Everything about Bulk Carrier totally explained
A
bulk carrier, bulk freighter, or
bulker is a
merchant ship specially designed to transport unpackaged
bulk cargo, such as grains, coal, ore, and cement in its
cargo holds. Since the first specialized bulk carrier was built in 1852, economic forces have fueled the development of these ships, causing them to grow in size and sophistication. Today's bulkers are specially designed to maximize capacity, safety, efficiency, and to be able to withstand the rigors of their work.
Today, bulkers make up 40% of the world's
merchant fleets and range in size from single-hold mini-bulkers to mammoth ore ships able to carry 365,000
metric tons of deadweight (DWT). A number of specialized designs exist: some can unload their own cargo, some depend on port facilities for unloading, and some even package the cargo as it's loaded. Over half of all bulkers have
Greek,
Japanese, or
Chinese owners and more than a quarter are registered in
Panama. Japan is the largest single builder of bulkers, and 82% of these ships were built in
Asia.
A bulk carrier's crew participates in the loading and unloading of cargo, navigating the ship, and keeping its machinery and equipment properly maintained. Loading and unloading the cargo is difficult, dangerous, and can take up to 120 hours on larger ships. Crews can range in size from three people on the smallest ships to over 30 on the largest.
Bulk cargo can be very dense, corrosive, or abrasive, and presents safety problems:
cargo shifting, spontaneous combustion, and cargo saturation can all doom a ship. The use of ships that are old and have corrosion problems has been linked to a spate of bulker sinkings in the 1990s, as have the bulker's large hatchways, important for efficient cargo handling. New international regulations have since been introduced to improve ship design and inspection, and to streamline the process of abandoning ship.
Definition
There are various ways to define the term bulk carrier. As of 1999, the
International Convention for the Safety of Life at Sea defines a bulk carrier as "a ship constructed with a single deck, top side tanks and hopper side tanks in cargo spaces and intended to primarily carry dry cargo in bulk; an ore carrier; or a combination carrier." However, most
classification societies use a broader definition where a bulker is any ship that carries dry unpackaged goods. The terms "VLOC," "VLBC," "ULOC," and "ULBC" for very large and ultra large ore and bulk carriers were adapted from the
supertanker designations very large crude carrier and ultra large crude carrier.
History
Before specialized bulk carriers existed, shippers had two methods to move bulk goods by ship. In the first method,
longshoremen loaded the cargo into sacks, stacked the sacks onto
pallets, and put the pallets into the cargo hold with a
crane. These methods were slow and
labor intensive. As with the
container ship, the problem of efficient loading and unloading has driven the evolution of the bulk carrier.
Specialized bulk carriers began to appear as
steam-powered ships became more popular. The first steam ship recognized as a bulk carrier was the
British coal carrier SS
John Bowes in 1852. She featured a metal
hull, a
steam engine, and a
ballasting system which used seawater instead of sandbags.—and most of this trade was
coastal. However, two defining characteristics of bulkers were already emerging: the
double bottom, which was adopted in 1890,
!Ships
!Traffic
!New
price
!Used
price
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| valign="top" |
Handysize
| valign="top" | 10,000 to 35,000
| valign="top" | 34%
| rowspan="2" valign="center" | 18%
| rowspan="2" valign="center" | $28M
| rowspan="2" valign="center" | $28M
|- valign="top"
|
Handymax
| 35,000 to 55,000
| 37%
|- valign="top"
|
Panamax
| 60,000 to 80,000
| 19%
| 20%
| $35M
| $34M
|- valign="top"
|
Capesize
| 80,000 and over
| 10%
| 62%
| $59M
| $68.4M
|}
Bulkers are segregated into six major size categories: small,
handysize,
handymax,
panamax,
capesize, and very large. Very large bulk and ore carriers fall into the capesize category but are often considered separately.
Other categories occur in
regional trade, such as Kamsarmax, with a maximum length of 229 meters, the maximum length that can load in the port of
Kamsarin the
Republic of Guinea. Other terms such as Setouchmax, Dunkirkmax, and Newcastlemax also appear in regional trade. These two segments represent 71% of all bulk carriers over and also have the highest rate of growth. This is partly due to new regulations coming into effect which put greater constraints on the building of larger vessels.
Capesize ships are too large to traverse the
Suez or Panama canals and must round the
Cape of Good Hope or
Cape Horn to travel between oceans. Capesize bulkers are
specialized: 93% of their cargo is iron ore and coal. covered by prominent hatch covers. They have
cranes which allow them to discharge cargo in
ports without shore-based equipment. This gives geared bulkers flexibility in the cargoes they can carry and the routes they can travel. (Photo: A typical geared handysize bulk carrier.)
