Tankers are categorised by what they carry rather than by raw size. The economics, the port infrastructure, and the regulatory regime differ substantially across categories — a chemical parcel tanker has very little operationally in common with a Suezmax crude carrier even though both are loosely “tankers” in casual usage.
Crude oil tankers
Crude oil tankers move unrefined petroleum from production regions to refineries. The size classes are Aframax (80,000–120,000 DWT, Caribbean and North Sea trades), Suezmax (120,000–200,000 DWT, Atlantic basin trades, sized to the Suez Canal), VLCC — Very Large Crude Carrier (200,000–320,000 DWT, Middle East-to-Asia and Middle East-to-US Gulf), and ULCC — Ultra Large Crude Carrier (above 320,000 DWT, rare today). Crude tankers load at dedicated export terminals or single-point moorings (SPMs) offshore.
Product tankers
Product tankers move refined petroleum products — gasoline, diesel, jet fuel, naphtha, fuel oil. They are smaller than crude tankers and have multi-tank construction so that several products can be carried simultaneously without contamination. Common sizes are MR — Medium Range (35,000–55,000 DWT) and LR1/LR2 — Long Range (55,000–85,000 / 85,000–120,000 DWT).
Chemical tankers
Chemical tankers carry industrial chemicals and biofuels in many small parcels. The largest chemical parcel tankers have 50+ separate cargo tanks with stainless steel or specialised coatings, allowing them to carry incompatible cargoes simultaneously. The trade is characterised by long voyages with multiple loading and discharging ports.
LNG carriers
Liquefied Natural Gas carriers transport LNG at −162°C in heavily insulated cargo tanks. Standard cargo capacities are around 174,000 cubic metres. LNG terminals are large dedicated facilities with cryogenic loading arms, vapour return systems, and stringent fire-safety perimeters. Major LNG export ports include Ras Laffan (Qatar), Sabine Pass (US Gulf), Yamal (Russia) and Gladstone (Australia); major import terminals are concentrated in Japan, South Korea, China, and Europe.
LPG carriers
Liquefied Petroleum Gas carriers transport propane, butane, ammonia, and other gases either fully refrigerated, semi-refrigerated, or fully pressurised depending on cargo and vessel design. The largest VLGCs carry up to about 86,000 cubic metres.
Why type matters at a port
Each tanker family requires distinct terminal infrastructure, distinct safety zoning, and distinct customs handling. A port that hosts crude tanker calls almost certainly has a refining or storage cluster nearby. A port that hosts LNG carrier calls almost certainly has a multi-billion-dollar liquefaction or regasification facility. Looking at the tanker mix in PortWatch is therefore an indirect window into a region’s industrial energy infrastructure.