Types of Ships

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Types of Ships

 

General Cargo Ships


Until ships started to be built to carry specific and specialized cargoes, all ships were simply general cargo ship, i.e. built to carry all types of cargoes e.g. drums of asphalt or caustic soda, cases of machinery, boxes or cartons containing ebearings or electronic goods, Radios, transistors, steel plates, paper rolls, cases of TEA, Bags of coffee seeds etc. General cargo ships hold were further compartmentalized by one or two deck under the main deck so that different type of cargo carried by these ships could be separately stored. The role of the general cargo vessel began to wane with the arrival of big size bulk carrier and tankers, but the decline of these general cargo vessel has accelerated since the advent of containerization (in the 1960).Not only are container ships able to carry greater volume of cargo in standardized cargo container, the time spent in loading and discharging has been dramatically reduced. Where a general cargo vessel may take 3-4 days to load or discharge, a container ship can achieve the same in a matter of hours, although generally small in size, are not suitable for container, or operating on coast and inland waters.

 

 

 

Bulk Carriers

 

Bulk carriers are the great work horses of the shipping world, carrying world, carrying raw dry cargoes such as coal, iron ore, grain, sulphur, scrap metal in their huge cavernous holds. All the time of writing this unit there is a huge demand for these vessels, driven by the extraordinary expansion of the Chinese economy. Recently imports of iron ore into China have boosted the earnings of bulk carrier owners.



The vessels in the top row are called geared bulk carriers, so called because they carry its own cargo cranes - very useful when visiting ports which do not have shore cargo handling equipment.



The vessels in the bottom row are gearless bulk carriers. These ships do not have its own cargo handling gear and hence dependent on shore side cargo loading and discharging equipment. They are normally much bigger in size than the geared bulk carriers.



Bulkers range from about 20,000 Deadweight tons (handy size) through the medium size (Panamax) vessels of up to 80,000 DWT, to the giant (cape size) vessels of over 200,000 DWT. Due to the role use that these vessels are put to, their life -expectancy is less than carrier accidents but the problem is now well under control.

 

 

 

Oil Tankers

 

Tankers are designed to carry liquid cargoes (not just oil). Oil tankers come in two basic types, the crude carrier, which carries crude oil, and the clean products tanker, which carries the refined products, such as petrol, gasoline, aviation fuel, kerosene and paraffin. Tankers range in all sizes, from the small bunkering tanker (used for refueling larger vessels of 1000DWT tons to the real giants: the VLCC (Very Large Crude Carrier) of between 2-300,000 DWT and the ULCC (Ultra Large Crude Carrier) of up to 500,000 DWT. 



Product carriers are smaller in size but product carriers of over 100.000 DWT are already operational.



It should be remembered that over 60% of the world oil is transported by these tankers and over 99% of that arrives safely without causing pollution. Most oil pollution seen on beaches comes from the engine rooms of vessels (of all types) and not necessarily from the cargo tanks of tankers.



HANDYSIZE TANKER = 20,000 30,000 DWT
HANDYMAX TANKER = approx, 45,000 DWT
PANAMAX TANKER = approx. 79,000 DWT
AFRAMAX TANKER = between 79,000 120,000 DWT
SUEZMAX TANKER = between 120.000 180,000 DWT
V.L.C.C. TANKER = between 200,000 300,000 DWT
U.L.C.C. TANKER = over 300,000 DWTS

 

 

 

Container


The container ship or Boxship is the great success story of the last 40 years. General cargo was historically carried in dry cargo vessels, without any particular specialization. Cargo loading and unloading was always a low laborious task, due to the varying shapes, sizes, weights and fragility of the numerous cargoes being carried on any one vessel. The idea of standardizing the carrying box, or container at 20 feet long was a breakthrough that allowed for vessels to be designed to lift, stack and store these specific shapes.



In 1937, a New Jersey truck driver named Malcolm McLean, sitting in his truck at the New Jersey Docks suddenly had a novel idea. Instead of large numbers of stevedores having to manually load cargo, why not create a standard shaped box into which goods can be handled in a standard way. His idea took 20years before the first container transit was undertaken (with his own money, because no ship owners would listen to his idea). In 1969 Malcolm McLean retired as a multi - millionaire!!!



So, from a "back of the fag -packet" idea was born the container ship. Initially, these were small vessels of up to 10,000DWT, carrying no more than a few hundred TEU (Twenty foot Equivalent Units), but have grown in size as the success and economies of these vessels have become more obvious. Today's container ships are being built to take 9,500 T.E.U with plan afoot to build 10-12,000 T.E.U. ships.



As well as the Twenty foot container, many goods needs larger boxes, so there is a larger standard sized container, the FEU (Forty Foot Equivalent unit). On board a modern containership, the complex method of loading the TEU and FEU in an order that will facilitate offloading at the other end is now largely computerized. These vessels are built for speed, and can reach upwards of 28 knots, moving cargoes around the globe.



Through transport or inter- modal transport means that these containers can be offloaded from a ship, and rapidly loaded onto trains or onto container lorries for onward transport to the place of delivery.

 

 

 

Pure Car Carrier

Pure Car Carrier is a ship designed to carry cars in different compartments of the ship Some ships are designed to carry cars in some compartments and trucks in other compartments. They are now known as Pure Car and Truck Carriers (PCTCs).

 

 

 

Chemical Tanker


They range in size and construction but one thing is common for them all. We are very much dependent upon the product they carry every day. Find out how we get ourselves toothpaste, cooking oil, plastic, paint, perfume, wine and spirits.



