Product Code Database
A bulk carrier or bulker is a merchant ship specially designed to transport unpackaged bulk cargo—such as Grain trade, coal, ore, , steel coils, or cement—in its .
Since the first specialized bulk carrier was built in 1852, economic forces have led to increased size and sophistication of these ships. Today's bulk carriers are specially designed to maximize capacity, safety, efficiency, and durability.
Today, bulk carriers make up 21 percent of the world's merchant fleets, and they range in size from single-hold mini-bulk carriers to mammoth ore ships able to carry 400,000 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 is loaded. Over half of all bulk carriers have Greek, Japanese, or Chinese owners, and more than a quarter are registered in Panama. South Korea is the largest single builder of bulk carriers, and 82 percent of these ships were built in Asia.
On bulk carriers, crews are involved in operation, management, and maintenance of the vessel, taking care of safety, navigation, maintenance, and cargo care, in accordance with international maritime legislation. Crews can range in size from three people on the smallest ships to over 30 on the largest.
Cargo loading operations vary in complexity, and loading and discharging of cargo can take several days. Bulk carriers can be gearless (dependent upon terminal equipment) or geared (having cranes integral to the vessel).
Bulk cargo can be very dense, corrosive, or abrasive. This can present safety problems that can threaten a ship: problems such as cargo shifting, spontaneous combustion, and cargo saturation. The use of old ships that have corrosion problems—as well as the bulk carriers' large hatchways—have been linked to a spate of bulk carrier sinkings in the 1990s. These large hatchways, important for efficient cargo handling, can allow the entry of large volumes of water in storms and accelerate sinking once a vessel has Ship stability or heeled. New international regulations have since been introduced to improve ship design and inspection and to streamline the process for crews to abandon ship.
A number of abbreviations are used to describe bulk carriers. "OBO" describes a bulk carrier that carries a combination of ore, bulk, and oil, and "O/O" is used for combination oil and ore carriers. 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.
Specialized bulk carriers began to appear as steamship became more popular. The first steam ship recognized as a bulk carrier was the British collier John Bowes, built in 1852.Bruno-Stéphane Duron, , mémoire de DESS, 1999. She featured a metal hull, a steam engine, and a Ballast tank which used seawater instead of sandbags. These features helped her succeed in the competitive British coal market. The first self-unloader was the lake freighter Hennepin in 1902 on the Great Lakes. This greatly decreased the unloading time of bulk carriers by using conveyor belt to move the cargo. Shipwrecks – A Deep Look, The Rise of the Self-unloading Freighter, The Heritage Museum and Cultural Center (HMCC) and Michigan Shipwreck Research Associates The first bulk carriers with Diesel engine began to appear in 1911.
Before World War II, the international shipping demand for bulk products was low—about 25 million tons for metal oresInternational Maritime Organization, 1999:1.—and most of this trade was coastal. However, on the Great Lakes, bulk carriers hauled vast amounts of iron ore from Minnesota and Michigan's northern mines to the steel mills. In 1929, 73 million tons of iron ore was transported on the Lakes, and an almost equal amount of coal, limestone, and other products were also moved. Two defining characteristics of bulk carriers were already emerging: the double bottom, which was adopted in 1890, and the triangular structure of the ballast tanks, which was introduced in 1905. After World War II, an international bulk trade began to develop among industrialized nations, particularly between the European countries, the United States and Japan. Due to the economics of this trade, ocean bulk carriers became larger and more specialized.International Maritime Organization, 1999: 1, 2. In this period, Great Lakes freighters increased in size, to maximize economies of scale, and self-unloaders became more common to cut turnaround time. The thousand-footers of the Great Lakes fleets, built in the 1970s, were among the longest ships afloat, and, in 1979, a record 214 million tons of bulk cargo were moved on the Great Lakes.
| + Major bulk carrier size categories | |||||
| Handysize | 10,000 to 35,000 | 34% | 18% | $25M | $20M |
| Handymax | 35,000 to 59,000 | 37% | |||
| Panamax | 60,000 to 80,000 | 19% | 20% | $35M | $25M |
| Capesize | 80,000 and over | 10% | 62% | $58M | $54M |
Mini-bulk carriers are prevalent in the category of small vessels with a capacity of under . Mini-bulk carriers carry from 500 to 2,500 tons, have a single hold, and are designed for river transport. They are often built to be able to pass under and have small crews of three to eight people.
