Bulk carrier
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A bulk carrier is ocean-going vessel used to transport bulk cargo items such as ore or food staples (rice, grain, etc.) and similar cargo. It can be recognized by the large box-like hatches on its deck, designed to slide outboard for loading. A bulk carrier could be either dry or wet. Most lakes are too small to accommodate bulk ships, but a large fleet of lake freighters has been plying the Great Lakes and St. Lawrence Seaway of North America for over a century.
Like other ships, bulk carriers have become bigger and more specialized in an effort to establish competitive and efficient cargo handling tools for specific industries and markets. But the economical movement of basic, unimproved commodities (which are the most common bulk cargoes) can only be accomplished with advanced, well-adapted technologies. In the past, moving bulk cargo was often inefficient and unwieldy.
In 1950 an exporter moving a cargo of grain from the US to Europe had two choices:
- Package the grain in 50 lb burlap sacks, muscle the sacks onto pallets and fly the pallets into the available cargo spaces of a breakbulk liner at the end of the ship’s crane. Reverse the process at the destination.
- Charter an entire tramp ship, have plywood grain bins, feeders and shifting boards built in the ship’s holds, and then load the loose grain aboard with a conveyor, pneumatic tube or grabs. At the destination the grain would be unloaded with similar equipment. Men with shovels would be needed in the hold to keep the cargo unloaded evenly.
Both methods were time consuming, labor intensive and inefficient.
Like the container ship, the modern bulk carrier had its roots in solving this problem of moving cargo on and off the ship efficiently. The idea originated with ship broker Ole Skaarup. In 1954 his small New York company repaired and chartered ships for bulk cargoes. He understood how inefficient the process was and imagined a new ship.
In a 1992 article in the American Bureau of Shipping’s Surveyor Magazine, Skaarup explained that to him “It seemed the most practical ship should have wide, clear cargo holds. Thus, it would require machinery aft, wide hatch openings to ease cargo handling and a hold configuration that could eliminate the need for shifting boards. To make the hatches acceptable as grain feeders, they would have to extend several feet above deck.”
But Skaarup also wanted a safe ship, that would be stable and seaworthy. When grain or similar bulk cargoes are loaded into a ship, they tend to pile in the middle of the hold and slope down to the bulkheads. This creates area for the cargo to shift, which can cause a ship at sea to become dangerously unstable. Skaarup thought he could eliminate this problem by building a ship with sloping ballast wing tanks at the top sides of the cargo hold. These tanks would fill the void left in a conventional hold and help stabilize the ship.
He took his idea to the Swedish shipping company, Nordstrom & Thulin. They were convinced, and with help from famed industrialist Marcus Wallenberg, Skaarup’s idea became a $2.5 million 19,000 DWT shipping experiment – the OS type design. The ship incorporated the sloped wing tanks, aft engine room and bridge, wide open cargo holds with smooth sides and sloping bulkheads. Conventional-thinking engineers at the Kockums Shipyard, where it was built, had fought with Skaarup over the lack of a centerline bulkhead and a dozen other important details, but he stood firm and the ship, called Cassiopeia, was an immediate success.
Thanks to the new features, Cassiopeia could be loaded at a cost savings of 50 cents per ton. This seemingly small figure allowed the ship to save its entire construction cost in 10 years, which is a monumental achievement in a ship designed to trade for at least 30 years. Soon other shipping companies wanted vessels like her. Today nearly 7,000 ships of the OS type have been built and they carry the vast majority of the world’s dry bulk cargoes.
As with other types of modern cargo ships, the bulk carrier has grown in size over the years. Today there are four types of bulk ships trading today (see chart below). Some of the commodities currently being moved in bulk ships include: iron ore; coal; grain; bauxite; phosphate rock; salt; cement; woodchips; and fertilizer.
[edit] Bulk carrier classes
- Handysize - 10,000 DWT - 40,000 DWT
- Handymax - 40,000 DWT - 60,000 DWT
- Panamax - 60,000 DWT - 100,000 DWT (DWT approx with 32.2m beam limitation due to width of Panama Canal locks)
- Capesize - 100,000 DWT and larger
(Source: Clarson Shipping Intelligence Network)
[edit] External links
- Bulk Carriers @ United Nations Atlas of the Oceans
- Super Cargo Ships book
- Google Maps Satellite Image of bulk carrier in Sunda Strait, Indonesia