A Chemical tanker is like an oil tanker but with more number of and smaller tanks; some vessels have up to 56 tanks. The tanks are specially equipped to handle many types of cargo. Here are some example of the cargo they carry and the problems they face:

 

 

 

Ro-Ro Ships

 

The Ro- Ro, or more fully the Roll on roll off vessel, come in a number of shapes and sizes, but generally in two types; the passenger ro- ro and the cargo ro-ro.



Passenger ro-ros have become a common sight wherever people want to travel over water with their vehicles. It is probably the only types of cargo vessel that most people have traveled on. Usually a rear door (but sometimes a bow door) allows for vehicles to be driven on and off, stored on the car deck below the passenger accommodation areas.



The cargo ro-ro- is less 'plush' than the passenger types, as these vessels are designed for the carriage of commercial vehicles where luxurious passenger accommodation is not a primary consideration. Considerable concern has been expressed over the bow- door type of ro-ro design. The HERALD OF FREE ENTERPRISE was one such vessel, where the practice of sailing before the bow door was fully closed had been allowed to develop. Tragically, on leaving Zeebrugge, the folly of this practice led to the disaster that claimed nearly 200 lives. If water is allowed to enter the car deck, the stability of the whole vessel can be rapidly affected. It is estimated that it takes only small amount of water over the whole car deck, for the vessel to become very unstable.



The ESTONIA was another such vessel where, in a storm, the shield over the bow door was ripped off. Once water penetrated the car deck the vessel began to turn over and sink.

 

 

 

Liquefied Petroleum Gas/Liquefied Natural Gas Carrier


Natural gas has 600 times the volume of LNG.
The LNG carrier (.Liquefied Natural Gas) and its cousin the LPG 



(Liquefied Petroleum Gas) carrier is a product of the late twentieth century. LNG and LPG are the preferred fuel types of certain countries for their industrial power needs. Japan is one such country, and so LNG needs to be transported to Japan but is not the easiest of cargoes to be transported. In its natural states, LNG is a gas so to transported it, it needs to be either pressurized into a liquid by reducing the temperature (simple application of Boy le's Law in physics!)



The shape of LNG Carrier is quite unmistakable, with the shape of the moss tanks (which are like enormous spherical thermos flasks!) visible along the deck, which has led to the nickname of 'Dinosaur Eggs Carrier'



Obviously, the carriage of an explosive gas - kept at below freezing temperatures as an unstable liquid present a very dangerous cargo, yet it is for this very fact, that LNG Carrier have about the best safety record of all maritime vessels. Only the best officers meticulously handled it and renewed frequently. There have been accidents involving LNG/LPG carrier, but where such events have occurred, the crews or salvors have so far, successfully managed to vent off the cargo into the atmosphere, thus rendering the lethal cargo harmless. Propane, butane - mixtures derived from oil refining or natural gas fractionation. For convenience of transportation, these gases are liquefied through pressurization.

 

 

 

Reefer Ships

 

In the year 1880 there was an important breakthrough, when 400 frozen carcases were carried safely by sea using a simple ship refrigeration plant to keep them hard- frozen on a two month voyage from Australia to the United Kingdom. This had huge implications, both for the consumers, who were able to source their produce from across the world, and seagoing refrigeration to develop their main export markets.



Since these beginnings, the 'reefer' trades have hugely expanded to handle all forms of fresh food, with substantial quantities of meat, fish dairy produce bananas, citrus and other fruits criss-crossing the world in specialized refrigerated ships. Cargoes are carried either frozen or chilled increasingly at controlled temperatures that can be varied to ensure that the produce reaches the market at its optimum condition often ripening on the voyage.



Reefer ships are effectively large refrigerators, heavily insulated with modern glass fibre or similarly efficient insulation, shuttered with bright metal that prevents taint and is easy to clean. They are ships that tend to be divided into many more spaces than conventional dry cargo ships, with several tweendecks and even locker spaces, so that different commodities can be separated and carried, if required, at different temperatures. Below decks a reefer ship resembles a large modern warehouse, and cargo is usually carried and handled in palletized form, moved about on conveyors or by electric fork lift trucks. Some cargo, such as bananas, is often handled through doors in the ship's side. Cleanliness and the maintenance of optimum temperatures are the prerequisites.



Modern refrigeration plant works with environmentally kind refrigerants such as R-22 and is largely automated. Air is cooled in a brine cooling system by screw compressors and cold air ducted to the cargo spaces. They can usually carry refrigerated containers on deck. A large reefer ship might typically offer about 500,000 cubic feet of refrigerated space, and be capable of loading 250 containers on deck.



Reefers operate seasonally, but because there is a heavy trade between the hemispheres, sailors can hopefully find employment. In recent years, too much new construction has led to over tonnage. The specialist refer ships, which are generally operated as tramps rather than in the liner trades, are seeing their cargo base increasingly attacked by large container ship, which are offering more slots for refrigerated boxes. Indeed the largest reefer capacity in a single ship is not on a 'traditional' reefer, but abroad a large container ship.



Reefer containers are either fitted with their individual refrigeration units which can be plugged in to the ship's electrical power source, usually, with apertures for ducted cold air. With the increase in exotic food cargoes, special containers have been devised that can tailor the internal atmosphere to the precise requirement of the foodstuffs.

 

 

 

Heavy Lift Ships

 

Heavy loads were first carried on conventional cargo ship, either handled by a port floating crane, or by the ship's "jumbo" derrick which would make short work of loads like boilers or railway engines, up to about 100 tonnes. But manufacturers, who liked to ship their product in one piece, rather than expensively assembling them on -site, were constantly building heavier and heavier items, and a small specialist sector of the shipping industry has developed to carry these very heavy and awkward loads.



There is no sign that there is any diminution in the quantities of heavy lifts offering- quite the reverse as planners try and get this sort of inconvenient freight off the roads.

 

 

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