about the iso 8573-1 standard - insco group · 3 iso 8573-1 (1991) unusually, the standard...

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1 About the ISO 8573-1 standard

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Page 1: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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About the ISO 8573-1 standard

Page 2: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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History of ISO 8573

The original version of 1991 (edition1) standard defined 5 classes on oil concentration

The best – Class 1, specifying an oil concentration of ≤ 0,01 mg/m3

at 1 bar(a) 14.5 psia and 20oC (68F)

Conformance to Class 1 was sometimes called “a technically oil-free solution”

Page 3: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 (1991)

Unusually, the standard recommended methods to remove oil from the compressed air.

Quote “Oil may be removed by high efficiency filters”

It also cautioned users about using oil-free compressors

Quote “The quality of air delivered by non-lubricated compressors is influenced by the quality of the intake air and the compressor design”

Oil vapors, which are not removed by coalescing filters were accorded negligible importance (when in fact quantity of vapors may be higher than aerosols)

Quote “Therefore below approximately 35 oC (95 oF), the oil vapor content may be disregarded”

In effect, the provisions in the standard were not adequate to assure the purity levels demanded by the industry and a new edition of the standard evolved: edition 2.

Page 4: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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Forms of oil in pipelines

When oil is present in pipelines, it is always in these three forms:

Aerosols are partially removed by coalescing filters and appear as condensateWall flow either appears in condensate or travels to the processVapors are not removed by coalescing filters!

Page 5: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 (2001)

Major changes:– The standard now spoke about total oil content (aerosol, liquid and vapour)– A standard was introduced on measurement of oil vapour ISO 8573 part 5– A new class (Class 0) was introduced to cover more stringent quality requirements

– The clause which recommended ways to remove oil was deleted– Representative samples were asked

Page 6: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 Testing Methods

ISO 8573-1 Part 2– Measurement of Aerosols

ISO 8573-1 Part 5– Measurement of oil fumes and vapors

Page 7: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 Part 2 - Aerosols

Method B1– Measurement of full flow with

membranes. – Measures all aerosols and wall

flow

Page 8: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 Part 2 - Aerosols

Method B2– Sampling probe at the center of the

pipe is used. – Wall flow is not measured

Page 9: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 Part 5 - Vapors

Chemical absorption of oil by use of activated carbon.

Page 10: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 Temperature factor

Reference Conditions:– The reference conditions are

specified as 20 oC (68 oF) and 1 bar (a) (14,5 psia).

– The above conditions are not representative. Filters receive air at 4-10 oC (7-18 oF) above cooling medium temperature which could reach 30 oC (86 oF)! Also, the working conditions of the compressor are at higher pressures.

Oil carry over will be greater at higher temperatures !

Page 11: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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Atlas Copco’s test

TÜV tested Atlas Copco’s Z series of oil-free rotary screw compressors at:– Three different temperatures: 20 oC, 40 oC and 50 oC at the measurement point– 2 different pressures: 1 bar(a) and 8 bar(a)

Why is this important?– Temperatures: oil carry-over increases exponentially with increasing temperatures.– Especially at 8 bar(a), the oil concentration goes up as compared to 1 bar(a)

As production environments change from place to place, country to country and application to application, it is important to test at all possible conditions.

Page 12: About the ISO 8573-1 standard - INSCO Group · 3 ISO 8573-1 (1991) Unusually, the standard recommended methods to remove oil from the compressed air. Quote “Oil may be removed by

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ISO 8573-1 Filter factor

Another factor influencing test results when measuring oil residue in compressed air:– using lubricated compressors in combination with filters

The saturation level of the filter may affect oil carry-over.

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