Bulk Cargo Carrier
Bulk cargo means unsegregated mass commodities including, without limitation, items such as petroleum products, coal and bulk salt which are carried loose and which are customarily loaded and unloaded by pumping, shoveling, scooping or other similar means. Bulk Cargo Carriers include a variety of dry and liquid bulk ships specializing in a variety of commodities -- salt, gypsum, vegetable oils, orange juice concentrate, and petroleum products, etc. Such ships find wide application in commerce, but have no military application.
Dry Bulk Carriers are designed to carry grain or similar cargoes in bulk (i.e., material that can be dumped, sucked, pumped, or blown). Loading and discharge are normally performed at specialized terminals, using cargo handling systems that are designed for specific commodities. Gravity is often used for loading; the various discharge methods include the use of pneumatic systems, conveyors, and excavation-type machinery. Most dry bulk carriers are not considered to be militarily useful. However, some are fitted with deck cranes so that, in some cases, their characteristics are similar to those of a general cargo ship.
Bulk cargo services cover several key sub-divisions based on specific vessel types. Liquid cargoes are carried in chemical tankers, liquefied gas tankers, crude oil tankers and refined petroleum product tankers. Non-liquid cargoes are carried by dry bulk carriers and other (multipurpose) carriers.
Vessels operating on bulk trades generally do not operate on scheduled services, but on specific voyages in fulfilment of short or long term contracts, where the entire cargo shipped on a particular voyage belongs to one owner. Additionally, carriers may ply variable routes according to local demand in particular ports, and can transport a variety of bulk cargoes. These are customarily identified as a separate sector of the industry, known as tramp shipping. This unscheduled, open market mode of operation, is one of the major differences between "liner" and "bulk" shipping. From a regulatory point of view, bulk vessels operate in a generally free market, and are subject only to international and national safety requirements, although because of the relative hazard of many bulk commodities (e.g. oil products and chemicals) these regulations are strictly enforced.
Traditionally transported in bags, finished cement is today carried largely in bulk, a powder cargo sufficiently fine to be handled pneumatically, moving through large diameter pipes on a column of air. Old cement ships were basically bulk carriers with bags handled manually in a laborious operation which could take days. Transporting cement requires specific handling and storage conditions, hence specialized cement carriers are the preferred method of transportation.
The world cement trade and shipping sector is a complex combination of a wide variety of regular movements and sporadic short-term opportunistic shipments. A high volume of trade represents movements between companies under the umbrella of the same multinational cement group, whilst independent cement traders are still a major factor determining price levels and patterns of trade. Construction booms and downturns can alter the regional cement trade profile dramatically - as witnessed in recent years in many of the world's leading markets. Similarly, the rush to build new production capacity to meet future demand can make significant volumes of cement and/or clinker available for export, with the location of the plant and inland logistics determining the economic feasibility of overseas shipments.
The Portland Cement Association reports that " Because the cost of shipping cement quickly overtakes its value, customers traditionally purchase cement from local sources.... In 2002, U.S. Portland cement consumption was 103.8 million metric tons... The gap between domestic production and consumption was filled in 2002 by 24.2 million metric tons of imported cement and cement clinker. About 56% of cement and clinker imported in 2002 came from four major countries: Canada, Thailand, China, and Greece... "
The specialist cement carrier fleet is a mixture of vessel types and sizes, with a similarly diverse employment profile. Developments in general dry bulk shipping markets have had massive effects on the international cement trade in recent years, with the prevalence of low freight rates favouring a host of shipping routes previously unfeasible, and the subsequent unprecedented rise in shipping costs causing prices to reach uncompetitive levels on certain routes. The development of bulk cement shipping costs is essentially due to a number of factor outside the cement sector. A further layer of complexity is imposed by the variability of shipping costs - bulk carrier freight rates are determined by factors outside the cement sector, but they can radically alter the cost competitiveness of supplies from one country in a variety of world markets. The volatility of shipping costs - as witnessed from 2002 to 2006 - therefore provides an extra layer of uncertainty for the future prospects of trade patterns and volumes.
