Air Quality Standards ISO 8573

7/24/15 Air Quality Standards ISO 8573.1 & ISO12500 | Compressed Air Best Practices

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Industrial Utility Efficiency

Air Quality Standards ISO 8573.1 & ISO12500Jay Francis, Vice President of Marketing, SPX Dehydration & Filtration

The next time y ou sit down for dinner, take a good look at y our food. Theres a v ery good chance

compressed air play ed an essential role in preparing y our meal for consumption.

Compressed air is a v ital energy source and is utilized in multiple operations in a food processing

facility . When properly treated, compressed air is regarded as a safe, clean utility , as compared to other

energy sources. Compressed prov ides the energy source for pneumatic conv ey ers that transport liquids,

powders and moisture sensitiv e product throughout the plant. It prov ides power for pneumatically

operated tools and equipment that renders meat products, aerates liquids and mixes granular

ingredients. It is ultimately used to package, wrap, seal, palletize and label food products prior to storage

or shipment.

Of the primary utilities employ ed in the food-manufacturing env ironment, compressed air is the only

utility generated by the end-user. This means the end-user directly influences the quality of this

energy source. High quality compressed air is critical for prov iding food products that are not only cost

effectiv e to process but also safe to eat. Therefore, its in all our best interests for food processors to select

the proper compressed air equipment. The ISO 857 3 air quality standards and ISO 1 2500 compressed

air filter standards make the basis for air treatment product selection much easier.

A Very Good Start ISO 8573.1

Food processors maintain a social responsibility for upholding the quality of their products and that

accountability begins with the selection of compressed air sy stem components. In most cases, end users

select compressed air sy stem components by comparing technical data from v arious air treatment

manufactures. In 1 991 , the International Standards Organization (ISO) established the 857 3

compressed air quality standard to facilitate compressed air sy stem component selection, design and

measurement.

ISO 857 3 is a multi-part standard, with Part 1 classify ing contaminant ty pe and assigning air quality

lev els, and Parts 2 through 9, define testing methods to accurately measure a full range of

contaminants within the end users facility .

ISO 857 3.1 identifies three primary contaminant ty pes as prev alent in a compressed air sy stem. Solid

particulates, water and oil (in both aerosol and v apor form) are recognized. Each is categorized and

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assigned a quality class ranging from class 0, the most stringent, to Class 9, the most relaxed. The end

user-user is responsible for defining the air quality required for their particular application or process.

Air treatment manufacturers present technical data in reference to ISO 857 3.1 . An easy to understand

ISO 857 3.1 : 2001 table defines the v arious air quality classes. The standard also determines that air

quality shall be designated by the following nomenclature:

Compressed Air Purity Classes A, B, C:

Where:

A= solid particle class designation

B= humidity and liquid water class designation

C= oil class designation

More than you thought

Compressed Air Contamination

Contaminants originate from three general sources.

1 . Contaminants in the surrounding ambient are drawn into the air sy stem through the

intake of the air compressor. Ingested contaminants appear in the form of water v apor,

hy drocarbon v apors, natural particles and airborne particulates.

2. As result of the mechanical compression process, additional impurities may be

introduced into the air sy stem. Generated contaminants include compressor lubricant,

wear particles and v aporized lubricant.

3 . A compressed air sy stem will contain in-built contamination. Piping distribution and air

storage tanks, more prev alent in older sy stems, will hav e contaminant in the form of

rust, pipe scale, mineral deposits and bacteria.

Water

Water v apor enters the sy stem through the intake of the air compressor. In total v olume, condensed

water v apor represents the majority of liquid contamination in a compressed air sy stem. On a ty pical

summer day of 80(F (21 (C) and 7 0% relativ e humidity , approximately 1 9.5 gallons (7 3 .8 liters) of

water enters a 1 00 scfm (1 7 0 nm3/hr) sy stem in a 24 hour period. This moisture will spoil food

products, cause pneumatic machinery failure and promote bacterial growth in the compressed air

piping. Compressed air sy stems serv ing the food processing industry must maintain dry , moisture free

conditions mitigating the risk of micro-organism growth.

