Compressed air users are often convinced to install oil-free compressors in place of their oil-lubricated counterparts on the grounds of improved air quality, as well as reduced costs for purification equipment and maintenance. Mattei dispels the myths surrounding oil-free compressors and the quality of air they deliver.


 

Myth 1: The air compressor is solely responsible for contamination in the compressed air system.

In a typical compressed air system, contamination comes from four different sources, these being:

Source 1: Atmospheric Air
Air compressors draw in huge amounts of atmospheric air, which continuously fill the system with contaminants such as water vapor, microorganisms, atmospheric dirt and oil vapor.

Source 2: The Air Compressor
In addition to the contaminants drawn in through the compressor intake, the compressor also adds wear particulates from its operation. Additionally, oil-lubricated compressors carry over oil aerosols and 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 an 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.

MYTH 2: OIL-FREE COMPRESSORS PROVIDE CONTAMINANT FREE AIR.

Generally, there are 10 contaminants found in a typical compressed air system that need to be removed or reduced for the system to run efficiently. These 10 contaminants are:

  • Water vapor
  • Oil vapor (from atmosphere)
  • Atmospheric dirt
  • Microorganisms
  • Oil aerosols
  • Oil vapor (from lubricated compressor)
  • Condensed liquid water
  • Water aerosols
  • Rust
  • Pipescale

The use of an oil-free compressor will only remove one contaminant from the 10 present (liquid oil). Oil vapor, present in the atmospheric air from vehicle exhausts and industrial processes are drawn into the compressor intake, cool and condenses to form aerosols which need to be removed or reduced to acceptable levels.

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, the same level of purification equipment is required.

MYTH 3: OIL-FREE COMPRESSORS DON’T NEED PURIFICATION EQUIPMENT.

One common practice when installing an oil-free compressor is to omit some or all of the downstream filtration.

Purification equipment in a compressed air system will typically incorporate a dual filter set-up and it is often believed that one of these filters is a particulate filter and the other is an oil removal filter.

The two filters used are coalescing filters, and are actually the most important pieces of purification equipment in the system as they remove six different contaminants (water aerosols, oil aerosols, atmospheric dirt, microorganisms, rust and pipescale).

Both filters perform the same contamination removal functions; however, they do so to differing levels of filtration. The first filter is a "general purpose" filter which protects the high-efficiency filter from bulk contamination. This dual-filter installation ensures a continuous supply of high-quality compressed air with the additional benefits of lower operational costs and minimal maintenance, as compared to a single, high-efficiency filter.

Omitting one of the coalescing filters as is often the practice with oil-free compressor installations will result in:

  • Poor air quality
  • High operational costs
  • Loss of guarantee

As adsorption and refrigeration dryers are designed to remove only water vapor, and not water in a liquid or aerosol form, they require the use of coalescing filters to work efficiently and achieve dewpoint.

MYTH 4: OIL-FREE COMPRESSORS DO NOT USE OIL.

By design, oil-free compressors do not use oil in the compression chamber and therefore oil does not contact the air being compressed. Oil is often used for the lubrication of moving parts and cooling of the machine.

Typically oil-free compressors will utilize elaborate and
complicated sealing systems to prevent the lubricating oil from entering the compressed air; however, should the sealing mechanism fail, there is the possibility of oil
entering the compressed air system.

On certain designs, care must also be taken regarding the location of the compressor intake, to prevent the ingesting of oil aerosols and vapor from the crankcase breather.

MYTH 5: OIL-FREE COMPRESSORS PROVIDE COMPRESSED AIR TO ISO 08573-1:2010 CLASS 0 STANDARDS.

ISO 8573-1 is the International Standard for Compressed Air purity and provides differing classifications for air quality. Class 0 is the most stringent of the classifications and many compressor manufacturers claim oil-free compressors are compliant with Class 0. 