Modern cement carriers are specialised ships that will carry no other cargo, and while classified as dry bulk carriers, are fully enclosed vessels which more resemble tankers. Cement is a difficult and dusty cargo, and specialist cement carriers incorporate pneumatic cargo handling gear with enclosed holds with special moisture control systems. Such vesseles can loading via gravity through opening on top of hold covers, or pneumatically via a network of pipes on deck at any rate shore installation can give. Discharging can be pneumatically via a network of pipes on deck. Some vessels are equipped with tow rotary bagging machines capable of bagging the totality of the bulk cement cargo from the vessels hold via a network of conveyors to stowable telescopic truck loading conveyors. Or vessels may be equipped for bulk truck loading facilities capable of discharging into bulk trucks.
Bulk Cargo Carrier Safety
On the basis of ship safety, the containerised liner trades have been the most satisfactory sector of the industry due to the trend towards greater containerisation of cargoes which necessitated the almost complete replacement of a large number of aged general cargo vessels by modern container vessels. In contrast, poor safety conditions prevailed in the carriage of dry bulk cargoes. In the 1990's around 200 dry bulk carriers were lost, resulting in over 800 seafarer fatalities.
Bulk carriers have been around for a long time, and have grown in size to take advantage of the economies of scale. Unfortunately this development has led to the mysterious loss of a large number of bulkers and their crews. The circumstances involving one of these - the Derbyshire - bring out certain important and contentious points. In 1980 the British-owned, British-designed, British-built, British-crewed bulk carrier disappeared during a typhoon in the Pacific. Her loss was attributed to the weather and, with constant pressure for a formal inquiry from the families of the 44 people who went down with the ship, a brilliant and dogged investigative operation was carried out some 15 years later by the United Kingdom Government at the instigation of and partly funded by the International Transport Workers' Federation. The wreck was discovered, at a depth of more than 2 miles, and thereafter it became clear that some of the original theories put forward about the loss were suspect.
Already some points of concern about bulk carriers have been confirmed and although the cargo hatches of bulk carriers are essential components of the design, like ro-ro bow doors they represent a point of weakness. A raised forecastle deflects some green water from the hatch covers and adds buoyancy to the ship but the Derbyshire's forecastle was flush with the deck. The indications are that the hatch cover of her Number 1 cargo hold was simply smashed in by the force of the seas pounding on to her deck. Before the crew realized what was happening the ship began to sink and did so in seconds.
About 1915 EST on November 10, 1975, the Great Lakes bulk cargo vessel SS EDMUND FITZGERALD, fully loaded with a cargo of taconite pellets, sank in eastern Lake Superior in position 46 59.91 N, 85 06.61 W, approximately 17 miles from the entrance to Whitefish Bay, MI. The ship was en route from Superior, WI, to Detroit, MI, and had been proceeding at a reduced speed in a severe storm. All the vessel's 29 officers and crewmembers were missing and presumed dead. No distress call was heard by vessels or shore stations. A storm of the intensity of the one recorded on November 10 would not occur every year; however, more intense storms have been recorded on the Great Lakes.
The FITZGERALD was carrying about 26,116 long tons of National Taconite Pellets. Taconite pellets are manufactured by a process known as "oxide pelletizing." This process begins with the mining of iron ore (magnetite), concentrated with the addition of bentonite, processed into balls of 3/8-inch to 5/8-inch diameter, and fired at temperatures of 2,2000 F to 2,4000 F, which changes its composition to relatively nonmagnetic hemotite. This process produces almost spherical pellets containing 67 percent iron, which are easily handled by belts and bulk cargo handling equipment.
