Metalcasting processes – from molding to melting, shakeout, grinding, and finishing – create emissions that are hazardous for workers and the environment.
Air Quality and Worker Health & Safety
Foundries processes result in several different types of dust and emissions, each with its own health concerns and exposure limits. These include: airborne silica, metallic dusts, and volatile organic compounds (VOCs.)
Respirable crystalline silica. Most of the dust that accumulates in foundry operations is a byproduct of metalcasting processes. Sand casting processes, of course, generate airborne silica dust. Respirable crystalline silica (RCS) — defined as particles of crystalline silica with a size of less than 4 microns (μ) — is dust that may be inhaled deeply into the lungs, where it can be the cause of considerable damage to workers’ health, including:
? Silicosis, a serious lung disease that can be fatal if left untreated;
? Lung cancer; and
? Kidney disease.
Metallic dust. Foundry workers also may be exposed to metallic dust and fumes produced during melting, pouring, or finishing processes.
? Molten metal releases dangerous gases or fumes that contain tiny molecules of the metals, additives, and contaminants present in the alloy. These molecules may be breathed deeply into the lungs, where they can also cross into the bloodstream and spread to other organs.
? Finishing processes such as abrasive blasting, shot peening, wheel blasting, grinding, or polishing create coarser metallic dust, which may be mixed with silica.
Many of the emissions produced in foundry operations have been designated as toxic air contaminants, including arsenic, cadmium, nickel, lead, and hexavalent chromium. Fume composition depends on the types of metals and alloys being used. Risks associated with breathing metal dusts include:
? Metal fume fever, an acute flu-like illness;
? Chronic lung diseases, including pulmonary fibrosis, chronic bronchitis, and chronic obstructive pulmonary disease;
? Manganism, a neurological disorder with symptoms similar to Parkinson’s Disease;
? Kidney damage; and
? Stomach ulcers
VOCs and other metalcasting emissions. Metalcasting releases organic emissions and noxious gases in addition to metal fumes. These emissions come from the burning of coke as fuel and from additives and contaminants in the molten metal or in the casting sand.
? Burning coke (or oil) as fuel releases carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen oxides, and organic particulate matter.
? Green sand molds contain a variety of binders or other chemicals used to improve the surface finish and reduce defects in castings. Common organic emissions from sand molds include acetophenone, benzene, cumene, dibenzofurans, dioxins, formaldehyde, methanol, naphthalene, phenol, pyrene, toluene, triethylamine, and xylene.
Most organic emissions result from burning or vaporization of organic resins used in moldmaking. During pouring, cooling, and casting shakeout, resins may be incinerated by the heat of the process, sublimated into the air, or adsorbed back into the mold. There is evidence that exposure to these substances can cause health problems, including cancer and disorders of the respiratory, reproductive, and central nervous systems.
Creating a Dust-Control Plan
Foundries must have a dust-control plan in place to protect workers from hazardous fumes and emissions.
Air-quality testing and monitoring.
? Air quality meters or sensors to measure the levels of particulate and gaseous emissions (e.g., VOCs, sulfur dioxide) at various locations in the facility.
? Wearable exposure monitors to determine exposure levels for individuals as they go about their normal shift activities.
Dust hazard elimination/reduction. Where possible, foundries should seek to eliminate sources of hazardous dust and emissions or reduce the volume of dust and fumes produced. Examples include:
? Substituting more hazardous materials with less hazardous materials (e.g., switching to a non-silica-based mold material to eliminate respirable crystalline silica.)
? Changing processes to reduce how much dust or fume ends up in the air (e.g., using water spray systems to keep dust from becoming airborne.)
Engineering controls. Engineering controls are a core element of the dust-control plan. Engineering controls are measures that are designed to reduce or eliminate exposure to hazards in the workplace by modifying the environment or the equipment used. Examples of engineering controls for dust and fumes include:
? Using exhaust ventilation fans or ambient air-filtration systems to pull rising fumes from hot processes out of the building. Exhaust ventilation is typically accompanied by the use of makeup air systems to bring in fresh air and dilute contaminants to acceptable levels, to meet the PEL.
? Keeping dust- and fume-creating processes under hoods or enclosures with the use of a source-capture dust-collection system. A dust collector (such as a cartridge-style dust collector or baghouse) is used to filter contaminants out of the air.
ABOUT KEVA
Keva Casting is a professional casting company that focuses on Construction, Machinery, Automobile, Hardware, Pipeline and many other industries.
We provide top quality products with the best service based on our complete production chain including our own mold design, advanced production techniques, and full management of the supply chain. Keva Casting has two factories located in Zhucheng, China's Shandong province.
We use "shell molding", which is a new technique that has been developed in recent years.This new technique has simplified production procedures and reduced air pollution compared with traditional sand casting and investment casting. Shell making and core making are faster to ensure production in enormous quantities. The dimensions and surface finishing are satisfactory for all kinds of industrial requirements. Besides supplying our own formwork & scaffolding systems, our casting products also supply OEM services in various industries.