Descriptions of Different Vessel Types

Tankers - are designed to carry liquid cargoes (not just oil) although the carriage of crude oil has brought the tanker unwelcome attention and largely unjustified criticism.

Oil tankers come in two basic flavours, 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 1000 DWT 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 over 300,000 DWT

HANDYSIZE TANKER = 20,000 - 30,000 DWT
HANDYMAX TANKER = approx 35,000 DWT
AFRAMAX TANKER = between 75,000 - 125,000 DWT
SUEZMAX TANKER = between 125,000 - 180,000 DWT
V.L.C.C. TANKER = between 200,000 - 300,000 DWT
U.L.C.C. TANKER = over 300,000 DWT

It should be remembered that over 60% of the world's oil is transported by these tankers, and over 99% of that arrives safely without causing pollution. Indeed most oil pollution seen on beaches comes from the engine rooms of vessels (of all types) and not from the cargo tanks of tankers.
Those who would critise the marine Tanker industry would do well consider walking to work in the morning, to an unheated office, with no power for computers, lights or communications. We have a lot to thank the tanker industry for, so don't knock it when you depend on it so much !

Increased regulation on the construction, maintenance and crew competence of tankers, such as under OPA(90); the U.S. Oil Pollution Act of 1990 has required double hull tankers to be built (of questionable value, but of undoubted high cost!)and COFRs (Certificates of Financial Responsibility) which demonstrate that the operator has the financial backing, should a pollution event occur, to pay for the necessary clean-up.

In the "real world" (i.e outside of the USA) international agreements such as the CLC and Fund Conventions have provided clear levels of compensation that the oil industry are committed to provide to protect the environment. The MARPOL convention is a major force in ensuring a professional attitude is required of any vessel owner/operator carrying persistent oil as cargo.

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Refrigerated Cargo Carrying Vessels ("Reefers") are purpose built to carry fruit, meat and other food products across the sea in a fresh and clean manner.

Perhaps the most famous of these types of vessels are the banana carriers, trading between the Caribbean and Europe. They are sleak and fast, as their trade demands, with cooling (refrigeration) equipment to keep their cargoes fresh.

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The LNG carrier - (Liquified Natural Gas) and it's cousin the LPG carrier (Liquified Petroleum Gas) are products 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 state, LNG is a gas, so to transport it, it needs to be either pressurised into a liquified form, or kept as a liquid by reducing the temperature (simple application of Boyle's Law in physics !).

The shape of the 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 Carriers".

Obviously, the carriage of an explosive gas - kept at below freezing temperatures as an unstable liquid presents a very dangerous cargo, yet it is for this very fact, that LNG Carriers have about the best safety record of all maritime vessels. Only the best officers and crews are employed on these vessels, and the vessels themselves are maintained meticulously, and renewed frequently. There have been accidents involving LNG / LPG carriers, 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.

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The Ro-Ro ship - or more fully the Roll on - roll off vessel, comes 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 common sights wherever people want to travel over water with their vehicles. It is probably the only type of cargo vessel that most people have travelled 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 type, as these vessels are designed for the carriage of commercial vehicles where luxurious passenger accommodation is not a primary consideration. Considerable concerns have been expressed over the bow-door type of ro-ro design. The HERALD OF FREE ENTERPRISE was one such vessel, where a 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 only needs one centimetre of water over the whole car deck, for the vessel to become so unstable that it can overturn. 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. In the bitter waters of the Baltic Sea, the loss of life was terrible. Another earlier accident was that of the SEASPEED DORA which led many to call these vessels "ro-ro-ro" ships - Roll on, roll off....roll over !!!