The FITZGERALD was one of a fleet of 14 to 18 vessels operated by the Columbia Transportation Division between 1972 and 1977. The vessel had a 860,950-cubic-foot cargo hold divided by two nonwatertight transverse "screen" bulkheads. Outboard and below the cargo hold were eight ballast tanks divided at the centerline into port and starboard tanks. The forward deckhouse contained the pilot house and accommodations for the deck crew. The engine room was located aft, above which were the rest of the accommodations and the crew's messing facilities. Below the weather deck and above the ballast tanks were two tunnels, one port and one starboard, used for access between the accommodation areas during adverse weather. There were 21 cargo hatch openings. Each opening measured 11 feet longitudinally and 48 feet transversely and had a 24-inch coaming above the weather deck. Each opening was made weathertight by a single-piece steel hatch cover.
The National Transportation Safety Board determined that the probable cause of this accident was the sudden massive flooding of the cargo hold due to the collapse of one or more hatch covers. Before the hatch covers collapsed, flooding into the ballast tanks and tunnel through topside damage and flooding into the cargo hold through nonweathertight hatch covers caused a reduction of freeboard and a list. The hydrostatic and hydrodynamic forces imposed on the hatch covers by heavy boarding seas at this reduced freeboard and with the list caused the hatch covers to collapse. The hatch cover failure would have been severe enough to allow rapid massive flooding of the cargo hold. Since there were no watertight bulkheads within the cargo hold, the flooding water would have progressed throughout the hold within minutes, causing the vessel to sink bow first to the bottom of the lake. Upon impact with the bottom, the midship portion disintegrated and the stern section rolled over, coming to rest upside down.
Bulk Cargo Ship Classes
Handy is the name for bulk carriers of less than 60,000 tons deadweight capacity. In many cases, the carrier itself may be equipped with cranes to handle all sorts of cargo. The type of handy bulk carrier of 40,000 tons or more of deadweight capacity is called the "handy-max" type. Handysize-vessels up to 30,000 dwt, which carry exclusively minor bulk cargoes. Historically, the Handysize drybulk carrier sector was seen as the most versatile. Increasingly, however, this has become more of a regional trading, niche sector. The vessels are well suited for small ports with length and draft restrictions and also lacking infrastructure.
Handymax-vessels between 30,000 dwt and 60,000 dwt. The Handymax sector operates in a large number of geographically dispersed global trades, mainly carrying grains and minor bulks including steel products, forest products and fertilizers. Vessels less than 60,000 dwt are built with on-board cranes that enable them to load and discharge cargo in countries and ports with limited infrastructure.
Panamax refers to the maximum size that can navigate the Panama Canal. This type can be up to 32.2 meters wide. Panamax bulk carriers are usually of 60,000 to 80,000 tons of deadweight capacity, and are suitable for carrying bulk cargo of industrial commodities like as salt, grain, coal and/or iron ore. Panamax vessels, defined as those with the maximum beam (width) of 32.2 metres permitted to transit the Panama Canal, carry coal, grain and, to a lesser extent, minor bulks, including steel products, forest products and fertilizers.
Cape is the type of large-scale bulk carrier primarily used for transporting raw materials for making steel (coal and iron ore). This type is considered to be at least 100,000 tons of deadweight capacity, and there are currently super-large ships in excess of 200,000 tons of deadweight capacity. Vessels over 80,000 dwt is the traditional definition of a Capesize bulk carrier, in terms of deadweight, the sector is changing. As per the orderbook detailed below, there have been a number of new super-Panamaxes ordered, which are 82,000 dwt to 85,000 dwt, but which are able to transit the Panama Canal with a full cargo. Thus, a more modern definition of Capesize would be based on vessels over 100,000 dwt. The Capesize sector is focused on long haul iron ore and coal trade routes. Due to the size of the vessels there are only a comparatively small number of ports around the world with the infrastructure to accommodate them.
Bulk Cargo Handling
A bulk cargo spout is a spout, which may or may not be telescopic and may or may not have removable sections, but is suspended over the vessel from some overhead structure by wire rope or other means. Such a spout is often used with a "thrower" or "trimming machine." A grain loading spout is an example of those covered by this definition.
A bulk cargo sucker is a pneumatic conveyor which utilizes a spout-like device, which may be adjustable vertically and/or laterally, and which is suspended over a vessel from some overhead structure by wire rope or other means. An example of an installation of this nature is the "grain sucker" used to discharge grain from barges.
