Experimental study of oil particle emission rate and size distribution during milling

Abstract

Metalworking fluids (MWFs) used in milling generate oil particles through impaction, action of centrifugal forces and evaporation/condensation mechanisms. The oil particles suspended in the factory atmosphere can affect the health of the labor force. In order to study the emission properties of these oil particles, this work investigates the oil particle emission rate and size distribution during milling using an environmental chamber method. Two commonly used operating modes for MWFs were selected, the minimum quantity lubrication (MQL) mode (40 ml/h) and the cooling mode (1 m³/h). The cooling mode without cutting was studied separately for comparison with the cooling mode with cutting. The results show that the oil particle emission rate in milling ranges from 7.2 to 641 mg/h, and the size distribution ranges from 0.265 to 12.5 µm. Evaporation/condensation is the main mechanism in the MQL mode. The majority of oil particles formed by evaporation/condensation are in the range of 0.265 to 1.8 µm. As the tool rotation speed increases, the particle emission rate increases, while the mass mean diameter (MMD) and the sauter mean diameter (SMD) decrease. Oil particles are mainly generated by the action of centrifugal force in the cooling mode, and mainly distributed in the range of 1.8 to 12.5 µm. The particle emission rate increases with the tool rotation speed, and the particle MMD and SMD increase with the tool rotation speed only in the cooling mode without cutting. The particle emission rate ranging from 1.8 to 12.5 µm, as well as PM5 and PM10, are a polynomial function of the square of tool rotation speed during the cooling mode. The coefficient of determination (R2) is above 0.99. © 2018 American Association for Aerosol Research.