Hot metal fragments are thrown off and pose an eye hazard. Eye protection must be used. Detached sprues should normally be returned to the charging region of the melting plant and should not be permitted to accumulate at the despruing section of the foundry.
After despruing but sometimes before most castings are shot blasted or tumbled to remove mould materials and perhaps to improve the surface finish. Tumbling barrels generate high noise levels. Enclosures may be necessary, which can also require LEV.
Dressing methods in steel, iron and non-ferrous foundries are very similar, but special difficulties exist in the dressing and fettling of steel castings owing to greater amounts of burnt-on fused sand compared to iron and non-ferrous castings. Fused sand on large steel castings may contain cristobalite, which is more toxic than the quartz found in virgin sand.
Airless shot blasting or tumbling of castings before chipping and grinding is needed to prevent overexposure to silica dust. The casting must be free of visible dust, although a silica hazard may still be generated by grinding if silica is burnt into the apparently clean metal surface of the casting.
The shot is centrifugally propelled at the casting, and no operator is required inside the unit. The blast cabinet must be exhausted so no visible dust escapes. Water or water and sand or pressure shot blasting may be used to remove adherent sand by subjecting the casting to a high-pressure stream of either water or iron or steel shot.
Sand blasting has been banned in several countries e. The water or shot is discharged through a gun and can clearly present a risk to personnel if not handled correctly. Blasting should always be carried out in an isolated, enclosed space. All blasting enclosures should be inspected at regular intervals to ensure that the dust extraction system is functioning and that there are no leaks through which shot or water could escape into the foundry.
It is advisable to post a notice on the door to the booth, warning employees that blasting is under way and that unauthorized entry is prohibited. In certain circumstances delay bolts linked to the blast drive motor can be fitted to the doors, making it impossible to open the doors until blasting has ceased. A variety of grinding tools are used to smooth the rough casting. Abrasive wheels may be mounted on floor-standing or pedestal machines or in portable or swing-frame grinders.
Pedestal grinders are used for smaller castings that can be easily handled; portable grinders, surface disc wheels, cup wheels and cone wheels are used for a number of purposes, including smoothing of internal surfaces of castings; swing-frame grinders are used primarily on large castings that require a great deal of metal removal. Production in the steel foundry as distinct from a basic steel mill is similar to that in the iron foundry; however, the metal temperatures are much higher.
This means that eye protection with coloured lenses is essential and that the silica in the mould is converted by heat to tridymite or crystobalite, two forms of crystalline silica which are particularly dangerous to the lungs. Sand often becomes burnt on to the casting and has to be removed by mechanical means, which give rise to dangerous dust; consequently, effective dust exhaust systems and respiratory protection are essential.
The light-alloy foundry uses mainly aluminium and magnesium alloys. These often contain small amounts of metals which may give off toxic fumes under certain circumstances. The fumes should be analysed to determine their constituents where the alloy might contain such components.
In aluminium and magnesium foundries, melting is commonly done in crucible furnaces. Exhaust vents around the top of the pot for removing fumes are advisable. In oil-fired furnaces, incomplete combustion due to faulty burners may result in products such as carbon monoxide being released into the air. Furnace fumes may contain complex hydrocarbons, some of which may be carcinogenic.
During furnace and flue cleaning there is the hazard of exposure to vanadium pentoxide concentrated in furnace soot from oil deposits. Fluorspar is commonly used as a flux in aluminium melting, and significant quantities of fluoride dust may be released to the environment. In certain cases barium chloride has been used as a flux for magnesium alloys; this is a significantly toxic substance and, consequently, considerable care is required in its use.
Light alloys may occasionally be degassed by passing sulphur dioxide or chlorine or proprietary compounds that decompose to produce chlorine through the molten metal; exhaust ventilation and respiratory protective equipment are required for this operation.
In order to reduce the cooling rate of the hot metal in the mould, a mixture of substances usually aluminium and iron oxide which react highly exothermically is placed on the mould riser. When the fumes are brown in colour, alarm may be caused due to suspicion of the presence of nitrogen oxides; however, this suspicion is unfounded. The finely divided aluminium produced during the dressing of aluminium and magnesium castings constitutes a severe fire hazard, and wet methods should be used for dust collection.
Magnesium casting entails considerable potential fire and explosion hazard. Molten magnesium will ignite unless a protective barrier is maintained between it and the atmosphere; molten sulphur is widely employed for this purpose. Foundry workers applying the sulphur powder to the melting pot by hand may develop dermatitis and should be provided with gloves made of fireproof fabric.
