Compressed Air Filters: What They Are, And Why They Matter

The first time I ever bought a brand new car was in 1995…it was a Ford Escort Wagon. My plan was to pay it off quick and run the tires off it. Well, I DID actually put new tires on it several times over the 11 years and 200,000 miles I had it. But, aside from fuel & tires, that car cost me less than $2,000 in repairs over all that time…an achievement that my mechanic said was due largely to the aforementioned planned maintenance, which largely consisted of regular oil changes, which, of course, included a new oil filter, every 3,000 miles. For the record, I didn’t run the wheels off it; I sold it when I took a job that included a company vehicle. Also for the record, I found out the fellow I sold my car to was still driving it after I left that job (and company vehicle.) He, too, believed in regular oil changes, and he might still have that 1995 Escort on the road for all I know.

So, yeah, I’m a big believer in the importance of fluid filtration.  If you’re a regular reader of the EXAIR Blog page, you likely are too.  The two main culprits that cause the most problems in a compressed air system are solid particulates and water.  These are easily addressed with a Filter Separator, like EXAIR Model 9004 Automatic Drain Filter Separator.  It has a 5 micron particulate element, and a centrifugal element that imparts a spinning motion to the air flow.  Since water is denser than air, any droplets of moisture are “flung” to the inside wall of the bowl, while the moisture-free air continues on through the discharge.

 

The particulate element captures solids larger than 5 microns, and the centrifugal element eliminates moisture.

Another common impurity in compressed air is oil.  Since oil-less compressors came along, this is easy to eliminate at the source…literally.  However, for other types of compressors (piston types in particular,) as they age, the oil that lubricates the moving parts can seep by the piston rings and get to the air side.  Oil doesn’t carry the same wear and corrosion problems that dirt & water do, but it causes particular problems in air conveyance and blow off applications: anything in your air is going to get on your product.  Ask any paint booth operator, for example, what happens when a metal surface hasn’t been cleaned of all traces of oil.  It really does look a “fish eye.”

The most common type of oil removal filter uses a coalescing element.  Oil entrained in pressurized gas flow isn’t as dense as water – so centrifugal elements won’t remove it – and it tends to act like particulate…but very fine particulate – so typical sintered particulate elements won’t remove it.  Coalescing elements, however, are made of a tight fiber mesh.  This not only catches any trace of oil in the air flow, but also much finer particulate than those sintered elements.  EXAIR Oil Removal Filters, like the Model 9027 shown below, provide additional particulate filtration to 0.03 microns.  That’s some pretty clean air.

The coalescing element of an Oil Removal Filter catches oil and very fine particulate.

For best results, we recommend both the Filter Separator and Oil Removal Filter.  Make sure you install the Filter Separator upstream of the Oil Removal Filter…that way, its 5 micron element catches all the “big” particles that would quickly clog the very fine coalescing element, necessitating an element replacement.  In fact, this arrangement will allow the Oil Removal Filter to operate darn near indefinitely, maintenance free.

If you have questions about keeping your compressed air clean, moisture free, and oil free, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Why 5 PSIG Matters

Last week I pointed out the important locations for measuring your compressed air system pressure throughout your compressed air system.   One of the critical points to measure system pressure was before and after each filter.  This leads into another question that I receive every once in a while, “How do I tell when the filter needs to be changed?”  The answer to this is easy, when you see more than a 5 PSIG pressure drop across the filter.  This means that the element within the filter has become clogged with sediment or debris and is restricting the volume available to your downstream products.

Filter
EXAIR 5 micron Auto Drain Filter Separator

 

This can lead to decreased performance, downtime, and even the possibility of passing contaminants through the filter to downstream point of use components.  In order to maintain an optimal performance when using EXAIR filter separators and oil removal filters, monitoring the compressed air pressure before and after the unit is ideal.

Replacement filter elements are readily available from stock, as well as complete rebuild kits for the filter units. Changing the filters out can be done fairly easily and we even offer a video of how to do it.

The life expectancy of a filter element on the compressed air is directly related to the quality of air and the frequency of use, meaning it can vary greatly.  If you tie a new filter onto the end of a compressed air drop that has not been used in years, you may get a surprise by the filter clogging rather quickly.   However, if you maintain your compressor and your piping system properly then the filters should last a long time. Generally we recommend checking your filters every 6 months.

If you have questions about where and why to filter your compressed air contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF