Should I Use a Post HEPA Filter on my MistBuster?
How the Airflow Could be Reduced
In many factories I see the large post HEPA filter sitting on top of many Mistbuster and Trimist electrostatic air filtration units.
I would say that in probably 80 – 90% of these applications the HEPA filter is actually causing more of a problem then a solution.
The main reason is that HEPA filters clog up and reduces the airflow. The oily mist generated in the CNC machining cabinet then escapes out the chip conveyor or from the bottom of the CNC unit.
Remember, there are two variables to control in order to achieve a cleaner environment.
1. High efficiency, but low Air flow: If you have a 99.9% efficient HEPA filter but the CFM is so greatly reduced, then it amounts to little or no air filtration because not enough air is being removed from the CNC unit through the super-efficient air filter. Air pressure builds and will evacuate the cabinet from somewhere – usually the chip feeder. Regardless, oil laden air escapes into the factory environment.
2. High air flow, but low Filtration Efficiency; Going to the other end of the spectrum; what if you had no filters in the unit? The CFM of air being evacuated from the CNC machining center would be adequate, with no air pressure build up, however the oily air would be discharged out the top of the unit and would make a mess on top of the CNC and or in the immediate area.
SOLUTION: Upgrade from the 2” mesh pre-filter that comes standard, with a baffle type pre-filter. Using this is key because you can “knock down” most of the heavy oil particulate at this stage of filtration, allowing the electrostatic cells to remove the rest of the fine particulate. The baffle allows for adequate CFM while simultaneously improving the efficiency of the Mistbuster / Trimist unit.