Retsch AS 300 - Manual (Page 19)

07/02/2012 Retsch GmbH
19
Working instructions
Sieving aids
When dealing with material that is difficult to separate, we rec-
ommend the additional use of sieving aids in the individual sieve
fractions. Depending on the width of the sieve meshing and the
preselected vibration intensity, pearls made of agate, rubber, por-
celain or nylon bristles and Vulkollan cubes may be used. Also re-
fer to the table below.
Ensure that the fabric of the sieve is not overstretched by over-
loading with sieving aids as this would have a detrimental effect
on the precision of your analytical sieve.
Overview table
Sieving aids Quantity per
sieve or charge
Supplier Area of use Caution !!
Rubber pearls 5 pcs, Ø20 mm RETSCH, Haan Materials to be screened
are fine, dry,
difficult to separate and
throw sieves are used When using mechanical sieving aids, there
is the danger that soft materials can disin-
tegrate and fine sieve fabrics can be dam-
aged!
Agate pearls 10 pcs, Ø10 mm RETSCH, Haan
Hard porcelain pearls approx. 10gr., Ø2
mm RETSCH, Haan
Vulkollan cubes 5 pcs, 12x12 RETSCH, Haan Planetary sieving ma-
chines
Bristles 3 pcs RETSCH, Haan
Plastic rings 3 pcs, various Ø
Brushes Manual sieving
Highly dispersed silicic acids 0.5 to 2% Degussa, Ffm Materials to be screened
are fine, sticky, fatty
and electrostatically
charged Check applicability and compatibility before
adding!
- - Aluminium oxide 0.5 to 1% Degussa, Ffm
- - active carbon
- - talcum Latex and rubber pow-
der
Remove grease Materials to be screened
are very fatty The granularity of the material to be
screened may not be altered by the solvent
used to remove grease or by the tempera-
ture and air used in drying.
Dry Materials to be screened
are very wet or damp
Guide dry, warm air through the
sieve set Hygroscopic materials to
be screened
Cleanse with steam Materials to be screened
are coarse and electro-
statically charged
First sieve of the fine sieve then
the coarse sieve If contamination from
other mechanical aids,
such as rubber pearls, is
to be avoided The coarse material functions like a me-
chanical sieving aid (pearls) on the fine
sieves.
Intermittent sieving RETSCH, Haan Materials to be screened
are fine, stick easily, or
only fall through the
mesh with difficulty Intermittent switching is built into the
majority of throw sieves and can be
switched on, if required.
Sieving material quantities
The sieve stack required for sieve analyses is composed of ana-
lytical sieves arranged one above the other, with progressively
larger holes towards the top, plus the base pan.
To ensure fast separation with exact results, the quantity of the
material to be screened should be adapted to the sieve diameter
and the nominal size of the openings.
The relevant standards on sieve analysis state guideline values in
this context.
In the case of sieving processes with only 1 to 3 sieves, we rec-
ommend the use of short threaded rods ( available as accesso-
ries ).
Overly long, protruding rods interfere with the material to be
screened due to their inherent vibration characteristics.