  • Class 0 does not mean zero contamination.
  • Class 0 requires the user and the equipment manufacturer to agree contamination levels as part of a written specification.
  • The agreed contamination levels for a Class 0 specification should be within the measurement capabilities of the test equipment and test methods shown in ISO 8573 Pt 2 to Pt 9. If not, agreement is required on test method to be used and the accuracy of the method/equipment.
  • The agreed Class 0 specification must be written on all documentation to be in accordance with the standard.
  • Stating Class 0 without the agreed specification is meaningless and not in accordance with the standard.
  • A number of compressor manufacturers claim the delivered air from their oil-free compressors is in compliance with Class 0. If the compressor was tested in clean room conditions, the contamination detected at the outlet will be minimal. Should the same compressor now be installed in typical urban environment, the level of contamination will be dependent upon what is drawn into the compressor intake, rendering the Class 0 claim invalid.
  • A compressor delivering air to Class 0 will still require purification equipment in both the compressor room and at the point of use for the Class 0 purity to be maintained at the application.
  • Air for critical applications such as breathing, medical, food, etc. typically only requires air quality to Class 2.2.1 or Class 2.1.1.
  • Purification of air to meet a Class 0 specification is only cost effective if carried out at the point of use.

MYTH 6: OIL-FREE COMPRESSORS GUARANTEE OIL-FREE AIR.

Atmospheric air typically contains between 0.05 and 0.5 ppm 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. Additionally, “guarantee” certificates are not available.

MYTH 7: OIL-FREE COMPRESSORS LOWER OVERALL COST OF OWNERSHIP.

It is often stated that using an oil-free compressor reduces the user's overall cost of ownership as costly filters can be eliminated, as is the need to change filter elements. System pressure losses are also slightly reduced, again lowering costs.

As purification equipment is based upon the contaminants entering through the compressor intake, contaminants added by the compressor and rust and pipescale in the compressed air system, no matter what type of compressor is installed, the same level of purification equipment is required. This negates the argument of lower overall cost of ownership.

Typically the purchase price of an oil-free compressor is 45% – 50% higher than that of an equivalent lubricated compressor. Maintenance of the air end is generally more frequent than lubricated equivalents, and in some models, complete replacement of the air end is required after only a short number of years, which actually increases the overall cost of ownership significantly.

 

MYTH 8: OIL-FREE COMPRESSORS WITH BUILT IN ZERO PURGE ADSORBENT DRYERS PROVIDE THE SAME DEWPOINT AS STANDALONE DRYERS.

Certain models of oil-free compressor can be supplied with an integral zero-purge adsorbent dryer, often at a significantly reduced cost compared to a standalone unit.

Disadvantages of Heat of Compression Type Dryers:

  • Applicable only to oil-free compressors with a continuously high discharge temperature
  • Compressor must run continuously to supply sufficient regeneration temperature, otherwise booster heating may be required
  • Booster heater for low load (heat) conditions reduces energy efficiency and increases operational costs
  • Higher ambient temperatures = higher compressed air dew point
  • Low dew points only available when compressor is working at full load, with very low ambient temperatures and a low compressed air inlet temperature
  • Inconsistent dew point
  • Regenerated sector moves directly to the drying section without cooling resulting in dew point peaks
  • Sealing of hot / cold sectors is a problem
  • High pressure drop
  • High velocity through ejector and drum = high pressure drop
  • Very low quantity of desiccant = higher loading and usage of desiccant resulting in more frequent servicing of the desiccant drum
  • Very expensive and sensitive drum = high spare part costs

Standalone dryers are sized based upon worst case conditions of minimum inlet pressure, maximum temperature and maximum flow rate. They will typically be selected to provide a pressure dew point of -4°F, -40°F or -100°F, in-line with the requirements of ISO 8573-1.

A constant pressure dew point of -14.8°F or better will inhibit the growth of microorganism within the compressed air system; therefore, a PDP of -40°F is typically used in many applications, often beyond the capabilities of dew point suppression dryers.

MYTH 9: OIL-FREE COMPRESSORS PROVIDE ZERO RISK OF CONTAMINATION.

As contamination in a compressed air system comes from four different sources and not just the air compressor itself, an oil-free compressor does not provide contaminant-free air. This negates the argument for zero risk of contamination.

MYTH 10: OIL-FREE COMPRESSORS ARE THE ONLY TYPE OF COMPRESSOR THAT SHOULD BE USED IN THE FOOD, BEVERAGE AND PHARMACEUTICAL INDUSTRIES.

The only reference document currently in use worldwide relating to the quality of compressed air for use in the food and beverage industries is the BCAS Code of Practice for Food Grade Compressed Air.

The Code of Practice states:

  • Where lubricated or oil-injected compressors are in use and non-food grade oil is used and the HACCP process identifies a risk, then the oil shall be replaced with food grade oils in-line with the procedures identified in the EHEDG Document 23
  • Where oil-free compressors are used, no lubricant is involved in the compression process. Therefore the procedures identified in the EHEDG Document 23 will not be required
  • Oil-free compressors that employ lubricants in those parts not involved in the actual compression of the air will still be subject to the HACCP process to determine the risks if any to the food production process

Example of compressed air system for food, beverage & pharmaceutical industry.

