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ObjectiveThis study focuses on the deposition characteristics of oil mist on metal and fabric surfaces in ship cabin. MethodsOil mist is released in an experimental cabin and allowed to deposit on the target surfaces. The mass difference before and after deposition on the surfaces is weighed to determine the deposition mass, and the oil mist deposition characteristics of surfaces with different orientations and materials are compared. The deposition on the horizontal downward surface is reasonably assumed to be gas phase deposition. Its contribution is then estimated and the particle phase deposition velocity is calculated. ResultsThe deposition mass on the horizontal upward surface of the metal is 3.98 times and 4.66 times greater than that on the vertical surface and horizontal downward surface. For fabric surfaces, the deposition mass on the horizontal upward surface is 1.08 times and 1.20 times greater than that of the vertical surface and horizontal downward surface. For material comparison, the deposition mass on the horizontal upward, vertical and horizontal downward surfaces of the fabric is 49.1 times, 169.8 times and 155.5 times greater than that of the metal surface facing in the same direction respectively. Estimates show that the contribution of phase deposition to the metal horizontal and vertical surfaces are 21.5% and 79.2% respectively. The contribution of phase deposition to the fabric surfaces is about 90%. ConclusionsThe oil mist deposition on fabric surfaces is much stronger than that on metal surfaces. The deposition on the metal horizontal upward surface is much greater than that on the vertical surface and horizontal downward surface. The deposition differences between the fabric surfaces in the three orientations are not significant. Regardless of orientation or material, gas phase deposition cannot be ignored as it plays a dominant role in ship cabin environments.

Metalworking fluids are used in many industries, especially those with metalworking processes. Despite their widespread use, these compounds have harmful effects on human health. Therefore, this study aimed to assess the semi-quantitative health risks of oil mists in the automotive industry. In this study, ACGIH, IARC indexes, LD50, and the risk of corrosion were used to determine the hazard rate, with the biggest index serving as the hazard rate's base. The actual exposure level was used to compute the exposure rate. Sampling and determination of oil mists were performed according to NIOSH 5026 method and using a membrane filter (37-mm). All risk rates of oil mists were in the high-risk range (H). The hazard rate level for all oil mists was equal to 4. The exposure rate for all oil mists except one of them was equal to 4. Considering the health risks identified in this study, it can be concluded that lathe workers in the automotive industries have a high risk in terms of metalworking fluids exposure. [ABSTRACT FROM AUTHOR]

Accidental crankcase explosions in marine diesel engines are presumably caused by the inflammation of lubricating oil in air followed by flame propagation and pressure buildup. This manuscript deals with the numerical simulation of internal unvented and vented crankcase explosions of lubricating oil mist using the 3D CFD approach for two-phase turbulent reactive flow with finite-rate turbulent/molecular mixing and chemistry. The lubricating oil mist was treated as either monodispersed with a droplet size of 60 μm or polydispersed with a trimodal droplet size distribution (10 μ m (10 wt%), 250 μ m (10 wt%), and 500 μ m (80 wt%)). The mist was partly pre-evaporated with pre-evaporation degrees of 60%, 70%, and 80%. As an example, a typical low-speed two-stroke six-cylinder marine diesel engine was considered. Four possible accidental ignition sites were considered in different linked segments of the crankcase, namely the leakage of hot blow-by gases through the faulty stuffing box, a hot spot on the crankpin bearing, electrostatic discharge in the open space at the A-frame, and a hot spot on the main bearing. Calculations show that the most important parameter affecting the dynamics of crankcase explosion is the pre-evaporation degree of the oil mist, whereas the oil droplet size distribution plays a minor role. The most severe unvented explosion was caused by the hot spot ignition of the oil mist on the main bearing and flame breaking through the windows connecting the crankcase segments. The predicted maximum rate of pressure rise in the crankcase attained 0.6–0.7 bar/s, whereas the apparent turbulent burning velocity attained 7–8 m/s. The rate of heat release attained a value of 13 MW. Explosion venting caused the rate of pressure rise to decrease and become negative. However, vent opening does not lead to an immediate pressure drop in the crankcase: the pressure keeps growing for a certain time and attains a maximum value that can be a factor of 2 higher than the vent opening pressure. [ABSTRACT FROM AUTHOR]

Mechanical processing and operations are widely involved in modern industry. Large amount of oil mist is tended to be produced and will diffuse in the processing workshop when metalworking fluids are applied on the high temperature workpiece. The ventilation modes and air distributions can influence the air pollutants dilution in machining workshops. Therefore, this paper presents both experimental investigation and simulation study on the oil mist particles diffusion under different ventilation modes. The results identified PM2.5 as the primary component among different oil mist particles generated during a typical machining process. The distribution of oil mist particles in a full-scale machining workshop laboratory was investigated under two ventilation modes: high-sidewall nozzle air supply and low-sidewall air supply. Results revealed obvious influences of both air supply modes on the distribution of oil mist particles. Under the high-sidewall-nozzle air supply mode, the airflow and the oil mist distribution in the workshop was relatively uniform; while the low-sidewall-vent air supply mode led to an uneven distribution of oil mist particles, and the maximum oil mist concentration appeared at the height of 3 m. Under both modes, the attempts to increase the airflow rate are not always successful. Compared with low-sidewall-vent air supply mode, the high-sidewall-nozzle air supply mode presents better performance in achieving lower overall particle concentration level. Overall, the results of this study give useful reference to improve the air quality of industrial plant by properly designing the ventilation mode of machining workshop.

