Crude oil tanker is an oil tanker engaged in the trade of crude oil. Product tanker is an oil tanker engaged in the trade of oil other than crude oil. A clean product tanker carries light petroleum products, a dirty product tanker carries heavy petroleum products. The product tanker is intended for transportation and distribution of crude oil derivatives from the refineries to consumers. The main difference between a product tanker and a crude carrier is, that with the former, several batches of cargo of different kinds are transported simultaneously and the respective cargo quantities are smaller. It requires a large number of cargo tanks and a complicated pumping and piping system to facilitate a separate handling process for each type of cargo.
High heat tankers are product carriers for the transportation of molten sulphur, bitumen, dirty petroleum products, coal tar, pitch and coal tar products. They maintain a cargo temperature between the ranges of 160°C and 240°C, which places very heavy demands on the heating, insulation of the tanks and pipework, as well as associated valves and pumps.
Crude-oil and petroleum-product tankers vary in size from small coastal vessels about 60 metres (200 feet) long, carrying from 1,500 to 2,000 deadweight tons (dwt), up to huge vessels that reach lengths of more than 400 metres (1,300 feet), carry as much as 550,000 dwt, and are the largest ships afloat. Between these two extremes are various size classes, though the exact specifications for each class vary among sources.