MYTH 11: OIL-FREE COMPRESSORS ARE MORE ENVIRONMENTALLY FRIENDLY THAN LUBRICATED MACHINES.

Oil vapor drawn into the intake of an oil-free compressor can condense into liquid oil that can mix with condensed water in the compressor, producing compressor condensate.

It is the responsibility of the compressed air user to identify the legal requirements for oil in water discharges in their country and comply with those requirements, disposing of oily compressor condensate in a legal and responsible manner. Depending upon the discharge limits and the volume of oil vapor in the atmospheric air, the use of an on-site oil / water separator may also be required on oil-free compressor installations.

MYTH 12: OIL-FILTERS IN OIL-INJECTED COMPRESSOR INSTALLATIONS CANNOT BE MADE 100% SAFE. A TOTAL GUARANTEE THAT NO OIL DROPLETS OR VAPOR WILL FIND THEIR WAY THROUGH IS SIMPLY AN ILLUSION.

No type of compressor (oil-free or oil-lubricated) can truly provide compressed air that is 100% oil free; however, with proper purification “Technically Oil-free Air” is available from both types.

Oil-free compressors do not introduce oil into the compression stage, however oil vapors present in the ambient air will travel into the compressed air system where they can cool and condense into aerosols and liquids.

As oil-free compressors do not include oil vapor removal technology, filtration is required downstream of the compressor to remove oil vapor, condensed liquid oil and oil aerosols.

MYTH 13: AN OPERATIONAL ERROR, CLOGGED UP FILTERS OR UNTIMELY REPLACEMENT COULD LEAD TO PRODUCT DEGRADATION.

Mattei's Absolute Zero (MAZ) MF Series guarantees performance for 12 months of continuous operation. Annual preventative maintenance removes risk and automatically extends the performance guarantee.

MYTH 14: FLUCTUATIONS IN AIR TEMPERATURE GIVE RISE TO VARIATIONS IN AIR QUALITY, BECAUSE OF THE INCREASE IN OIL CARRYOVER AND THE SHORTENED LIFETIME OF ACTIVE CARBON FILTERS. SO TO ME, OIL-FREE AIR COMPRESSION IS THE ONLY PROCESS THAT TRULY DESERVES THE “QUALITY” LABEL.

In a typical in-line activated carbon filter with a fixed volume of activated carbon, temperature will affect the lifetime of the filter; air quality is not affected unless preventative maintenance is forgotten.

Mattei does not recommend the use of in-line activated carbon filters in the compressor room or for plant scale protection, instead we recommend the Mattei Absolute Zero (MAZ) Series oil vapor removal filters, which differ from traditional in-line filters as they are sized and selected based upon all of the system operating conditions to provide “Technically Oil-Free Air” for a 12-month period. Temperature is no longer an issue, and air quality in accordance with international compressed air standards is guaranteed.

Increases in air temperature are an issue for oil-free compressors as higher temperatures entering the compressor inlet means a higher concentration of oil vapor.

Oil-free compressors also contain oil for lubrication of bearings and gearboxes, and as the oil in the sump of the “oil-free” compressor heats up during operation, vapors can exit the crank case vent filter into the compressor room where they can be drawn into the compressor intake filter.

MYTH 15: BREATHING OIL FUMES IS HAZARDOUS, SO ANY COMPRESSED AIR SYSTEM THAT RELEASES OIL VAPOR IS ON MY BLACKLIST. NOT ONLY COULD THESE OIL FUMES TAMPER WITH PRODUCT INTEGRITY, BUT THEY ARE UNHEALTHY FOR OUR WORKFORCE AND THE ENVIRONMENT WE ARE TRYING TO PROTECT.

Mattei Absolute Zero (MAZ) filtration guarantees performance for 12 months of continuous operation. Annual preventative maintenance removes risk and automatically extends the performance guarantee.

It is not uncommon to replace air compressors many times compared to the storage and distribution piping. A compressed air system which was once operated with a lubricated compressor and replaced with an oil-free compressor will still contain oil in the air receiver and piping system which will continue to release vapors for many years after the compressor is replaced. Point of use oil vapor removal filters will be needed to remove oil fumes no matter what type of compressor is installed.