The transport and prediction of the concentration of particles in confined spaces are crucial for human well-being; this has become particularly evident during the current worldwide pandemic. Computational fluid dynamics (CFD) has been widely used for such predictions, relying on Eulerian–Eulerian (EE) and Eulerian–Lagrangian (EL) models to study particle flow. However, there is a lack of research on industrial factories. In this study, a scaled laboratory in an industrial factory was established for oil mist particles in a machining factory, and oil mist dispersion experiments were conducted under roof exhaust and mixed ventilation conditions. After that, the oil mist concentration distribution in the factory under the same working conditions was calculated by Eulerian and Lagrangian methods, and the corresponding calculation errors and resource consumption were compared. It was found that the simulation results of both methods are acceptable for mixed ventilation and roof exhaust ventilation systems. When there are more vortices in the factory, the Lagrangian method increases the computation time by more than 53% to satisfy the computational accuracy, and the computational error between the Eulerian and Lagrangian methods becomes about 10% larger. For oil mist particles with an aerodynamic diameter of 0.5 μm, both Eulerian and Lagrangian methods have reliable accuracy. Based on the same flow field, the Lagrangian method consumes more than 400 times more computational resources than the Eulerian method. This study can provide a reference for the simulation of indoor particulate transport in industrial factories. [ABSTRACT FROM AUTHOR]

In the field of metal cutting, the cutting oil scatters in air as a microscale oil mist, which adversely affects the work environment. A baffle plate-type mist trap was manufactured as simple equipment for collecting oil mist floating in air. The oil mist collection rate and pressure loss were determined using experiments and numerical simulations while varying the number of baffle plates and inflow velocity of air. The experimental results showed that the pressure drop increased with the number of baffle plates, whereas the oil mist collection rate improved. It was also clarified that larger particles can be collected as the number of baffle plates increased. Numerical simulations showed that a high amount of oil mist was trapped upstream of the second baffle plate, and the baffle plate placed further downstream had minimal contribution to oil mist collection. In both the experiments and numerical simulations, the oil mist collection efficiency was the highest when six baffle plates were arranged. This is because the pressure drop increases depending on the number of baffle plates, whereas the mist collection rate is almost constant when many baffle plates are placed.

Accidental crankcase explosions in marine diesel engines are presumably caused by the inflammation of lubricating oil in air followed by flame propagation and pressure buildup. This manuscript deals with the numerical simulation of internal unvented and vented crankcase explosions of lubricating oil mist using the 3D CFD approach for two-phase turbulent reactive flow with finite-rate turbulent/molecular mixing and chemistry. The lubricating oil mist was treated as either monodispersed with a droplet size of 60 μm or polydispersed with a trimodal droplet size distribution (10 μm (10 wt%), 250 μm (10 wt%), and 500 μm (80 wt%)). The mist was partly pre-evaporated with pre-evaporation degrees of 60%, 70%, and 80%. As an example, a typical low-speed two-stroke six-cylinder marine diesel engine was considered. Four possible accidental ignition sites were considered in different linked segments of the crankcase, namely the leakage of hot blow-by gases through the faulty stuffing box, a hot spot on the crankpin bearing, electrostatic discharge in the open space at the A-frame, and a hot spot on the main bearing. Calculations show that the most important parameter affecting the dynamics of crankcase explosion is the pre-evaporation degree of the oil mist, whereas the oil droplet size distribution plays a minor role. The most severe unvented explosion was caused by the hot spot ignition of the oil mist on the main bearing and flame breaking through the windows connecting the crankcase segments. The predicted maximum rate of pressure rise in the crankcase attained 0.6–0.7 bar/s, whereas the apparent turbulent burning velocity attained 7–8 m/s. The rate of heat release attained a value of 13 MW. Explosion venting caused the rate of pressure rise to decrease and become negative. However, vent opening does not lead to an immediate pressure drop in the crankcase: the pressure keeps growing for a certain time and attains a maximum value that can be a factor of 2 higher than the vent opening pressure.

The transport and prediction of the concentration of particles in confined spaces are crucial for human well-being; this has become particularly evident during the current worldwide pandemic. Computational fluid dynamics (CFD) has been widely used for such predictions, relying on Eulerian–Eulerian (EE) and Eulerian–Lagrangian (EL) models to study particle flow. However, there is a lack of research on industrial factories. In this study, a scaled laboratory in an industrial factory was established for oil mist particles in a machining factory, and oil mist dispersion experiments were conducted under roof exhaust and mixed ventilation conditions. After that, the oil mist concentration distribution in the factory under the same working conditions was calculated by Eulerian and Lagrangian methods, and the corresponding calculation errors and resource consumption were compared. It was found that the simulation results of both methods are acceptable for mixed ventilation and roof exhaust ventilation systems. When there are more vortices in the factory, the Lagrangian method increases the computation time by more than 53% to satisfy the computational accuracy, and the computational error between the Eulerian and Lagrangian methods becomes about 10% larger. For oil mist particles with an aerodynamic diameter of 0.5 μm, both Eulerian and Lagrangian methods have reliable accuracy. Based on the same flow field, the Lagrangian method consumes more than 400 times more computational resources than the Eulerian method. This study can provide a reference for the simulation of indoor particulate transport in industrial factories.

