Crude carriers transport crude oil from oil wells in the Persian Gulf, Alaskan waters, the North Sea, and other oilfields to oil refineries, where it is converted into useful petroleum products.
The largest tankers afloat are called ultra large crude carriers (ULCCs). These enormous ships hold more than 300,000 tons and extend well over 300 m (1,000 ft) in length. ULCCs are so large they cannot pass through the Suez and Panama canals, nor can they enter most harbors. Instead, most ULCCs unload into smaller tankers at offshore pumping stations. Comparing the size of a ULCC with the Titanic illustrates the size of these giant ships. The Titanic measured just over 268 m (880 ft) in length and 46,328 tons. The Batillus, a ULCC built in 1976, stretches 414 m (1,358 ft) and holds 275,267 tons, five times more than the Titanic