MYTH 16: ANOTHER BY-PRODUCT OF AN OIL-INJECTED COMPRESSOR IS OIL-CONTAMINATED CONDENSATE. IT CAN’T JUST BE DISCHARGED IN THE SEWER SYSTEM; IT IS UNETHICAL AND INCREASINGLY BECOMING ILLEGAL.

Oil vapor drawn into the intake of an oil-free compressor will cool and condense within the compressed air system where it will mix with condensed water vapor. This produces oily, acidic compressor condensate.

Even oil-free compressors require oil / water separators to comply with environmental legislation and local discharge limits for oil & water.

MYTH 17: MANY PEOPLE RELY ON OIL-INJECTED AIR FOR THE LUBRICATION OF THEIR EQUIPMENT AND THE CORROSION PROTECTION OF THEIR PIPING.

This is a complete myth as Filter Regulator Lubricators (FRL) are employed on machinery and equipment in order to meter and provide the exact amount of lubrication.

 

MYTH 18: AT FIRST, I LIKED THE LOWER INVESTMENT COST OF OIL-INJECTED COMPRESSORS, BUT THEN I LOOKED AT THE BROADER PICTURE. THE REQUIRED FILTERS INTRODUCE A PRESSURE DROP, WHICH NEEDS TO BE OVERCOME AT AN INCREASED ENERGY COST. THIS IS NO LIGHT MATTER, SINCE ENERGY COSTS MAKE UP OVER 70% OF THE TOTAL LIFECYCLE COST OF A COMPRESSOR. FILTER CARTRIDGES NEED TO BE REPLACED PERIODICALLY.

Oil-free compressors require “exactly” the same filtration products as oil-lubricated machines (due to 9 of the 10 contaminants found in a compressed air system not being related to an oil-lubricated compressor); therefore, the total cost of ownership calculations tend to show in favor of oil-lubricated machines.

Energy efficient filtration, like the Mattei Absolute Zero (MAZ) MF Series, has a much lower resistance to airflow and a higher dirt loading capacity compared to other types of compressed air filters providing the user with the lowest total cost of ownership.

MYTH 19: OIL IS CONSUMED AT A COST, AND OIL RESIDUE MUST BE DISPOSED OF…AT AN ADDITIONAL COST.

Oil-free compressors still use oil for lubrication of bearings and gearboxes. This oil still requires purchasing and disposal at additional cost.

MYTH 20: THE INHERENT RISK OF PRODUCT CONTAMINATION IS SOMETHING I DARE NOT TO THINK ABOUT, AS THE INCURRED COSTS COULD BE ASTRONOMICAL. SO ALL IN ALL, THE EXTRA INVESTMENT FOR AN OIL-FREE COMPRESSOR PAYS FOR ITSELF. AND THAT’S THE BOTTOM LINE.

Oil-free compressors do not deliver contaminant-free air and do not contain any technology for contaminant removal; therefore, without the same filtration as an oil-lubricated compressor, there is still an inherent risk of product contamination.

MYTH 21: A MISCONCEPTION I OFTEN HEAR IS THAT OIL-FREE AIR IS THE PRIVILEGE OF INDUSTRIES SUCH AS PHARMACEUTICALS, FOOD & BEVERAGES, COSMETICS OR ELECTRONICS. I DON’T KNOW WHY WE SHOULDN’T ALL BENEFIT OF THE INHERENT QUALITIES OF OIL-FREE AIR. GIVEN THE CHOICE, I ASSUME WE ALL PREFER TOTAL PRODUCT SAFETY, LOWER OPERATING AND MAINTENANCE COSTS, AND A HEALTHIER WORKING AND LIVING ENVIRONMENT.

MYTH 22: THE LUBRICATED COMPRESSOR AIR / OIL SEPARATOR HAS LONG BEEN SEEN AS A POTENTIAL RISK SHOULD IT FAIL AS ALL OF THE OIL IN THE SUMP OF THE COMPRESSOR OVERLOADS THE PURIFICATION SYSTEM AND CARRIES OVER INTO THE PIPING SYSTEM AND ULTIMATELY THE POINT OF USE. THE ONLY WAY TO GUARANTEE SAFETY IS TO USE AN OIL-FREE COMPRESSOR.

Modern air / oil separators are very robust and failures are extremely rare, but if the potential for risk is too great Mattei now has a cost effective alternative to the oil-free compressor, the Mattei Oil Mist Safeguard.

