Lubricant Purification

A Fluid Metric Compressor Oil Purifier (COP) is a proactive maintenance contamination control system specifically designed for oil-flooded rotary screw air compressors. The COP installs easily on any compressor to continuously remove the acids and ultra-fine solids known to reduce the service life of expensive compressor fluids, separators, bearings, coolers and more. By removing these harmful contaminants, the COP retards the oil degradation process which extends the oil’s service life and helps protect vital compressor internals against destructive wear, corrosion and fouling.


The heart of the COP is its patent pending Dual Core Cartridge that combines state-of-the-art Mechanical and Chemical separation technologies. As a small slip-stream of

contaminated oil flows from outside-in through the COP’s cartridge, ultra-fine or clearance-size solids are removed down to 3 microns absolute. The pre-filtered oil then passes through the ion exchange media which adsorbs and neutralizes both weak and strong acids that build up in the oil. Fluid Metrics utilizes a proprietary high capacity ion exchange media that is proven to safely remove acids in synthetic compressor lubricants without affecting the oil’s protective additives. By proactively
removing these harmful contaminants, the COP helps maintain the oil’s original physical, chemical and performance properties; dramatically extending the oil’s service life; and providing increased protection to expensive compressor components.


Designed with the user in mind, the COP’s Installation Kit includes all the following features to simplify installation and servicing of the unit:


• Mounting Bracket & Hardware

• Supply & Return Hydraulic Hoses

• Isolation Valves

• Flow Meter

• Sample, Vent & Drain Valves

• Air Vent Sight Glass

• Pipe & Hose Fittings

• Premium Baseline Oil Analysis Kit

• Installation & Operation Manual

Purifier Elements 
Ion Exchange technology relies on the electrical attraction of oppositely charged matter (ions) to selectively adsorb and neutralize materials.  An Ion is an atom, or group of atoms, that has an electrically positive (cationic) or negative (anionic) charge.  When compressor fluids degrade, they produce acidic compounds comprised of cationic Hydronium ions.  The Fluid Metrics COP utilizes a specially formulated anionic media whose negative charge attracts the positively charged acid molecules.  When oil containing acids comes in contact with Fluid Metrics’ ion exchange media, the acid molecules are adsorbed by the media and removed from the oil.  These harmful acid molecules are permanently bonded to the media which neutralizes the oil and controls Total Acid Number or TAN.  Unlike other ion exchange processes, this is a one-way reaction where nothing is released back into the oil that would cause sludge or otherwise change or harm the oil.


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Frequently Asked Questions

What is Oil Purification?

Oil purification is an advanced Proactive Maintenance technique designed to address the root cause of oil degradation and most routine compressor maintenance. Oil purification is proven to extend the service life and change intervals of compressor fluids and other critical components by removing the harmful contaminants that accelerate oil degradation, produce acids, and promote corrosion, wear and fouling. Oil purification has been used extensively in expensive turbine oil systems and other large industrial fluid applications. Now, this same proven technology is available on a smaller scale to purify rotary screw compressor fluids.


Why should I purify my rotary screw compressor's oil? 

Simply put, oil purification is a better, less expensive, less time consuming way to maintain rotary screw compressors. Purification of rotary screw compressor fluids essentially maintains the compressor from the inside out by continuously reducing the harmful acidic and ultra-fine solid contaminants that are the Root Cause of most compressor maintenance and repairs. Oil purification is proven to increase the service life and extend the change intervals of compressor fluids, separators, bearings, valves, seals and other vital components. By increasing the service life of these components, oil purification produces operation & maintenance cost savings from reduced fluid, separator and parts purchases, lower separator energy consumption, reduced compressor maintenance and repair labor, reduced oil disposal and less equipment downtime.

How does the Fluid Metrics Compressor Oil Purifier (COP) purify the oil?  

