Oil Tankers

Oil Tankers have been used to move large amounts of Oil across waterways and oceans since the late 19th century. Today, roughly 78% of all oil transported around the world is done by oil tankers.

What are oil tankers?

Oil tankers are ships designed for large transportation of oil and it’s by-products. They are also known as petroleum tankers. Basically, there are two main types of oil tankers: product tankers and crude tankers.

Crude tankers as the name implies, are oil tankers used to transport bulk quantities of unrefined oil from it’s point of extraction to the place where it would be refined. Take for example, moving unrefined oils from the oil wells in Nigeria to the refineries located along the coast of the United States is done by using crude tankers.

Product tankers are designed to transport refined oil from refineries to areas where it would be marketed and consumed. Product tankers are usually smaller in size. Take for example, product tankers are used to move refined oil – gasoline – from refineries in the European region to consumer markets such as West African Nations.

Oil tanker classes, sizes and their capacities

Oil tanker dimensions range from General Purpose (GP) to Ultra-Large Crude Carriers (ULCC) on the AFRA scale.

Most often times, oil tankers are classified by their size as well as capacity. The capacity of an oil tanker is dependent on it’s size measured in Deadweight Tonnes (DWT). DWT is actually the total load a ship can safely carry (including oil, provisions, cargo, crew, and anything else that’s supposed to be on the ship at the time of sailing) but not including the weight of the ship itself.

Oil tankers’ capacity can range from a few thousand Deadweight Tonne to a mammoth large size of 550,000 Deadweight Tonne (DWT).

In the shipping industry, there is a system known as the Average Freight Rate Assessment (AFRA) system. The AFRA system was established by the Royal Dutch Shell over sixty years ago, and it is overseen by the London Tanker Brokers’ Panel (LTBP). LTBP is a self-regulating group of shipping stockbrokers.

The Average Freight Rate Assessment (AFRA) is used to order oil tankers or oil vessels according to their DWT (Deadweight tons). We earlier explained that Deadweight Ton is a ship’s capacity to safely carry cargo. The barrel per metric ton conversion is specific to the crude oil and varying types of petroleum products, as the densities of liquid fuel varies by grade and type.

oil tanker sizes

U.S. Energy Information Administration, London Tanker Brokers’ Panel https://www.eia.gov/todayinenergy/detail.php?id=17991

Note: AFRAMAX is not an endorsed vessel classification on the AFRA scale but is shown here for comparison.

  • The General Purpose (GP) and Medium Range (MR) oil tankers on the scale, are normally used to move refined petroleum products over short distances. Example, transporting refined oil products from Europe to the East Coast of the United States. They can easily access most sea ports across the globe because of their small sizes. Basically, a General Purpose oil tanker can carry between 80,000 barrels and 190,000 barrels of gasoline. A Medium Range oil tanker can carry between 190,000 barrels of gasoline ad 350,000 of barrels gasoline.
  • Long Range (LR) oil tankers are very common among oil vessel fleets, as they can carry both refined oil by products and crude oil. The Long Range oil vessel can access most large sea ports where crude oil and refined oil products are moved and marketed. These Long Range (LR1) oil tankers can carry between 310,000 barrels and 550,000 barrels of light crude oil.
  • AFRAMAX are oil vessels within 80,000 DWT and 120,000 DWT. Big companies in the oil and gas industry uses this more for logistical purposes. Many oil tankers are built within these specifications. The London Tanker Brokers’ Panel (LTBP) does not issue a cargo assessment targeted at AFRAMAX oil tankers.
  • Very Large Crude Carriers (VLCC) are in control for most crude oil freights around the globe, as well as the North Sea, known as the crude oil price standard Brent. Standardly, a Very Large Crude Carrier (VLCC) can transport between 1.8 Million barrels and 2.2 Million barrels of a West Texas Intermediate (WTI) type crude oil. With the current West Texas Intermediate (WTI) prices near $57 per barrel, a fully loaded Very Large Crude Carrier (VLCC) could carry crude oil worth up to 125 million dollars.
  • Ultra-large Crude Carrier (ULCC) is often used less than other oil tankers because of it’s mammoth size. It’s large size requires special features hence limiting the port where it can load or offload cargoes. This extra large oil vessel can transport between 2 million barrels and 3.7 million barrels of crude oil. The Louisiana Offshore Oil Port (LOOP) is the only port in the United States that can handle such large oil vessels when fully loaded.

Oil spills, Incidents and Accidents

While oil tankers carry unrefined crude oil and refined products from crude oil that we use every day (such as jet fuel, gasoline, asphalt, and diesel), they also pose as risks – as well as the potential for oil spills.

Collisions, groundings, allisions (when a ship hits a stationary object) are the most common types of oil tanker accidents that lead to main vessel-source oil spills.

The hazards associated with oil spillage in the ocean are not limited to oil vessels – all vessels that make use of crude oil products as fuel also pose some potential risk of an oil spill in the sea. When crude oil-based products are discharged from vessels; whether commercial ships or not, it is known as a ship-source oil spill.

There are significant consequences of enormous oil spills on the ecosystem, indigenous communities, wildlife, coastal environments, and even local economies. According to ClearSeas, the occurrence and volume of oil spills in Seas and oceans has been globally decreasing since the 70s.

Oil spill response and prevention

There are new regulations to improve the safety of oil tankers, modern robust oil vessel design codes, better procedure and self-regulations, superior emergency response systems and preparedness. These new developments in the oil and gas freight industry has resulted in lower oil tanker accidents and fewer oil spills too.

Preventing oil spills is a responsibility that lies on the shoulders of local bodies, national, provincial, international bodies, vessel owners and operators.

Double Hulls – Mandatory

Oil tankers are required to have double hulls. This regulation was issued in 2015 as a response to the Valdez incident which occurred in 1989. Double hulls provide more protection in scenarios of incidents. For example, an oil tanker, SKS Satilla once gashed her side but yet no spill occurred because it was double-hulled.

It is required of all oil tankers to possess two layers on the side and bottom of the vessel. These layers need to be water-tight.

Better Navigational Aids

Navigating the ocean with oil tankers are quite safer using modern auditory, visual, and electronic utilities that marks appropriate shipping routes and warns of obstacles.

Tug escorts

In designated areas, tug boats are requested to escort loaded oil vessels, and assist incoming and outgoing oil tankers. Tug boats can steer, slow, or even stop oil vessels if it loses it’s steering coordination or power.

tug escorting oil tanker
john bateson / Tanker Adygeya being escorted in by four tugs

Marine Inspections

Some nations regularly deploys marine inspectors to ensure oil tankers transiting their waters are in safe operating conditions. Inspections may occur only once a year periodically within the year. The Canadian government requires that all oil vessels be examined once a year.

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