A Guide to Vessel Classification
Ships may seem like something old fashioned, or even romantic, to those unfamiliar with logistics and shipping in general. The truth is, to this day ships are used extensively as part of global supply networks and most consumer goods arrive on our shores via this route. The advantages of using shipping as a means of moving products and materials over air freight are important to mention. While both are implicated in some degree of environmental damage, air freight is proven to be a much worse contender in terms of emissions. Planes may be able to move a lot of cargo, but the fuel requirements of doing so are enormous relative to the amount of goods that can be transported.
Shipping by sea, however, allows greater amounts of cargo to be transported over long distances for comparatively less fuel per tonne. The main constraint on products that are suitable for shipping by sea is how robust they are. For example, delicate fruits and vegetables with a short shelf life are better off being transported by air as a journey by sea would take too long and the produce would spoil. For goods such as furniture, raw materials, crude oil, and more robust produce, shipping makes perfect sense.
As such a wide range of goods are transported in this way, it’s important that ships are built to specifications which make them the ideal vessel for the job. The result is that there are several classes of vessel in use, many of which have at least a few subclasses, some of which are highly specialised. A shipping company will have an in-depth knowledge of their own capabilities, and will be able to assign the right type of cargo to the right kind of ship.
Tanker Vessels
If there is a need to move large quantities of fluids, then a tanker will always be the best option. They are characterised by having large holds, often split into individually sealing sections, which can carry huge amounts of fluid cargo. There are essentially three different types of tankers: oil tankers for carrying crude oil and petroleum products; gas takers for gas stored in a liquid state; and chemical tankers which carry liquid chemicals such as agricultural products.
As with all the vessel types mentioned in this article, tankers are made in a range of sizes and built to a range of specifications to suit the task at hand. Larger vessels with higher capacities are generally used for longer transoceanic journeys, while smaller vessels can be more efficient for shorter trips. The largest tanker to date is called the Seawise Giant at 1504 ft in length.
Container Ships
The best way to move a huge amount of cargo at once is to make effective use of the available space, and to design a ship with this specific use in mind. Container ships are a prime example of this in the shipping sector as they are made with a flat deck and also have several holds internally. The structure and shape of the deck is designed to accommodate standardised containers which are stacked and secured in place. This is the most efficient way to move cargo that has a longer shelf life and is commonly used to move consumer goods.
When a ship is built and kitted out for its assigned use, there are many components that must work together to ensure safe operation of the vessel. Surveys and asset classification are needed to ensure that potential risks involved with any stage of the shipping process are identified and mitigated. The largest container ship to date is the MSC Irina, at 1312 ft in length.
Roll-on / Roll-off Vessels
Known in the industry as a Ro-Ro, these shipping vessels are designed for a rather niche purpose. The cargo they are designed to carry is vehicles with wheels, such as cars, lorries and motorcycles. The cargo vehicles will either be driven onto the ship, or will be brought on board using wheeled platforms. This type of vessel is commonly used in the import of vehicles from overseas. Many cars are transported in this way, though other niche, industrial equipment is also transported via Ro-Ro.
Working at sea is not without risk, and there are many rules and regulations in place to protect people, vessels and cargo alike. SOLAS is a convention which aims to set a baseline for safety at sea and is internationally recognised. The largest Ro-Ro to date is the Salome, with a capacity of 43878 t DWT.