that could contaminate or react.
Traps that cost marks
Confusing IMO chemical tanker types with IGC gas carrier types; assuming any tanker can carry any cargo; forgetting that segregation, tank material and coating, not just tank size, decide suitability.