There are two main types of dry cargo: bulk cargo and break bulk cargo. Bulk cargoes, like grain or coal, are transported unpackaged in the hull of the ship, generally in large volume. Break-bulk cargoes, on the other hand, are transported in packages, and are generally manufactured goods. Before the advent of containerization in the 1950s, break-bulk items were loaded, lashed, unlashed and unloaded from the ship one piece at a time. However, by grouping cargo into containers, 1,000 to 3,000 cubic feet (28 to 85 m3) of cargo, or up to about 64,000 pounds (29,000 kg), is moved at once and each container is secured to the ship once in a standardized way. Containerization has increased the efficiency of moving traditional break-bulk cargoes significantly, reducing shipping time by 84% and costs by 35%. As of 2001, more than 90% of world trade in non-bulk goods is transported in ISO containers. In 2009, almost one quarter of the world’s dry cargo was shipped by container, an estimated 125 million TEU or 1.19 billion metric tons worth of cargo.

The earliest container ships were converted tankers, built up from surplus T2 tankers after World War II. In 1951 the first purpose-built container vessels began operating in Denmark, and between Seattle and Alaska. The first container ship in the United States was the Ideal X,] a T2 tanker, owned by Malcom McLean, which carried 58 metal containers between Newark, New Jersey and Houston, Texas on its first voyage, in April 1956.

In 1955, McLean built his company, McLean Trucking into one of USA’s biggest freighter fleets. In 1955, he purchased the small Pan Atlantic Steamship Company from Waterman Steamship and adapted its ships to carry cargo in large uniform metal containers. On April 26, 1956, the first of these rebuilt container vessels, the Ideal X, left the Port Newark in New Jersey and a new revolution in modern shipping resulted.

The earliest container ships were converted T2 tankers.

Container vessels eliminate the individual hatches, holds and dividers of the traditional general cargo vessels. The hull of a typical container ship is a huge warehouse divided into cells by vertical guide rails. These cells are designed to hold cargo in pre-packed units – containers.

Shipping containers are usually made of steel, but other materials like aluminum, fiberglass or plywood are also used. They are designed to be entirely transferred to and from trains, trucks or trailers to and from a ship. There are several types of containers and they are categorized according to their size and functions.

Today, approximately 90% of non-bulk cargo worldwide is transported by container, and modern container ships can carry up to 15,000 twenty-foot equivalent units (TEU) (Maersk E Class). As a class, container ships now rival crude oil tankers and bulk carriers as the largest commercial vessels on the ocean.

Although containerization caused a revolution in the world of shipping its introduction did not have an easy passage. Shipping lines, railway (railroad in the US) companies and trade unions vehemently opposed and tried to block the use of containerized ships. It took ten years of legal battles before container ships would be pressed into international service. In 1966, a container liner service from USA to the Dutch city of Rotterdam commenced.

Size categories - Container vessels are differentiated into 7 basic size categories:


Feeder – Container vessels under 3,000 TEU are usually named feeders. Feeders are little vessels which typically work among smaller container ports. Some feeders gather their cargo from little ports, drop it off at big ports for transshipment on larger vessels, and distribute containers from the big port to smaller regional ports. This size of ship is the most probably to carry cargo cranes on its board.


Panamax – The size of a panamax container ship is limited by the Panama canal’s lock chambers, that might refuge vessels with a beam of up to 32.31 meters, a length overall of up to 294.13 meters, and a draft of up to 12.04 meters.

Post-panamax – The “post panamax” category container vessel has historically been used to define vessels with a moulded breadth over 32.31 meters, however the Panama Canal expansion project is the reason for some changes in terminology.


New panamax – The “new panamax” category of container vessel is based on the maximum ship-size which is goin to be able to transit a new third set of locks. The new locks are being built to refuge a container vessel with a length overall of 366 meters (1,201 ft), a maximum width of 49 meters (161 ft), and tropical fresh-water draft of 15.2 meters (50 ft). A ship like that would be wide enough to carry ninetheen rows of containers, have a total capacity of nearly 12,000 TEU and be comparable in size to a capesize bulk carrier or a suezmax tanker ship.


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