Merchant Ships - Specialized Cargo Ships

Most solid cargoes carried across the oceans are handled by either containers or bulk carriers, but some cargoes have requirements that can't be satisfied by either kind of ship. Much like unusual liquid cargoes, these are transported by specialized ships, designed for the purpose.

Loading frozen meat aboard reefer Clan McDougall

In the second half of the 19th century, the British faced a problem. The rapidly-growing population had made it increasingly difficult to produce enough food in the British isles. Grain imports could make up for some of this, but other products, most notably meat, required a great deal of land and couldn't be practically shipped in from overseas, where Argentina and Australia produced great surpluses. Mechanical refrigeration could change that, but while work on freezing carcasses began as early as 1861, it would be twenty years before a refrigeration plant was created that could be fitted to a ship and used to reliably and economically carry meat halfway around the world.

Dunedin

Reefers, as the refrigerated ships became known, were usually designed for high speed, limiting deterioration of the cargo and reducing the chances for things to go wrong. But not all of the ships fitted with insulated cargo holds and cooling plants were of this type. A few early reefers, most notably Dunedin, were sailing clippers. By WWI, a typical voyage from Australia or New Zealand was 30-40 days, requiring the meat to be frozen, but shorter runs, from the Americas, allowed the beef to be kept chilled instead, improving quality. Eventually, new techniques allowed Australian beef to be handled in the same manner.

San Benito and Limon of United Fruit's Great White Fleet

Nor was meat the only product to benefit from refrigeration. Starting around 1890, tropical fruits began to see significant maritime trade, first bananas, nearly unknown in Europe before then. This trade was dominated by the United Fruit Company, whose "Great White Fleet"¹ of fast reefers carried small numbers of passengers as well as fruit. These ships were set up very differently from meat carriers, with holds designed to ensure adequate ventilation, and most reefers were focused entirely on a single cargo on a specific route.

Dole California, a containerized reefer ship

The decades after WWII saw several major changes in the reefer fleet. One was the multi-temperature ship, which could handle multiple different type of cargo, greatly increasing flexibility for shipowners. Pallets were also introduced, reducing times required to load and unload ships. But these improved reefers faced competition from containerization. Only a few years after the shipping container entered use, reefer containers began to be built, usually powered by electricity from the host ship. These offered all of the handling and cost benefits of containers, and most container ships were built to accommodate some number of these containers. A few ships use a different cooling system, with centrally-supplied air. Despite this, the dedicated reefer has survived, and international trade in cooled goods remains robust.

Livestock carrier Al Shuwaikh leaves Freemantle

There is also a trade in live animals, which require their own specialized ships. Before refrigeration, this was the only way to transport meat across oceans, but it was not particularly efficient, and mortality rates were high. There was also extensive trade in horses, usually in support of military operations. The largest customers were Indian rulers, whose territory was ill-suited to raising horses, and who bought thousands every year to make up for losses. Trade in live animals began to revive after WWII, when the "seagoing cowboys" shipped hundreds of thousands of farm animals to war-ravaged countries to help reestablish agricultural herds. They used converted war-surplus cargo ships, but as long-term markets for livestock developed, particularly in the Middle East to satisfy Muslim religious requirements,² specialized ships were built or converted. These have special systems to make sure the animals are kept fed and watered, and their waste is disposed of.

Mine countermeasures ship Gladiator aboard dockship Condock V

One of the most prominent types of specialized cargo ship is the heavy-lift vessel. While ships fitted with heavy booms or cranes for cargoes like locomotives, larger boats and bridge sections date back to the early part of the 20th century, there were several major developments in the last quarter of the century. First were dockships, essentially civilian versions of the Landing Ship Dock which could ballast down to float large cargoes in or out. Most also had heavy gantry cranes and a roll on-roll off capability, allowing them to handle cargoes of 500 tons or more.

USS Cole is brought home aboard heavy lift ship Blue Marlin

But the most prominent of these types were the semi-submersible heavy lift ships. These had a broad, open deck with minimal superstructure, and were fitted to ballast down so that heavy cargo could be floated onboard. They were intended primarily to replace towing of heavy offshore equipment like drilling rigs, allowing greater speed and safety. But they have found other uses, most dramatically carrying damaged warships home for repairs. There are only a handful of these vessels, but they play an important part in the global maritime industry.

A semi-submersible log carrier barge

Some semi-submersible vessels are used for other purposes, most notably a handful of log carriers operating in British Columbia. These ships have a broad, low cargo deck in the middle, loaded high with logs by onboard cranes in the bays and rivers along the coast. When they arrive at the mills, they are ballasted down and tipped, so that the logs slide off. Nor are they the only vessels in the forest product trade. These products, not just logs but also wood chips and lumber, can be loaded in bulk carriers or containers, but their low density means that they don't fit particularly well with ships designed for high-density cargoes like ore and coal. As a result, specialized ships are used, with larger cargo holds and cranes to speed loading and unloading. Even more specialized are the newsprint carriers, a small fleet operating primarily around Europe that are equipped with dehumidifiers and heaters to ensure the quality of their cargo.

Nuclear fuel carrier Pacific Grebe

Many nuclear plants are located on the coast, and a small fleet of vessels exists solely to service them, transporting nuclear fuel in and nuclear waste out. These ships tend to be ro-ros, built to the highest standards and with extensive shielding for the cargo. A trio of nuclear fuel/waste carriers, operated under the British flag, are the only armed merchant vessels I am aware of currently in service. Until the last few decades, the seas were seen as a good place for disposal of hazardous waste, and a number of vessels were built specially for this task. Many had clamshell doors in the bottom to make disposal easier, but stricter environmental regulations have seen this category of merchant ship disappear.

Car carrier Grande Roma

A much larger fleet are the car carriers. Cars are a low-density cargo,³ and most ships would have insufficient volume to carry them economically. The resulting vessels are extremely boxy, with intricate mazes of decks and ramps to allow cars and trucks to be driven off quickly and efficiently. In recent years, car carriers have branched out somewhat into medium-heavy cargo up to ~150 tons, with ships being fitted with suspended decks that can be lifted to increase the available height for things like locomotives and heavy turbines, or just to accommodate heavy trucks in place of cars. The largest vessels can transport over 8,000 cars at a time, which are delivered to the piers over side ramps.

Car carrier Pisces Leader with her ramp down

Transporting cargo across the sea is the main purpose of merchant shipping, resulting in an enormous diversity of vessels, from the extremely obvious, such as passenger and container ships, to the obscure, such as the orange juice tankers and log carriers. But not every non-military vessel is merely concerned with transporting cargo, and we'll begin to look at the world of service vessels next time.