A special ship mainly used for carrying goods. A cargo hold in which most of the spaces are used to store cargo. There are many types of cargo ships, which vary greatly in size, with displacement ranging from hundreds of tons to hundreds of thousands of tons.

 

Dry bulk carrier

 

Also called bulk cargo ship, it is specially used to transport coal, mineral sand, grain, fertilizer, cement, steel and other bulk materials. At present, its number is second only to that of oil tankers. The features are that the cab and engine room are arranged at the tail, and the cargo hatch is wide; The inner bottom plate is connected with the side plate with upward inclination to facilitate the concentration of cargo toward the center of the cargo hold. There are inclined top side tanks on both sides of the deck and at the hatch to limit the movement of cargo; There are many ballast tanks for ballast navigation. According to the different goods carried, it can also be divided into ore carriers, coal carriers, bulk grain carriers, bulk cement carriers, wood carriers, etc.

 

Tanker

 

A ship specialized in carrying liquid cargo. Liquid cargo mainly includes oil, liquefied gas, fresh water and chemical liquid. Among them, petroleum and its products have the largest transportation volume. According to the different cargoes carried, it can also be divided into crude oil tankers, product oil tankers, liquid chemical tankers, liquefied gas tankers, etc.

 

Crude oil tanker

 

Ships specially used for carrying crude oil are called oil tankers for short. Due to the huge volume of crude oil transportation, the carrying capacity of oil tankers can reach more than 500000 tons, making them the largest among ships. Generally, the structure is single bottom. With the improvement of environmental protection requirements, the structure is evolving into double shell and double bottom. The superstructure is located at the stern. There is no large hatch on the deck, and crude oil is loaded and unloaded by pumps and pipes. Heating facilities are provided to heat crude oil at low temperature to prevent its solidification from affecting loading and unloading. The draft of super large oil tankers can reach 25 meters, and they are often unable to dock for loading and unloading. Instead, they must use underwater pipelines to load and unload crude oil.

 

Product oil tanker

 

Ships specialized in transporting diesel oil, gasoline and other petroleum products. The structure is similar to that of crude oil tanker, but the tonnage is small. There are high requirements for fire and explosion prevention.

 

General cargo ship

 

Also called ordinary cargo ship, general dry cargo ship or unified cargo ship, it is mainly used to load miscellaneous goods in general packaging, bags, boxes and barrels. As the bulk of miscellaneous cargo is small, the tonnage of general cargo ship is smaller than that of bulk cargo ship and oil tanker. The typical cargo capacity is about 10000~20000 tons, generally double deck, equipped with perfect cargo lifting equipment. There are many layers in cargo hold and deck, which is convenient for separating cargo. The new general cargo ship is generally multi-purpose, which can carry not only ordinary general cargo, but also bulk cargo, large cargo, refrigerated cargo and containers.

 

Container ship

 

Also known as container ship, container ship or container ship, it is a ship specially used for carrying containers. All or most of its cabins are used to load containers, and containers can also be stacked on the deck or hatch cover. The cargo hold opening of a container ship is wide and long, and the size of the cargo hold is standardized according to the requirements for carrying containers. The loading and unloading efficiency is high, which greatly shortens the port dwell time. In order to obtain better economy, its speed is generally higher than that of other cargo ships, up to 30 knots.

 

Liquid chemical vessel

 

Ships specially used to transport toxic, volatile and dangerous liquid chemicals, such as methanol, sulfuric acid, benzene, etc. The cargo hold area is of double shell structure to reduce the risk of cargo spillage when the ship is damaged. The cargo hold shall be separated from the crew's accommodation, drinking water and engine room by empty spaces. The cargo tank volume is limited to a certain extent according to the dangerous degree of the cargo it carries.

 

Liquefied gas carrier

 

Ships specialized in transporting liquefied gases. The liquefied gas transported includes liquefied petroleum gas, liquefied natural gas, ammonia, ethylene, liquid chlorine, etc. The boiling point of these liquid goods is low, and most of them are flammable and explosive dangerous goods. Some of them are highly toxic and corrosive. Therefore, the cargo hold structure of liquefied gas carrier is complex and the cost is high.

 

Liquefied gas carriers are divided into three types according to the storage mode of liquefied gas: pressure type, cold pressure type and cooling type. In a pressurized liquefied gas carrier, the cargo is loaded in a spherical or cylindrical pressure resistant liquid tank at room temperature. The temperature and pressure of the cargo are controlled by the cold pressed and cooled liquid cargo gas carriers, so the heat insulation of the liquid tank and the cooling device of the cargo are required.

 

Reefer

 

A ship specially used to transport goods requiring refrigeration, such as fruits, vegetables, meat and fish. Multi deck is often set, and the cargo hold is usually divided into several independent enclosed spaces. The ship has a high-power refrigeration device, which can keep the proper temperature required by the cargo in each refrigerated cargo hold in a relatively harsh environment.

 

Barge

 

The ship specially carrying cargo barges is also called mother and child ship. Its transportation mode is similar to that of container transportation, because cargo barge can also be regarded as a container that can float on the water. The transportation process is as follows: first load the cargo on the square cargo barge (sub vessel) with uniform specifications, then load the cargo barge onto the barge (mother ship), after the cargo barge arrives at the destination, unload the cargo barge onto the water, and then distribute the cargo barge to their respective destinations by the tugboat. The barge is characterized by high loading and unloading efficiency and convenient sea river combined transport without wharf and storage yard. However, due to the high cost and complex distribution organization of cargo barge, its development is also limited.

 

Ro ro ship

 

The multi-purpose ship that uses vehicles to load and unload goods is also called roll on roll off ship at first. The trailers with large cargoes such as containers and the pallets with wheels with cargoes are regarded as freight transport units, and the tractors or forklifts are used to directly enter and exit the cargo hold for loading and unloading. Ro ro ships are usually equipped with cargo doors and gangways at the stern. Vehicles can directly drive into each deck through gangways, cargo doors and movable ramps or lifting platforms between decks. Therefore, Ro Ro ship does not need the traditional cargo handling equipment on the ship or on the wharf to obtain high handling efficiency.