A Shipper’s Guide to Cargo Vessel Types and Sizes
A Little History of the Container Vessel
If you have read our article on container types and sizes, then you know that the first container vessel was actually a modified tanker vessel (more below), the Ideal X, which journeyed from New Ark, New Jersey to Houston, Texas on April 26, 1955. It carried just under 60 containers - 35-foot trailers with removed chassis.
Today, the largest containerships can carry well over 20,000 twenty-foot equivalent units (TEUs). A 20-foot container measures 1 TEU, a 40-foot container measures 2 TEU, meaning that large containerships carry thousands of containers. The technical progress and size growth that containerships have experienced is astonishing.
The ability to load more cargo onto one single ship increases efficiency and thus reduces carbon emissions. The popularity of the containership is due to the multi-modal quality of the standard ISO container, which can be loaded onto trucks, barges or transported by rail.
Modern containerships have their holds (the space where the cargo is stored) divided into bays with cell guides (they are also referred to as cellular ships) in which the crane operators can snugly fit the 20- and 40-foot containers. This enables efficient, speedy loading. Every deep-sea container’s hold is capped with a hatch cover, which benefits both the stability and safety of the ship.
Container vessels vary by many sizes and design elements in order to host special equipment and commodities such as reefer containers or hazardous cargo, but it is worth mentioning that some may be equipped with cranes. Such ships are referred to as geared (as opposed to gearless ships, which do not feature a crane) or as lift-on/lift-off (LoLo). While this means that these vessels can visit ports that do not offer cranes, those are becoming rarer – and so are LoLo containerships.
The way the supra structure of the ports developed enables fast and easy loading of the containerships today. Tide, water depth and size of port basins, availability of pilots & tug boats, size & reach of (gentry) cranes, availability of van carriers or reach stackers, hinterland connectivity (road, rail & waterways), customs facilities – they all work in conjunction to make container shipping happen.
Planning container loading – a life-size game of Tetris
The correct arrangement of the containers on the ship is called the stowage plan. A container vessel typically calls at several port during its journey: each time the ship berths at port, a certain number of containers will be loaded or unloaded. Correct container arrangement is key to port handing efficiency – imagine having to unload a container and realize that it is located at the bottom of the vessel bay, under a stack of other containers.
The load plan is designed by vessel planners based on the booking and shipping instructions (including Verified Gross Mass), and takes load and discharge ports, equipment types, commodities (e.g. hazardous material) and weight into consideration. The chief officer monitors the discharge and loading process and intervenes onboard the vessel if necessary.
An efficient stowage plan contributes to the safety of life at sea. Uneven weight distribution across the vessel can have dramatic consequences, as the vessel can bend. Stacking heavier cargo on top of a container stack can cause it to collapse and threaten the life of the sailors.
Refer to our Verified Gross Mass and Safety of Life at Sea (SoLaS) resources, to make sure your cargo is transported safely.
All containerships are mandatorily equipped with an Automatic Identification System (AIS). This device shares the GPS coordinates of the ship, preventing collisions between vessels and providing visibility in difficult weather condition. It also enables track and trace services such as myDHLi.
Other Key Cargo Vessel Types
Cargo ships vessels are classified on the basis of the type of cargo that they carry, their packaging (or lack thereof) or the way it is meant be loaded onto the vessel.
Containership sizes are often ranked by their TEU capacity, ranging from a few hundred TEUs for feeder vessels “Feeder and Barges” to 18,000 TEUs or more for Ultra-Large Container Vessels (UCLVs) “Panamax, and Other Straits”.
Size matters because the ability to load more containers onto the ship is key to efficiency, but that is not all. Being able to operate in certain port terminals or being able to navigate through the Panama or Suez canals are just as defining a factor for efficient seaborne cargo transportation.
Feeders and Barges
Feeder vessels have a capacity ranging from 300 to a maximum of 1,000 TEUs. They can operate in smaller ports that large sized container vessels cannot berth at. Their will feed cargo to these large ships – referred to as mother vessels – in deep-sea hubs and transport cargo from the large vessels back to shore. Strong coordination saves time and enables the larger vessels to cover a reduced number of ports. Feeder vessels can be geared or gearless.
While they do not qualify as feeder vessels, container-carrying barges are used to transport containerized cargo through inland waterways that bigger vessels can also not enter. In this type of intermodal transport, the barge can carry up to 300 TEUs in Europe, while in North America they can range 450-900 TEUs.
Similarly, vessels operating on the Saint Lawrence Strait are limited in capacity due to draught limitation, but they are not feeders. They are specialized ships that require an “ice-class“, which enables them to operate throughout the year – even through a massive ice drift.
Panamax, and Other Straits
Panamax and Neo-Panamax ships can be routed through the Panama Canal in Central America, as they are nearly as wide as its locks allow for. Neo-Panamax ships are wider (up to 49 meters), longer and deeper (a ship’s depth is also referred to as draft) than Panamax, as they fit the canal’s new dimensions since larger locks have been constructed. This enables Neo-Panamax ships to carry up to 14,000 TEUs, while Panamax vessels can only carry around 5,000.
Some transportation routes bypass the Panama Canal, thus imposing less restrictions on the design of the ships using it. These larger ships are called Post-Panamax. They gave way to other very large and now Ultra-Large Container Vessels (ULCV), carrying 18,000 TEUs and more. Suezmax ships can be routed through the Suez Canal– most often, this size covers tanker vessels. Their beam (the ship’s width) measures up to 50 meters, and can be even wider if the ship has a reduced draft.
Even larger with an even greater cargo capacity (20,000 TEUs and up), some ships are referred to as Post-Suezmax, because their dimensions exceed what the strait or canal can allow for.
Only a few ports across the globe, such as Rotterdam or Singapore, have the infrastructure to handle the ultra-large container vessels. However, even a Panamax ship will be unable to call at certain ports if it is fully loaded. The ports that very large or fully-laden ships can berth at are called deepwater ports, As explored above, the feeder vessels will ensure the good connection between the terminals.