OIL MIST FILTRATION IN CNC MACHINING CENTRES
Today, CNC machining centres, which are used in almost all sectors, especially in automotive, medical, defence industry, aerospace, use coolant and lubricant fluids while metal processing.
The high heat generated during processing causes these liquids to evaporate rapidly. Inhalation of these vapours is a health risk and their release into the atmosphere is prohibited.
These oil droplets remain suspended in the air and can be 1-10 microns in size, while oil fumes can be 0.1-1 microns in size. The current OSHA standard for mineral oil vapour is 5 mg of mineral oil vapour and 15 mg/m3 TWA (total particulate) per cubic metre of air averaged over an 8-hour work shift.
These vapours also cause considerable damage to the sensitive mechanical and electronic systems of the machines. When the concentration increases and reaches the lower explosion limit, there is a risk of explosion due to contact with surfaces with a temperature above 200 degrees and a spark.
The formation of oil vapour and oil fumes is not limited to CNC machining centres. They also occur in oil grinding, forging, machining of some plastics, heat treatments, casting and other machining processes.
For all these and similar reasons, oil vapour extraction and filtration systems should be used to filter these vapours in the fastest way and to recover and reuse these condensed liquids.
These systems can be specific for each machining centre, or they can be designed centrally to absorb and filter oil vapours generated in more than one CNC machining centre at the same time.
These filtration devices can have centrifugal, electrostatic or mechanical filtration. Each manufacturer aims to separate oil vapours with a different technology.
How can we calculate the flow rate of an oil mist filter in a machining centre?
The volume of this area is calculated in m³ by measuring the width x length x height in the closed area of the processing center. The equipment in the cabin is then subtracted from this volume (usually 20% of the volume). Although this net volume may vary according to the vapor density, in general, the required flow rate can be easily calculated by multiplying by 360 ACH.
For example, if the closed volume is 2 m³, the 20% equipment volume is subtracted from this number to obtain a net volume of 1.6 m³. When this volume is multiplied by 360, an oil mist filter with a flow rate of approximately 576 m³/h will generally be sufficient.
Many CNC machining centre manufacturers drill at least one suction hole for pipe/hose connection on this closed volume. Connection to the filter system can be made using this hole. In addition, many manufacturers also specify the required air flow rate in their user manuals.
Check out our oil mist filter solutions.
HiVent Technology, 16/03/2024, Ankara