The Fluid Metrics COP combines Ion Exchange technology with ultra-fine particle filtration to continuously remove chemically reactive and catalytic contaminants that accelerate oil degradation and promote wear, corrosion, and fouling. Installed in a bypass loop in the compressor’s main oil circuit, the Fluid Metrics COP continuously purifies a very small slip-stream of oil and does not replace or interfere with the compressor’s main oil filter. Unlike portable filter carts that only provide temporary mechanical filtration, the Fluid Metrics COP helps maintain the oil in like-new condition by providing continuous mechanical and chemical filtration.

What is Ion exchange technology and how does it purify compressor fluids?

Ion Exchange technology relies on the electrical attraction of oppositely charged matter (ions) to selectively adsorb and neutralize materials. An Ion is an atom, or group of atoms, that has an electrically positive (cationic) or negative (anionic) charge. When compressor fluids degrade, they produce acidic compounds comprised of cationic Hydronium ions. The Fluid Metrics COP utilizes a specially formulated anionic media whose negative charge attracts the positively charged acid molecules. When oil containing acids comes in contact with Fluid Metrics’ ion exchange media, the acid molecules are adsorbed by the media and removed from the oil. These harmful acid molecules are permanently bonded to the media which neutralizes the oil and controls Total Acid Number or TAN. Unlike other ion exchange processes, this is a one-way reaction where nothing is released back into the oil that would cause sludge or otherwise change or harm the oil.

How long has Ion Exchange technology been around?

Ion exchange technology was first used commercially in water purifying applications back in the year 1915. Early ion exchange media were naturally occurring zeolite soils which were effective but had low adsorption capacity and selectivity and often leached unwanted material back into the fluid. These short-comings led to the development of synthetic ion exchange media which are designed to have much greater adsorption capacity and selectivity while not adding any contaminants to the process fluid. Synthetic Ion exchange media are used extensively today in chemical, industrial, petrochemical, pharmaceutical, food processing, nuclear, mining and water treatment applications.

What Ion Exchange technology does Fluid Metrics use in its Compressor Oil Purifiers?

Fluid Metrics utilizes a proprietary high capacity anionic exchange media that undergoes a special process specifically developed for this application. Fluid Metrics’ ion exchange media complies with Food Grade regulations and conforms to FDA regulation 21 CFR 173.25. This ion exchange technology has been extensively tested by The Dow Chemical Company, the world’s leading maker of synthetic rotary screw compressor lubricants. Nearly three years of Dow testing proved conclusively that ion exchange technology is ”extremely effective at removing acids and controlling TAN and pH” in synthetic compressor fluids; and, that this technology ”did not contaminate or otherwise harm the treated lubricants in any way.”

Doesn’t the compressor’s standard oil filter provide adequate protection?

Standard compressor oil filters are full flow filters designed for relatively high flow rates and thus have to balance filtration efficiency (micron rating) with pressure drop. Because of this, most OEM oil filters are only rated for 10 microns nominal (25 microns absolute) which only provides a basic level of protection for bearings and does nothing to remove the ultra-fine solids and harmful acids found in compressor fluids. As a result, these highly reactive acidic and solid contaminants are allowed to accumulate in the oil which accelerates oil degradation, bearing, valve and seal wear, corrosion, and the fouling of separators and coolers. Standard filters ignore the root causes of compressor fluid and separator replacement and guarantees an expensive and never-ending cycle of high fluid, separator, and parts consumption.

How long will the oil last with a COP installed on my compressor?

Under normal compressor operating environments, purifying the oil with the Fluid Metrics Compressor Oil Purifier (COP) will extend fluid service life 3-5 times the oil’s rated service life. Actual fluid life extensions will depend on a variety of factors including lubricant type, degree and type of contaminant loading, and compressor fluid operating temperature.


Can the COP harm my compressor’s oil?

No. The COP is designed to selectively remove only the harmful acidic and fine solid contaminants and will not affect the oil’s additives or introduce any harmful constituents into the oil.

What types of compressor fluids does the COP work with?

