air quality standards iso 8573
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Air Quality SandardTRANSCRIPT
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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
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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.
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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)
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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.
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. 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.
b. Testing conditions shall be controlled: inlet air pressure- 1 01 .5 psig (7 bar); inlet air
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temperature- 68 (F (20 (C); ambient temperature- 68(F (20(C).
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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