More than 70% of all equipment failures can be attributed to lubricant contamination. As one leading air compressor OEM states, “Particulate contamination is the #1 enemy of air compressors…a surefire way to destroy your investment. It will reduce the life of the air end, the separator and the fluid, and will increase horsepower leading to increased energy consumption.” Studies show that the most harmful particulate contaminants in terms of bearing life are the ultra-fine solid particles less than 10 microns in size. Found in all rotary screw air compressor oils, even new oils, these ultra-fine solids are the enemy of your compressors’ reliability and a leading cause of high maintenance and repair costs.
While any size solids in compressor oils are problematic, the most destructive and challenging to control are these ultra-fine “clearance-size” particles. At less than 10 microns in size, these solids are too small to be effectively removed by the compressor’s inlet air filter or oil filter and will steadily accumulate in the oil. Once in the oil, they circulate throughout the compressor causing harm by interfering with lubrication (oil films), increasing friction, wear, and fouling, and reducing the life of critical compressor internals.
When ignored, these ultra-fine solids accelerate wear of expensive air-end bearings and shaft seals, while simultaneously fouling the compressor’s air-oil separators, oil coolers, and oil-injection lines. This results in increased operating temperatures, faster oil degradation, reduced oil life, increased separator pressure drop, increased energy consumption, reduced separator life, and reduced bearing life. Put another way, ultra-fine solids are bad for your compressor and your maintenance budget.
Standard Compressor Inlet Air Filters Are Inadequate
Unfortunately, all rotary screw air compressors suffer from the same inherent design flaw that makes them uniquely vulnerable to ultra-fine solid contamination. Unlike other lubricated rotating machinery, rotary screw air compressors are designed to literally vacuum up any ultra-fine particles present in the air forcing them at high volumes and velocity directly into the oil.
To help protect the compressor, its first line of defense against these harmful contaminants is its inlet air filter. Unfortunately, the performance of these filters is largely unknown. Most air compressor inlet filters are rated per the SAE J726C or ISO 5011 test standards, which only measure a filter’s dust holding capacity (by weight) and pressure drop, but provide no information on the filter’s actual filtration efficiency for a given particle size (microns).
With actual particle sizes and filtration efficiencies unpublished, you’ll commonly hear these inlet filters are rated to remove 5 microns (nominal) in size. Depending on their filtration efficiency, this can equate to more than 20 microns absolute, which still allows the smallest, most destructive, ultra-fine particulates to pass right through and contaminate the oil. While these factory-supplied inlet filters may be sufficient in “clean” indoor environments, they can be grossly inadequate in many industrial environments, like paper mills, cement plants, power plants, steel mills, mining operations, and others.
Improving inlet air filtration to prevent these ultra-fine solids from entering the compressor and contaminating the oil is obviously the best solution, but unfortunately, there aren’t any good options. Air compressor performance (flow rate and compression efficiency) is highly dependent on inlet air pressure, and is negatively impacted by the inlet filter’s pressure drop (limited to about 20 in. W.C. < 0.8 psi). However, in order to reduce the filter’s micron rating and minimize its pressure drop, the filter’s surface area (size) would have to increase exponentially. And unfortunately, no compressor manufacturer wants to supply an oversized inlet air filter that will reduce their compressors’ performance and increase their package sizes and costs, making them less competitive.
Standard Compressor Oil Filters Are Inadequate
Given the air filter’s inability to stop ultra-fine solids from entering the compressor, the compressor’s oil filter becomes the compressor’s internals next line of defense. Unfortunately, like the air filter, the oil filter is not designed to remove the ingested solids, nor can it remove the ultra-fine rust and wear particles produced internally.
The standard OEM oil filter is normally rated for 10 microns nominal, or only about 20 microns absolute. While 20 microns is still smaller than the eye can see and a 20 micron oil filter may seem adequate, it only provides about the same level of filtration as a household coffee filter, and does little to protect compressor bearings, limit wear, or maximize bearing and air-end life.
As previously referenced, a well-known study on the effects of particle size on bearing life shows there is minimal benefit in bearing life until the oil is filtered down below 15 microns. However, the study shows a dramatic 4-fold increase in bearing life when filtration is improved from 20 microns down to 3 microns absolute. This stands to reason since only the smallest, ultra-fine particles are able to penetrate tight bearing clearances and interfere with critical oil films where lubrication and wear occur.
There is a Solution – Compressor Oil Purifier
To address the many problems caused by ultra-fine solids in compressor oils, Fluid Metrics developed its award-winning Compressor Oil Purifier (COP) specifically designed for oil-injected rotary screw air compressors. The COP is a low flow, “bypass” device that installs easily on any compressor to supplement its standard oil filter and continuously remove the ultra-fine solids the standard oil filter does not.
The COP utilizes proprietary purification elements that combine ultra-fine filtration to remove solids down to 3 microns absolute (Beta 3 > 200), with an ion exchange media that removes acids, dissolved solids, and the precursors of varnish. ISO Particle count testing of oil from compressors with a COP installed shows it is able to keep in-service compressor oils more than 30 times cleaner (fewer solids) than the OEM’s standard 20 micron absolute oil filter, and twice as clean as brand-new oil straight from the container.
With the COP continuously removing harmful ultra-fine solids and reactive acids, and maintaining in-service oil cleanliness at or below new oil particle counts, rotary screw compressor users will benefit from:
- Reduced Bearing & Seal Wear / Increased Air-end life
- Reduced Separator Fouling & Pressure Drop / Increased Separator life
- Reduced Energy Consumption / Lower Electrical Costs
- Reduced Oil Oxidation – Degradation / Increased Oil Service Life
- Increased Protection & Compressor Reliability
- Reduced Compressor Maintenance, Repairs & Downtime
- Reduced Oil and Separator Consumption / Change frequency / Waste Disposal
- Reduced Environmental Impact / Improved Sustainability
- Reduced Cost of Ownership
When compressor reliability, maintenance cost, and the environment matter, contact us today to learn more about how the COP will benefit you.