A tanker is a ship designed to transport liquids in bulk.
Tankers can range in size from several hundred tons, designed for servicing small harbours and coastal settlements, to several hundred thousand tons, with these being designed for long-range haulage. A wide range of products are carried by tankers, including:
-hydrocarbon products such as oil, LPG, and LNG
-Chemicals, such as ammonia, chlorine, and styrene monomer
Different products require different handling and transport, thus special types of tankers have been built, such as "chemical tankers" and "oil tankers". "LNG carriers" as they are typically known, are a relatively rare tanker designed to carry liquefied natural gas.
Among oil tankers, supertankers were designed for carrying oil around the Horn of Africa from the Middle East; the FSO Knock Nevis being the largest vessel in the world. Knock Nevis was formerly the ULCC "Jahre Viking".
Apart from pipeline transport, supertankers are the only method for transporting large quantities of oil, although such tankers have caused large environmental disasters when sinking close to coastal regions, causing oil spills.
Tankers used for liquid fuels are classified according to their capacity.
In 1954 Shell Oil developed the afra system (average freight rate assessment) for fiscal reasons. Tankers were divided in groups of different sizes. To make it an independent instrument, Shell consulted London Tanker Brokers Panel (LTBP). At first, they divided the groups as General Purpose for tankers under 25,000 deadweight tonnage (dwt), Medium Range for ships between 25,000 and 45,000 dwt and Large Range for the then enormous ships that were larger then 45,000 dwt. During the 1970s the ships became larger and larger and the list was extended, where the tons are long tons:
10,000 - 24,999 dwt - General Purpose tanker
25,000 - 44,999 dwt - Medium Range tanker
45,000 - 79,999 dwt - LR1 (Large Range 1)
80,000 - 159,999 dwt - LR2 (Large Range 2)
160,000 - 319,999 dwt - VLCC (Very Large Crude Carrier)
320,000 - 549,999 dwt - ULCC (Ultra Large Crude Carrier)
For use on the oil market, the following groups are used:
10,000 - 60,000 dwt - Product tanker
60,000 - 80,000 dwt - Panamax
80,000 - 120,000 dwt - Aframax
120,000 - 200,000 dwt - Suezmax
200,000 - 315,000 dwt - VLCC
320,000 - 550,000 dwt - ULCC