Shipbreaking is any breaking down of a vessel's structure to dismantle the vessel, including the removal of gear, equipment, or any component of the vessel. This term is commonly referred to as "ship scrapping" and "ship disposal." As ship that is to be broken up is said to be "sent to the breakers".
Ship dismantling is a manual process that does not lend itself to automation. The result is substantially higher labor costs for ship scrapping activities. The obsolete equipment on military ships has little or no value in today's markets, resulting in substantially less revenue for the scrap recycler.
The skills required to dismantle a ship are a unique blend of technical knowledge and physical labor. Technical knowledge is needed to properly eliminate hazardous materials and safely remove heavy sections of steel hulls. Ship scrapping is still a labor-intensive process with much of the work being done using hand held cutting tools.
The two methods of scrapping a ship are the afloat method and the dry-dock method. The afloat method is generally less expensive than the dry-dock method, but this cost savings comes with greater difficulty than the dry-dock method. Scrapping a ship while in the water is more difficult because of the scrappers need to strip the inside of the ship before dismantling can begin. Workers must strip the interior through doors and hatches and remove the propeller(s) and rudders while the ship is in the water. Then, the scrappers remove the superstructure and topside components and progressively cut the main and lower decks from bow to stern. As they remove material from the ship it becomes lighter and is pulled ashore, a little more each day, with each high tide. Scrapping a ship in a dry-dock is more expensive, yet it is easier to scrap the vessel. Since the ship is not in the water, the workers can immediately begin separating the vessel into large sections, then move the large sections to other areas to be cut into smaller sections.
Ship scrapping consists of removing mechanical, hydraulic or electronic components that have potential market value for resale or reuse and then physically cutting the remainder of the hull to allow the recycling of metals and other material by sale to salvage yards or smelters. After salvageable equipment has been removed from the ship, the dismantling begins. The interior spaces are cleared to allow the hull structure to be cut apart. Components within the compartment, such as piping, electrical cables, lockers, partitions, furnishings and habitability equipment, are cut and removed. Heavy steel hull and structural materials are cut with hand held gas torches and saws. The majority of the hull sections cut from the ship are under 10 tons in weight, allowing them to be handled by a variety of common cranes and lifting equipment. Non-reusable equipment, wiring, piping, and non-structural material is cut free using saws, grinders, abrasive cutting wheels, hand held shears, plasma and gas torches. Non-recyclable material is disposed of as waste in accordance with the applicable regulatory requirements. The need to remove hazardous materials such as asbestos, lead, PCB's, residual fuels and other liquids makes ship scrapping in compliance with all the applicable environmental regulations a challenging task.
After removal from the fleet site, a ship is towed to the site where ship scrapping will occur. The ship is then scrapped while either moored, beached, or in drydock. Most ship scrapping is performed at slips, which are dredged openings in the bank of the ship channel. Slips are generally 400 to 700 feet long and 100 to 120 feet wide at the entrance. A large winch at the head of the slip is used to drag the hull farther into the slip as work progresses. The scrapping process usually occurs in a series of steps:
A diagram of all rooms, compartments, tanks, and storage areas is used (or prepared if not available) to identify areas that may contain hazardous materials, such as fuels, oils, asbestos, PCBs, and hazardous waste. Preliminary sampling of media is conducted, starting in the compartment that will be cut first.
The removal of fuels, oils, other liquids (e.g., bilge and ballast water), and combustible materials from the ship generally occurs throughout the ship scrapping process. The U.S. Coast Guard requires booms around the ship to help contain any spills. Following removal activities, a marine chemist is contracted to certify that the ship is safe for workers or safe for hot work allowing the issuance of hot work permits. Hot work permits allow cutting torches and saws to be used to dismantle the ship. During the ship scrapping process, water will continue to accumulate and will have to be removed.
Fixtures, anchors, chains, and small equipment are removed initially. Large reusable components (e.g., engine parts) are removed as they become accessible. Reusable materials and equipment may be sold directly with little or no refurbishment by the scrapping facility. Propellors may also be removed so the hulk can be pulled into shallow water.
Asbestos-containing material (ACM) is removed from cut lines so that large sections of the ship can be removed. The engine rooms usually contain the most asbestos and, therefore, take the longest for asbestos removal to be complete. PCB-containing materials that are accessible are removed, as well as PCB-containing materials from areas to be cut. Some PCB-containing materials may be left in place on the room-sized pieces, only to be removed after the large piece is moved to shore.
Following asbestos and PCB removal, paint is removed, if required, from surfaces to be cut. The presence of hard-to-remove and potentially toxic materials may require specific cut-line preparation, such as grit blasting.
During the cutting phase, the upper decks and the superstructure and systems are first cut, followed by the main deck and lower decks. Metal cutting is typically done manually using oxygen-fuel cutting torches, but may be done with shears or saws (for nonferrous metals). Typically, as large parts of the ship are cut away, they are lifted by crane to the ground where they are cut to specific shapes and sizes required by the foundry or smelter to which the scrap is shipped. As cutting continues and the weight of the structure is reduced, the remaining hulk floats higher, exposing lower regions of the hull. Bilge water is sampled and discharged appropriately. Ultimately, the remaining portion of the hull is pulled ashore and cut.
