10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Characterization of Nanometer-Sized Oil Mist Generated in Metal Machining Process
MORIAKI IWASAKI, Kojiro Hirai, Kanta Fukumori, Hidenori Higashi, Takafumi Seto, Kanazawa University
Abstract Number: 308 Working Group: Workplace Aerosol
Abstract Oil mist generated by metal machining has negative effects to human and working environments in the factory. In this study, size distributions of nanometer-sized oil mist generated from three industrial metal (steel) machining process, lathe machining, cutting, and grinding, were investigated using the electrical mobility-based instrument (EEPS, TSI model 3090) and optical particle spectrometer (Welas model 2000) at the exhaust pipe. In all three machining processes, the number concentration of nanoparticles (< 100 nm) increased up to 107 particle/cc after the each machining process started. Peak size of the generated nanoparticles was almost consistent at around 60 nm in the mobility diameter. Condensation of thermally evaporated oil is considered to be major source of nanoparticles in the lathe machining and grinding processes, where water-soluble and insoluble lubricant oil were used, respectively. On the other hand, more steep and clear feature of nucleation and growth was seen in the cutting process, while no lubricant oil was used. In this process, small amount of water-soluble oil remained on the surface of the works after the previous machining process (lathe machining) and these small amount of residual oil might be the precursor of nanoparticles generated in the following cutting process.
In the real industrial processes, the machining was operated in the closed chamber, however, the work pieces were replaced from the front door by the worker. Therefore, the timing for opening the door was synchronized with some time delay from the machining period. In addition, the air of the machining chamber was continuously exhausted in the cutting and grinding process. In spite of these countermeasure, the high number concentration (> 8,000 particles/cc, > 300 nm) of the aerosol was detected at the grinding process, probably because the large consumption of oil (water-insoluble) for cooling the work. It was found that the time delay between opening the door and the exhaust pumping effectively decrease the leakage of oil mist to the working environment of the lathe machining and cutting processes.