Tanker operations
Oil, products and liquids — measured by the millimetre.
Tankers carry liquids in bulk: crude oil, refined products (gasoline, diesel, jet, naphtha), chemicals, vegetable oils, LNG and LPG. The cargo is pumped, not poured, through manifolds and loading arms, and quantity is measured to extraordinary precision because a small percentage of a huge cargo is a lot of money.
Tanker classes
- MR (Medium Range, ~45,000 DWT) — clean products on regional routes.
- LR1 / LR2 (Long Range) — larger product carriers.
- Aframax (~80,000–120,000 DWT) — crude on shorter hauls.
- Suezmax (~120,000–200,000 DWT) — the largest that can transit the Suez Canal laden.
- VLCC (Very Large Crude Carrier, ~200,000–320,000 DWT) and ULCC — the long-haul crude giants.
Measuring liquid cargo
Liquid quantity is established by ullage (the empty space measured from the top of the tank down to the liquid surface), then corrected for temperature, density and water content to give a standardised volume and weight. Shore-tank figures and ship figures are compared; the difference is captured in a Vessel Experience Factor. Surveyors seal samples at every stage. Quality is verified against a tight specification — wrong sulphur, density or flash point can make a product off-spec and unsellable at the agreed price.