Oil mist coalescence and filtering are extensively used in the fields of natural gas purification and chemical production. However, it remains technically challenging to capture high-concentration, small-sized, oil mist droplets under complex industrial field conditions. To solve this problem, three novel high-efficiency coalescence filter cartridges are proposed, which have improved filter material arrangements. The filtering performance of the cartridges was evaluated in the laboratory and at a natural gas pipeline pressure station under different working conditions to understand the mechanism by which high-concentration small-sized droplets are captured. According to the laboratory results, the filtration efficiency for droplets> 0.2 µm can reach 99.99% if the first layer in the cartridge has a small pore size (1.5 µm). The use of a filtering material with a large pore size can reduce the pressure drop. An arrangement of layers with increasing pore sizes can significantly improve the quality factor of the cartridges and decrease secondary entrainment. In the field test, the size distributions of the oil mist under compressor "hot standby" and operating conditions were gained for the first time. The median size of oil mist droplets was 1.2 µm during hot standby and 0.5 µm during operation. Under both compressor modes, the downstream oil mist concentrations of the proposed cartridges were> 95% lower than that of an existing commercial cartridge once filtering reached a steady state. In a long-cycle test under field conditions, the proposed cartridges showed more stable filtering performance than the existing product, with the filtration efficiency being about 40% higher after 15 days. Moreover, the oil mist coalescence mechanism was determined by microscopic characterization of liquid channels. • An improved filter cartridge for oil mist separators was proposed. • An arrangement of layers with increasing pore sizes can significantly improve the quality factor and decrease secondary entrainment. • The proposed cartridges showed more stable filtering performance than the existing product. • The oil mist coalescence mechanism was determined by microscopic characterization of liquid channels. [ABSTRACT FROM AUTHOR]

Oil mist adversely affects the health of workplace workers, and for this reason, regulations on the limitation of the oil-mist exposure of workers are becoming stricter. In order to reduce the amount of the exposure of workers to oil mist, it is important to effectively remove oil mist from machine tools. In this study, the collection efficiency according to the geometry of the oil-mist-collection cyclone consisting of several disks and the output power and rotation speed of the motor were evaluated. Most of the generated oil mists were less than 10 μm, and the mist removal was assessed using an optical particle counter. The cyclone airflow rate increased linearly with the rotational speed, and the rate was affected more by the cyclone geometry than by the power consumption. The mist-removal performance was significantly enhanced when plate- and cone-type disks were added to the rotating blades. The removal efficiencies of PM10 and PM2.5 under the maximum operational conditions of 5000 rpm and a flow rate of 3.73 m3/min were 93.4% and 78.4%, respectively. The removal capacity was more affected by the cyclone geometry than the rotational speed. The experimental results were similar to those predicted by the modified Lapple theory when an appropriate slope parameter (β) was used. [ABSTRACT FROM AUTHOR]

The electrostatic precipitator (ESP) is widely used in the purification of oil mist particles in the industrial workshops. Different from the solid particles, the deposition of oil mist particles in the ESP can reach a steady state and form a saturated oil film on the electrode plate. Based on the deposition experiment data, this paper has established the oil film flow model in ESP coupled with the corona discharge, the gas flow and the oil mist particle deposition model. The characteristics of oil mist particles deposition and the oil film flow were studied. The results show that the oil film is thin in the electrode plate where the current density is high. The oil film is thick at the inlet of ESP and the corresponding collection plate in the middle of the adjacent electrode wires. The peak value appears at the corresponding plate in the middle of the first two electrode wires, which is more than 50 µm. The average oil film thickness is about 9 µm in the current study. As the inlet velocity increases or the applied voltage decreases, the oil film distribution becomes more uniform, and the oil holding capacity of the electrode plate increases. [ABSTRACT FROM AUTHOR]

A large number of metalworking fluids in industrial manufacturing processes generate high-concentrations of oil mist pollution, which is a typical semi-volatile aerosol and is generally composed of liquid particles and volatile gas components. Long-term exposure to oil mist pollution brings a series of occupational diseases to workers. For the semi-volatile aerosol, the traditional filter sampling method will lead to particle volatilization, which underestimates the concentration of particles and overestimates the concentration of gas. Therefore, this study combined the advantages of the electrostatic method and the Tenax tube adsorption method, to develop a more accurate measurement technology. First, a dichotomous sampler that could efficiently separate the gas and liquid phases of aerosols was optimized through a numerical model, which was validated by literature results. Next, a test table for oil mist sampling was built with a sampler which was fabricated by 3D printing, and the performance of the sampler was evaluated. The results show that the sampling technique can separate the gas and particulate phases of the oil mist efficiently and accurately. Compared with the traditional single sampling methods, the new sampler can better determine the true concentration of oil mist. [ABSTRACT FROM AUTHOR]