The sulphur in contact with the metal is constantly burning, so considerable quantities of sulphur dioxide are given off. Exhaust ventilation should be installed. Workers should be informed of the danger of a pot or ladle of molten magnesium catching fire, which may give rise to a dense cloud of finely divided magnesium oxide. Protective clothing of fireproof materials should be worn by all magnesium foundry workers.
Clothing coated with magnesium dust should not be stored in lockers without humidity control, since spontaneous combustion may occur. The magnesium dust should be removed from the clothing. French chalk is used extensively in mould dressing in magnesium foundries; the dust should be controlled to prevent talcosis.
Penetrating oils and dusting powders are employed in the inspection of light-alloy castings for the detection of cracks.
Dyes have been introduced to improve the effectiveness of these techniques. Certain red dyes have been found to be absorbed and excreted in sweat, thus causing soiling of personal clothing; although this condition is a nuisance, no effects on health have been observed. Toxic metal fumes and dust from typical alloys are a special hazard of brass and bronze foundries.
Exposures to lead above safe limits in both melting, pouring and finishing operations are common, especially where alloys have a high lead composition. The lead hazard in furnace cleaning and dross disposal is particularly acute.
Overexposure to lead is frequent in melting and pouring and can also occur in grinding. Zinc and copper fumes the constituents of bronze are the most common causes of metal fume fever, although the condition has also been observed in foundry workers using magnesium, aluminium, antimony and so on.
Some high-duty alloys contain cadmium, which can cause chemical pneumonia from acute exposure and kidney damage and lung cancer from chronic exposure. Casting in permanent metal moulds, as in die-casting, has been an important development in the foundry.
In this case, pattern making is largely replaced by engineering methods and is really a die-sinking operation. Most of the pattern making hazards are thereby removed and the risks from sand are also eliminated but are replaced by a degree of risk inherent in the use of some sort of refractory material to coat the die or mould. Aluminium is a common metal in die casting. Automotive hardware such as chrome trim is typically zinc die cast, followed by copper, nickel and chrome plating.
The hazard of metal fume fever from zinc fumes should be constantly controlled, as must be chromic acid mist. Pressure die-casting machines present all the hazards common to hydraulic power presses. In addition, the worker may be exposed to the mist of oils used as die lubricants and must be protected against the inhalation of these mists and the danger of oil-saturated clothing.
The fire-resistant hydraulic fluids used in the presses may contain toxic organophosphorus compounds, and particular care should be taken during maintenance work on hydraulic systems. Precision foundries rely on the investment or lost-wax casting process, in which patterns are made by injection moulding wax into a die; these patterns are coated with a fine refractory powder which serves as a mould-facing material, and the wax is then melted out prior to casting or by the introduction of the casting metal itself.
Wax removal presents a definite fire hazard, and decomposition of the wax produces acrolein and other hazardous decomposition products. Wax-burnout kilns must be adequately ventilated. Trichloroethylene has been used to remove the last traces of wax; this solvent may collect in pockets in the mould or be absorbed by the refractory material and vaporize or decompose during pouring. The inclusion of asbestos investment casting refractory materials should be eliminated due to the hazards of asbestos.
Foundries stand out among industrial processes because of a higher fatality rate arising from molten metal spills and explosions, cupola maintenance including bottom drop and carbon monoxide hazards during relining. Foundries report a higher incidence of foreign body, contusion and burn injuries and a lower proportion of musculoskeletal injuries than other facilities. They also have the highest noise exposure levels.
A study of several dozen fatal injuries in foundries revealed the following causes: crushing between mould conveyor cars and building structures during maintenance and trouble-shooting, crushing while cleaning mullers which were remotely activated, molten metal burns after crane failure, mould cracking, overflowing transfer ladle, steam eruption in undried ladle, falls from cranes and work platforms, electrocution from welding equipment, crushing from material-handling vehicles, burns from cupola bottom drop, high-oxygen atmosphere during cupola repair and carbon monoxide overexposure during cupola repair.
The bursting or breaking of abrasive wheels may cause fatal or very serious injuries: gaps between the wheel and the rest at pedestal grinders may catch and crush the hand or forearm. Unprotected eyes are at risk at all stages. Slips and falls, especially when carrying heavy loads, may be caused by badly maintained or obstructed floors. Injuries to the feet may be caused by falling objects or dropped loads. Sprains and strains may result from overexertion in lifting and carrying.
