Types of Ships
Cargo ships can be classified into various categories depending upon their size, types of cargo carried, nature of the business it is involved in.
Types of ships depending upon cargo carriage.
Ships can be divided into various types depending upon the cargo carriage they are
- Cargo Ships
Dry Cargo Ships
i. General cargo ships
ii. container ships
iii. Bulk carriers
iv. Roll on Roll off ships
Liquid cargo ships
i. Oil Tanker
ii. Chemical tanker
iii. Gas Tanker
2. Passenger Ships
i. Cruise Liner
3. Other ships.
i. Tug boats
ii. Offshore supply vessel
iv. Fishing vessel
v. Other Speciality Vessel
vi. High-speed craft
vii. Pleasure yacht
viii. Ice Breaker
Let’s know each type in detail.
Cost is a factor that worries all ship owners. A ship can be transformed from one type to another in shipyard but that is doe only when a particular type of vessel is not doing good business and the owner is optimistic about his new type of ship.
For example, few container vessels are converted to bulk carriers and few of my friends worked on those ships as well.
General Cargo Ships
General cargo ships are the oldest form of cargo ships which used to carry various forms of cargo at the same time but in smaller parcels.
Goods carried individually, unitized or palletized in boxes, barrels, bales, crates, packages or bundles, are called general cargoes. Such cargo is generally carried in non-specialized compartments. These ships have their own arrangements for loading and discharging cargo. You will generally find a lot of combinations of derricks, cranes, purchases etc on the decks of these ships to facilitate the operations.
Pallets are wooden tray like structures supported by bearers. When loaded, the whole load can be moved by mechanical means, such as a fork lift. Pallets are available in certain standard sizes, where 40″ × 48″ (100 cm x 122 cm) is the most common among them. The use of pallets eliminates package handling and reduces labour usage, but it does not overcome crushing damage, the stowage factor is increased due to loss of space and there can be a reduction in stability.
The general arrangement of a General Cargo ship
Shipping lines implemented various unitization measures in order to reduce theft and discharge the same amount of cargo, which was loaded at the load port. Pre-slinging of cargoes, palletization, barge-carrying ships, ro-ro ships and containerization are all examples of unitization.
You will find most of the goods are transported in containers today and the container ship is the heart of intermodal transportation. Containerization is a system of packing smaller parcels into one larger package for ease of handling during transportation.
In the last few decades, there has been a major shift from transporting individual items of cargo in general cargo ships to transporting prepacked standardized containers suitable for carriage by road, rail and sea, in specially designed container ships.
Container Ships on Liner Trade. The ships used in the liner sector have changed radically from the traditional liner ships of the WWII era to the highly sophisticated fully cellular container ships of today. The earlier container ships were all of the converted types.
Over the years, their size has increased tremendously. Generally, they are classed based on the number of 20ft containers (TEUs) they can carry.
The larger container ships that call only a limited number of load and discharge ports are referred to as mother ships. Feeder ships are smaller ships that transship the containers to or from the larger ports to the smaller ports in the region.
The development of specialized containers with a wide range of types, sizes and configurations permits containerization of many cargoes. The main advantages of containerization are:
- Low handling cost;
- Limited labor for handling;
- Loss due to damages in transit/handling is reduced or eliminated;
- Pilferage loss is eliminated;
- Increases rate of loading and discharging in ports;
- Dunnage requirement is eliminated;
- Reduces losses due to broken stowage.
Materials used for the construction of containers depend on the nature of the cargo to be carried and the way they are handled. Some basic materials generally used are steel, aluminium, fibreglass, reinforced plastic, wood and GRP (glass reinforced plastic). All these are susceptible to a degree of corrosion or damage due to certain chemicals.
Containers are designed for multi-modal transportation ie, by ships, trucks, railcar, barges and by air. The container ships are categorized by their capacities.
The use of intermodal containers for the transport of a great variety of cargo has become increasingly popular in recent years. The popular intermodal container, adaptable to carriage by truck chassis, railcar, barge and ocean-going vessels, is the most common form of containerization. The considerations governing the preparation and storage of the cargo in these containers are applicable to other methods of cargo transport as well.
