Norgren Filter Contents - Manual (Page 2)

Filters
Littleton, CO USA Phone 303-794-2611 www.norgren.com ALE-Filter
GENERAL PURPOSE FILTER
COALESCING FILTER
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Louvre
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1.1 GENERAL OVERVIEW
Three main types of filters exist: The general
purpose filter for water and particles, the coalescing
oil removal filter for oil aerosols and the activated
carbon filter for the removal of oil vapors.
The general purpose filter is used for most
filter applications and is available from 1/8" to 2"
pipe sizes. Uses are main headers, branch lines,
tools, cylinders, valves and valve circuits, air
agitators etc. Oil removal filters are used where very
clean, oil-free air is required, such as for the supply
to fluidic devices, instrumentation, air gauging
equipment and air bearings.
Activated Carbon filters are used for
systems where the oil vapors in the air are not
acceptable; such as instrumentation and paint
spraying.
1.1.1 How Do General Purpose Filters Work?
The dirt and moisture-laden air enters the inlet port
and is directed into the louvers which centrifugally
separate the entrained liquids and dirt which fall to
the bottom of the bowl. Near the bottom of the bowl
a baffle creates a quiet zone, preventing the
turbulent air re-entraining the contaminants. The air,
now free of water droplets and large dirt particles,
passes through the filter element which removes
small dirt particles. Solid particles eventually plug
the element necessitating replacement.
1.1.2 How Do Oil Removal Filters Work?
Air enters the filter and passes through the
element from inside to outside, where oil aerosols
impinge on the borosilicate micro-fibers and are
coalesced into larger drops. The drops are carried
through the element until they reach the outer
porous sock. The outer sock, because of its cellular
construction, retains these liquids and allows them
to drain by gravity to the bottom of the bowl.
Solid partilces are retained in the element
and cause the pressure drop to slowly increase
throught the working life of the element. When the
pressure drop across the element reaches 10 psid,
the service life indicator on top of the filter will
show more red than green and the element should
be replaced.
1.1.3 How do Vapor removal Filters Work?
Carbon filters are used to remove oil vapors and
odors. The activated carbon has a porous structure
which results in a large surface area. The oil vapors
are attracted and adhere to this surface. There is
usually a small sintered medium included in an
activated carbon element to prevent the carbon
particles from migrating downstream. The carbon
filter reduces the maximum oil content of air leaving
the filter to 0.003ppm at 70°F, i.e. To ISO 8573 class
1.7.1. If protected upstream by general and oil
removal filters life is between 400 and 1000 hours.
1.1.4 Why use a Pre-Filter?
A pre-filter is simply a general purpose filter placed
upstream of a higher grade filter to remove the
majority of the water and larger particle
contaminants and thus lengthen the life of the higher
grade filter element.
A 5 micron pre-filter should always be used
ahead of an oil removal filter.
An oil removal (coalescing) filter must be
used ahead of a vapor removal adsorbing filter.
1.2 AIR QUALITY
1.2.1 What is ISO 8573?
(See ALE-1-G for specification)
This is an international standard on air quality. It
covers compressed air for general industrial use.
The air quality is specified using a 3 digit
code expressing the remaining content of a specific
contaminant after the filter (or dryer).
1.2.2 Air Classes for Norgren Filters:
Particulate filters condition compressed air to
different degrees, dependent on the micron rating of
the filter. The finer filter, 5 µm, will achieve ISO 8573
class 3.7. or class 3. Applying a 40 µm filter will
result in ISO 8573 class 5.7. or class 5 air.
Coalescing filters improve the quality of
downstream air to ISO 8573 class 1.7.2, the particle
size is reduced down to 0.01µm, with a remaining
oil content of less than 0.01ppm. Coalescing filters
cannot remove oil which is in the vapor state in the
supply air. One way to remove vapor is to reduce the
temperature of the air flow allowing the vapor to
condense, alternatively remove the vapor chemically
using an activated carbon filter.