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Combined carriers are designed to transport both liquid and dry bulk cargoes. If both are carried simultaneously, they're segregated in separate holds and tanks. Combined carriers require special design and are expensive. They were prevalent in the 1970s, but their numbers have dwindled since 1990. (Photo: The oil pipeline and dry bulk hold aboard the
Maya.)
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Gearless carriers are bulkers without cranes or conveyors. These ships depend on the shore-based equipment of the ports they visit for loading and unloading. Due to their large size, they can only dock at the largest and most advanced ports. The use of gearless bulkers avoids the costs of installing, operating, and maintaining cranes. (Photo:
Berge Athen, a 225,000 ton gearless bulker.)
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Self-dischargers are bulkers with
conveyor belts which allow them to discharge their cargo quickly and efficiently. (Photo: The
John B. Aird a self-discharger on the Great Lakes.)
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Lakers are the bulkers prominent on the
Great Lakes, often identifiable by having a forward
house which helps in transiting
locks. Operating in fresh water, these ships suffer much less
corrosion damage and have a much longer lifespan than saltwater ships. As of 2005, there were 98 lakers of or over. (Photo:
Edmund Fitzgerald, a Great Lakes bulker.)
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BIBO or
"Bulk In, Bags Out" bulkers are equipped to bag cargo as it's loaded. The
CHL Innovator, shown in the photo, is a BIBO bulker. In one hour, this ship can load and package 300 tons of bulk sugar into 50 kg sacks.
|}
Fleet characteristics
The world's bulk transport has reached immense proportions: in 2005, 1.7 billion metric tons of coal, iron ore, grain, bauxite, and phosphate was transported by ship. Today, the world's bulker fleet includes 6,225 ships of over 10,000 DWT, and represent 40% of all ships in terms of tonnage and 39.4% in terms of vessels. Including smaller ships, bulkers have a total combined capacity of almost 346 million DWT. Combined carriers are a very small portion of the fleet, representing less than 3% of this capacity. All of the 98 bulkers registered in the Great Lakes trade are over 20 years old.
]]
Flag states
As of 2005, the
United States Maritime Administration counted 6,225 bulkers of or greater worldwide. More bulkers are registered in
Panama, with 1,703 ships, than any four other
flag states combined. These three nations account for over 53% of the world's fleet.
The Fednav Group in
Canada operates a fleet of over 80 bulkers, including two designed to work in Arctic ice.
Croatia's
Atlantska Plovidba d.d. has a fleet of 14 bulkers. The
H. Vogemann Group in
Hamburg, Germany operates a fleet of 19 bulkers.
Portline in
Portugal, owns 10 bulkers.
Dampskibsselskabet Torm in
Denmark and Elcano in
Spain also own notable bulker fleets. Other companies specialize in mini-bulker operations: England's
Stephenson Clarke Shipping Limited owns a fleet of eight mini-bulkers and five small Handysize bulkers, and
Cornships Management and Agency Inc. in
Turkey owns a fleet of seven mini-bulkers.
Builders
Asian companies dominate the construction of bulk carriers. Of the world's 6,225 bulkers, almost 62% were built in Japan by shipyards such as
Oshima Shipbuilding and
Sanoyas Hishino Meisho.
Ship breaking
Generally, ships are removed from the fleet go through a process known as
ship breaking or scrapping.
Ship-owners and buyers negotiate scrap prices based on factors such as the ship's empty weight (called light ton displacement or LDT) and prices in the scrap metal market. In 1998, almost 700 ships were scrapped in places like
Alang, India and
Chittagong, Bangladesh.
During the 1990s, bulkers were involved in an alarming number of
shipwrecks. This led ship-owners to commission a study seeking to explain the effect of various factors on the crew's effectiveness and competence. The study showed that crew performance aboard bulk carriers was the lowest of all groups studied.
Deck officers and
stevedores oversee the operations. Still, from time to time, loading errors are made that cause a ship to capsize or break in half at the pier.
The loading method used depends on both the cargo and the equipment available on the ship and on the dock. In the least advanced ports, cargo can be loaded with shovels or bags poured from the hatch cover. This system is being replaced with faster, less labor-intensive methods.
Double-articulation cranes, which can load at a rate of 1,000 tons per hour, represent a widely used method, The immense size of cargo holds and the tendency of cargoes to be physically irritating add to the difficulty of cleaning the holds. When the holds are clean, the process of loading begins.
It is crucial to keep the cargo level during loading in order to maintain stability. As the hold is filled, machines such as
excavators and
bulldozers are often used to keep the cargo in check. Leveling is particularly important when the hold is only partly full, since cargo is more likely to shift. Extra precautions are taken, such as adding longitudinal divisions and securing wood atop the cargo.