Since compressed air used in food processing operations may come in direct contact with the food, a

compressed air dry er producing a sub-zero pressure dew point is required. Dew point, specified as

temperature, is the point at which the water v apor held in the compressed air is equal to the

compressed airs capacity to hold water v apor. Desiccant dry ers- using activ ated alumina- will adsorb

water v apor from the air most effectiv ely , deliv ering ISO 857 3.1 Quality Class 2 (-40( F/-40( C)

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pressure dew point), ideal for the food processing industry . At this lev el of dry ness, bacteria will cease to

grow.

Liquid Oil and Oil Vapor

The most scrutinized and often discussed contaminant classified by ISO 857 3.1 is oil. Compressed air

free from oil is a requirement in a food processing env ironment.

End users are giv en the choice of selecting from sev eral air compressor technologies, some of which

require lubrication in the compression chamber for cooling and sealing purposes, and others that

operate less lubricant in the compression chamber. The end user determines which compressor design

best meets the desired requirements. The purpose of this discussion is not to tip the scale toward either

technology , but to address air treatment requirements in food processing applications.

Lubricated compressors are ty pically less expensiv e to purchase and hav e a lower cost of ownership.

Dependent on the age of the compressor and prev entativ e maintenance programs performed, a

lubricated rotary screw air compressor will introduced 2 to 1 0 ppm/w of oil into the air sy stem. A well

maintained 250 scfm lubricated air compressor, with a conserv ativ e 4 parts per million carry -ov er,

will add up to 4.8 gallons (1 8.2 liters) of oil into the air sy stem ov er an 8000 hour operation.

Lubricant free compressors generally hav e a higher initial cost and greater maintenance costs ov er the

life cy cle of the equipment. Lubricant is only required for the bearings and timing gears, which is

segregated from the compression chamber. This compressor technology presents no risk of lubricant

migrating into the process air.

Both air compressor technologies are subject to the inherent challenges presented by quality of the

intake air. Ingested contamination in the form of water v apor, solid particulate and hy drocarbon v apor

must be addressed regardless if the compressor is lubricated or free from lubricant. Depending on the

location of the compressor intake, oil v apor lev els in industrial areas may contain 20-30 ppm of

airborne hy drocarbon aerosols. Hy drocarbon v apors, the primary component of fossil fuel combustion,

will condense in a piping sy stem when cooled forming a liquid contaminant.

Because compressed air may come in direct and indirect contact with food processing, an elev ated lev el

of filtration is required. A high efficiency coalescing filter capable of remov ing solids and liquids is

recommended. It should be capable of remov ing solid and liquid aerosols 0.01 micron and larger. The

remaining oil content should be 0.007 ppm, or less. An activ ated carbon filter, installed in series, is also

recommended downstream of the coalescing filter. The adsorption filter will remov e trace odors and oil

v apor to 0.003 parts per million by weight. This filter combination will ensure specified filtration lev els

achiev e ISO 857 3.1 Class 1 for oil and v apor remov al.

Solid Particles

In a general industrial area, there are nearly 4,000,000 airborne particles per cubic foot of air. When

this ambient air is compressed to 1 00 psig, the concentration of solid contamination will reach

significant proportions. Most air compressor intake filters are rated to capture sold particles 4 to 1 0

microns in size and larger and are rated at 90-95% efficiency . Approximately 80% of airborne particles

are 1 0 micron or less. Spores, pollen and bacteria are less than 2 micron in size. This may seem like a lot

of particulate matter, but keep in mind, a solid particle 40 um in size is barely v isible to the naked ey e.

Ev en a well maintained and routinely changed intake filter will allow solid particles to enter the air

sy stem.

