Reference
Tanker Market
Ships for liquid cargo in bulk. What it carries, how it is built and the limits that define the class.
- Cargo gear
- Self-discharging by cargo pump
- Capacity measured in
- Deadweight tonnes (DWT), cargo volume in cubic metres or barrels
- Typical size
- From under 10,000 to over 300,000 DWT
- Cargo type
- Bulk liquids and gases
About the tanker market
Tankers carry liquid cargo in bulk, and the market divides by what is in the tanks rather than by hull size alone. Crude oil, refined products, chemicals, liquefied gases and asphalt each demand a different specification of ship.
What they share is the essential architecture: a double hull, cargo split between segregated tanks, an inert gas system to keep the vapour space below the oxygen level that would support ignition, and the ship's own pumps and manifold so it can discharge without shore lifting equipment.
The five specialised tanker types below differ in tank coating and construction, in the cleaning regime between cargoes, and in the regulatory regime they trade under.
What it carries
How it is built
- A double hull — cargo tanks separated from the sea by ballast space on the sides and bottom — mandatory under MARPOL for oil tankers.
- Cargo divided between several tanks, with longitudinal and transverse bulkheads limiting the free surface effect of liquid movement.
- An inert gas system that keeps tank atmospheres below the oxygen level at which the vapour space could ignite.
- Cargo pumps and a fixed pipeline system with a manifold amidships, so the ship discharges its own cargo.
- Heating coils in tanks intended for cargo that must stay warm enough to pump.
Why it is used
- Moves very large volumes of liquid with no packaging at all.
- The ship discharges itself, so terminals need pipework and storage rather than heavy lifting equipment.
- Segregated tanks allow several grades to travel on the same voyage without mixing.
What to check before fixing
- Tank cleaning between cargoes takes time and cost, and the previous cargoes carried determine what may be loaded next.
- Vetting inspections by oil majors govern which ships are acceptable, over and above class and flag requirements.
- Pollution liability is severe, and both the ship and the terminal operate under strict transfer procedures.
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