1.2 The existence of oil mist Next page Diesel Engine Fan Blades,Cooling Fan Blades,Axial Cooling Fan Parts,Engine Cooling Fan Changzhou Keyleader Fan Technology Co. Ltd. , https://www.keyleaderfan.com
In the metal processing of car, milling, drilling, grinding, etc., due to the use of metal cutting fluid, a large amount of oil mist particles are formed in the air. This phenomenon has caused widespread concern about air quality problems in workers' breathing areas. Because long-term exposure to this oil mist is very unfavorable to workers' health, according to the National Institute of Occupational Safety and Health (NIOSH), as many as 1.2 million workers are exposed to metal cutting fluid oil mist every year... Therefore, for metal The study of cutting fluid oil mist is a significant topic.
1 Metal cutting fluid oil mist generation
1.1 Mechanism of oil mist generation
In order to effectively lubricate, cool and clean, the metal cutting fluid undergoes the process of pump circulation, jetting and high-speed rotation of the tool or workpiece, and the high temperature evaporation, which determines the cause of the oil mist is very complicated. Mechanical, physical, and chemical factors interweave and work together. However, not all factors have a decisive influence on the generation of oil mist. The formation of oil mist in metal cutting fluid during processing can be mainly attributed to two mechanisms, atomization and evaporation: atomization is the conversion of mechanical energy into surface energy of droplets. The process is mainly caused by the intense impact of the liquid on the fixed and rotating unit in the machine tool system, which is broken up to form small droplets floating in the working environment; the evaporation occurs due to the large amount of heat generated in the cutting zone, which is passed through the cutting The liquid causes its temperature to be significantly higher than the saturation temperature, and boiling occurs on the solid-liquid contact surface to generate steam. These vapors then condense with small droplets or other particles in the surrounding air to form an oil mist. Figure 1 is a schematic diagram of the mechanism of oil mist formation during processing. 
The metal cutting process can produce the following three types of oil mist:
(1) A clean oil mist generated by jet impact, free of solid dust;
(2) Smoke generated by evaporation or burning due to high temperature of heating or high-speed cutting;
(3) Oil mist containing grinding dust generated by metal cutting fluid jetting during grinding.
Oil mist is produced in different ways, and its particle diameter range is also quite different. Under normal circumstances, the oil mist generated by the mechanical atomization process mainly exists in the form of droplets, and the diameter of the droplets is wide, usually 2 to 10 um. The oil vapor generated by evaporation also forms a very small diameter condensate suspension during the condensation process, and the particle size is usually less than 2 um. Medical research has shown that oil vapors and large particle droplets are relatively less harmful to human lungs. Oil mist in the form of oil vapor is inhaled into the lungs and exhaled. They are not captured by the alveoli, and large droplets of oil cannot enter the lungs through the nose and bronchi. Only in the form of droplets, oil mist particles with a diameter of less than 5um can reach the alveoli smoothly and precipitate in the lungs, thus causing greater harm to the human body.
2 Harm of metal cutting fluid oil mist
The presence of metal cutting fluid oil mist increases the risk of fire hazard slipping on the oil mist floor. If the mist air is discharged from the workshop, it will also pollute the environment. The biggest harm to the cutting fluid oil mist is that it is in contact with ring. Long-term exposure of workers to metal cutting fluids has a significant increase in diseases such as diseases, allergic skin diseases and malignant tumors, and may cause hereditary effects. Metal cutting fluids are complex in composition, and additives and contaminants may cause sudden asthma as a stimulating factor, worsen the condition of the original asthma, or cause airway discomfort in patients without asthma. Among the four types of metal cutting fluids, soluble oils and pure oils are associated with asthma. The three categories of pure oil, soluble oil and synthetic oil have been confirmed because the inhalation process causes airway dysfunction and respiratory diseases in workers. Even if the oil mist concentration is only 0.41 ~ 0.55mg / m, long-term exposure of workers to this oil mist can lead to chronic bronchitis, chest discomfort and airway irritation. In the early days, there was no research on allergic pneumonia in workers exposed to metal cutting fluid oil mist. However, due to the surge in the number of workers suffering from allergic pneumonia in recent years, the fact that long-term exposure to oil mist can cause pneumonia has been studied and Confirmed. Research data on the effects of metal cutting fluid oil mist on workers' lung function is still scarce. One of the reasons for this is that the observed decline in lung function is mostly unrecoverable. In addition, the decrease in lung function is related to the amount of oil mist contacted, which is a result of long-term accumulation. However, the results of the animal-based study showed that when the dog was exposed to 5 to 100 mg/m oil mist for more than 12 months, fat-containing alveolar and macrophage fatty granuloma appeared, and the respiratory tissue showed morphological changes.
Another major hazard of metal cutting fluid oil mist is its carcinogenicity. The carcinogenicity of metal cutting fluid depends mainly on the concentration of its additives, the contamination and the conditions of use. At present, there is no research on the carcinogenicity of metal cutting fluids for humans, and experimental studies on animals have found that oil mist of cutting fluid can cause skin tumor/skin cancer, lung cancer and pancreatic cancer. There is still much debate about the carcinogenicity of cutting fluid oil mist: Although many epidemiological studies have reported the carcinogenic tendency of metal cutting fluids and their oil mists, the latent period of cancer is particularly long, epidemiological Research can often only assess the hazards caused by a substance 20 to 30 years ago. To this end, researchers have pointed out that the composition of the metal cutting fluid decades ago is completely incapable of representing the current cutting fluid. In particular, the refinery process has undergone tremendous changes, and polycyclic aromatic hydrocarbons (PAHs) and other undesirable components have been removed to a greater extent. Therefore, it is not appropriate to extend the originally proven carcinogenic tendency to the current cutting fluid. However, due to the complexity of the composition of the metal cutting fluid, it is very difficult to simply prove that it is not carcinogenic. The study of the effects of oil mist on cutting fluids on genetics is minimal compared to studies on other aspects of health hazards. According to a 1995 study by Fuchs J et al., the IARC (United Nations International Agency for Research on Cancer) characterized N-nitrosodiethanolamine (NDELA) as a 2B carcinogen (which may be carcinogenic to humans). NDELA strongly affects the breakage of DNA strands in mononuclear blood cells. Workers exposed to air with a NDELA concentration greater than 500 mg/m had a significantly greater number of DNA strand breaks than those exposed to concentrations below 50 mg/m. Although EPA (US Environmental Protection Agency) has banned NDELA as an additive to metal cutting fluids, triethanolamine (TEA) and diethanolamine (DEA) can still react under the action of nitrosating agents in metal cutting fluids. Generate NDELA in .
Formation and control of metal cutting fluid oil mist (Figure)