Marine Knowledge Encyclopedia

Cargo ships are mainly dedicated vessels. Most of its space is used for cargo storage. There are many kinds of cargo ships, and the size of the cargo ships varies from hundreds of tons to hundreds of thousands of tons.

Dry bulk carrier

Also known as bulk cargo ships, it is used for the transportation of bulk materials such as coal, ore, grain, fertilizer, cement, and steel. Its number is second only to tankers. Its characteristic is that the cab and engine room are arranged at the rear, and the cargo hatch is wide; the inner floor and the side are connected with the upwardly inclined side board, which facilitates the cargo to be centralized in the center of the cargo tank; and the inclined upper side tanks are arranged at both sides of the deck and the hatchway. To restrict cargo movement; there are more ballast tanks for ballast navigation. According to the different cargoes carried, they can be divided into ore carriers, coal carriers, bulk grain carriers, bulk cement ships, and wooden transport ships.

Tanker

Ships carrying liquid cargo specially. Liquid cargoes mainly include oil, liquefied gas, fresh water, and chemical liquids. The largest volume of transportation is oil and its products. According to the different cargoes carried, they can be divided into crude oil vessels, product oil tankers, liquid chemical vessels, and liquefied gas vessels.

Crude oil ship

Ships dedicated to carrying crude oil, referred to as oil tankers. Due to the large volume of crude oil transported, the oil tanker can also carry more than 500,000 tons, which is the largest in the ship. The structure is generally single-bottomed. With the improvement of environmental protection requirements, the structure is evolving toward the form of double shells and double bottoms. The superstructure is located at the stern. There are no large hatches on the deck and crude oil is pumped and piped. Heating facilities are provided to heat crude oil at low temperatures to prevent its solidification and affect loading and unloading. Very large tankers have a draught of up to 25 meters and often cannot be docked for loading and unloading, but must use subsea pipelines to handle crude oil.

Product Oil Tanker

Specializes in ships carrying diesel oil, gasoline and other petroleum products. The structure is similar to that of a crude oil ship, but its tonnage is small. There is a high fire and explosion protection requirements.

General cargo ship

Also known as a general cargo ship, a general dry cargo ship or a cargo ship, it is mainly used for general cargo, bagged, boxed, and barreled cargo. Due to the small volume of miscellaneous goods, the tonnage of general cargo ships is also smaller than that of bulk carriers and oil tankers. The typical loading capacity is between 1 and 20,000 tons. It is generally a double deck and is equipped with a complete lifting equipment. There are more strata and decks for cargo separation. The new type of general cargo ship is generally a multi-purpose type, capable of carrying ordinary groceries, as well as carrying bulk, bulk cargo, refrigerated cargo, and containers.

Container Ship

It is also called a container ship, a container ship or a cargo container ship. It is a ship that carries containers specially. All or most of its cabins are used to load containers, and containers can often be stacked on decks or hatches. The cargo hatches of the container ships are wide and long, and the dimensions of the cargo holds are standardized according to the requirements of the carrying cases. The high loading and unloading efficiency greatly shortens the time for stopping the port. In order to obtain better economy, its speed is generally higher than that of other cargo ships and can reach a maximum of 30 knots or more. Liquid chemical ship

Specially used for the transportation of toxic, volatile, dangerous chemicals, such as methanol, sulfuric acid, benzene, etc. The cargo hold area is a double shell structure to reduce the risk of spillage when the ship is damaged. The cargo holds are separated from the crew accommodation spaces, drinking water and engine room by empty bays. The cargo tank volume is limited by the degree of danger of the cargo it ships.

Liquefied gas carrier

Specialized in the transport of liquefied gas to ships. The liquefied gases transported include liquefied petroleum gas, liquefied natural gas, ammonia, ethylene, and liquid chlorine. These liquids have low boiling points, are mostly flammable and explosive dangerous goods, and some are highly toxic and corrosive. Therefore, the structure of the cargo tanks of liquefied gas transporters is complex and costly.

Liquefied gas carriers are classified into three types according to the storage of liquefied gas: pressure type, cold pressure type and cooling type. In the pressure type liquefied gas carrier, cargo is loaded in a spherical or cylindrical pressure tank at room temperature. Cold-pressed and cooled gas-cargo vessels control the temperature and pressure of the cargo, and therefore require thermal insulation of the tank and cooling of the cargo.

Refrigerated ship

Ships that carry special cargoes that require refrigeration, such as fruits, vegetables, meat, and fish. Multiple decks are often provided, and the cargo compartment is usually divided into separate enclosed spaces. The high-powered refrigeration equipment on board allows the proper temperature required for cargo to be maintained in each refrigerated cargo compartment in a relatively hostile environment.

Barge carrier

Ships that specialize in carrying cargo barges, also known as mother-child boats. Its mode of transport is similar to that of container transport, as the cargo barge can also be regarded as a container that can float on the surface. The transportation process is: the goods are first loaded on a square freighter (sub-ship) of a uniform specification, and then the cargo is unloaded and loaded on a barge (mother ship). After the barge transports the cargo to the destination port, the cargo is unloaded. To the water, and then to the respective destination by the tugboat. The characteristics of a barge carrier are that it does not require docks and yards, and has high loading and unloading efficiency, which facilitates sea-river transport. However, due to the high cost, the collection and distribution organization of cargo barges is complex and its development is also limited. Roll-on ship

Multipurpose vessels that use cargoes to load and unload cargo from above and below are also initially rolled up and down. Containers with large cargo such as containers, and trailers with cargoes are used as freight units, which can be loaded and unloaded directly by a tractor or forklift. Ro-Ro ships are usually provided with cargo doors and springboards at the stern. Vehicles can directly enter the decks through the ramps, cargo doors and active ramps or lifting platforms between decks. Therefore, the ro-ro ship does not require the traditional lifting equipment on board or on the quay to achieve high loading and unloading efficiency.