The Mattei Oil Mist Safeguard is the ideal alternative to expensive “oil-free” compressors, providing efficient removal of bulk liquid oil and oil-mist carryover from piston or oil flooded rotary compressors.

With an extremely low pressure drop and long service life, the Mattei Oil Mist Safeguard compliments and protects the existing purification equipment providing total peace of mind.

MYTH 23: CAN OIL-INJECTED COMPRESSORS WITH OIL REMOVAL FILTERS DELIVER OIL-FREE AIR?

Ambient air in an urban environment typically contains between 0.5 mg/m3 – 0.05 mg/m3 of oil vapor.

Air compressors draw in large volumes of this contaminated air and as they have no means of removing contamination, oil vapor enters the storage and distribution system where it cools and condenses to form aerosols and liquid oil. The concentration of oil vapor entering the compressor can increase significantly if the compressor intake draws air from a car park or near a road.

Oil-free compressors do not contain any technologies for the removal of oil vapor. To achieve oil-free air requires no oil to enter the compressor intake. Nothing in = Nothing out.

Oil vapor in = Concentrated oil vapor out (concentrated as it's compressed).

Oil-free compressor manufacturers claim there is next to no oil vapor present in ambient air (only 0 mg/m3 – 0.003 mg/m33), as otherwise they are unable to claim “oil-free.”

MYTH 24: TEMPERATURES CAUSE AN INCREASE IN THE VAPOUR CONTENT OF THE AIR, WHICH CAN CARRY THROUGH TO THE END PRODUCT. MOREOVER, HIGH TEMPERATURES SHORTEN THE LIFETIME OF ACTIVATED CARBON FILTERS. AN INCREASE IN TEMPERATURE FROM 20°C (68°F) TO 40°C (104°F) CAN CUT FILTER LIFETIME BY UP TO 90%. EVEN WORSE, THE ACTIVATED CARBON FILTER DOES NOT WARN THE USER WHEN IT IS SATURATED. IT WILL SIMPLY ALLOW OIL TO PASS ON TO PROCESSES.

Unlike other manufacturers of purification equipment, Mattei's Absolute Zero filters are sized and selected based upon the system conditions to provide oil-free air for a 12-month period. Temperature is no longer an issue, and air quality is guaranteed.

MYTH 25: WITH OIL-FREE AIR COMPRESSORS, AIR QUALITY IS INDEPENDENT OF TEMPERATURE. THIS WAS DEMONSTRATED BY THE INDEPENDENT TESTING WHICH SHOWED NO TRACES OF OIL AT TEMPERATURES OF 20°C (68°F), 40°C (104°F) AND 50°C (122°F).

Oil-free compressors do not contain any technologies for the removal of oil vapor. To achieve oil-free air therefore requires no oil to enter the compressor intake.

Nothing in = Nothing out.

Oil vapor in = Concentrated oil vapor out (concentrated as it is compressed).

The testing above provides no mention of inlet concentration nor does it introduce any “oil challenge” to show the effects of increasing oil vapor content entering the compressor; therefore, the test results are incomplete and inconclusive.

The MAZ coalescing and adsorption filters are tested in accordance with ISO 12500-1 and ISO 8573-5, with defined inlet concentrations of oil (aerosol / vapor) and performance third-party validated by Lloyd's Register.

MYTH 26: WHAT IS THE IMPACT OF AMBIENT TEMPERATURE? ONE ASPECT INFLUENCING THE EFFICIENCY AND PURITY OF AIR SYSTEMS IS TEMPERATURE. WHEN USING OIL-INJECTED COMPRESSORS WITH OIL REMOVAL FILTERS, OIL CARRYOVER THROUGH FILTER MEDIA INCREASES EXPONENTIALLY ACCORDING TO THE TEMPERATURE AT THE FILTRATION INTERFACE. FILTER PERFORMANCE IS OFTEN SPECIFIED AT 20°C (68°F). IF THE AMBIENT TEMPERATURE IN THE COMPRESSOR ROOM INCREASES TO 30°C (86°F), THE COMPRESSOR OUTLET TEMPERATURE COULD BE 40°C (104°F) WITH THE OIL CARRYOVER 20 TIMES THE SPECIFIED VALUE. SUCH TEMPERATURES ARE NOT UNUSUAL EVEN IN COLDER COUNTRIES, WHERE THE COMPRESSOR ROOM TEMPERATURE IS SUBSTANTIALLY HIGHER THAN THAT OUTSIDE.