Badly maintained hoisting appliances may fail and cause materials to fall on workers. Electric shock may result from badly maintained or unearthed ungrounded electrical equipment, especially portable tools.
All dangerous parts of machinery, especially abrasive wheels, should have adequate guarding, with automatic lockout if the guard is removed during processing. Dangerous gaps between the wheel and the rest at pedestal grinders should be eliminated, and close attention should be paid to all precautions in the care and maintenance of abrasive wheels and in regulation of their speed particular care is required with portable wheels.
Strict maintenance of all electrical equipment and proper grounding arrangements should be enforced. Workers should be instructed in correct lifting and carrying techniques and should know how to attach loads to crane hooks and other hoisting appliances.
Suitable PPE, such as eye and face shields and foot and leg protection, should also be provided. Provision should be made for prompt first aid, even for minor injuries, and for competent medical care when needed. Dust diseases are prominent among foundry workers. Silica exposures are often close to or exceed prescribed exposure limits, even in well-controlled cleaning operations in modern production foundries and where castings are free of visible dust.
Exposures many times above the limit occur where castings are dusty or cabinets leak. Overexposures are likely where visible dust escapes venting in shakeout, sand preparation or refractory repair. Silicosis is the predominant health hazard in the steel fettling shop; a mixed pneumoconiosis is more prevalent in iron fettling Landrigan et al. In the foundry, the prevalence increases with length of exposure and higher dust levels. There is some evidence that conditions in steel foundries are more likely to cause silicosis than those in iron foundries because of the higher levels of free silica present.
In most countries, the occurrence of new cases of silicosis is declining, in part because of changes in technology, a move away from silica sand in foundries and a shift away from silica brick and towards basic furnace linings in steel melting.
A major reason is the fact that automation has resulted in the employment of fewer workers in steel production and foundries. Exposure to respirable silica dust remains stubbornly high in many foundries, however, and in countries where processes are labour intensive, silicosis remains a major problem. Silico-tuberculosis has long been reported in foundry workers.
Where the prevalence of silicosis has declined, there has been a parallel falling off in reported cases of tuberculosis, although that disease has not been completely eradicated. In countries where dust levels have remained high, dusty processes are labour intensive and the prevalence of tuberculosis in the general population is elevated, tuberculosis remains an important cause of death amongst foundry workers.
Many workers suffering from pneumoconiosis also have chronic bronchitis, often associated with emphysema; it has long been thought by many investigators that, in some cases at least, occupational exposures may have played a part. Cancer of the lung, lobar pneumonia, bronchopneumonia and coronary thrombosis have also been reported to be associated with pneumoconiosis in foundry workers. A recent review of mortality studies of foundry workers, including the American auto industry, showed increased deaths from lung cancer in 14 of 15 studies.
Because high lung cancer rates are found among cleaning room workers where the primary hazard is silica, it is likely that mixed exposures are also found. Studies of the carcinogens in the foundry environment have concentrated on polycyclic aromatic hydrocarbons formed in the thermal breakdown of sand additives and binders.
It has been suggested that metals such as chromium and nickel, and dusts such as silica and asbestos, may also be responsible for some of the excess mortality. Differences in moulding and core-making chemistry, sand type and the composition of iron and steel alloys may be responsible for different levels of risk in different foundries IARC Increased mortality from non-malignant respiratory disease was found in 8 of 11 studies. Silicosis deaths were recorded as well. These resulted from exposures after the ls and strongly suggest that the health risks prevalent in the older foundries have not yet been eliminated.
Prevention of lung disorders is essentially a matter of dust and fume control; the generally applicable solution is providing good general ventilation coupled with efficient LEV. Low-volume, high-velocity systems are most suitable for some operations, particularly portable grinding wheels and pneumatic tools. Hand or pneumatic chisels used to remove burnt-on sand produce much finely divided dust. Brushing off excess materials with revolving wire brushes or hand brushes also produces much dust; LEV is required.
Dust control measures are readily adaptable to floor-standing and swing-frame grinders. Portable grinding on small castings can be carried out on exhaust-ventilated benches, or ventilation may be applied to the tools themselves.