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Oil mist poses a long-term threat to both the environment and human health, and the high stability of fine oil mist particles makes them difficult to remove efficiently using traditional methods. This study reports on a strategy for the efficient removal of oil mist based on triboelectric negative air ions (TENAIs), delving into the charging and migration characteristics of the air/oil mist system during the oil mist removal process by TENAI. It was found that TENAIs could charge oil mist particles, causing the oil droplets to accelerate or change direction. During this process, submicron oil droplets coalesce into larger droplets, which are then efficiently removed under the coupled action of gravity and electric field forces. Experimental results indicate that the addition of the triboelectric negative air ion system increased the velocity of the oil mist flow field by 15–20 times, and the removal efficiency was enhanced by 280%. This study reveals the microscopic mechanism by which negative air ions promote rapid aggregation and settling of particles, providing a scientific basis for the efficient and sustainable management of oil mist. [Display omitted] • Introduced a new, efficient, and sustainable strategy for oil mist management. • Developed a triboelectric system for oil mist removal, achieving a 280% increase in oil mist removal efficiency. • Unveiled the core mechanisms behind oil mist removal by triboelectric negative air ions. [ABSTRACT FROM AUTHOR]

The use of metalworking fluids during machining can generate oil mist and endanger the health of workers. In order to study the characteristics and emission laws of oil mist generated by machining, this study constructed a test bench to simulate the turning process. Parameters affecting the oil mist generated in the minimum quantity lubrication (MQL) mode and flood cooling mode were studied by means of single-factor experiments, and the formation mechanisms of oil mist were analyzed. The results show that the oil mist generated by the MQL system has two main sources, the initial escape of oil mist into the air and the evaporation/condensation of oil mist. The centrifugation has almost no effect on oil mist formation in the MQL mode. The mass concentration of oil mist generated by the MQL system is proportional to the cutting oil flow rate. When the work-piece is at room temperature, increasing the air supply pressure and nozzle distance, increases the oil mist mass concentration. For the flood cooling mode, the concentration of centrifugal aerosol is linearly and positively correlated with the relative centrifugal force generated by the work-piece, and the coefficient of determination (R2) is above 0.97. The oil mist mass concentrations in MQL mode is 8.33 mg/m3~ 305.88 mg/m3. The MMD and SMD are 0.74 µm to 4.42 µm and 0.31 µm to 2.14 µm, respectively. The oil mist mass concentrations in flood cooling mode is 0.2 mg/m3~ 22.42 mg/m3. The MMD and SMD are 1.81 µm to 6.58 µm and 0.45 µm to 5.13 µm, respectively.

Oil mist adversely affects the health of workplace workers, and for this reason, regulations on the limitation of the oil-mist exposure of workers are becoming stricter. In order to reduce the amount of the exposure of workers to oil mist, it is important to effectively remove oil mist from machine tools. In this study, the collection efficiency according to the geometry of the oil-mist-collection cyclone consisting of several disks and the output power and rotation speed of the motor were evaluated. Most of the generated oil mists were less than 10 μm, and the mist removal was assessed using an optical particle counter. The cyclone airflow rate increased linearly with the rotational speed, and the rate was affected more by the cyclone geometry than by the power consumption. The mist-removal performance was significantly enhanced when plate- and cone-type disks were added to the rotating blades. The removal efficiencies of PM10 and PM2.5 under the maximum operational conditions of 5000 rpm and a flow rate of 3.73 m3/min were 93.4% and 78.4%, respectively. The removal capacity was more affected by the cyclone geometry than the rotational speed. The experimental results were similar to those predicted by the modified Lapple theory when an appropriate slope parameter (β) was used.

• Increase of treated area ratio leads to a variation on the wettability from oleophilic to oleophobic. • Treated filter medium under the optimal spraying time has the highest quality factor. • Optimal spraying time varies with filter media due to different structures. • Quality factors of dual-layer filters with overlapped strips are higher than those with staggered ones. Fibrous coalescence filters are widely used to remove oil mists from air and gas streams in industrial applications. The wettability of filter media significantly affects the filtration performance. Although some efforts have been made to improve the filtration performance based on the modification of filter media wettability by surface treatment method, of which the influence on liquid transport mechanism in the filters and the filtration performance is still needed to elucidate. In this paper, oleophilic filter media were treated by fluorocarbon copolymer solution using a spraying method. The effects of the treated area ratio, spraying time and combinations of patterned filter media on the filtration performance were investigated experimentally. The results show that the increase of the treated area ratio contributes to a variation on the wettability from oleophilic to oleophobic, resulting in a decrease in the jump pressure drop and an increase in the filtration efficiency. The treated filter medium under the optimal spraying time has the highest quality factor, which is 2 ∼ 3 times the untreated one. For the dual-layer patterned filters with alternative oleophobic and oleophilic strips, when the number of oleophobic strips patterned in the first layer filter medium is the same, the pressure drop and filtration efficiency of the overlapped arrangement are lower than those of the staggered arrangement. In all configurations, the highest quality factor is found in the dual-layer filter with the overlapped arrangement and four oleophobic strips patterned in the first layer, resulting from the lowest steady pressure drop and relatively high filtration efficiency. [ABSTRACT FROM AUTHOR]

