Machinery's Handbook, 31st Edition
EXPOSURE TO METALWORKING FLUIDS 1253 Each MWF class consists of a wide variety of chemicals used in different combina- tions and the risk these chemicals pose to workers may vary because of different manu- facturing processes, various degrees of refining, recycling, improperly reclaimed chem - icals, different degrees of chemical purity, and potential chemical reactions between components. Exposure to hazardous contaminants in MWFs may present health risks to workers. Contamination may occur from: process chemicals and ancillary lubricants inadvertently introduced; contaminants, metals, and alloys from parts being machined; water and clean ing agents used for routine housekeeping; and, contaminants from other environmental sources at the worksite. In addition, bacterial and fungal contaminants may metabolize and degrade the MWFs to hazardous end-products as well as produce endotoxins. The improper use of biocides to manage microbial growth may result in potential health risks. Attempts to manage microbial growth solely with biocides may result in the emergence of biocide-resistant strains from complex interactions that may occur among different member species or groups within the population. For example, the growth of one species, or the elimination of one group of organisms may permit the overgrowth of another. Studies also suggest that exposure to certain biocides can cause either allergic or contact dermatitis. Fluid Selection, Use, and Application.— The MWFs selected should be as nonirritat- ing and nonsensitizing as possible while remaining consistent with operational require- ments. Petroleum-containing MWFs should be evaluated for potential carcinogenicity using ASTM E1687-10 (R2014), “Standard Test Method for Determining Carcinogenic Potential of Virgin Base Oils in Metalworking Fluids”. If soluble oil or synthetic MWFs are used, ASTM Standard E1497-17, “Standard Practice for Selection and Safe Use of Water-Miscible and Straight Oil Metal Removal Fluids” should be consulted for safe use guidelines, including those for product selection, storage, dispensing, and mainte- nance. To minimize the potential for nitrosamine formation, nitrate-containing materi- als should not be added to MWFs containing ethanolamines. Many factors influence the generation of MWF mists, which can be minimized through the proper design and operation of the MWF delivery system. ANSI Technical Report B11 TR2-1997, “Mist Control Considerations for the Design, Installation and Use of Machine Tools Using Metalworking Fluids” provides directives for minimizing mist and vapor generation. These include minimizing fluid delivery pressure, matching the fluid to the application, using MWF formulations with low oil concentrations, avoiding contamination with tramp oils, minimizing the MWF flow rate, covering fluid reservoirs and return systems where possible, and maintaining control of the MWF chemistry. Also, proper application of MWFs can minimize splashing and mist generation. Proper application includes: applying MWFs at the lowest possible pressure and flow volume consistent with provisions for adequate part cooling, chip removal, and lubrication; applying MWFs at the tool/workpiece interface to minimize contact with other rotating equipment; ceasing fluid delivery when not performing machining; not allowing MWFs to flow over the unprotected hands of workers loading or unloading parts; and using mist collectors engineered for the operation and specific machine enclosures. Properly maintained filtration and delivery systems provide cleaner MWFs, reduce mist, and minimize splashing and emissions. Proper maintenance of the filtration and delivery systems includes: the selection of appropriate filters; ancillary equipment such as chip handling operations, dissolved air-flotation devices, belt-skimmers, chillers or plate and frame heat exchangers, and decantation tanks; guard coolant return trenches to prevent dumping of floor wash water and other waste fluids; covering sumps or coolant tanks to prevent contamination with waste or garbage (e.g., cigarette butts, food, etc.); and, keeping the machine(s) clean of debris. Parts washing before machining can be an important part of maintaining cleaner MWFs. Since all additives will be depleted with time, the MWF and additives concentrations should be monitored frequently so that components and additives can be made up as
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