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Oil mist extraction and oil mist filters 

Machining without cooling lubricant mist 
(oil and emulsion mist)

Machining or simply cutting is the collective term for manufacturing processes in which chips are removed from a workpiece with the aid of a tool. Typical machining processes are turning, drilling, milling, grinding, sawing and planning. The high productivity required today in the manufacture of metal parts demands high feed rates and cutting speeds. 

The equally high speeds cause a high level of heat development on workpieces and tools. The required cooling is usually achieved by supplying cooling lubricant during machining. It provides cooling and lubrication and removes the chips. The mechanical and thermal energy causes the cooling lubricant to atomize and evaporate and enter the environment, polluting employees, equipment and buildings.

Cooling lubricant mist (cooling lubricant mist, oil mist, emulsion mist) is harmful to health and dangerous to humans due to its respiratory properties. This not only affects employees who work directly on the machining process, but also neighbouring employees. In addition, the oil and emulsion mist spreads throughout the entire hall as a so-called diffuse emission. This affects all skilled workers in the hall.

This summary provides a comprehensive and compact overview of the hazards caused by cooling lubricant mist. It also shows how it is possible to ensure a safe and legally compliant machining process.

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Content:

Danger to humans - why cooling lubricant mist is harmful

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The hazards posed by oil and emulsion mists result on the one hand from the different ingredients and on the other hand from the fineness of the emission. Different types of cooling lubricant mist are produced depending on the machining process, the material and the cooling lubricant used.

Therefore, oil and emulsion mist is categorized according to its effect on humans.

  • Oil mist and oil smoke that is harmful to the respiratory tract and lungs
    Exposure leads to impairment of the respiratory tract, the consequences are respiratory diseases such as bronchitis.

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  • Toxic and carcinogenic oil mist and oil smoke
    Depending on the additives used in the cooling lubricant, a toxic or carcinogenic effect of oil mist can be assumed. Organizational and technical protective measures are therefore essential.

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Cooling lubricant mist is this fine

The smaller the cooling mist emissions are, the deeper they can penetrate the human respiratory tract. Gaseous emissions such as vapours cannot be retained by the human body on its own. We divide emissions into the following categories based on their size:

  • Inhalable aerosols:
    Aerosols with a diameter of less than 10 micrometers are inhaled.
  • Respirable aerosols:
    Aerosols of around 2.5 micrometers in size penetrate the lungs.
  • Alveoar aerosols:
    Aerosols with a diameter of approx. 1 micrometer penetrate the branches of the lungs.
  • Ultrafine aerosols:
    Aerosols smaller than 0.1 micrometers can no longer be stopped even by the branches of the lungs. They reach the blood.
  • Gaseous emissions:
    Gaseous emissions are distributed throughout the body via the bloodstream. Depending on the effect, a distinction can be made between asphyxiating, irritating, corrosive or direct effects on tissue and cells. 

Regulations and legal base 

Cooling lubricants are very difficult to classify legally due to the wide range of ingredients. One possibility is to differentiate them based on their miscibility with water:

  • Water-miscible cooling lubricants are mixtures of water and various additives (oils, corrosion inhibitors, biocides, high-pressure additives). They are referred to as emulsions.
  • Non-water-miscible cooling lubricants are usually based on mineral oils and contain numerous additives. They are referred to as oil.

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In Germany and Austria, the limit value for the workplace is the sum of cooling lubricant mists and vapours:

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limit value category Germany Austria
Sum limit value from aerosol and vapor AGW 10 mg/m³ 20 mg/m³
of which maximum proportion of aerosols AGW keine Begrenzung des Aerosolanteils 1 mg/m³

Reduction of sources of danger

Employers are obliged to carry out a risk assessment for their machining work. It must be carried out before work commences. The results of the assessment must be evaluated and documented. This also includes suitable protective measures to prevent and reduce hazards from cooling lubricant mist and smoke.

The following sequence is necessary for the assessment:

  • Substitution
    Substitution refers to the use of lubrication systems that are free or low in cooling lubricant (e.g. minimum quantity lubrication). However, dispensing with oil or emulsion is often only possible and economical to a limited extent.
  • Ventilation-related protective measures
    These include technical measures such as the extraction and separation of cooling lubricant emissions using extraction and filter systems or the provision of ventilation solutions.
  • Organizational protective measures
    Organizational protective measures include employee training and general occupational health precautions. And measures to prevent the evaporation of cooling lubricants. For example, by sealing off machines, covering chip containers, using closed cooling lubricant circuits and preventing components from drying out.
  • Individual protective measures
    Individual protective measures include, for example, personal protective equipment such as respiratory protection.

