Maintenance Technology September 2017 - 34

COMPRESSED AIR

Select the
Correct Filter

Particulate filters

In these designs, compressed air flows
from the outside to the inside of the filter
element. The compressed air first passes
through a baffle arrangement that causes
centrifugal separation of the largest
particles and liquid drops, but not liquid
vapors. The air then passes through
the filter element. The filter element
is usually a sintered material such as
bronze. Particulate filters are inexpensive
and easy to replace. Filter elements
generally range from 40-micron down to
5-micron.
Coalescing filters

Choosing the correct type of filter for an application is key to achieving maximum
contaminant removal and, with it, desired performance from a compressed air
system. Photo: Exair Corp.

COMPRESSED AIR SYSTEMS can't help it: They will contain contaminants that can lead to issues and increased costs through contamination
of product, damage to air-operated devices, and air-line clogging and
restriction. According to a recent blog post by Brian Bergmann of Exair
Corp. (exair.com, Cincinnati), that's why proper filtration is crucial. But
all filters aren't created equal.
The different types of contaminants associated with compressed air
systems, including solid particles, liquid water, and vapors of water
and oil, call for different types of filters. Understanding how each type
works and the advantages it offers is essential for achieving maximum
contaminant removal.
Bergmann provided a breakdown to help compressed air users select
the correct types of filters for their applications:

This type of filter operates differently than the particulate type. The
compressed air flows from the inside
to the outside through a coalescing
media. Very fine water and oil aerosols
come into contact with fibers in the
filter media and, as they collect, coalesce
(combine) to form larger droplets toward
the outside of the filter element. When
the droplets reach a certain size, they fall
off and collect at the bottom of the filter
housing. The filter element is typically
made up of some type of glass fiber. As is
the case with particulate-filter elements,
coalescing-filter elements are relatively
inexpensive and easy to replace. Filtration down to 0.01 micron at 99.999%
efficiency is possible.
Adsorption filters

This type of filtration typically uses
activated carbon to remove the finest
oil vapors, hydrocarbon residues, and
odors from compressed air systems.
The mechanism of filtration involves
molecules of the gas or liquid adhering
to the surface of the activated carbon.
This is usually the final stage of filtration, and only required for certain
applications where the product would be
affected, such as in blow molding or food
processing. MT
-Jane Alexander, Managing Editor

Brian Bergmann is an application engineer with Cincinnati-based Exair Corp. For more information on various compressed
air topics and solutions, visit exair.com.

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MAINTENANCE TECHNOLOGY

SEPTEMBER 2017

http://www.exair.com http://www.exair.com

Table of Contents for the Digital Edition of Maintenance Technology September 2017