Reference
Product Tankers
Refined products in coated tanks. 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)
- Typical size
- Commonly 10,000–75,000 DWT
- Cargo type
- Refined petroleum products
About product tankers
Tankers carrying refined petroleum products — petrol, diesel, jet fuel, naphtha and gasoil — from refineries to distribution terminals.
The tanks are coated, usually with epoxy, which keeps the cargo clean and lets the ship switch between grades after cleaning. Segregated tanks and separate pumping arrangements allow several grades to travel on one voyage without contamination.
The trade divides between 'clean' products, which need the coated tanks and careful cleaning, and 'dirty' products such as fuel oil, where staining matters far less.
What it carries
How it is built
- The trade is sized into classes of its own: Handymax for smaller ports, and Medium Range (MR) — the most widely traded product tanker size — where the volumes and the port infrastructure are larger.
- 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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