Brushing can also be carried out on a ventilated bench. Dust control on large castings presents a problem, but considerable progress has been made with low-volume, high-velocity ventilation systems. Instruction and training in their use is needed to overcome the objections of workers who find these systems cumbersome and complain that their view of the working area is impaired. Dressing and fettling of very large castings where local ventilation is impracticable should be done in a separate, isolated area and at a time when few other workers are present.
Suitable PPE that is regularly cleaned and repaired, should be provided for each worker, along with instruction in its proper use. Since the s, a variety of synthetic resin systems have been introduced into foundries to bind sand in cores and moulds. These generally comprise a base material and a catalyst or hardener which starts the polymerization. Many of these reactive chemicals are sensitizers e. In one study, 12 out of 78 foundry workers exposed to Pepset cold-box resins had asthmatic symptoms, and of these, six had a marked decline in airflow rates in a challenge test using methyl di-isocyanate Johnson et al.
Welding in fettling shops exposes workers to metal fumes with the consequent hazard of toxicity and metal fever, depending on the composition of the metals involved. Welding on cast iron requires a nickel rod and creates exposure to nickel fumes. The plasma torch produces a considerable amount of metal fumes, ozone, nitrogen oxide and ultraviolet radiation, and generates high levels of noise. An exhaust-ventilated bench can be provided for welding small castings. Controlling exposures during welding or burning operations on large castings is difficult.
A successful approach involves creating a central station for these operations and providing LEV through a flexible duct positioned at the point of welding. This requires training the worker to move the duct from one location to another. Good general ventilation and, when necessary, the use of PPE will aid in reducing the overall dust and fume exposures. The highest levels of noise in the foundry are usually found in knockout and cleaning operations; they are higher in mechanized than in manual foundries.
The ventilation system itself may generate exposures close to 90 dBA. Noise levels in the fettling of steel castings may be in the range of to dBA, while those actually encountered in the fettling of cast iron are in the to dBA range. The British Steel Casting Research Association established that the sources of noise during fettling include:. Noise control strategies vary with the size of the casting, the type of metal, the work area available, the use of portable tools and other related factors.
Certain basic measures are available to reduce noise exposure of individuals and co-workers, including isolation in time and space, complete enclosures, partial sound-absorbing partitions, execution of work on sound-absorbing surfaces, baffles, panels and hoods made from sound-absorbing or other acoustical materials.
The guidelines for safe daily exposure limits should be observed and, as a last resort, personal protective devices may be used. This bench incorporates an exhaust system to remove dust.
This improvement is encouraging and leads to hope that, with further development, even greater noise reductions will become possible. This is more prevalent in steel fettlers than in iron fettlers and more frequent among those using rotating tools. The critical vibratory rate for the onset of this phenomenon is between 2, and 3, revolutions per minute and in the range of 40 to Hz.
HAVS is now thought to involve effects on a number of other tissues in the forearm apart from peripheral nerves and blood vessels. It is associated with carpal tunnel syndrome and degenerative changes in the joints.
Vibration transmitted to the hands of the worker can be considerably reduced by: selection of tools designed to reduce the harmful ranges of frequency and amplitude; direction of the exhaust port away from the hand; use of multiple layers of gloves or an insulating glove; and shortening of exposure time by changes in work operations, tools and rest periods.
There are thousands of uses for castings, but some of the more common examples of castings that you see in everyday life include fire hydrants, valve bodies, and engine blocks and many automotive components. Foundry work is one of the oldest manufacturing methods on earth.
Despite the age of the foundry business, the techniques that are used in a foundry for melting metal and making molds have been updated due to countless technological advances over the years. There are more than 2, foundries in the United States today and tens of thousands around the world.
Not only has technology dramatically changed the foundry industry, but the emphasis on safety and consistent procedures have also made foundries today wholly different than they were even 50 years ago.
Due to the different nature of metals, varying inputs are required and different toxic wastes are released from each type. After the metal has been melted, it is poured into the cast already made previously and made to cool and set.
Silica sand, moisture, oils and green sand are mixed together to form a mould cavity. Metal is then poured in this cavity. When the metal is cooled, it is easily separated from the mould. This type of sand should b capable of handling high temperatures and pressure, allow gases to escape, have a constantly small grain size and be non-reactive with metals.
The wastes produced by foundries depend on the type of metal, foundry types. They contain metal, semi-volatile and volatile organic compounds.
Emission control systems can be installed to capture these gases. Liquid wastes in foundry results from water used to chill metal. A water treatment plant can be installed for water waste.
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