A large number of metalworking fluids in industrial manufacturing processes generate high-concentrations of oil mist pollution, which is a typical semi-volatile aerosol and is generally composed of liquid particles and volatile gas components. Long-term exposure to oil mist pollution brings a series of occupational diseases to workers. For the semi-volatile aerosol, the traditional filter sampling method will lead to particle volatilization, which underestimates the concentration of particles and overestimates the concentration of gas. Therefore, this study combined the advantages of the electrostatic method and the Tenax tube adsorption method, to develop a more accurate measurement technology. First, a dichotomous sampler that could efficiently separate the gas and liquid phases of aerosols was optimized through a numerical model, which was validated by literature results. Next, a test table for oil mist sampling was built with a sampler which was fabricated by 3D printing, and the performance of the sampler was evaluated. The results show that the sampling technique can separate the gas and particulate phases of the oil mist efficiently and accurately. Compared with the traditional single sampling methods, the new sampler can better determine the true concentration of oil mist.

Metalworking fluids used in industrial workshops may present a major threat to the health of workers who have been exposed to a high oil mist concentration over a long period of time. Therefore, monitoring the temporal and spatial distribution of particulate matter concentration has great practical significance for the control of oil mist. Traditional particle monitors are generally cumbersome, expensive, and difficult to maintain, which to some extent restricts their extensive use in workshops. Recent years have witnessed tremendous developments in the area of low-cost sensors, which are of great help in obtaining high-density pollution data. In this paper, we evaluate the performance of an inexpensive laser sensor (A4-CG) during long-term oil mist monitoring in a machine shop for the first time. With the use of Lora technology, we developed an online oil mist monitoring network to access real-time concentration, temperature, and humidity information from distributed monitors. According to the results, the sensor data correlated well with measurements by the reference instrument (R2 = 0.96), which means that the distributed sensor network can accurately detect the concentration level of oil mist in the workshop. In fact, most of the sensors demonstrated stable operation for up to half a year according to cluster analysis, while several sensors exhibited serious data drift. Furthermore, the results indicate that the peak oil mist concentration in most areas during production exceeded the value of 0.5 mg m−3 recommended by NIOSH, and it was found that appropriately lowering the relative humidity can make sampling more accurate, while lowering the temperature can reduce the oil mist concentration in the workshop. Thus, measures to control oil mist such as generation and distribution of pollution sources should be on the agenda. [ABSTRACT FROM AUTHOR]

• Contact angle and surface tension of oil/refrigerant mixture were measured. • The contact angle of the PAG/CO 2 mixture decreased with refrigerant concentration. • PAG and PAG/CO 2 mixture showed complete wetting on metal plates. • The wetting progressed according to Tanner's law. Separation of oil from refrigerant is important to reduce the oil circulation rate in a refrigeration cycle. Since the oil separation depends on the droplet size of oil mist in a compressor and the condition of the oil film on the inner surface of the compressor shell, this study examined the wettability of a metal surface with the oil/refrigerant mixture and surface tension. The wettability of metal surfaces with PAG/CO 2 mixture was evaluated by measuring the contact angle of droplets on the metal surface. The surface tension of the mixture was measured using a pendant drop method. It was found that the wetting of the metal surface with the oil/refrigerant mixture showed a complete wetting, and the contact angle decreased with the refrigerant concentration. Taking the Ohnesorge number into account, the initial spreading of oil mist on the metal surface under discharge conditions should immediately become a viscus-dominant condition. [ABSTRACT FROM AUTHOR]

Mechanical processing and operations are widely involved in modern industry. Large amount of oil mist is tended to be produced and will diffuse in the processing workshop when metalworking fluids are applied on the high temperature workpiece. The ventilation modes and air distributions can influence the air pollutants dilution in machining workshops. Therefore, this paper presents both experimental investigation and simulation study on the oil mist particles diffusion under different ventilation modes. The results identified PM2.5 as the primary component among different oil mist particles generated during a typical machining process. The distribution of oil mist particles in a full-scale machining workshop laboratory was investigated under two ventilation modes: high-sidewall nozzle air supply and low-sidewall air supply. Results revealed obvious influences of both air supply modes on the distribution of oil mist particles. Under the high-sidewall-nozzle air supply mode, the airflow and the oil mist distribution in the workshop was relatively uniform; while the low-sidewall-vent air supply mode led to an uneven distribution of oil mist particles, and the maximum oil mist concentration appeared at the height of 3 m. Under both modes, the attempts to increase the airflow rate are not always successful. Compared with low-sidewall-vent air supply mode, the high-sidewall-nozzle air supply mode presents better performance in achieving lower overall particle concentration level. Overall, the results of this study give useful reference to improve the air quality of industrial plant by properly designing the ventilation mode of machining workshop., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

