The Engineering Book: From the Catapult to the Curiosity Rover: 250 Milestones in the History of Engineering

1979

Seawise Giant Supertanker

The modern world has an incredible appetite for oil and refinery products. Something approaching 100 million barrels of oil get consumed every day on planet earth. How to move all that oil around? When oil has to cross an ocean, then a supertanker is the ticket. The largest supertankers carry more than three million barrels of oil and do it with incredible efficiency.

A big supertanker is an immense, engineered structure. Fully laden, the largest ships can weigh 600,000 tons and measure 1,475 feet (450 meters) in length. The longest ship ever built was the Seawise Giant, constructed by Japanese company Sumitomo Heavy Industries in 1979. Designing something this big and this heavy falls into a branch of engineering known as naval architecture. Engineers are creating an object the size of the Empire State Building, but this object moves across the water, endures storms and waves, may run into obstacles, etc. Safety is a special concern because crude oil is so toxic.

The dominant architecture used in supertankers today relies on two huge internal steel beams running the length of the ship. These beams give the ship its strength. They create three areas (center, port, and starboard) for tanks that hold the oil. Rather than one long tank running the length of the ship, there are dozens of smaller tanks that minimize sloshing. The tanks also make a double hull possible. The tank itself represents one hull, while the outer skin of the ship is another, with significant space between the two. If the ship runs into something, the hope is that only the outer hull takes damage, with the spacing acting as a buffer that protects the tanks.

The largest two-stroke diesel engines in the world power the largest supertankers. To give you a sense of the size, imagine one cylinder of the engine with the piston at bottom dead center. If you stand on top of the piston, the cylinder wall rises more than 8 feet (2.4 meters) high and the piston diameter is more than 3 feet (1 meter). An engine has 14 of these cylinders and weighs 2,300 tons, producing over 100,000 hp. The engine alone is an engineering marvel, riding inside another engineering marvel.

Aerial view of crude oil tanker and storage tanks in the port of Coruña, Galicia, Spain.