Panama Canal - Lock Size

Lock Size

The size of the locks determines the maximum size of a ship that can pass through them. Because of the importance of the canal to international trade, many ships are built to the maximum size allowed. These are known as Panamax vessels. A Panamax cargo ship typically has a DWT of 65,000–80,000 tonnes, but its actual cargo is restricted to about 52,500 tonnes because of the 41.2 feet (12.6 m) draft restrictions within the canal. The longest ship ever to transit the canal was the San Juan Prospector (now Marcona Prospector), an ore-bulk-oil carrier that is 973 ft (296.57 m) long with a beam of 106 ft (32.31 m).

Initially the locks at Gatun had been designed to be 28.5 meters (94 ft) wide. In 1908, the United States Navy requested that width be increased to at least 36 meters (118 ft), which would allow the passage of U.S. naval ships. Eventually a compromise was made and the locks were built 33.53 meters (110.0 ft) wide. Each lock is 320 meters (1,050 ft) long, with the walls ranging in thickness from 15 meters (49 ft) at the base to 3 meters (9.8 ft) at the top. The central wall between the parallel locks at Gatun is 18 meters (59 ft) thick and over 24 meters (79 ft) high. The steel lock gates measure an average of 2 meters (6.6 ft) thick, 19.5 meters (64 ft) wide, and 20 meters (66 ft) high. It is the size of the locks, specifically the Pedro Miguel Locks, along with the height of the Bridge of the Americas at Balboa, that determine the Panamax metric and limit the size of ships that may use the canal.

The 2006 third set of locks project will create larger locks, allowing bigger ships to transit through deeper and wider channels. The allowed dimensions of ships will increase by 25% in length, 51% in beam, and 26% in draft, as defined by New Panamax metrics.