Air Filters are an important part of maintaining an efficient and effective compressed air system. I have often told customers, “The compressed air product is only as good as the compressed air going into it” in other words: “garbage in-garbage out”. Contaminants in the air can quickly clog up and ruin not only the compressed air device, but also your product that depends on it. Oils, vapors, dust, pollen and other particulates are often found in manufacturing facilities. These contaminants, along with moisture, pipe scale, and rust, can easily be produced or find their way into your compressed air distribution system. Therefore, it’s vital to ensure that you eliminate contaminants where the compressed air is being applied, to prevent problems. Most compressed air systems employ filtration at the outlet of the air compressor. This is essential, however filtration at the point of use is also critical. This ensures that additional moisture, rust, etc. is not present in the compressed air piping system before reaching the intended source/product.
We recommend that you use a 5 micron automatic drain compressed air filter to remove water and particulate from the air supply. If there is oil in the compressed air (from an older compressor that may be bypassing it) then we recommend using an automatic drain .01 micron coalescing filter after the 5 micron filter. This keeps the small air passages in your Cold Air Gun (or other cooling device) from getting clogged with dirt and grime that prevents it from operating efficiently. The 5 micron filter will also remove water droplets from the compressed air. Without this filter, the water can freeze inside the vortex tube product and in some cases completely block the flow of cold air.
Compressed air filters cannot remove water vapor (humidity) in the compressed air. Water vapor can condense inside the vortex tube product and freeze, blocking the internal passages. If water vapor is present in the compressed air, it can only be removed with a compressed air dryer. There are several types of air dryers available: refrigerated, desiccant, deliquescent and membrane. For most vortex tube products, we recommend the refrigerated type. If the application is for cooling an enclosure then the dryer should be rated for a pressure dewpoint of 40°F or lower. If the application calls for extremely low cold air temperatures then a pressure dewpoint of -40°F may be necessary. If this is the case then a desiccant type dryer may be necessary. (Refer to the “Air Supply” section of our Vortex Tube Short Course for more information.)
The filter should be sized to handle the volume of air passing through it to obtain a 1 to 3 psig pressure drop across it. If the filter is undersized then the pressure drop may exceed 5 psig, or the filter element is partially clogged and may need replacement, see below. Reducing any sources of pressure drop in a compressed air system takes load off the air compressor and saves money. The same principle applies to any component in the compressed air supply-valves, pressure regulators, fittings, etc.
After the compressed air filter has been properly sized for the application, the internal filter element must be changed occasionally. Frequency of element replacement depends on the quality of compressed air. At the very least the element should be changed annually. However, when there is a 10 psig pressure drop or more across the filter, the element should be replaced. Install pressure gauges immediately before and after the filter to monitor the pressure drop. (The filters supplied with Vortec’s ProtEX Vortex AC product line have pressure drop indicators on them making notification of filter element replacement a “no-brainer”.)
How to Change a Filter Element:
Changing a filter element is a simple procedure. The process is easiest if the filter has been installed in a location where it is easy to access.
- First, and most importantly, the compressed air supply must be shut off on the line to the filter and the air pressure bled out of the system.
- Next the filter bowl must be removed. Some bowls use a “bayonet” type of attachment requiring a 45 degree rotation of the bowl and others simply thread onto the filter body.
- After the bowl is off you will need to remove a plastic baffle under the bowl, typically by unscrewing it.
- Remove the old element and install the new one. Replacement elements can be purchased from the filter manufacturer’s distributor. (Filter element part numbers can be found in the FAQ section of the Vortec website.) Be careful not to lose the auto-drain float that is in the bottom of the bowl.
- Reassemble the filter in the reverse order of disassembly and ensure the bowl is properly attached to the body. Slowly turn the compressed air supply back on and check for leaks around the bowl. If leaks are apparent then the O-ring bowl seal may need replacement.