Solid particulate must be remov ed from process air serv ing the food industry . In pneumatic control



circuits, solids particles plug control v alv e orifices, affect accuracy of gauging and score air cy linders

walls, causing leaks. Particles may restrict flow through air jet nozzles used to clean food preparation

surfaces or adv ersely affect the consistency of spray coatings applied on food products.

To achiev e the recommended ISO 857 3.1 Class 2 classification for solid particulate remov al, a 1 .0

micron particulate filter is recommended. The particulate filter will also enhance the serv ice life of high

performance coalescing filters by minimizing solid loading.

Meeting the Newest Challenge - ISO 12500

The ISO 857 3 Air Quality standard is serv ing the industry well by raising end user awareness of how to

measure and define the quality of compressed air. Using this, the end-user can make educated decisions

as to the filtration performance required to generate a certain quality lev el. Howev er, this standard

does not address how manufacturers are to test and rate the filters. The play ing field is not lev el and

consumers become confused. The ISO 1 2500 filter standard addresses this issue and establishes how

manufacturers test and rate compressed air filters.

The standard defines critical performance parameters (namely , inlet oil challenge, inlet compressed air

temperature and pressure measurement techniques) that will deliv er certifiable filter performance

information suitable for comparativ e purposes.

ISO 1 2500 is a multi-part standard, with ISO 1 2500-1 encompassing the testing of coalescing filters for

oil aerosol remov al performance, ISO 1 2500-2 quantifies v apor remov al capacity of adsorption filters,

and; ISO 1 2500-3 outlines requirements to test particulate filters for solid contaminant remov al.

The SPX Dehy dration and Filtration Research and Dev elopment center, located in Canonsburg,

Pennsy lv ania, maintains adv anced testing resources to conduct ISO 1 2500-1 , 2 , and 3 filter testing.

Three separate test laboratories were constructed, each equipped with stainless steel piping, state of the

art instrumentation and contaminant measurement equipment. SPX D & F maintains capabilities to

generate dehy drate and filter compressed air through 3000 scfm.

Test Methods

The following describes methods SPX Dehy dration and Filtration has elected to perform filter

performance testing under the guise of ISO 1 2500 standards.



ISO 12500-1:2007 Filters for Compressed Air Part 1: Oil Aerosols

ISO 1 2500-1 has identified two opposing inlet oil aerosols concentrations to determine the performance

and pressure drop characteristics of coalescing filters. The inlet concentrations, 1 0 mg/m3 and 40

mg/m3, were selected to prov ide a wide challenge v ariance. Filter manufacturer may elect to publish

performance date at either of the two inlet concentrations. The challenge concentration selected shall

appear in published technical data.

Note: 1 mg/m = 0.84 ppm by weight

a. The ISO 1 2500-1 coalescing filter test begins with a clean, reliable source of compressed

air.

b. Testing conditions shall be controlled: inlet air pressure- 1 01 .5 psig (7 bar); inlet air

temperature- 68 (F (20 (C); ambient temperature- 68(F (20(C).

c. An initial (dry ) pressure drop measurement is taken. Initial pressure drop ratings are

relev ant to quantify cost of operation in that condition.

d. A Laskin nozzle generator dev elops a supply of aerosol s with a peak distribution profile

0.1 to 0.3 microns in size. Aerosols in this range are the most difficult to remov e. These oil

aerosols are injected into the clean compressed air stream.

e. A white light scattering photometer measures the upstream concentration to ensure the

mixture complies with the 1 0mg/m3 or 40 mg/m3 aerosol challenge.

f. Air then enters the coalescing ty pe filter.

g. Once the filter reaches equilibrium, often referred to as the wetted condition,

measurements are taken to determine the effectiv eness of the filter. A white light

scattering photometer is used to measure of penetration of the oil aerosols through the

coalescing element. The pressure drop across the filter housing is also measured and

recorded.

h. Three sets readings are taken. The manufacturer publishes the av erage performance

v alue deriv ed from the three tests.

