Filter elements should only be changed when differential pressure is high.
You install compressed air filtration to improve air quality. DP gauges/indicators are blockage indicators not air quality indicators. To ensure your compressed air quality, filter elements should be changed annually in line with manufacturer's instructions.
Coalescing filters are ONLY for oil removal.
Coalescing filters have a even higher capture rate with solid contaminants than with liquids.
Oil contamination is not present in atmospheric air.
Atmospheric air typically contains between 0.05mg/m3 and 0.5mg/m3 of oil vapor from sources such as car exhausts and industrial processes. As oil free compressors use large quantities of atmospheric air and atmospheric air contains oil vapor which can cool and condense in the compressed air systems, the use of oil free compressors does not guarantee oil free air.
Liquid oil and oil aerosol are the only contaminants present in a compressed air system.
Generally, there are ten contaminants found in a typical compressed air system that need to be removed or reduced for the system to run efficiently.
The ten contaminants are:
Rust Atmospheric Dirt
Only two of these contaminants, liquid oil and oil aerosol are introduced by a lubricating compressor. The purification equipment required to reduce, or remove the remaining contaminants by virtue of their operation also remove liquid oil and oil aerosols. Therefore regardless of the type of compressor installed, purification equipment is required.
Compressed air contamination is a compressor issue.
In a typical compressed air system, compressed contamination comes from four different sources, these being:
Source 1 - Atmospheric Air
Air compressors draw in huge amounts of atmospheric air, which continuously fills the system with contaminants such as water vapor, micro-organisms, atmospheric dirt & oil vapor.
Source 2 - The Air Compressor
In addition to the contaminants drawn in through the compressor intake, the compressor also adds additional wear particulates from its operation. Additionally, oil lubricated compressors carry over liquid oil, oil aerosols & oil vapor from the compression process. Once through the compression stage, the after-cooler will also condense water vapor, introducing it into the compressed air in both a liquid and aerosol form.
Source 3 - Compressed air storage devices
Source 4 - Compressed air distribution piping
The air receiver (storage device) and the system piping that distributes the compressed air around the facility both store large amounts of contamination. Additionally, they cool the warm, saturated compressed air which causes condensation on a large scale, adding liquid water into the system. This saturated air and liquid water leads to corrosion, pipescale and microbiological growth.
Static Oil Water Separators are not suitable for synthetic lubricants / PAG's. This is evident with cloudy outlet water.
Oil Water Separators are designed to reduce oil in water levels to acceptable limits. Some lubricants such as synthetics / PAG's also contain detergents and additives to extend the life of the compressor. Oil water separators are not designed to remove detergents and additives. Oil in water content cannot be accurately determined from visual inspection and lab analysis should be used. Lab analysis on cloudy outlet water is the only way of accurately testing oil in water content and will show it is within acceptable limits.
Any dryer (refrigerated or desiccant) can be installed outdoors.
All standard dryers are designed for internal installation. However, many are often installed outside, (with a lean-to roof in some cases and without a lean-to roof in some cases). Outside installation is acceptable provided there is lean-to roof with freeze / snow protection, blowing rain protection, and a roof / ceiling high enough to avoid hot air re-circulation. Outside installation of standard dryers with no roof is not recommended.
In the case where outside installation without roof is a necessity, request an outdoor modification package including freeze protection, UV protection in paint, fastners and electronics, and Nema 4 components throughout. A Nema 4 electrical enclosure alone is not sufficient for an outdoor without roof installation.
Most dryers do not provide dryness levels to the same levels quoted in sales literature.
Dryer installations are often plagued with a variety of mistakes which impact the level of compressed air dryness which they provide. Classic installation mistakes are: insufficient space above or in front of condenser air discharge which causes recirculation and high pressure faults…dramatic undersizing of the dryers when forgetting that cooling water and ambient air in Summer is at far higher temperatures than in Winter…wrong power supplies are amazingly frequent. Often dryers are on the same power line as other capital equipment and so the actual voltage is subject to tremendous dips which play havoc with dryer operation and dryness performance.
Compressed air filters also dry compressed air.
Compressed air filters are capable of removing bulk liquid water and some water aerosol from compressed air. Compressed air filters are not capable of reducing the level of moisture vapor in compressed air or reducing the pressure dew point of compressed air.