Precoat Filtration
Filteraid 
Filter cake 
 septum
PRINCIPLE OF PRECOAT FILTRATION
Filter aids
Inorganic mineral
powders or organic
fibrous materials, used
in combination with
filtration hardware to
enhance filtration
performance.
Commonly used filter
aids include diatomite,
perlite, and cellulose.
Some of these materials
have been in use for
over 75 years.
Perlite
Perlite in the natural state is a dense
glassy rock formed by volcanic action.
When crushed and heated to over 800C,
it pops like popcorn, expanding to 20 or
more times its original volume. Milling
and classifi-cation process gives perlite
filter aids the structure and correct
particle size range distribution needed
for optimum performance.
http://www.unitedperlite.com/perlite.htm
http://www.singerprocess.com/perlite.htm
http://www.perlite.dk/filterai.htm
Perlite is an amorphous
mineral consisting of fused
sodium potassium aluminum
silicate. The expansion is due
to the presence combined
water in the crude perlite rock.
Performance improvement
Steel mesh septa
Polymeric filter septa
Woven ▲ Fiber filters

Small filters