Coke Oven
There it is heated to 2300°F by gas fires. Many individual ovens are placed side-by-side to make a coke oven battery. When the coal is baked inside the oven, the moisture and volatile chemicals are driven off. What is left is a porous material that is almost pure carbon -- coke.
The gases and volatile substances baked out of the coal are captured and used as fuel for the ovens and other steelmaking operations. The smoky emissions from coke batteries are also separated into commercially valuable chemicals at the coke by-products plant.
The finished coke is pushed out of the oven to a traveling hopper – hot car. The hot car transports the coke to the coke quenching station, where it is cooled with thousands of gallons of water.
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HAZARDS
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Coke oven workers face health hazards that are well known to OSHA. Coke oven emissions can cause cancer (carcinogenic) and are the subject of the OSHA Coke Oven Standard.
High levels of coal dust are present in the coal preparation plant. Coal prep workers are also exposed to toxic waste from the byproducts plant, which are often added to the coal and run back through the coke ovens.
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Coke oven workers also face a variety of safety hazards. Large moving machines charge coke into the ovens, remove the coke oven doors at the end of the coking cycle, push the hot coke into waiting rail cars, and tranport it to the quench tower. Workers have been injured and killed by this equipment.
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Twenty workers hace died from traumatic injuries in USW represented coke plants since 1980.
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MAKING IRON IN A BLAST FURNACE
The first step in any integrated steelmaking process is the smelting of iron ore.
For this, raw materials are needed: coke, limestone and iron ore. Coke is the fuel for the iron smelting process because it burns inside and outside at the same time. Limestone absorbs impurities in the molten iron to form a substance called slag. Iron ore contains the iron that is released in the blast furnaces. Coke, iron ore, and limestone are hoisted to the top of the blast furnace -- a huge steel stack, lined with brick. The ingredients are heated to over 3000°F. Air is superheated and injected into the ovens as a hot blast fanned by turbo blowers. The molten iron falls to the bottom and is drawn off. Molten slag flows from the furnace into a large pit. After the slag cools and hardens, the pit is dug out with heavy equipment and loaded onto a truck.
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HAZARDS
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Blast furnace workers can be exposed to lethal concentrations of carbon monoxide(CO) The furnace generates large amounts of CO, which is burned in blast furnace “stoves” to heat the air for the furnace. Blast furnace gas is also used as a fuel in boiler houses and other equipment throughout the mill. OSHA has a PEL (Permissible Exposure Limit) for CO. A 1980 agreement negotiated by USW and the major steel producers required companies to do a process hazard evaluation for CO. They developed engineering controls to reduce exposure with periodic drills, worker training and installation of alarms and monitors.
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Before 1980, two to six workers died each year from CO. Since 1981 when the agreement was fully implemented, a total of two workers have died from CO in USWA-represented plants.
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Blast furnace workers are exposed to molten metal which occasionally have “breakouts”.
When molten metal is spilled over a wet surface, it causes the water to flash into steam with great force. This can cause an explosion that can destroy an entire building.
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Twenty-two workers have died in blast furnace operations in USW represented plants since 1980.
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MAKING STEEL IN A BASIC OXYGEN FURNACE (BOF)
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The blast furnace operations are linked to the steel plant by a railroad network. Locomotives pull bottles cars with molten iron to the Basic Oxygen Furnace Plant (BOF). To transform the iron into steel, the excess carbon and other impurities must be removed. A BOF is basically a pear shaped metal bowl lined with special heat resistant brick.
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The BOF is tilted sideways and charged with a partial load of scrap. Molten iron from the blast furnace is added on top of the scrap. Pure oxygen is blown into the vessel, which causes heat that burns impurities out of the iron. Lime is also added as a fluxing agent to absorb impurities such as sulfur and phosphorous, then the “heat is tapped.” The vessel is tilted and the molten steel is poured into a waiting ladle. Certain alloys are added to the ladle as needed to meet the right chemistry for the particular steel that is being made. The vessel has a slag stopper that prevents the slag from entering the ladle. The vessel tilts in the other direction where the molten slag is poured into a slag pot. The vacuum degasser removes harmful gases, which also reduces the carbon levels to the desired amount for the chemistry requirements.
Electric Furnace Steelmaking is used primarily by non-integrated producers, although some integrated producers also operate electric furnaces. The electric furnaces melt steel scrap and other iron-bearing materials using an intense electric current. Electric furnaces are charged with cold metal. Large electrodes are lowered close to the surface of the charge and then energized to produce lightening-like electric arcs. The enormous energy in the arcs melts the charge rapidly and keeps it molten. It is also common practice to insert a hand-held oxygen lance through the side-mounted door. The oxygen helps burn away excess carbon.
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HAZARDS
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Workers in steelmaking are exposed to spills and splashes of molten metal and slag, intense radiant heat from steelmaking vessels, and moving equipment like overhead cranes and ladle transfer cars.
Steel scrap is used to supplement molten metal from the blast furnace. If the slag contains toxic materials like lead and cadmium, significant levels can escape into the workplace environment. Toxic metals like manganese can be used as alloying agents.
Some maintenance procedures have their own hazards. For example, the workers who change the lances used to introduce oxygen into steelmaking vessels work from high platforms, under hot conditions, in significant levels of air contaminants.