Handysize and Handymax ships are general purpose in nature.Lamb, 2003. 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. Handymax ships are typically 150–200 m in length and 52,000 with five cargo holds and four cranes. These ships are also general purpose in nature.
The size of a Panamax vessel is limited by the Panama canal's lock chambers, which can accommodate ships with a beam of up to 32.31 m, a length overall of up to 294.13 m, and a draft of up to 12.04 m.Autoridad del Canal de Panamá 2005, pp. 1112.
Capesize ships are too large to traverse the Panama canal and must round Cape Horn to travel between the Pacific and Atlantic oceans. Earlier, Capesize ships could not traverse the Suez Canal and needed to go around the Cape of Good Hope. Recent deepening of the Suez canal to 66 ft (20 m) permits most Capesize ships to pass through it.
Capesize bulk carriers are specialized: 93% of their cargo is iron ore and coal. Some ships on the Great Lakes Waterway exceed Panamax dimensions but they are limited to use on the Great Lakes as they cannot pass through the smaller St. Lawrence Seaway to the ocean.
Very large ore carriers and very large bulk carriers are a subset of the capesize category reserved for vessels over . Carriers of this size are almost always designed to carry iron ore.
In October 2022, Mitsui O.S.K. Lines (MOL)'s bulk carrier Shofu Maru arrived in Newcastle on its maiden voyage, becoming the first bulk carrier to be partially powered by hard sail wind power propulsion technology. A five percent fuel savings was anticipated.
| +General Bulk Carrier Types ! Illustration !! Description | |
| Geared bulk carriers are typically in the handysize to handymax size range although there are a small number of geared panamax vessels, like all bulk carriers they feature a series of holds covered by prominent hatch covers. They have cranes, or that allow them to load or discharge cargo in without shore-based equipment. This gives geared bulk carriers flexibility in the cargoes they can carry and the routes they can travel. (Photo: A typical geared handysize bulk carrier.) | |
| Combined carriers are designed to transport both liquid and dry bulk cargoes. If both are carried simultaneously, they are 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 Maya.) | |
| Gearless carriers are bulk carriers without cranes or conveyors. These ships depend on shore-based equipment at their ports of call for loading and discharging. They range across all sizes, the larger bulk carriers (VLOCs) can only dock at the largest ports, some of these are designed with a single port-to-port trade in mind. The use of gearless bulk carriers avoids the costs of installing, operating, and maintaining cranes. (Photo: Berge Athen, a 225,000-ton DWT gearless bulk carrier.) | |
| are bulk carriers with , or with the use of an excavator that is fitted on a traverse running over the vessel's entire hatch, and that is able to move sideways as well. This allows them to discharge their cargo quickly and efficiently. (Photo: John B. Aird a self-discharging lake freighter.) | |
| Lake freighter are the bulk carriers prominent on the Great Lakes, often identifiable by having a forward superstructure that helps in transiting locks. Operating in fresh water, these ships suffer much less corrosion damage and have a much longer lifespan than saltwater ships.International Maritime Organization, 1999:6. As of 2005, there were 98 lakers of or over. (Photo: Edward L. Ryerson, a Great Lakes bulk carrier.) | |
| BIBO or "Bulk In, Bags Out" bulk carriers are equipped to bag cargo as it is unloaded. CHL Innovator, shown in the photo, is a BIBO bulk carrier. In one hour, this ship can unload 300 tons of bulk sugar and package it into 50 kg sacks. | |
| (Photo: , a 45,000-ton DWT open hatch bulk carrier.) |
As of 2005, the average bulk carrier was just over 13 years old. About 41% of all bulk carriers were less than ten years old, 33% were over twenty years old, and the remaining 26% were between ten and twenty years of age.UNCTAD 2006, p. 23. All of the 98 bulk carriers registered in the Great Lakes trade are over 20 years old and the oldest still sailing in 2009, the St. Mary's Challenger, was 106 years old.Office of Data and Economic Analysis, 2006:2.
Several companies have large private bulk carrier fleets. The multinational company Gearbulk Holding Ltd. has over 70 bulk carriers. The Fednav Group in Canada operates a fleet of over 80 bulk carriers, including two designed to work in Arctic ice. and Croatia's Atlantska Plovidba d.d. has a fleet of 14 bulk carriers. The H. Vogemann Group in Hamburg, Germany operates a fleet of 19 bulk carriers. Portline in Portugal, owns 10 bulk carriers. Dampskibsselskabet Torm in Denmark and Elcano in Spain also own notable bulk carrier fleets.According to description of the main ship-owners, from the French Marine–Marchande website. Other companies specialize in mini-bulk carrier operations: England's Stephenson Clarke Shipping Limited owns a fleet of eight mini-bulk carriers and five small Handysize bulk carriers, and Cornships Management and Agency Inc. in Turkey owns a fleet of seven mini-bulk carriers.