A bulk carrier is a merchant ship specially designed to transport unpackaged bulk cargo, such as grain, coal, ore, and cement, in its cargo holds. Since the first specialized bulk carrier was built in 1852, economic forces have led to continued development of these ships, resulting in increased size and sophistication. Today’s bulk carriers are specially designed to maximize capacity, safety, efficiency, and durability.
There are a large variety of bulk carriers at present. They range from small 100 metres long to massive 350,000 tonnes capacity. Modern-day bulk carriers are characterised by a single screw type vessel with a high block coefficient. It should have low water flow resistance which will enhance its power. Further, the flow of water towards the rudder and propeller should be sufficient, considering the body shape.
A solid bulk cargo means the goods which are solids in particle or granular form, with or without moisture. They are generally homogeneous in composition and loaded directly into a vessel’s cargo spaces without bagging or packaging. Coal, sulphur, ores, fertilisers and grains are some of the cargoes carried in bulk.
ALSO READ: What are Bulk Carrier Ships?
Roll on Roll off ships
Roll-on Roll-off (Ro-Ro) uses a non-container cargo handling system. The cargo units have wheels or tracks and the means to be rolled either by own power or pushed or pulled by external motive power into a ship. A Ro-Ro ship is a ship designed with extensive covered decks within the hull with ramps or elevators to stow these cargo units.
Basically, you can say its a vehicle carrier ship. Maybe bus, truck or cars.
Ro-Ro ships may be specialized with some ships designed as pure car-carriers and others designed to carry heavy rolling units with deckhead height to accommodate large dimensioned cargo types and decks reinforced to carry extra weight. Certain Ro-Ro ships are assigned to military use capable of carrying an armored brigade together with its wheeled or tracked units and support vehicles.
Ro-Ro ships have a stern ramp or supplementary side ramp for handling cargo. Stern ramps are wide mechanical road links between the dock and the ship. Decks within a Ro-Ro ship vary in height in accordance with the cargo to be carried. Car decks have minimal deckhead height clearance just adequate to accommodate regular automobiles.
Areas used for project cargo and large cargo units have substantial overhead clearance that may even permit stacking of non-wheeled cargo units on top of one another.
Various liquid cargoes are transported by sea on tankers. There are two basic types of oil tankers. One is the crude oil tanker which carries mostly a single grade of crude oil. Some of the ULCC’s (ultra-large crude carriers) can be up to 500,000 Deadweight.
The other type of tanker is the product carrier which can carry different grades of cargo at the same time. These are generally smaller than the crude oil tankers.
In addition to classifying vessels as crude tankers and product tankers, they can be further sub-categorized. While most tankers are built to bring oil from one port to another, there are replenishment oilers that ferry fuel to vessels at sea in order to refuel them. Then there are the mother ships which stay only in deeper waters and brink bulk oil from oil wells at deep sea to outer deep water limits of ports. The lightering vessels load oil from the mother ships and discharge it to shore refineries. Sometimes sea-bound tankers are used as floating storage units when they become too old or uneconomical to operate.
There are certain terms exclusively used to describe oil tankers for their categorization:
- Single Hull-hull construction means that the ship has only one skin between the sea water and the loaded oil inside the vessel. These types are no longer in production and existing ones are being banned in most countries.
- Double Hull – Double-hull construction means that the ship has two hulls, one inside the other like a double skin. It is a mandatory design feature on newly built oil tankers. This offers an extra layer of protection if the tanker is damaged in accident that might otherwise result in catastrophic oil spills.
- OBO – An OBO or ore-bulk-oil carriers have been made with the idea of bringing something on the return leg of their trips, so that they can make money both ways. Hence bulk iron ore is carried on return trips, in the same compartment which had oil previously.
- LR1 – Large Range 1 – tankers have a DWT between 45,000 to 80,000 tonnes
- LR2 – Large Range 2 – tankers have a DWT between 80,000 and 159,999 tonnes
- VLCC – Very Large Crude Carriers carry between 160,000 and 319,999 DWT. Oil carriers of this size and above are known as supertankers.
- ULCC – Ultra Large Crude Carriers are the largest oceangoing vessels – their deadweight tonnage is 320,000 tonnes and above. These are mammoth giants and are comparable in length to the height of some of the world’s tallest buildings.