• Slow increase of Δp (creep) during steady state is caused by accumulation of oil. • Creep is most pronounced for highly efficient filter media. • Different steady states for pre-saturated and initially dry filters. • Temporarily reduced air flows might result in pre-saturated steady states. This paper addresses the phenomenon of a slow Δ p increase ("creep") sometimes observed in mist filters during their so-called steady-state operation, especially at relatively high flow rates and aerosol loads (Kolb et al., 2017). This creep phenomenon draws into question the concept of steady state and awaits a physical explanation on the basis of more systematic data. The present study was performed with conventional glass microfiber filter media at filter face velocities in the range of 1–70 cm/s, using submicron oil aerosol at loading rates up to 1.1 g/(m2 s). Experiments started either with a dry filter (designated as S 0 = 0, where S stands for the liquid saturation level), or with a completely pre-saturated filter (designated as S 0 = 1). The S 0 = 0 runs reached "steady state" (defined here as the onset of drainage) after approximately 0.3 h and were then loaded continually for another 100 h. Runs starting at S 0 = 1 reached a steady state very quickly. With regard to Δ p, all filters featured Δ p creep when starting from S 0 = 0. For coarse filter grades, Δ p creep effectively ended in less than 40 h at moderate flow velocities; finer grades crept further and did not stop creeping within any reasonable loading time. When starting from S 0 = 1, a steady Δ p endpoint was reached rapidly, but was considerably higher than the level attained by creep. It was further shown that creep is associated with a slow increase in the saturation level and that S approached the (higher) level of pre-saturated filters. The increase in S during creep was associated with the formation of additional fine oil channels. Conversely, oil channels were completely absent in pre-saturated filters and the liquid was uniformly dispersed. Using simple theoretical considerations for flow in porous media, the observed differences in Δ p are explained in part by the difference in S between S 0 = 0 and S 0 = 1 filters, and in additionally also by taking into account the different liquid distribution patterns. We conclude that the onset of drainage under steady external conditions – the stage conventionally viewed as the beginning of steady-state operation – does not automatically represent an internal steady state with regard to saturation levels or pressure drop; and presumably also not for the oil distribution pattern. The internal saturation reaches a stable endpoint sooner than the pressure drop, which may continue to creep for the lifetime of the filter. Of and when a transition from channel patterns to homogeneous oil distribution occurs during steady operation is not known. However, the transition can be forced rather quickly by operating the filter intermittently at a very low flow velocity. [ABSTRACT FROM AUTHOR]

Metal working fluidis widely used as coolant, lubricant and rust remover in mechanical processing. Oil mist will be formed in the process of metal working fluid. The composition of oil mist is complex, which can produce many adverse effects on the environment and operators. This paper reviews the health hazards of metal working fluid oil mist on human skin, respiratory system, teratogenic and carcinogenic aspects, and discusses the establishment of occupational exposure limits in workplaces of oil mist in foreign countries, in order to provide reference for the prevention and control of occupational health risks of metal working fluid oil mist and the establishment of occupational exposure limits of oil mist in workplaces in China.

Building on work by Kampa et al. (2014) about the liquid distribution in multi-layer oil mist filters, a mesoscale empirical model is proposed for their efficiency. It decomposes the total penetration into a product of independent ‘building blocks’ that are aligned with the mesoscale liquid distribution in steady state, essentially in the form of an oil film and a channel region. The film (typically one very thin region per sandwich) is associated with a film penetration P film and the channel region (consisting typically of multiple layers) with a channel penetration P channe l . The first layer of wettable media also represents a separate contribution P 1st layer . A method is described to derive these unit penetrations from a set of measurements. Experiments are then carried out with filters composed of conventional glass microfiber media, both wettable and non-wettable to compressor oil, in which the fractional penetration of the entire sandwich was measured by SMPS between about 30 and 700 nm. It is shown that the film penetration is substantially reduced for particles above about 100 nm in comparison to that of the dry media due to enhanced inertial deposition, while the channel penetration is generally higher across the board, probably because of a loss of active fiber in the partially saturated media. The last part of the paper is dedicated to practical consequences of this efficiency model. It is shown that the fractional efficiency for an arbitrary number of (identical) layers can be predicted quite accurately from the unit penetrations. Additional measurements of the total downstream concentration as a function of time are used to discuss and explain changes from start-up until steady state. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to assess short-term changes in pulmonary function in drill floor workers currently exposed to airborne contaminants generated as a result of drilling offshore. We also aimed to study the prevalence of pulmonary fibrosis using high-resolution computed tomography (HRCT) scans of another group of previously exposed drill floor workers.Methods: Pulmonary function was measured before and after a 14-day work period in a follow-up study of 65 drill floor workers and 65 referents. Additionally, 57 other drill floor workers exposed to drilling fluids during the 1980s were examined with HRCT of the lungs in a cross-sectional study.Results: The drill floor workers had a statistically significant decline in forced expiratory volume in 1 s (FEV1) across the 14-day work period after adjustment for diurnal variations in pulmonary function (mean 90 mL, range 30-140 mL), while the small decline among the referents (mean 20 mL, range − 30 to 70 mL) was not of statistical significance. Larger declines in FEV1 among drill workers were associated with the fewer number of days of active drilling. There were no signs of pulmonary fibrosis related to oil mist exposure among the other previously exposed drill floor workers.Conclusion: After 14 days offshore, a statistically significant decline in FEV1 was observed in the drill floor workers, which may not be related to oil mist exposure. No pulmonary fibrosis related to oil mist exposure was observed. [ABSTRACT FROM AUTHOR]