i. At the giv en inlet concentration of oil, the 1 2500-1 test will confirm:

Oil aerosol penetration (expressed as mass per unit v olume (mg/m3 )

Oil aerosol filtration efficiency (expressed in percent (% captured)

Pressure drop (p)



ISO 12500-2:2007 Filters for compressed air Part 2: Oil Vapors

ISO 1 2500-2 determines the adsorption capacity and pressure drop of hy drocarbon v apor remov al

filters. Adsorption filters, utilizing an activ ated carbon medium, possess the polarity to attract

hy drocarbon v apors from an air stream onto a porous surface. The adsorption process will continue

until the activ ated carbon media is fully consumed. A mass measurement is taken confirming the

v apor remov al filters adsorptiv e capacity expressed in milligrams of hy drocarbon adsorbed.

a. The ISO 1 2500-2 adsorption filter test begins with a clean, reliable source of compressed

air.



c. A precision rotameter measures the concentration of n-hexane liquid. N-hexane is widely

used in laboratory testing for hy drocarbon measurement and possesses the properties

required to conduct adsorption filter testing, i.e., easy to ev aporate, colorless, light

distinguishable odor, and easy to measure.

d. A heater v aporizes the n-hexane liquid at 1 55.6(F (68(C). When heated, n-hexane

changes phase and turns into a v apor.

e. The v apor enriched air is injected and mixed with the clean air source.

f. The mixture of air and n-hexane v apor enters the adsorption filter. An initial (dry )

pressure drop measurement is taken. Note: Adsorption filters are designed to remov e

v apor and not liquid contaminants. Establishing a dry pressure drop is useful to

determine cost of operation.

g. An infrared spectrometer is used to detect the presence of n-hexane v apor at the filter

outlet.

h. The filter is continually monitored until v apor penetrates through the adsorptiv e filter

element. Breakthrough indicates the filter is fully consumed and is incapable of adsorbing

additional v apor.

i. An adsorptiv e capacity v alue (total amount adsorbed) is established in milligrams.

j. Three filters of the same size shall be tested under identical conditions. The manufacturer

is publishes the av erage performance v alue deriv ed from the three tests.

ISO 12500-3:2009 Filters for Compressed Air Part 3: Particulates

Note: One micron particle measures 0.000039 of an inch.

ISO 1 2500-3 prov ides guidance for the testing and methods for determining particulate filter remov al

efficiency , by particle size. Filters shall be challenged by solid particulate in the range 0.01 < 5.0 um,

fine ty pe filters, and particulate of 5.0 > 40 um, for course ty pe filters.

a. The ISO 1 2500-3 particulate filter test begins with a clean, reliable source of compressed

air.





c. Initial pressure drop measurements across the filter housing are taken and recorded.

d. To generate solid particles for the test, a salt solution is atomized and then dried, forming

salt particles ranging from 0.050 to 0.1 microns in size.

e. These particles are then injected into the clean air stream.

f. A Scanning Mobility Particle Sizer (SMPS) prov ides high resolution counting of particles

by size and plots a distribution curv e for the filter inlet challenge.

g. The SMPS is also used to measure the particle distribution downstream of the filter, thus

determining the filters penetration characteristics.

h. Filter efficiency , by particle size, can be calculated (expressed in percent (%).

i. Three filters of the same size shall be tested under identical conditions. The manufacturer

publishes the av erage performance v alues deriv ed from the three tests.

Complimenting Each Other

The ISO 857 3 standard will continue to benefit end-users by defining air quality lev els and methods to

determine contaminants present in their air sy stem. The ISO 1 2500 test standards will benefit air

treatment manufacturers by prov iding the means to commercially separate filter products through

certifiable performance. We all benefit, appreciating that ISO, a global international standards

organization, continues to refine its standards for the betterment of the compressed air industry and

priv ate sector.

For more information please contact Jay Francis, Vice President of Marketing-SPX Dehydration & Filtration.

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