Chemical Tanker operations differ from any other liquid bulk transportation, in that a large number of cargoes of different properties and characteristics and inherent hazards may be carried simultaneously, on a single voyage, and that numerous products may be handled at one berth, typically including both discharge and loading as well as tank cleaning. Even the less sophisticated chemical tankers are more complex to operate than oil tankers.
Chemical tankers are considered more hazardous comparing to oil tankers and hence wages are more on this type of ship. Be ready to loose your hair if willing to join chemical tanker HAHAHA…
Gas carriers range in capacity from the small pressurized tankers of between 500 and 6,000 m3 (17600 and 212000 sq.ft.) for shipment of propane, butane, and the chemical gases at ambient temperature up to the fully insulated or refrigerated seagoing tankers of over 100,000 m3 (3500000 sq.ft.) capacity for the transport of LNG and LPG.
Between those two distinct types is a third tanker type – semi-pressurized gas carrier. These very flexible tankers are able to carry many cargoes in a fully refrigerated condition at atmospheric pressure or at temperatures corresponding to carriage pressure of between five and nine bar.
A passenger ship is specially designed and equipped for the transport of persons. According to the provisions of the International Convention for the Safety of Life at Sea (SOLAS) any ship with accommodation for more than 12 passengers is a passenger ship. Persons other than passengers are regarded as crew.
Ferries – Vessels used for transiting passengers (and vehicles) on short-distance routes are called ferries.
Cruise Ships – Mainly used for recreational activities, cruise ships are like luxurious floating hotels with state-of-the-art facilities.
They can further be classified as..
Liners, Cruise Ships, Pilgrimage ShipsCross Channel Ferries, Coastal Ferries, Harbour FerriesArctic and Antarctic Cruises.
Tugs: A tug (tugboat) is a boat or ship that manoeuvres vessels by pushing or towing them. It can be seagoing, escort tug, Harbour tugs
The seagoing tug has lower aft deck which helps in towing operation. The seagoing tug has heavy-duty mooring equipment. It serves many purposes such as
- salvage operation
- Anchor handling in offshore industry
- Environmental service
- ship with power failure
Escort Tugs are generally used to escort large vessels in narrow channel. Escort tug came in to picture after few tanker grounding incidents.
Harbour tugs Assist the pilot in berthing a vessel. Generally, two to three tug boats are employed to berth a ship in port.
Tug boats may be port-owned or privately owned. The tug master remains in touch with the pilot and acts as per his guidance.
Engine power is normally less than 3000 BHP.
Harbour tugs are normally used in ports, inland water ways, fighting fires etc.
Off Shore Supply Vessel
Vessels that supply Food, store etc to offshore rigs are known as a supply vessel. Life is difficult in supply vessel because of rolling and pitching. Although it comes with its own advantages like fresh food, mobile network availability.
Various types of barges are seen in marine use like bunker barge, cargo barge, etc.
As the name suggests bunker barge supplies bunkers to ships. Cargo barges are used while the ship is in anchorage and loading cargo or discharging cargo. Big ships can not enter to few ports because of draught restrictions.
Fishing vessels can be trawler or non-trawler type.
For trawler type of fishing vessel, additional power is required as it has to pull nets.
Non-trawler type vessels have many varieties.
many factors are taken into account while considering a fishing vessel such as
cargo hold size
method of fishing
The yacht can be a motor yacht or a sailing yacht. The length of a yacht is approximately 15m in length
The yacht is normally used by
wealthy business persons
Very rich people for pleasure trips
companies or individuals for yacht racing
Dredgers are used to remove muds and sediments from the narrow channel and makes passage clear of sand deposits that comes from sea towards the port area or harbourarea.
Dredgers are mainly classified into two types:
- Mechanical dredgers
- Hydraulic dredgers
dredgers remove mud and sediments and store them in a hopper that is a tank used to store all debris and mud. While dredging both mud and water comes to the hopper. After precipitation mud remains in the tank and water flows out from the top. These muds are dumped ashore and sometimes deep in the sea.
An ice breaker is a ship that breaks a sheet of ice from seawater. channels and rivers. They operate in sub-zero regions. You can say areas near Russia.
The forward part of these ships is made strong enough to pass through ice passages. Ice breaks by the weight of the sloping forward part of the ship. Some ice breakers are nuclear-propelled one.