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14 workers have died in USW-represented steel melt shops since 1980. In all, 24 workers have died from traumatic injuries in USW-represented steelmaking operations since 1980
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Radiation is a special hazard in any operation using steel scrap. Radiation sources used in medical and industrial radiography are sometimes scrapped illegally. All steel plants now have radiation detectors that scan all shipments of steel scrap, but a shielded source in the middle of a scrap bale could escape detection.
The Nuclear Regulatory Commission knows of 29 incidents in which a radioactive source was melted in a U.S. or Canadian metal mill through June 1996. Many of these incidents involved substantial worker exposure and high remediation costs for the employer.
Many of the hazards of oxygen furnace steelmaking are also present around electric furnaces. In addition, electric furnaces generate intense noise, and there is a danger of electrical shock. If the steel scrap is not sufficiently dry, water can explode under the molten metal bath. Molten metal breakouts are somewhat more frequent than in oxygen steelmaking.
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STEELMAKING PROCESS
At an Argon stirring station molten metal is stirred with an injection of oxygen and argon gas. It burns away the excess carbon and allows a certain amount of chromium to remain.
After the chemistry and temperature has been adjusted, the ladle of steel is transported by overhead crane to the continuous caster which converts molten steel into steel slabs.
The liquid steel flows from a ladle into a tundish, which creates a constant flow into the mold. The mold acts like a heat sink, pulling heat out of the steel and forming a solidified shell of steel around a liquid core. The continuous ribbon of steel that exits the machine is called a strand. By then it is solid and cut with torches into slabs of the desired length.
The slabs are shipped to the “hot mill”.
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Hot rolling mills take slabs of steel and transform them into plates, sheets and strips. Plates may be ½ to 2 inches thick, while sheets and steel strip are thin (usually less than ½ inch). Slabs of steel are heated again in ovens to hot rolling temperature, somewhere above 2100°F. The slab is rolled between heavy steel rollers that break off the scale. The scale on the slab’s surface is a thick layer of impurities, which are broken loose by the rollers and high-pressure water sprays. The rolls squeeze the steel down to the proper thickness and increase the slab’s length.
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Cold rolling is done, by running steel between pairs of hardened rolls. This process makes the steel or strip more uniform. Depending on the customer, the cold rolling process will include some of these processes: pickling, tandem mill rolling, annealing, temper mill rolling,electro galvanizing; and all involve exposure to particular hazards.
For example:
• Pickling agents include strong acids and concentrated hydrogen peroxide.
• Annealing (steel heated and cooled in such a way that internal stresses are reduced and the microstructure of the steel is improved) in some cases takes place in a nitrogen or hydrogen atmosphere. Mixtures of hydrogen and air are explosive. Nitrogen is a simple asphyxiant (cause an insufficient intake of oxygen). Annealing furnaces use refractory ceramic fibers (RCF’s) for insulation. RCF’s are classified by the International Agency for Research on Cancer (IARC) as carcinogenic. Exposures to RCF can be high.
• Galvanizing (coating steel with zinc) exposes workers to molten zinc, and in some cases, electric shock.
From the last finishing stand, the strip travels along a turnout table where coilers coil the strip and place it on a conveyor for shipment to the Strip Finish Building.
In the Strip Finish Building, the coil of steel is processed through a Bliss Mill or shear to meet customer specifications. The customer service line is used to rewind exposed coils for inspection and the coil edges can be side trimmed to meet customer specifications. It may also be sent to the electro galvanizing line where it is coated with zinc, which prevents rust.
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HAZARDS
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Workers can be trapped in the rolling equipment unless it is carefully guarded. Thin steel strip and sheet has sharp edges. Sometimes a “cobble” occurs in which a steel sheet, strip or rod sticks, backs up, and flies out all over the shop.
Workers can also be endangered by rolling lubricants and other metalworking fluids, an issue to which OSHA has devoted much recent attention.
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85 workers have died in steel finishing operations in USW-represented plants since 1980.
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MAINTENANCE
Maintenance workers face all the hazards in areas to which they have been assigned, along with special hazards of their own. Maintenance workers enter confined spaces.
Their health and safety depends on the implementation of good lock-out/tag-out programs.
They must work in plant emergencies, often under adverse conditions. Most production jobs have written “job safety analyses” (JSA’s) but JSA’s usually only exist for the most routine of maintenance jobs. Some maintenance jobs are done very rarely. Some have never been done before because the equipment in question never failed in that particular way before.
Making Non-Routine Work Safe
The increased risk of maintenance workers is represented in the fatality statistics. Since 1980, 99 maintenance workers have been killed in USW-represented steel plants.
TRANSPORTATION
Transportation workers ship steel to off-site finishing plants and to customers. But their biggest job is moving raw materials and semi-finished products throughout the mill. In large mills transportation uses in-plant railroads with full-size track, cars and engines.
OSHA has no standards for in-plant railroads and the Federal Railroad Administration has no jurisdiction.
In-plant railroads are the leading cause of death by traumatic injury in steel mills.
Forty-nine (49) workers have died in rail accidents in USW-represented plants since 1980; eleven (11) while driving trucks or loading barges. (These numbers do not include crane operators or workers killed by mobile equipment operated entirely within a particular department)
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