Oil and coolant mist collectors are often defined by the smallest particle size they can filter, but calculated airflow is just as important. In fact, focusing on filtration size or failing to consider other factors like airflow may be leading to less than optimal performance. Filtration size might be the right starting point, but we’ll go over some of the reasons why you need to consider airflow when using oil and coolant mist collectors for industrial air filtration.
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What Is Air Flow and Why Is It Important for Industrial Air Filtration
In the context of industrial air filtration, airflow describes the nature and rate at which air is circulated and discharged using a mechanical ventilation system. This could be across a facility, within a particular production room, or in a machine enclosure. Airflow is measured using units of volume (e.g. cubic feet or meters) and time (e.g. minutes or seconds). Aeroex uses cubic feet per minute (or “cfm”) as its standard unit of measurement. Airflow also has a direction or vector, such as from areas of high to low pressure or from a source of forced air to a source of air capture. The direction, volume, and velocity of airflow all play important factors in the performance and outcomes of your filtration scheme.
Airflow is important for industrial air filtration because it is a key determinant of the ability to capture or mitigate the effects of airborne contamination caused by industrial processes like machining. This can be true both at the macro level for a large facility or at the source of a single machine. Consider the following examples.
Example #1 – Air Flow Considerations for Source Control Applications
You are machining at high cycles and use coolants or lubricants to maintain the temperature of your tools, but need to maintain visibility or prevent the over-accumulation of oils and mists. Therefore, your ventilation and oil mist collection system will need to recycle the enclosure every few seconds. By extension, your oil mist collector needs to have the airflow capacity to do so. The “direction” of airflow is of less concern here because it is a closed system with source control. Aeroex often recommends source control solutions because contaminants are captured quickly before they are released into the shop atmosphere where they disperse – you can often capture at the source with less airflow than what is required under ambient conditions.
Example #2 – Air Flow Considerations for Ambient Control Solutions
You may use an ambient control method for air filtration when source control is not feasible – for example, some grinding applications without enclosures may not achieve 100% success with source control. Ambient control is also used as a “finishing” method complementing source control to achieve the cleanest possible air. Here, you need to consider the entire volume of the room rather than just an enclosure, and you also need to consider the direction of airflow relative to your air filtration system. The placement of different sinks and sources of ventilation will determine the overall flow in a facility, and proper engineering is needed to ensure the entire room is circulated. If there are corners circulated less frequently or at limited capacity then there are areas of higher risk. Ambient control often requires high airflow because you will be recycling an entire room of air, usually several times per hour.
Engineering the airflow of a room or facility is a complex topic, and deploying an industrial air filtration system may mean consulting an engineer – Aeroex has experienced staff who can make sure any deployment is planned properly. The below figure depicts some examples of common airflow dynamics.
Figure – Types of Air Flow Dynamics for Planning Ambient Industrial Air Filtration (Source: Building Performance Institute)
Risks of Inadequate or Mismatched Air Flow
Performance is often described in terms of the smallest size of particles captured by a filter, but if your oil mist collector cannot deliver the required airflow then the contaminants are not being removed at a rate that can ensure the quality or safety you expect. The filters selected can impinge on airflow, especially among cheaper membrane filters without the proper screening or depth loading to prevent clogging or deliver higher volumes of air. While filters may often guarantee using things like the HEPA standard, an improperly sized filter will negatively impact the air flow generated. Once airflow is restricted, contaminants will bypass the filter and carry into the airspace downstream of your filtration system – an outcome your filtration system was intended to prevent. For this reason, Aeroex uses depth-loading filters and provides a wide range of capacity options, ranging anywhere from hundreds of cubic feet per minute to thousands.
While it’s common among other suppliers to be overpromised on a system with inadequate airflow, you also want to avoid overpaying for capacity you don’t need at additional cost.
Why Is Filtration Size Mistakenly Emphasized Over Airflow?
Within the industrial air filtration space, we often speak in terms of particle size because it’s something all applications can relate to. Contaminant particle size, within a theoretical range, is common to all applications. While particle size can vary with temperature, dispersion method, etc, its chemical composition means that particle size will be within an accepted range. This means that the design and business case of a filtration system can relate to everyone via consideration of particle size. This commonality creates a shared language but can omit the factors that make each situation unique (notably your airflow requirements).
Airflow will depend on your enclosure size, amount of oils and coolants being applied, machine type and technique used, desired air exchange frequency, etc. At the ambient level, you will also need to consider the size and orientation of the facility, along with the other airflow contributors.
Get The Right Airflow Advice
So, while filtration size can start the conversation, don’t make the mistake of not selecting your mist collector based on calculated airflow. At Aeroex, we will diligently and patiently understand all your needs including calculated airflow to recommend the right mist collector. If you want to learn more or get started, contact Aeroex today.
