Tanker Types and Capacities

An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries. Product tankers, generally much smaller, are designed to move refined products from refineries to points near consuming markets.

Oil tankers are often classified by their size as well as their occupation. The size classes range from inland or coastal tankers of a few thousand metric tons of deadweight (DWT) to the mammoth ultra large crude carriers (ULCCs) of 550,000 DWT. Tankers move approximately 2,000,000,000 metric tons (2.2×109 short tons) of oil every year. Second only to pipelines in terms of efficiency, the average cost of oil transport by tanker amounts to only two or three United States cents per 1 US gallon (3.8 L).

Some specialized types of oil tankers have evolved. One of these is the naval replenishment oiler, a tanker which can fuel a moving vessel. Combination ore-bulk-oil carriers and permanently moored floating storage units are two other variations on the standard oil tanker design. Oil tankers have been involved in a number of damaging and high-profile oil spills. As a result, they are subject to stringent design and operational regulations.

10,000آ–24,999 DWT: General Purpose tanker
25,000آ–54,999 DWT: Medium Range tanker
55,000آ–79,999 DWT: Long Range 1 (LR1)
80,000آ–159,999 DWT: Long Rang e 2 (LR2)
160,000آ–319,999 DWT: Very Lar ge Crude Carrier (VLCC)
320,000آ–549,999 DWT: Ultra La rge Crude Carrier (ULCC)

Panamax

Panamax and New Panamax are terms for the size limits for ships traveling through the Panama Canal. Formally, these limits and requirements are published by the Panama Canal Authority (ACP), titled "Vessel Requirements". The allowable size is limited by the width and length of the available lock chambers, by the depth of water in the canal, and by the height of the Bridge of the Americas since that bridge's construction. These dimensions give clear parameters for ships destined to traverse the Panama Canal and have influenced the design of cargo ships, naval vessels, and passenger ships.

Panamax specifications have been in effect since the opening of the canal in 1914. Ships that do not fall within the Panamax-sizes are called post-Panamax. In 2009 the ACP published the "New Panamax" that will be in effect when the canal's third set of locks, larger than the current two, becomes operational.

The increasing prevalence of vessels of the maximum size is a problem for the canal, as a Panamax ship is a tight fit that requires precise control of the vessel in the locks, possibly resulting in longer lock time, and requiring that these ships transit in daylight. Because the largest ships traveling in opposite directions cannot pass safely within the Culebra Cut, the canal effectively operates an alternating one-way system for these ships.

Aframax

An Aframax ship is an oil tanker smaller than 120,000 metric tonnes and with a breadth above 32.31 m. The term is based on the AFRA - Average Freight Rate Assessment - a tanker rate system created in 1954 by Shell Oil to standardize shipping contract terms. Due to their favorable size, Aframax tankers can serve most ports in the world. These vessels serve regions which do not have very large ports or offshore oil terminals to accommodate very large crude carriers and ultra large crude carriers. Aframax tankers are optimal for short to medium haul crude oil transportation. Aframax class tankers are largely used in the basins of the Black Sea, the North Sea, the Caribbean Sea, the South and East China Seas, and the Mediterranean. Non-OPEC exporting countries may require the use of tankers because the harbors and canals through which these countries export their oil are too small to accommodate very-large crude carriers and ultra-large crude carriers.

Suezmax

Suezmax is a naval architecture term for the largest ship measurements capable of transiting the Suez Canal in a laden condition, and is almost exclusively used in reference to tankers. Since the canal has no locks, the only serious limiting factors are draft (maximum depth below waterline), and height due to the Suez Canal Bridge. The current channel depth of the canal allows for a maximum of 20.1 m (66 ft) of draft, meaning that a few fully laden supertankers are too deep to fit through, and either have to unload part of their cargo to other ships ("transshipment") or to a pipeline terminal before passing through, or alternatively avoid the Suez Canal and travel around Cape Agulhas instead. The canal was deepened in 2009 from 18 to 20 m (60 to 66 ft).

The typical deadweight of a Suezmax ship is about 160,000 tons and typically has a beam (width) of 50 m (164.0 ft). Also of note is the maximum head room ("air draft") limitation of 68 m (223.1 ft), resulting from the 70 m (230 ft) height above water of the Suez Canal Bridge. Suez Canal Authority produces tables of width and acceptable draft, which are subject to change. From 2010 the wetted surface cross sectional area of the ship is limited by 1006 m2, which means 20.1 m (66 ft) of draught for ships with the beam no wider than 50.0 m (164.0 ft) or 12.2 m (40 ft) of draught for ships with maximum allowed beam of 77.5 m (254 ft 3 in).

VLCC (Malaccamax)

Malaccamax is a naval architecture term for the largest size of ship capable of fitting through the 25-metre-deep (82 ft) Strait of Malacca. Bulk carriers and supertankers have been built to this size, and the term is chosen for very large crude carriers (VLCC). They can transport oil from Arabia to China.

ULCC

Ultra large crude carriers are oil tankers of about 300,000 - 550,000 DWT. Typically used for carrying crude oil on long-haul routes from the Arabian Gulf to Europe, America and the Far East via the Cape of Good Hope, normally discharging at custom-built terminals.