The aim of this experimental study is to investigate the separation performances of a new set of small cyclones. The diameter of these cyclones spans the range of 20–45 mm, which is the typical size of these devices when they are used for separating oil mist from blow-by gases in internal combustion engines. To reproduce the flow rates and oil load of combustion engines, we developed a flow bench, with a polydisperse aerosol generator producing engine oil droplets with diameter in a 0.3–10 µm range. Measurements of the aerosol particle concentrations upstream and downstream of the cyclone permitted the determination of the particle collection efficiency, for the six devices that were tested, with flow rates ranging from 20 to 200 Nl/min which are typical operating conditions. For the six cyclones, the geometry is normalized and all internal dimensions within the cyclone are proportional to its diameter. With the operating conditions of this study, the annular Reynolds number varied in the range 1.27×10 3 to 12.2×10 3 . From the measured fractional collection efficiency curves, dimensionless cut-off aerodynamic diameters were determined. These measurements have been compared with available correlations for the determination of this dimensionless diameter as a function of the annular Reynolds number. Different correlations are proposed in this study, for the evaluation of the cut-off diameter and for the shape of the collection efficiency. We were able to establish that the collection efficiency curve dimensionless slope is correlated to a Reynolds number. [ABSTRACT FROM AUTHOR]

The dependence of the differential pressure drop Δ p and the level of internal oil saturation S on the flow velocity of the air were investigated experimentally for a typical oil mist filter composed of oleophilic glass microfiber layers. Over a wide range of filter face velocities ( v = 5–70 cm/s) and liquid loading rates ( R = 15–125 mg / ( m 2 s ) ), and within the accuracy of the measurements, the “wet” pressure drop of the filter Δ p - Δ p 0 (i.e. the increase in Δ p over the “dry” pressure drop Δ p 0 ) was constant and did not show a systematic dependence on v . When decomposing the wet pressure drop into its components Δ p -jump and channel- Δ p , the Δ p -jump was also independent of the oil loading rate. The level of internal liquid saturation S was inversely proportional to v , with an empirical fit function S = 1 / ( 1 + v / v ∗ ) . The characteristic velocity v ∗ was found to depend on the oil loading rate, and presumably also depends on the media structure which was not varied here. This filter behavior is consistent with the “jump-and-channel” model proposed recently by Kampa et al. (2014). The experiments further showed that the “steady-state” pressure drop under constant filter operating conditions underwent a gradual increase with time (termed “ Δ p -creep”) that depends on operating conditions. This Δ p -creep diminishes gradually and was found to become stronger with increasing loading rate and filter face velocity. At the highest rate of increase (i.e. v = 70 cm/s, R = 125 mg / ( m 2 s ) ), an experiment lasting for 1100 h did not suffice to attain an asymptotic level for Δ p . Creep was found to be associated with a gradual increase in saturation and must therefore be classified as an(other) instability phenomenon in oil mist filters. [ABSTRACT FROM AUTHOR]

A comparative investigation was conducted on bubble formation and drop entrainment rates from oil mist filters in steady state operation, in order to establish a firm link between the two mechanisms. Rates were measured as a function of key filter operating parameters at different points of the filter surface, using wettable glass microfiber media as typical representatives of this application. Also, data for the thickness of the drainage film were obtained along the rear filter surface. For a given set of operating conditions, the bubble formation rate, the entrainment rate and the thickness of the oil film were found to increase roughly in proportion between the top and the bottom of the (vertically installed) filter. Bubble formation rates increased roughly tenfold along that path, from typically about 500–5000 bubbles per s and cm 2 , while entrainment rose from about 1000–3000 small drops per s and cm 2 . The drop size was narrowly confined to between about 1 and 2 µm, regardless of vertical position on filter surface and operating conditions. Both rates increased systematically with oil loading rate, but were relatively independent of the airflow velocity. The average number of fragment drops per bubble was on the order of 1, independent of oil loading rate. Independent measurements of bubble fragmentation on a free oil surface also gave an average fragment-to-bubble ratio close to unity for small bubbles (≤3 mm), but showed an increase ∼d 2 for larger bubbles. Overall, these measurements lend strong support to the contention that bubbling is the dominant mechanism of entrainment from the type of oil mist filter media investigated. [ABSTRACT FROM AUTHOR]

Lubrication oil used in refrigerant compressors forms oil mist in the compressor shell. Some of the oil mist is discharged into a refrigeration cycle with refrigerant and causes degradation of heat transfer in heat exchangers. Since the generation of the oil mist is related to the Weber number, it is necessary to measure the surface tension of the oil/refrigerant mixture before discussing the oil mist generation in the compressor. In this study, the maximum bubble pressure method was adapted to measure the surface tension of PAG (polyalkylene glycol) oil/CO 2 mixture. The density of the mixture needed for the measurement was also carried out. It was found that the surface tension of PAG/CO 2 mixture sharply decreases with an increase in the concentration of the refrigerant in the mixture. The surface tension of the mixture under 10 MPa and 100 °C is estimated to be 14.6 mN m −1 by an extrapolation. [ABSTRACT FROM AUTHOR]