Filtration is a multi-stage process, and of the 10 main contaminants in a compressed air system, filtration will remove or reduce 9 contaminants.

To reduce oil (liquid / aerosol / vapor) requires the use of water separators (if bulk liquid is present), coalescing and adsorption filters which are typically installed in series.

Filtration performance of coalescing filters varies from manufacturer to manufacturer; therefore, claims that oil carryover increases by 20 x cannot be substantiated. Additionally, the increase in carryover is not an issue so long as the final stage of filtration, the adsorption filter, is sized correctly for flow, pressure & temperature.

Unlike other manufacturers of purification equipment, Mattei's MAZ filters are sized and selected based upon the system conditions to provide oil-free air for a 12-month period. Temperature is no longer an issue, and air quality is guaranteed.

MYTH 27: AREN’T OIL-FREE COMPRESSORS MORE EXPENSIVE?

No, not if you look at the total cost of ownership. Oil-free technology greatly reduces expenditures in four ways:

  • Avoiding expensive filter replacements
  • Reducing maintenance costs
  • Reducing costs of treating oily condensate
  • Eliminating the costs of extra energy needed to combat pressure drops in filters

These costs, although not evident at the time of purchase, are very high and contribute substantially to the total cost of ownership.

Oil-free compressors require filtration just as oil-lubricated compressors do; therefore, arguments relating to avoiding expensive filter replacements and cutting maintenance costs do not apply.

There are 10 contaminants that must be removed or reduced in a typical compressed air system for safe and efficient operation. As air compressors do not include technologies to remove these contaminants, purification equipment (filters and dryers) are required for every compressor type.

Coalescing filters are the most important piece of purification equipment in a compressed air system as they remove 6 of the 10 contaminants.

Coalescing filters are installed in pairs, and most users believe one to be an oil removal filter and the other to be a particulate filter. In fact, each filter removes 6 contaminants. The first filter, a General Purpose filter, is used to protect the High Efficiency filter from bulk contamination. This ensures high quality compressed air with low operational costs and minimal maintenance time. Omitting one of the coalescing filters as is often the practice with oil-free compressor installations will result in:

Poor air quality / High operational costs / Loss of performance guarantee

The filtration requirements of oil-free compressors are therefore “exactly” the same as those of an oil-lubricated machine.

MYTH 28: OIL-FREE AIR COMPRESSORS ELIMINATE THE RISK OF A CONTAMINATED END-PRODUCT, PRODUCTION DOWNTIME AND DAMAGED REPUTATION. CLASS 0 COMPRESSORS ARE WELL WORTH THE INVESTMENT.

ISO 8573-1 is the International Standard for Compressed Air purity and provides differing classifications for air quality. Class 0 is the most stringent of the classifications, and many compressor manufacturers claim oil-free compressors are compliant with Class 0. However, please note:

  • Class 0 does not mean zero contamination.
  • Class 0 requires the user and the equipment manufacturer to agree contamination levels as part of a written specification.
  • The agreed contamination levels for a Class 0 specification should be within the measurement capabilities of the test equipment and test methods shown in ISO 8573 Pt 2 to Pt 9. If not, agreement is required on test method to be used and the accuracy of the method / equipment.
  • The agreed Class 0 specification must be written on all documentation to be in accordance with the standard.
  • Stating Class 0 without the agreed specification is meaningless and not in accordance with the standard.
  • A number of compressor manufacturers claim the delivered air from their oil-free compressors is in compliance with Class 0. If the compressor was tested in clean room conditions, the contamination detected at the outlet will be minimal. Should the same compressor now be installed in a typical urban environment, the level of contamination will be dependent upon what is drawn into the compressor intake, rendering the Class 0 claim invalid.
  • A compressor delivering air to Class 0 will still require purification equipment in both the compressor room and at the point of use for the Class 0 purity to be maintained at the application.
  • Air for critical applications such as breathing, medical, food, etc. typically only requires air quality to Class 2.2.1 or Class 2.1.1.
  • Purification of air to meet a Class 0 specification is only cost effective if carried out at the point of use.

MYTH 29: WHAT ABOUT THE ENVIRONMENT? WITH OIL-FREE TECHNOLOGY, LEAKS AND ENERGY WASTE ARE MINIMIZED.