Capture and separate 
cooling lubricant mist 
efficiently and economically

Air technology measures are essential in machining. They ensure that mist, smoke and steam are captured, removed and filtered. To ensure that this happens as efficiently as possible, many influencing factors need to be assessed. These include the machining process, the cooling lubricants used, the materials being processed, the machinery, the size of the workpiece and the production infrastructure. As a result, the ventilation solution is usually as individual as the requirements themselves.

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We therefore recommend a sensible structuring of the solutions:

Recording cooling lubricant emissions

Modern machining centers are often already encapsulated. Processing takes place in a closed room and the CNC processing machines are often equipped with connections for extraction. However, open machining centers can also be found. For these, the capture of emissions must be planned individually.

Such capture devices can be designed as open, semi-open or closed systems (extraction hoods, enclosures, encapsulation). The more open the capture system is, the higher the required capture air volume flow. All emission sources must be included when capturing emissions. The capture air volume flow rate must be designed for the respective application.

Experience and effects: 

  • The degree of capture is heavily dependent on the correct design. Process engineering expertise is required to determine the required air flow rate.
  • The closer to the machining process and the better the encapsulation, the higher the capture rate.
  • It is important to ensure that only the cooling lubricant emissions in the ambient air are extracted and that the cooling lubricant remains in the machining process.
  • The correct selection of the extraction speed is crucial to avoid extracting an unnecessarily large amount of cooling lubricant.
  • Depending on the type of extraction (extraction arm, extraction hood, enclosure), the required volume flow varies greatly. It ranges from a few 100 m³/h to over 20,000 m³/h.

Further Information 
Kappa SUCTION HOODS

Oil and emulsion mist extraction 
on individual machines 
(add-on filter, single machine extraction)

Manufacturers of machining centers usually provide their machines with defined extraction connections and give recommendations for the design of cooling lubricant mist filters.

If the required extraction volume is low, a top-mounted filter can be used. They are usually placed on the roof of the processing machine and connected to the processing area with a usually short pipe. Oil and emulsion mist filters as top-mounted filters extract the polluted air from the machining area and ensure that the cooling lubricant emissions are filtered. The separated emissions are usually fed back into the processing machine and fed into the cooling lubricant circuit.

If a slightly higher extraction capacity is required for the processing machines to be extracted, it is advisable to place the cooling lubricant mist separator next to or behind the CNC machine.

The filtration efficiency used varies greatly depending on the separation technology used.

Experience and effects: 

  • Whether a top-mounted or floor-standing filter is suitable depends on the CNC machine, the work process and the required performance.
  • Top-mounted filters are generally offered with extraction capacities of 400 to 2,500 m³/h. Floor-standing filters can be designed with significantly higher extraction capacities.
  • Both filter types are limited to the extraction of the processing area. Other emission sources are not extracted.
  • The cleaned air can be fed back into the hall.
  • The hall air quality is impaired by the air recirculation. Depending on the separation principle, residual emissions are returned to the hall air.
  • Vaporous emissions cannot be filtered. They remain in the hall air.
  • Moisture cannot be captured. They remain in the hall air.
  • The odor typical of machining cannot be captured. They remain in the hall air.

CENTRAL OIL- & EMULSION MIST EXTRACTION
(central extraction, group extraction)

Central filter systems can supply several processing machines up to the entire machine park. The cooling lubricant emissions extracted at the work areas are transported to the central filter unit via a central pipe network. When designing and dimensioning the piping, particular attention must be paid to a constant flow velocity. This is the only way to prevent deposits. When piping, particular attention must be paid to an oil-tight design to avoid leaks.


Exhaust air operation enables the removal of emissions, moisture and waste heat:

Conventional filters cannot separate the vapors produced by machining. In addition, “concentration” can occur in the hall when the cleaned air is returned to the hall. This leads to the condensation of emissions on surfaces and subsequently to employee exposure. By removing the cleaned air from the hall with the help of a central filter system, this concentration is prevented. Central filter systems can also help with the handling of excess humidity.

One challenge in the air conditioning of machining halls is the amount of waste heat released by the production process. Here too, central filter systems are an excellent tool for removing waste heat from the hall. If suitable filters are used, the air can even be fed back into the work areas, thus ensuring a productive temperature range. Heating cost savings included.