The Fluid Metrics COP is effective at extending fluid life and change interval of most of today’s synthetic and hydro-treated compressor fluids. These include Polyglycol / POE, PAO, Food Grade PAO’s, and Esters based fluids. Some of the more common OEM brand names that fall in this category are Sullube®, SRF®, Ultra Coolant®, AEON 9000®, QuinSyn Plus®, and HD Roto Fluid®.

Can the COP be installed on any brand compressor?

Yes. The COP purifies a small slip stream of the compressor’s main oil flow and installs in bypass to the compressor’s standard oil filter. The COP uses existing oil pressure to circulate the oil and needs less than 15 psig of differential pressure. Since the designs of compressor oil circuits differ among manufacturers, installation requirements will vary. Consult your Fluid Metrics’ distributor for installation specifics.
How does the Fluid Metrics COP extend compressor fluid service life?

Compressor fluid service life, or the rate at which the oil degrades, is a function of fluid contamination and temperature. The Fluid Metrics COP combines Ion Exchange and Ultra-Fine Particle Filtration technologies to remove the acidic and fine solid contaminants known to accelerate oil degradation and reduce fluid service life. By removing these highly reactive and catalytic contaminants, the rate of the oil-degrading chemical reactions is significantly slowed and oil service life drastically extended.

How does the Fluid Metrics COP extend oil separator life in rotary screw compressors?

Oil separator life is generally determined by the pressure drop caused by fouling of the separator element(s) from ultra-fine solid contaminants. The Fluid Metrics COP reduces the number of ultra- fine solids that foul oil separators and increases pressure drop. In field tests conducted on highly contaminated compressor fluids, the COP reduced ultra-fine solids to levels with fewer ultra-fine particulates than brand new oil and drastically slowed the increase in separator pressure drop. Reducing these solids keeps the separator elements cleaner; extends their service life; and lowers the compressor’s energy consumption.


Exactly what is oil degradation?

Oil degradation is a series of harmful chemical reactions that occur between the oil’s base stock, its additives, and foreign contaminants like oxygen (air), water (humidity), metal particles (rust & wear), chemical vapors, and many others. These reactions change the oil’s chemical and physical properties which negatively impact the oil’s performance ability and reduce its useful service life. Oxidation, the chemical reaction of an oil molecule with oxygen, is the most common and most harmful of these reactions resulting in permanent chemical changes to the oil’s base molecules. Once initiated, this auto-catalytic reaction is self-sustaining and continuously accelerates producing acids and other reactive byproducts. Evidence that compressor oil is oxidizing can be seen from increasing acid levels or TAN, decreasing pH, increasing viscosity, rust in filters, and varnish or sludge formation. Degraded oil that is left in the compressor too long can cause serious and catastrophic failure to rotary screw compressors.

Why do compressor fluids degrade?

In a word – Contamination. Contamination is the root cause of oil breakdown or degradation. Absent any contamination, most synthetic oils will last indefinitely.

What is contamination?

Contamination is any foreign matter or energy that comes in contact with the oil. The most common contaminants include oxygen, acids, water, dirt, rust, wear metals, chemical vapors, pollution, and heat. In rotary screw compressors, the source of these contaminants can be external (ingested from the surrounding air), or internal (byproducts of chemical reactions, condensation, wear, and corrosion). Common external contaminants that should be avoided include acid gases like those found in diesel exhaust, boiler exhaust, and cooling tower exhaust. External contaminants can often be eliminated by installing a remote air inlet to obtain cleaner, drier, cooler air from a different source. Internal contaminants, and those external contaminants that are ingested by the compressor, can both be controlled by continuous oil purification.
How does the Fluid Metrics COP reduce compressor energy costs?