Some shippers choose instead to charter a ship, paying a daily rate instead of a set price per ton. In 2005, the average daily rate for a Handymax ship varied between $18,000$30,000. A Panamax ship could be chartered for $20,000$50,000 per day, and a Capesize for $40,000$70,000 per day.UNCTAD 2005.
Half a million deadweight tons worth of bulk carriers were scrapped in 2004, accounting for 4.7% of the year's scrapping. That year, bulk carriers fetched particularly high scrap prices, between $340 and $350 per LDT.
| + Typical bulk carrier crew | Sea captain | ||
| 1 Chief mate 1 Second mate 1 Third mate 1 Boatswain 1 Deck cadet 26 Able seaman 02 Ordinary seaman | 1 Chief engineer 1 Second engineer 1 Third engineer 12 01 ETO 02 Motormen 13 Oilers 03 Greasers 13 Wipers | 1 Chief steward 1 Chief cook 1 Steward's assistant | |
During the 1990s, bulk carriers were involved in an alarming number of . 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. Among bulk carrier crews, the best performance was found aboard younger and larger ships. Crews on better-maintained ships performed better, as did crews on ships where fewer languages were spoken.
Fewer are employed on bulk carriers than on similarly sized ships of other types. A mini-bulk carrier carries two to three deck officers, while larger Handysize and Capesize bulk carriers carry four. LNG carrier of the same size have an additional deck officer and sailor.
Because bulk cargo is so difficult to discharge, bulk carriers spend more time in port than other ships. A study of mini-bulk carriers found that it takes, on average, twice as much time to unload a ship as it does to load it. A mini-bulk carrier spends 55 hours at a time in port, compared to 35 hours for a lumber carrier of similar size. This time in port increases to 74 hours for Handymax and 120 hours for Panamax vessels. Compared with the 12-hour turnarounds common for container ships, 15-hour turnarounds for car carriers, and 26-hour turnarounds for large tankers, bulk carrier crews have more opportunities to spend time ashore.
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, and the use of shore-based , reaching 2,000 tons per hour, is growing. A crane's discharge rate is limited by the bucket's capacity (from 6 to 40 tons) and by the speed at which the crane can take a load, deposit it at the terminal and return to take the next. For modern gantry cranes, the total time of the grab-deposit-return cycle is about 50 seconds.
Conveyor belts offer a very efficient method of loading, with standard loading rates varying between 100 and 700 tons per hour, although the most advanced ports can offer rates of 16,000 tons per hour.International Maritime Organization, 1999:7. Start-up and shutdown procedures with conveyor belts, though, are complicated and require time to carry out. Self-discharging ships use conveyor belts with load rates of around 1,000 tons per hour.
Once the cargo is discharged, the crew begins to clean the holds. This is particularly important if the next cargo is of a different type.Hayler, 2003:5–11. 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 and 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.George, 2005:341, 344. Extra precautions are taken, such as adding longitudinal divisions and securing wood atop the cargo. If a hold is full, a technique called tomming is used, which involves digging out a hole below the hatch cover and filling it with bagged cargo or weights.
The overall cargo weight is the limiting factor in the design of an ore carrier, since the cargo is so dense. Coal carriers, on the other hand, are limited by overall volume, since most bulk carriers can be completely filled with coal before reaching their maximum draft.
For a given tonnage, the second factor which governs the ship's dimensions is the size of the ports and it will travel to. For example, a vessel that will pass the Panama Canal will be limited in its beam and draft. For most designs, the ratio of length-to-width ranges between 5 and 7, with an average of 6.2. The ratio of length-to-height will be between 11 and 12.
As a result of the 1973 oil crisis, the 1979 energy crisis, and the resulting rise in oil prices, experimental designs using coal to fuel ships were tested in the late 1970s and early 1980s. The Australian National Lines (ANL) constructed two 74,700-ton coal-burner ships called River Boyne and River Embely. along with two constructed by TNT called TNT Capricornia and TNT Capentaria and renamed Fitzroy River and Endeavor River. These ships were financially effective for the duration of their lives, and their were able to generate a shaft-power of . This strategy gave an interesting advantage to carriers of bauxite and similar fuel cargoes, but suffered from poor engine yield compared to higher maintenance cost and efficient modern diesels, maintenance problems due to the supply of ungraded coal, and high initial costs.
