Compressed air systems are used throughout the food manufacturing plant for machine
motion and for a variety of manufacturing
processes. Using the correct compressed air
preparation system for an application is critical to ensure the safety and quality of food
production because compressed air contains
dirt particles and considerable amounts of
water and oil. These contaminants must be
filtered out to achieve trouble-free operation
of the system components and product quality and safety.
The quality of compressed air is defined
by the grade of particle filtration, the residual
oil content, and the pressure dew point.
Solid particles occur in the form of dust,
classified according to the particle size in
microns. Sintered filters remove dust and
water in the range of 5 to 40 microns. A
coalescing filter removes smaller particles,
as well as oil, in the range of 0.01 to 1
microns. To eliminate water vapor, air dryers reduce the pressure dew point. An
active carbon filter is needed to remove any
odors or oil vapors, and this is critical in the
food industry to prevent contamination and
achieve quality taste.
To ensure that manufacturers around the
world follow the same guidelines, an international air quality standard was created.
ISO Standard 8573-1:2010 specifies purity
classes relating to the quality of compressed
air. The Classes range from 0 to 9, with 0
being the highest quality and 9 the lowest
quality. For example, a classification of 1.4.1
indicates a Class 1 rating for solid particles,
Class 4 for water and
Class 1 for oil. When
air preparation systems
are designed to meet
specific classes and
are properly maintained, they will help to
achieve quality air.
Combustible dust is one of the biggest safety issues facing food manufacturers. Many dusts generated in food processing are potentially explosive
– among them sugar, flours, milk powder, malt and starches. To capture such
dusts, a high efficiency cartridge dust collector will usually be the filtration
system of choice.
(1) Conduct a risk assessment, preferably with the help of an outside
professional engineer, to determine the required level of fire and explosion
protection for your filtration system.
( 2) Make sure dust testing is part of this analysis. Many commercial
test laboratories offer a low-cost test to establish whether a dust sample is
combustible. If the test is positive, then the explosive index (Kst) and the
maximum pressure rise (Pmax) of the dust should be determined by ASTM
E 1226-12a, Standard Test Method for Explosibility of Dust Clouds. Any dust
above 0 Kst is now considered to be explosive, and most dusts fall into this
( 3) If you find you do have a combustible dust issue, select an
equipment supplier who has a proven track record in explosion prevention and can help you sort through the applicable NFPA standards.
( 4) Be sure the dust collector design incorporates the necessary
fire/explosion protection devices and technologies throughout the
system, from the housing to the ductwork to the filters inside.
Look for components that are manufactured in accordance with
NFPA standards and/or that carry CE and ATEX certifications,
and ask for test data to support these claims.
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