Purpose: To study longitudinal changes in lung function in asphalt pavers and a reference group of road maintenance workers, and to detect possible signs of lung disease by high-resolution computed tomography (HRCT) scans. Methods: Seventy-five asphalt pavers and 71 road maintenance workers were followed up with questionnaires and measurements of lung function. Not every worker was tested every year, but most of them had four or more measurement points. The 75 asphalt pavers were also invited to have HRCT scans of the lungs at the end of the follow-up period. Results: Mean annual decline in forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV) of the asphalt pavers was 58 and 35 ml, respectively. Adjusted for age at baseline, packyears of smoking and BMI, the asphalt pavers had a significant excess annual decline in FVC and FEV compared to the references. The screedmen, the most exposed group of the asphalt pavers, showed a significantly larger decline in FVC than the other asphalt pavers ( P = 0.029). Fine intralobular fibrosis without evident cysts was identified with HRCT in three subjects (4 %). Conclusion: We conclude that our findings may indicate an excess annual decline in FVC and FEV related to exposure to asphalt fumes. The screedmen, who carry out their work behind and close to the paving machine, had the largest decline in lung function. The finding of adverse pulmonary effects in asphalt pavers calls for better technological solutions to prevent exposure. [ABSTRACT FROM AUTHOR]

Internal gas velocity fluctuations and their effects on the mist diffusion process were examined in a long horizontal pipe to understand oil mist transportation, particularly in the laminar-to-turbulent flow transition region. Three hot-wire anemometers and aerosol concentration monitors were used to deduce these effects as the two-phase mist flow gradually developed in the stream-wise direction. We found significant axial mist diffusion at Reynolds numbers ( Re ) < 1000 because of passive scalar transport by Poiseuille flow. However, this diffusion was restricted by the non-zero inertia of the mist at a Stokes number, O (10 −5 ), relying on the Brownian motion of the mist. At Re > 2400, a sharp mist waveform was maintained by a turbulent flow with active radial mixing. New data were obtained within the range of 1000 < Re < 2400, which cannot be explained by interpolation between the above-mentioned two states. The mist concentration displays multiple temporal peaks at Re < 2000 owing to perturbations of localized turbulence as well as radial anisotropy as being conveyed more than 2000-diameters in distance. This behavior is caused by intermittent disturbances induced by the pipe wall roughness, which sharply distorts the wall-aligned laminar mist layer left by parabolic axial stretching of local laminar flow. [ABSTRACT FROM AUTHOR]

[Display omitted] • A method for preparing glass fibre media with good oleophobic properties and mechanical strength was developed. • Trends in pressure drop and droplet penetration ratio of combined filters over time were investigated systematically. • Filter with decreasing pore size gradient had low pressure drop and best comprehensive performance for submicron droplets. • A mechanism of filter with increasing pore size gradient to improve filtration efficiency for submicron droplets was proposed. • A drainage layer was conducive to capturing re-entrained micron droplets. Pore size is a key factor that influences the removal of oil mist droplets by a coalescence filter. However, the influence of the pore size distribution among different filter layers on filtration performance has not been thoroughly explored. In this work, a method for preparing glass fibre filtration media with a specific structure as well as good oleophobic properties and mechanical strength was developed by combining the wet-spinning method and immersive modification. The prepared single-layer media were combined in various three-layer structures with increasing pore size gradient, decreasing pore size gradient and uniform pore size distribution. The trends in the pressure drop and droplet penetration ratio of the resulting combined filters over time were analysed systematically. The results demonstrated that in the combined filter, the first layer material had a significant influence on the filtration process and steady-state performance. Throughout filtration, the pressure drop of the filter with a decreasing pore size gradient had layering characteristics, which was conducive to capturing droplets within different particle size intervals in different stages and thereby relieving the operational pressure on different layers. Hence, the filter with a decreasing pore size gradient had a relatively low steady-state pressure drop and the best comprehensive filtration performance for submicron droplets. However, the filter with an increasing pore size gradient had the highest separation efficiency for submicron droplets and its concentration of steady-state downstream droplets was 19% lower than that in the filter composed of three layers of minimum pore size materials. The proposed mechanism by which the filter with the increasing pore size gradient improved the coalescence filtration efficiency for submicron droplets was based on capillary theory. [ABSTRACT FROM AUTHOR]

Volatile organic compounds(VOCs) are regarded as a harmful cause substance not only causing air pollutions but also causing global warming phenomenon. For this reason, VOCs are managed politically to reduce emissions by each country. In particular, the vapor from the gas station contains VOCs which is harmful to the human body such as carcinogens benzene and pollute the atmosphere, the Ministry of Environment defined every gas station must install vapor recovery equipment to recover volatile organic compounds. Recently, there are many accidents caused by existing vapor treatment methods, the liquefaction recovery technology is getting the spotlight to cool the vapor at the field. However, because the liquefaction recovery technology have risks of fire or explosion in accordance with temperature, the real time monitoring is critical factor. In this paper, we implement an Android-based monitoring application for liquified vapor recovery device which attached sensor module for temperature and power to monitoring real time information. [ABSTRACT FROM AUTHOR]