This document discusses size separation techniques. Size separation, also known as sieving or screening, separates particles into different sizes based on their dimensions. It is important for processes like formulating uniform dosage forms and quality control testing. The key method described is using sieves of various mesh sizes to separate particles. Other separation techniques discussed include sedimentation, cyclone separation, and filters. Sieves come in different materials and mesh counts. Factors like agitation and centrifugal forces are used to help separation during sieving. The objectives and mechanisms of different size separation methods are outlined.

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Size separation
Presented by : Ms.VIBHA
Assistant Professor
Rajiv Academy for
Pharmacy Mathura
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CONTENT
• Size separation
• Importance of size separation
• Sieve
• Grades of powders
• Classification of size separation
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Size separation:
• Size separation is a unit operation that involves
the separation of a mixture of various sizes of
particles into two or more portions by means of
screening surfaces.
• Its also known as sieving, shifting, classifying or
screening.
• This is based on the size, shape, and density of
the particles
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Objective
• To formulate a uniform dosage form
• To prepare granules of required size
• As a quality control tool for analysis
• To test the efficiency of a size reduction
equipment or process
• To separate undesirable particles
• To optimize the process condition (screening
feed rate)
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Sieve
• It is simplest and sieving is the most frequently used
• It is made up of wood or metal fitted with a wire cloth which
is made up of copper alloys, stainless steel, silk, nylon or
terylene , having a specific diameter of the wire.
• Each sieve is given a definite number which indicate a
number of the meshes present in a length of 2.54 cm or
one inch.
• Sieve numbers: 4,6,10, 22, 44, 60, 85, 120
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Different Sieves
Fig : 28.1
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Different meshes
Fig : 28.2
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Sieves commonly used in pharmaceutical processing includes:
•Woven wire sieves:
•Bolting cloth sieves
•Closely spaced bars
•Punched plates
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Grading of powders
Coarse powder : 10/44
Moderately coarse powder : 22/60
Moderately fine powder : 44/85
Fine powder : 85
Very fine powder : 120
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Classification
• Sieving method.
• Sedimentation method.
• Cyclone separation method.
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Objectives
• Size separation by sieving or
• sifting by different methods.
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Mode of size separation
• Separation of coarse particles from fine particles by using
set of sieves.
Sieving Methods:
• Agitation
• Brushing
• Centrifugation
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Agitation method
Sieves are agitated in a number of
ways.
– Oscillation
– Vibration
– Gyration
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Oscillation method
• Moves back and forth
• Material roll on the surface of the sieve
•The motion is parallel to the plane of the sieve.
•The sieves can be slightly inclined.
•The reciprocating motion is induced by means of an
ordinary eccentric on rotating shaft.
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Vibration method
• Sieve move with High speed either electricity or
mechanically.
• Rapid vibration imparted to the particles on the sieve
• Particles are less likely to “blind” the mesh
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Gyration method
• Rotatary movement small amplitude.
• Considerable intensity.
• Spinning motion to the particles.
• Particles suitably oriented to pass through the sieve.
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Mechanical Sieve Shaker
Fig: 29.1
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Brushing method
• Brush is fitted about midpoint of sieve.
• Reorient the particles on the surface of sieve.
• Prevent blocking of sieve.
• Spiral brush is used for large scale production.
• Fitted on to a horizontal cylindrical sieve.
• Rotates about the longitudinal axis.
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Centrifugal method
• Centrifugal force separates particles.
• A vertical cylindrical sieve.
• Rotates with high speed.
• Current of air created by rotor movement.
• Particles are thrown outwards.
• Assist in sieving.
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Cyclone Separator
Principle:
•It is used to separate solid from fluids
• It depends not only on the particle size, but also on density of
particles
• It is also possible to allow fine particles to be carried by the fluid
Working:
• Feed is introduced tangentially at very high velocity of air
• Rotatory movement takes place within the vessel
• Centrifugal force through the solids to the walls
• As the speed of air diminishes the particles fall to the conical
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23.  It consists of a short vertical, cylindrical vessel with a
conical base.
 Upper part of vessel is fitted with a tangential inlet.
 Solid outlet is arranged at bottom of the vessel.
 Fluid outlets at centre of the top of vessel.
 Such an arrangement prevents the air short-
circulating directly from the inlet to the outlet of the
fluid.
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Fig: 31.2 Cyclone separator
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25.  used to separate the solids from gases
 used to separate the solids from liquids
 used to separate the heavy or coarse fraction
from fine dust
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26. Principle:
 Centrifugal force is used to separate solids
 The air environment is obtained by means of rotating
disc and blades
To improve separation the stationary blades are used.
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28.  It consists of a cylindrical vessel with a conical base.
 Feed inlet is fitted to the upper part of the
vessel.
 Rotating disc and lades are attached to the
central shaft.
 At the base of the vessel two outlets , one for
fine and other for heavy particles.
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29.  Disc and blades are allowed to rotate with the help of
motor.
 Sample powder introduced through feed inlet.
 Feed falls on rotating disc.
 Fine particles are dropped and collected at the outlet
for fine particles.
 Fine particles are removed at the outlet meant for
heavy particles.
 It used in ball mill and hammer mill.
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30. Principle:
 In a bag filter, size separation of fines.
 The fines is achieved in two steps.
 In the first step, the milled powder is passed through a bag filter
(cloth) by applying suction on the opposite side of feed entry.
 In the next step, pressure applied in order to shake the bags so that
powder adhering to the bag falls off, which is collected from the
conical balance
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32.  It consist of a number of bags made of cotton or wool fabric.
 A hopper is arranged at the bottom of the filter to receive the
feed.
 At the top of the metal container, a provision is made for the
exhaust.
 Adjacent to this, a bell crank level arrangement is made to bring
the filters to normal atmospheric conditions.
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33.  The working of bag filter consist of two steps
 In the first step, the feed is separated from air by passing it
through the cloth bags
 In the subsequent step, the bags are shaken to collect the
fines that are adhere to the bags.
Uses:
 Its used along with the cyclone separator.
 It is connected to the discharge end of the fluidized energy
mill
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34.  Drum and basket revolving at high speed.
 Drum and basket may be perforated or
non-perforated.
 Feed enter at centre.
 There is liquid outlet.
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