Hatches
A hatch or hatchway is the opening at the top of a
cargo hold. The mechanical devices which allow hatches to be opened and closed are called hatch covers. In general, hatch covers are between 45% and 60% of the ship's breadth, or beam, and 57% to 67% of the length of the holds. Often, hatch areas are reinforced by locally increasing the scantlings or by adding structural members called stiffeners. Both of these options have the undesired effect of adding weight to the ship.
As recently as the 1950s, hatches had wooden covers that would be broken apart and rebuilt by hand, rather than opened and closed. Newer vessels have hydraulic-operated metal hatch covers that can often be operated by one person. Hatch covers can sliding forwards, backwards, or to the side, lift up or fold up. It is essential that the hatch covers be watertight: unsealed hatches lead to accidental cargo hold flooding, which has caused many bulkers to sink. The Load Line Conference of 1966 imposed a requirement that hatch covers be able to withstand load of 1.74 tons/m² due to sea water, and a minimum scantling of 6 mm for the tops of the hatch covers. The
International Association of Classification Societies then increased this strength standard by creating its
Unified Requirement S21 in 1998. This standard requires that the pressure due to sea water be calculated as a function of freeboard and speed, especially for hatch covers located on the forward portion of the ship. Some manufacturers have preferred high-tensile steel recently in order to reduce the tare weight. However, the use of high-tensile steel for longitudinal and transverse reinforcements can reduce the hull's rigidity and resistance to corrosion.
Double hulls have become popular in the past ten years. One of the advantages of the double hull is to make room to place all the structural elements in the sides, removing them from the
holds. This increases the volume of the holds, and simplifies their structure which helps in loading, unloading, and cleaning. Double sides also improve a ship's capacity for ballasting, which is useful when carrying light goods: the ship may have to increase its draft for stability or seakeeping reasons, which is done by adding ballast water.
A recent design, called Hy-Con, seeks to combine the strengths of single-hull and double-hull construction. Short for Hybrid Configuration, this design doubles the forward-most and rear-most holds and leaves the others single-hulled. This approach increases the ship's solidity at key points, while reducing the overall tare weight.
Since the adoption of double hull has been more of an economic than a purely architectural decision, some argue that double-sided ships receive less comprehensive surveys and suffer more from hidden corrosion. In spite of opposition, double hulls became a requirement for Panamax and Capesize vessels in 2005.
Freighters are in continual danger of "breaking their back" and thus longitudinal strength is a primary architectural concern. A
naval architect uses the correlation between longitudinal strength and a set of hull thicknesses called
scantlings to manage problems of longitudinal strength and stresses. A ship's hull is comprised of individual parts called
members. The set of dimensions of these members is called the ship's scantlings.
Safety
The 1980s and 1990s were a very unsafe time for bulk carriers. Many bulkers sank during this time, 99 were lost between 1990 and 1997 alone. These regulations required the upper ballast tanks designed in a manner to prevent shifting. They also required cargoes to be leveled, or trimmed, using excavators in the holds. The practice of trimming reduces the amount of the cargo's surface area in contact with air which has a useful side-effect: reducing the chances of spontaneous combustion in cargoes such as coal, iron, and metal shavings. When very fine concretes and aggregates mix with water, the mud created at the bottom of the hold shifts easily and can produce a
free surface effect. This level of loss focused attention on the safety aspects of bulk carriers, and a great deal was learned. The
American Bureau of Shipping concluded that the losses were "directly traceable to failure of the cargo hold structure" and
Lloyd's Register of Shipping added that the hull sides couldn't withstand "the combination of local corrosion, fatigue cracking and operational damage."
- Sea water enters the forward hatch, due to a large wave, a poor seal, corrosion, etc.
- Advanced methods of loading were not foreseen when the ships were designed. These unexpected shocks, over time, can damage the hull's structural integrity.
- Recent use of high-tensile steel in construction has negative side-effects. This material is prone to corrosion and can develop metal fatigue in choppy seas.
- According to Lloyd's Register, a principal cause was the attitude of ship-owners, who sent ships with known problems to sea.
The new rules adopted in the 1997 annexes to the
SOLAS convention focused on problems such as reinforcing bulkheads and the longitudinal frame, more stringent inspections (with a particular focus on corrosion) and routine in-port inspections.
Crew safety
Since December 2004, Panamax and Capesize bulkers have been required to carry free-fall
lifeboats located on the stern, behind the house. One argument against the use of free-fall lifeboats is that the evacuees require "some degree of physical mobility, even fitness" to enter and launch the boat. Also, injuries have occurred during launches, for example, in the case of incorrectly secured safety belts.
In December 2002, Chapter XII of the SOLAS convention was amended to require the installation of high-level water alarms and monitoring systems on all bulkers. This safety measure quickly alerts watch standers on the bridge and in the engine room in case of flooding in the holds.
In cases of catastrophic flooding, these detectors could speed the process of abandoning ship.
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