Oil-free compressors do not prevent leaks in the storage and distribution system; therefore, this argument is invalid.

MYTH 30: OIL-FREE AIR COMPRESSORS ELIMINATE THE RISK OF A CONTAMINATED ENDPRODUCT, PRODUCTION DOWNTIME AND DAMAGED REPUTATION. CLASS 0 COMPRESSORS ARE WELL WORTH THE INVESTMENT.

ISO 8573-1 is the International Standard for Compressed Air purity and provides differing classifications for air quality. Class 0 is the most stringent of the classifications and many compressor manufacturers claim oil free compressors are compliant with Class 0. However, please note:

  • Class 0 does not mean zero contamination.
  • Class 0 requires the user and the equipment manufacturer to agree contamination levels as part of a written specification.
  • The agreed contamination levels for a Class 0 specification should be within the measurement capabilities of the test equipment and test methods shown in ISO 8573 Pt 2 to Pt 9. If not, agreement is required on test method to be used and the accuracy of the method / equipment.
  • The agreed Class 0 specification must be written on all documentation to be in accordance with the standard.
  • Stating Class 0 without the agreed specification is meaningless and not in accordance with the standard.
  • A number of compressor manufacturers claim the delivered air from their oil-free compressors is in compliance with Class 0. If the compressor was tested in clean room conditions, the contamination detected at the outlet will be minimal. Should the same compressor now be installed in a typical urban environment, the level of contamination will be dependent upon what is drawn into the compressor intake, rendering the Class 0 claim invalid.
  • A compressor delivering air to Class 0 will still require purification equipment in both the compressor room and at the point of use for the Class 0 purity to be maintained at the application.
  • Air for critical applications such as breathing, medical, food, etc. typically only requires air quality to Class 2.2.1 or Class 2.1.1.
  • Purification of air to meet a Class 0 specification is only cost effective if carried out at the point of use.

MYTH 31: ALSO, THE NEED FOR CONDENSATE TREATMENT IS ELIMINATED. THE AMOUNT OF LUBRICATING OIL REQUIRED IS A FRACTION OF THE QUANTITY IN OIL-INJECTED COMPRESSORS. THIS MEANS YOU CAN SAFEGUARD THE ENVIRONMENT AND BETTER COMPLY WITH INTERNATIONAL REGULATIONS.

Oily condensate is still produced in oil-free compressor installations due to the atmospheric oil vapor cooling, condensing and mixing with condensed water within the storage and distribution system.

Additionally, the difference in oil volume between the two types of technology is minimal, so the small additional cost associated with the oil-lubricated machine is not enough to justify the extra costs in maintaining an oil-free type with its many extra parts.

MYTH 32: OIL-FREE AIR COMPRESSORS ELIMINATE THE RISK OF A CONTAMINATED END-PRODUCT, PRODUCTION DOWNTIME AND DAMAGED REPUTATION. CLASS 0 COMPRESSORS ARE WELL WORTH THE INVESTMENT.

ISO 8573-1 is the International Standard for Compressed Air purity and provides differing classifications for air quality. Class 0 is the most stringent of the classifications and many compressor manufacturers claim oil free compressors are compliant with Class 0. However, please note:

  • Class 0 does not mean zero contamination.
  • Class 0 requires the user and the equipment manufacturer to agree contamination levels as part of a written specification.
  • The agreed contamination levels for a Class 0 specification should be within the measurement capabilities of the test equipment and test methods shown in ISO 8573 Pt 2 to Pt 9. If not, agreement is required on test method to be used and the accuracy of the method / equipment.
  • The agreed Class 0 specification must be written on all documentation to be in accordance with the standard.
  • Stating Class 0 without the agreed specification is meaningless and not in accordance with the standard.
  • A number of compressor manufacturers claim the delivered air from their oil-free compressors is in compliance with Class 0. If the compressor was tested in clean room conditions, the contamination detected at the outlet will be minimal. Should the same compressor now be installed in a typical urban environment, the level of contamination will be dependent upon what is drawn into the compressor intake, rendering the Class 0 claim invalid.
  • A compressor delivering air to Class 0 will still require purification equipment in both the compressor room and at the point of use for the Class 0 purity to be maintained at the application.
  • Air for critical applications such as breathing, medical, food, etc. typically only requires air quality to Class 2.2.1 or Class 2.1.1.
  • Purification of air to meet a Class 0 specification is only cost effective if carried out at the point of use.

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