Experience and effects: 

  • Central filter systems usually have extraction capacities of 1,500 to over 20,000 m³/h. For larger volumes, several systems are combined into one unit.
  • They are suitable for reducing emissions from a wide variety of emitting locations (mechanical processes, reworking stations, chip collection containers).
  • Central filters can be excellently scaled by integrating several filter stages.
  • The hall air quality can be significantly improved by the possibility of exhaust air operation.
  • Gases, vapors and moisture can be removed from the hall by discharging the purified air.
  • The smell in the hall can be improved by exhaust air ducting.

FUrther INformation
Kappa AirdryTM OIL- & EMULSION MIST SEPARATOR

OIL AND EMULSION MIST SEPARATION 
WITH ROOM AIR TECHNOLOGY 
(ventilation, air extraction, hall air cleaning)

Cooling lubricant emissions not only pollute the workplace, but the entire hall. Seamless capture is very difficult to achieve with the aforementioned solutions. Residual emissions often remain in the hall air, which are distributed throughout the hall and lead to deposits.

In order to fully protect all work areas in the hall from cooling lubricant emissions, a ventilation solution is required. The hall is equipped with ventilation elements. These elements must perform better and be more efficient than conventional building ventilation, for example. It must handle all the chemical characteristics of cooling lubricant emissions.

It is also crucial for such systems to introduce fresh air draught-free into the floor area without it mixing with the contaminated hall air. With this technology, fresh air can ensure that the cooling lubricant emissions are displaced to the hall ceiling together with the contaminated hall air. There, all emissions can be removed from the hall together with the process waste heat. Central filter units then ensure a high degree of separation of the oil and emulsion mist, so that the entrained waste heat can be recovered with a high degree of efficiency and used to heat the fresh air.

Cooling lubricant emissions are very difficult to handle due to their chemical characteristics. They appear as steam, as spray mist and, last but not least, as greasy deposits on machines. A modern shop air cleaning system not only recognizes the different manifestations of cooling lubricants, it also knows how to deal with them.

Experience and effects 
about room air technology - Kappa A.I.R.TM hall air cleaning system 
incl. heating and cooling

  • A modern hall air cleaning system in the machining hall displaces cooling lubricant emissions - both gaseous vapours and aerosols and smoke - from the work area. Fogging of the hall is prevented.
  • It removes cooling lubricant emissions from the hall and thus prevents emissions from being transferred to neighboring work areas. Condensation of vapors on surfaces and machines is prevented.
  • It also records emissions and ventilates the entire hal
  • Waste heat is dissipated from the hall, enabling the recovery of process waste heat as well as heating and cooling.
  • A modern hall air purification system ensures a constant temperature range.
  • The extraction, filter and air technology is precisely adapted to the prevailing requirements in modern hall air purification systems.

FURTHER INFORMATION
Kappa A.I.R.TM HALL AIR CLEANING SYSTEM

WHAT OTHERS SAY

FAQs

Strict rules apply to the recirculation of filtered air. They vary from country to country. In the case of air recirculation, the portion that has not been separated is returned to the work area. In principle, the residual content of air pollutants in the recirculated air must not significantly increase the concentration of hazardous substances in the work areas. Because gaseous emissions are not retained by filters, air recirculation should be avoided.

Do you have questions about air recirculation? We will be happy to help you.

Our experience shows that workplace extraction systems are often not sufficient to reduce coolant emissions. A hall ventilation system is required to remove fugitive emissions.

Do you have questions about hall ventilation or hall air purification? We will be happy to assist you.

Flammable and possibly explosive mixtures can form during machining. A potential hazard is present above all with non-water-miscible cooling lubricants. For this reason, an expert opinion on possible fire and explosion hazards must always be drawn up during system planning. If necessary, appropriate measures must be taken..

Do you have questions about fire and explosion protection? We will be happy to assist you.

Vapours and gaseous emissions can hardly be separated. When the cleaned air is returned to the hall, the emission load is concentrated.

Do you have questions about filter technology and the separation of vapours? We will be happy to assist you.

Our experience shows that the proportion of vapor is generally much higher than the proportion of aerosols. It is usually 70 to 90%. In the reference literature, values can be found that put the proportion as much as 200 times higher.

Do you have questions about emissions? We will be happy to help you.