Tanker: The first cargo ship carrying liquid cargo was born in 1887. Tankers are specialized in transporting crude oil, with a wide hull and rows of oil pipes on the deck for loading and unloading crude oil. The largest tanker can reach about 300,000 tons. The loading and unloading of this ship has been fully mechanized and automated, with high efficiency, and it can load and unload crude oil in one day. However, oil tankers are often transported in one direction. If oil is transported to the origin of crude oil, it is often empty when it goes. Therefore, some oil tankers are designed as dual-purpose oil and cargo ships. The cabin is divided into three parts, with two mediastinum, the middle cabin is filled with other goods, and the two ends are filled with crude oil, which can avoid empty load and improve economic benefits.
Container ship: Container transportation began in the late 1950s, which had a great influence on shipping. The cabin under the deck of a container ship is divided into many compartments for placing containers. One or two containers can be put on the deck. At the port, containers can be loaded and unloaded by cranes in a few hours. The advantages of this kind of ship are rapid loading and unloading, convenient transshipment to railway and highway transportation, difficult loss of goods and good transportation quality, so it is widely used and has great development prospects. The largest container terminals in the world are China, Hongkong, Singapore and Amsterdam, the Netherlands.
LNG carrier: Special ships are needed to transport natural gas. People use the characteristic that natural gas becomes liquid below-160℃ to transport it. In this way, the transportation efficiency is greatly improved, but the requirements for ship construction are much stricter. Some countries, such as France, use two layers of thin steel plates (0.7/ 1.2 mm thick) and two layers of thick insulation to build the cabins of natural gas ships. This kind of ship has complicated manufacturing process and high cost. Other countries, such as Norway, use alloy steel inner wall, insulation layer and common steel outer protective layer to build the cabin of natural gas carrier, which is more popular than the former.
Bulk carrier: Relatively speaking, bulk carrier is the most comprehensive cargo ship, which can carry more kinds of goods. The cargo hold of this ship is octahedral in cross section and funnel-shaped at the top, which is conducive to filling the cargo hold when loading. There is an inward inclined surface below, which is conducive to cleaning the cabin when unloading. This kind of bulk carrier is used to transport a large number of bulk goods, such as coal, ore and grain. In the fleet, its tonnage is second only to that of oil tankers.
There is an automatic unloading ship in the bulk carrier. The bottom of its cargo hold is made of many funnels, and the bucket door is automatically controlled. Below the bucket door is an automatic conveyor belt that runs through all cargo holds. After the bulk cargo is unloaded, it flows from the bucket door to the conveyor belt, is transported to the elevator at the stern, and then is sent to the loading and unloading bridge on the deck and transported to the dock. The efficiency of this automatic ship unloading is more than 10 times higher than that of general bulk carriers, and it can unload about 20,000 tons of goods per hour at the earliest.
Ro-ro ship: This kind of ship was first invented and used by the United States in 1959. The ship has openings at the fore and aft or both sides, and there is a springboard extending to the dock at the opening. When loading, the goods are loaded on the trailer, and then the trailer is loaded on the ship by truck and fixed on each deck. This kind of ship is very suitable for transporting vehicles, containers, tubular goods or extra-large goods (weighing thousands of tons) full of goods, and is also widely used for transporting cars. Cars made in Japan and South Korea are shipped to America and Europe in this way.
Barge carrier: This kind of ship is a new achievement in the late 1960s. People usually call it the Rush. It is actually a mother-child ship, and several barges are loaded on the mother ship. Each barge is about18m long and 9m wide, and can carry about 500 tons of cargo. There is a large crane on the mother ship. Because the inland river is generally shallow, ocean-going freighters can't sail and carry people, and the goods they carry can only be transshipped, which is both manpower, material resources and time-consuming. After berthing at the estuary, the barge carrier lifts the sub-barge off the mother ship with a crane, puts it into the water, and then is towed along the inland river to the destination port and inland river wharf for unloading. When loading the ship, the sub-barge is fully loaded with goods, towed by tugboat from the dock to the mother ship moored at sea, and then hoisted to the mother ship by crane for the destination.
In addition, there are ferries for transporting cars and trains, as well as many special ships such as refrigerated ships and dredgers. The shipping industry plays a great role in the economic development of human society.