As recently as the 1950s, hatches had wooden covers that would be broken apart and rebuilt by hand, rather than opened and closed.Hayler, 2003:5–9. Newer vessels have hydraulic-operated metal hatch covers that can often be operated by one person. Hatch covers can slide 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 bulk carriers to sink.
Regulations regarding hatch covers have evolved since the investigation following the loss of the . 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 S21International Association of Classification Societies 2007, p. 21-1. 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.
Bulk carriers have a cross-section typical of most merchant ships. The upper and lower corners of the hold are used as , as is the double bottom area. The corner tanks are reinforced and serve another purpose besides controlling the ship's trim. Designers choose the angle of the corner tanks to be less than that of the angle of repose of the anticipated cargoes. This greatly reduces side-to-side movement, or "shifting," of cargo which can endanger the ship.
The double bottoms are also subject to design constraints. The primary concern is that they be high enough to allow the passage of pipes and cables. These areas must also be roomy enough to allow people safe access to perform surveys and maintenance. On the other hand, concerns of excess weight and wasted volume keep the double bottoms very tight spaces.
Bulk carrier hulls are made of steel, usually mild steel.George, 2005:221. Some manufacturers have preferred high-tensile steel recently in order to reduce the tare weight.International Maritime Organization, 1999:8. However, the use of high-tensile steel for longitudinal and transverse reinforcements can reduce the hull's rigidity and resistance to corrosion. Forged steel is used for some ship parts, such as the propeller shaft support. Transverse partitions are made of corrugated iron, reinforced at the bottom and at connections. The construction of bulk carrier hulls using a concrete-steel sandwich has been investigated.
have become popular in the past ten years. Designing a vessel with double sides adds primarily to its breadth, since bulk carriers are already required to have . 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 cargo hold. 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 fewer 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 backs"George, 2005:217. 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 to manage problems of longitudinal strength and stresses. A ship's hull is composed of individual parts called members.George, 2005:218. The set of dimensions of these members is called the ship's scantlings. Naval architects calculate the stresses a ship can be expected to be subjected to, add in safety factors, and then can calculate the required scantlings.
These analyses are conducted when traveling empty, loading and unloading, when partially and fully loaded, and under conditions of temporary overloading. Places subject to the largest stresses are studied carefully, such as hold-bottoms, hatch-covers, bulkheads between holds, and the bottoms of ballast tanks. Great Lakes bulk carriers also must be designed to withstand springing, or developing resonance with the waves, which can cause fatigue fractures.
Since 1 April 2006, the International Association of Classification Societies has adopted the Common Structural Rules. The rules apply to bulk carriers more than 90 meters in length and require that scantlings' calculations take into account items such as the effect of corrosion, the harsh conditions often found in the North Atlantic, and dynamic stresses during loading. The rules also establish margins for corrosion, from 0.5 to 0.9 mm.
The 1960 SOLAS Convention sought to control this sort of problem.International Maritime Organization, 1999:2. 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 airInternational Maritime Organization, 1999:4. which has a useful side-effect: reducing the chances of spontaneous combustion in cargoes such as coal, iron, and metal shavings.
Another sort of risk that can affect dry cargoes is absorption of ambient moisture. 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. The only way to control these risks is by good ventilation practices and careful monitoring for the presence of water.
The International Maritime Organization sets out international standards and codes for the safe stowage and transportation of bulk carrier cargoes. These include the International Maritime Solid Bulk Cargoes Code, the International Code for the Safe Carriage of Grain in Bulk and the Code of Safe Practice for Ships Carrying Timber Deck Cargoes. (2025). 9781856096324, Witherby Publishing Group. ISBN 9781856096324 (2025). 9781856096324, Witherby Publishing Group. ISBN 9781856096324
The accident studies showed a clear pattern:
Previous practices had required ships to withstand the flooding of a single forward hold but did not guard against situations where two holds would flood. The case where two after (rear) holds are flooded is no better, because the engine room is quickly flooded, leaving the ship without propulsion. If two holds in the middle of the ship are flooded, the stress on the hull can become so great that the ship snaps in two.
Other contributing factors were identified:
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. The 1997 additions also required bulk carriers with restrictions (for instance, forbidden from carrying certain types of cargoes) to mark their hulls with large, easy-to-see triangles.
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 bulk carriers. 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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