Scrap metals, including steel, aluminum, copper, copper nickel alloy, and lesser amounts of other metals, are sorted by grade and composition and sold to remelting firms or to scrap metal brokers. Valuable metals, such as copper in electric cable, that are mixed with nonmetal material may be recovered using shredders and separators. The shredders produce a gravel-like mixture of metal particles and non-metal "fluff". The metals are then separated from the fluff using magnetic separators, air flotation separator columns, or shaker tables. Fluff is a term used in the recycling trade for solid and liquid nonrecoverable, nonmetallic materials obtained during the ship scrapping process. Fluff is not salable. Because it contains regulated hazardous waste (e.g., asbestos, PCBs, hydrocarbons), it must be managed and disposed of according to the hazardous waste regulations (40 CFR 261-270).
Machinery components are typically removed throughout the scrapping process. During the preparation phase of scrapping, small articles and the propellors are removed which allows the hulk to be pulled into shallow water where scrapping usually takes place. As layers of the ship are cut, large reusable or recyclable components are removed as they become accessible.
When removed from the ship, ship machinery components are typically handled in the shipyard, or what is commonly called the scrap yard. These components, which may be stripped of valuable materials and/or cut into smaller pieces, may contain or be contaminated with hazardous materials, including asbestos, polychlorinated biphenyls (PCBs), oils, and fuels.
Other materials that are not recycled, including hazardous materials and other wastes, are disposed of according to applicable laws and regulations.
Shipbreaking and Scrap Metal
Metal cutting is the process of cutting a ship apart for the recovery of materials, including several grades and types of scrap metal (see below). During ship scrapping, the upper decks (i.e., the superstructure) and systems of the ship are cut first, followed by the main deck and lower decks. As large parts of the ship are cut away, they are lifted by crane to the ground where they are further cut into the shapes and sizes required by buyer (e.g., smelter, scrap metal broker). As cutting continues and the weight of the structure is reduced, the remaining hulk floats higher exposing lower regions of the hull for cutting. Finally, the remaining portion of the hull is pulled ashore and cut into sections.
The metals on ships are typically cut using a variety of torches and mechanical cutters. While not as common as torches or cutters, some facilities employ the use of detonation charges to cut ship hulls.
An oxygenfuel torch is the tool of choice for cutting steel. It burns a wide variety of fuel (e.g., acetylene, propane, butane, fuel gas, natural gas) and uses either oxygen (liquid or compressed) or liquid air as the oxidizer and "cutting gas" that serves to burn (oxidize) iron along the cut line. Oxygen-fuel torches operate with a flame temperature of 3,500E- 4,000EF and flame velocities of 290 - 425 feet per second. Dozens of different styles of torches and torch tops are available depending on the type and supply pressure of the fuel and oxidizer, the thickness of the metal to be cut, and the environment where the work is done. The cutting speed of these torches ranges from 17 to 26 inches per minute depending on the steel thickness, fuel, oxidizer, and torch tip.
Electric arc or plasma arc torches generate temperatures high enough to liquefy almost any metal by the discharge of electric arcs. A cutting gas, often air, is used to blow away the molten metal. Manual electric arc torches are much slower than oxygen-fuel torches, cutting at rates of no more than 10 inches per minute.
Large industrial shears can quickly reduce large metal parts to small dimensions suitable for a remelting furnace with less labor than torch or saw cutting. There are dozens of sizes of stationary and mobile shears available. Large shears have cutting rates measured in tens of feet per minute. The thickness, toughness, and dimensions of the metal to be sheared, the required cutting rate, and the product dimensions are important for selecting the proper kind of shears for the job.
Several kinds of electric power metal cutting saws are available, including those with circular and reciprocating blades. Saws can be used only on nonferrous metals.
Ship scrapping generates several grades and kinds of scrap metal, commonly called scrap species, that are bought and sold in scrap materials markets. The scrap markets can be broadly classified as those dealing in ferrous scrap and nonferrous scrap.
Ferrous scrap from ships comes from forgings and castings, shell plating, framing, deck plating and beams, bulkheads, pillars and girders, miscellaneous hull steel, foundations, and steel superstructures. In addition, some structural steel outfit, hull attachments, doors and hatches, deck outfit, steward's outfit, hull engineering items, piping, and miscellaneous machinery are ferrous scrap. Of these sources, the largest proportion is co-called "carbon steel," described in the scrap trade as No. 1 heavy melting scrap.
While there are many kinds of nonferrous scrap, one of particular interest is copper-yielding scrap (i.e., cuprous scrap). Cuprous scrap, which has a number of subspecies, includes bronze, brass, and various other copper alloys. While copper and copper alloys represent a small fraction of the total weight of the metals recovered from a ship, they return a large fraction of the revenue because of their high value.
|Join the GlobalSecurity.org mailing list|