Unloaders are used to unload bulk cargoes such as coal and grain from the holds of ships. The conventional unloader comprises a travel frame, a slewing table mounted on the travel frame so as to be turnable freely, a boom mounted on the slewing table so as to be swingable up and down freely, a vertically conveying section mounted freely swingably on the front end of the boom, and a screw feeder for scraping and taking in bulk cargo mounted at the bottom of the vertically conveying section. The screw feeder has a cylindrical screw casing and a screw in the screw casing. The screw feeder, rotating the screw, scoops up bulk cargo through the bottom end of the screw casing, carries it upward, and feeds it into a receiving space between the two belts of the vertically conveying section.
The screw comprises a screw shaft, a spiral blade, and paddle-like discharge blades. Directly by the discharge blades, a discharge port for feeding bulk cargo to the receiving space is made in the screw casing.
At the back of the receiving space, a pair of tail pulleys are arranged up and down. The pair of belts are installed on the upper and lower tail pulleys, respectively, and through the vertically conveying section to catch therebetween and carry bulk cargo through the vertically conveying section. The space between and in front of the upper and lower tail pulleys is the receiving space.
Even while a ship is at its moorings, it rocks on the waves, especially on a rough sea in winter, which may cause the bottom of the ship to push up the bottom of the screw feeder. Accordingly, the screw feeder is so mounted on the bottom of the vertically conveying section that it can, when pushed up, move upward relative to the stationary vertically conveying section in order to prevent damage to the unloader.
When the screw feeder is pushed up largely and the discharge blades and the discharge port are raised above the receiving space of the vertically conveying section, the bulk cargo thrown out by the discharge blades does not enter the receiving space, but dashes against the upper tail pulley and scatters outside.
In case of the conventional unloader, bulk cargo in a ship's hold is carried by a vertical, upward-conveying section inserted in the bulk cargo through a horizontal boom to a downward-conveying section which is connected to the base of the horizontal boom. Then, bulk cargo slides down on a chute through the downward-conveying section onto a discharge conveyor on the ground side. To cope with such large-sized ships as are built in these years, the position of the base of the horizontal boom of such an unloader has to be raised high, which makes large the height difference between the horizontal boom and the discharge conveyor and, hence, the fall of bulk cargo. Therefore, bulk cargo dashes harder upon the discharge conveyor, becoming liable to break, generating larger noises and more dust, and posing a larger risk of damage to the discharge conveyor.
A multi-mode ship is designed to carry bulk cargoes, including "clean" bulk cargoes or food grade bulk cargoes such as wheat, rice, soy bean meal, grains, etc. These bulk cargoes are carried in a bulk cargo hold in the lower part of the ship which is designed to permit alternate carriage of either vehicles or bulk cargoes. The multi-mode ship also provides a bulk cargo transport system for self loading and unloading of bulk cargo. The design further provides for a bulk/car compartment that is cleaned to car carriage standards, by broom sweep and air spray, water wash, and/or vacuum trucks. The car ventilation systems are preferably isolated when bulk cargoes are handled.
The multi-mode ship uses bulk cargo flow-through vehicle decks that are capable of supporting commercial vehicles, military vehicles, and other general cargo. Bulk cargo is loaded into a multi-mode ship with a bulk cargo transport system. Bulk cargo is loaded on board the multi-mode ship and is discharged from some or all of the vehicle decks, where the bulk cargo flows downward through the vehicle decks and settles on the bottom of the multi-mode ship. The bulk cargo then piles upward through the vehicle decks until it reaches the desired load. The bulk cargo transport system may include conveyors, upper and lower, and at least one vertical conveyor for transporting bulk cargo to, from, and within a cargo hold of the multi-mode ship. Further, the multi-mode ship preferably includes liquid storage tanks that are shaped to provide a preferably funnel-like storage area within the cargo hold for funneling bulk cargo toward the lower conveyors of the bulk cargo transport system to further provide efficient and complete unloading of the cargo hold of bulk cargo.
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