The Fluid Metrics COP minimizes separator fouling and pressure drop. Compressor energy consumption (horsepower and kilowatts) is a function of compressor and motor efficiency, flow rate (cfm), and discharge pressure (psig). As a general rule, compressor horsepower increases 5 % for every 10 psig increase in compressor discharge pressure (or ½ % power per psig). The oil separators in rotary screw compressors create a pressure drop that can vary from 2 – 15 psig depending on separator design and the degree of fouling of the separator element(s).   This pressure drop causes the compressor to work harder to maintain system air pressure wasting significant money in unnecessary energy costs. Fouling of separator elements is caused by the ultra-fine solid contaminants that are carried by tiny oil aerosols and impinge on the surface of the separator. The Fluid Metrics COP removes the ultra-fine solids too small to be trapped by conventional filters and minimizes fouling and pressure drop of separator elements.

Can anything be done to completely stop oil from degrading in rotary screw air compressors?

Not completely. However, the speed at which these oils degrade can be dramatically slowed by addressing the root cause of oil degradation - Contamination. Oil degradation rates are drastically affected by temperature and contamination. By design, rotary screw compressors continuously pump oxygen, water vapor, and other reactive and catalytic contaminants into the oil while adding heat which elevates the oil’s temperature. Minimizing the oil’s operating temperature and its level of reactive contaminants will significantly slow the rate of oil degradation and dramatically extend its useful service life and change interval.

From a lubricant standpoint, how do oil-flooded rotary screw compressors compare to other rotating equipment applications?

Rotary screw compressors are one of the most severe applications possible for an industrial lubricant!   Unlike other types of rotating equipment, oil-flooded air compressors are inherently open to the atmosphere and continuously ingest airborne solid and vapor contaminants forcing them into the oil. Oil flooded rotary screw air compressors are very effective dust collectors and wet gas scrubbers that strip solid and vapor contaminants from the ingested air and deposit them into the oil. Even barely detectable levels of airborne contaminants can be absorbed by the oil where they accumulate and concentrate to destructive levels. Air compressor users are often unaware they may have a problem with airborne contaminants until a catastrophic failure occurs and post-failure oil analysis reveals the nature of contamination. Combine this continuous, forced-contamination with heat, constant aeration and agitation, and air compressor fluids are required to perform in one of the most aggressive environments possible.

What will happen if the oil is allowed to stay in the compressor past its useful service life?

Oil that has degraded past the manufacturer’s recommended limits can cause catastrophic failures to rotary screw compressors. As oil degrades, its ability to lubricate, cool, and inhibit corrosion deteriorates and negatively impacts the performance and service life of every component that comes in contact with the oil. Depending on the type of oil, sludge and varnish can also form resulting in expensive failures to bearings and air-ends and extended compressor down-time.

What can be done to control contamination in compressor fluids?

Effective contamination control is a three step process that begins with prevention. Providing the cleanest, driest and coolest inlet air supply and maintaining the inlet air filters will reduce the external ingested contaminant loading to the compressor fluid.   Next, compressor oil purification, like the Fluid Metrics COP, that removes both the acidic and ultra-fine solid contaminants reduces the internal contaminant loading to the fluid. Lastly, maintaining compressor fluid levels by regularly adding
make-up oil helps replenish oil additives and prevent the concentration of contaminants caused when fluid volumes decline from oil carryover and leaks.

How do you know when it’s time to change the oil in rotary screw compressors?

Oil analysis is the only way to know for sure when it’s time to change the oil. Oil suppliers routinely provide general oil change guidelines like “every 8,000 hours, or once a year, or as determined by fluid analysis...whichever occurs first”. Time based guidelines are never accurate as they ignore the compressor’s actual operating conditions and environment.   Some OEM “8,000 hour rated fluids” have been known to only last 2,000 hours in some environments while others have tested satisfactory at 10,000 hours. Without performing periodic fluid analysis, users are just guessing about the condition of their fluid and run the risk of either doing harm to their compressor by running their oil past its useful life or wasting money by changing their oil too often. Oil analysis is an easy, inexpensive way to accurately determine fluid change intervals. It is recommended that users consult their fluid suppliers to obtain their specific condemning values of the key chemical and physical parameters monitored by routine oil analysis.