1. Objectives Size separation Importance of size separation Sieve
Grades of powders
Classification of size separation PH

2. Materials usually sieved in houses For separation of
Wheat flour
Mirchi powder
Turmeric powder
Sand used for construction ( By using different sieve sizes ) PH

3. Size separation: Importance:
Separation of the particles according to their sizes
Importance:
To formulate a uniform dosage form
To prepare granules of required size
To separate undesirable particles PH

4. Sieve
It is used to sifting the powders
It is made up of wood or metal fitted with a wirecloth which is
made up of copper alloys, stainless steel, hair, 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: 10, 22, 44, 60, 85, 120 PH

5. Different Sieves
Fig : 28.1 PH

6. Different meshes
Fig : 28.2 PH

7. Grading of powders Coarse powder : 10/44
Moderately coarse powder : 22/60
Moderately fine powder : 44/85
Fine powder : 85
Very fine powder : PH

8. Classification Sieving method. Sedimentation method.
Cyclone separation method. PH

9. Objectives Size separation by sieving or sifting by different methods.PH

10. Sieving Sieving Methods:
Separation of coarse particles from fine particles by using
set of sieves.
Sieving Methods:
Agitation
Brushing
Centrifugation PH

11. Agitation method
Oscillation
Vibration
Gyration PH

12. Oscillation method Moves back and forth
Material roll on the surface of the sieve PH

13. Vibration method Sieve move with High speed
Rapid vibration imparted to the particles on the sieve
Particles are less likely to “blind” the mesh PH

14. Gyration method Rotatary movement small amplitude.
Considerable intensity.
Spinning motion to the particles.
Particles suitably oriented to pass through the sieve. PH

15. Mechanical Sieve Shaker
Fig: 29.1 PH

16. Sieve details Set of 12 sieves Arranged in ascending order
From 6 to 200 No
Large size sieve at the top
Small size at the bottom
Receiver at the bottom of the small size sieve PH

17. Sieving procedure Powder kept in top sieve Shake the sieve
Sieve gyrates and vibrates
Weight of powder on each sieve
Find the percentage of residue in each sieve
Percentage = Residue in each sieve X 100
Total wt of powder PH

18. Advantages Size analysis data under controlled condition Inexpensive
Simple & Rapid process
Little variation between operation PH

19. Disadvantages Over loading sieve result error
Insufficient time leads to wrong results
Electrostatic attractions leads to aggregation
Humidity, Hygroscopic powders leads to aggregation
Pale like or long fibrous will not pass PH

20. 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. PH

21. Centrifugal method A vertical cylindrical sieve.
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. PH

22. Objective
Size separation by Sedimentation methods PH

23. When you walk or play in water of a pond, it becomes dirt
When you walk or play in water of a pond, it becomes dirt. After some time water become clear, why ? PH

24. Sedimentation methods
Sedimentation means Settle down of the particles to the bottom
Fluid is stationary.
Separation of particles of various sizes.
Depends mainly on particle velocity.
Division of particles in to various fractions.
Depends on time of sedimentation. PH

25. Sedimentation method is expressed by Stoke’s equation de =
18n x
(p – p0)g t
Where
De =effective or Stoke’s diameter
n = viscosity of the dispersion liquid in poises
x/t =rate of sedimentation or distance of fall x in time t
g = gravitational constant
p = density of the particles
po = density of the medium PH

26. Andreasen method: Particle size analysis.
The apparatus is called Andreasen apparatus.
Consist of 500ml sedimentation vessel.
Fitted with ground glass joint.
Passed 10ml of pipette with two way stop clock. PH

27. Fig : 30.1 PH

28. Procedure 1% suspension is prepared & placed in sedimentation vessel.
10 ml of sample is withdrawn at speficified interval of time &
depth.
Sample dried, residue is weighed.
Larger particles settles at faster rate than the Smaller
particles .
From weights of dried samples the % of initial suspension is
calculated.
Particles having sizes smaller than the size calculated by
stoke’s equation for that time. PH

29. Sedimentation Tank
The upper layer is removed, giving single separation or.
Suspension may be collected as a number of fractions.
Arranging for the pump inlet to remain just below the
surface.
A suspension is placed in a tank allowed to stand for suitable
time.
Suspension pumped out will then contain successively
coarser particles. PH

30. Continuous Sedimentation Tank
A shallow tank with inlet& outlet pipes.
The force act on the particles entering in the tank.
Divides in to components.
Horizontal component due to flow of the liquid
Carries the particles forwards. PH

31. Continuous Sedimentation Tank
Vertical component due to gravity.
Particles to fall towards the bottom of the tank.
This depends on the stoke’s law.
Velocity of fall is proportional to the diameter.
Coarsest particles nearest to inlet, finest particles
nearest to the outlet. PH

32. Fig: 30.2 PH

33. Objectives Elutriation Cyclone separator Methods of size separationPH

34. Elutriation In elutriation movement of fluid against the direction of
sedimentation of the particle
The apparatus consist of a vertical column
An inlet near the bottom
An outlet at the base for coarse particle
An overflow near the top for fluid and fine particles
Velocity gradient across the tube results in the separation of particles of different sizes PH

35. Fig : 31.1 Simple Apparatus for ElutriationPH

36. Cyclone separator Principle: Construction:
Mainly used to separate the solids from fluids
Main principle involved in this is separation of solids by
centrifugal force
Construction:
It consist of vertical,cylindrical vessel with conical base
Inlet is fitted at the top,solid outlet at the base
Fluid outlet is at the center of the top portion PH

37. Working: Suspension is introduced tangentially
Rotary moment of suspension is developed
Causes the particles to move by centrifugal force
Producing the vertex
Troughs solid particles on the walls of cyclone
Coarser particles separates and fall through outlet
Fine particles are allowed to be carried with fluid
Separation of particles depends on the fluid velocity PH

38. Application: Disadvantages Solid-gas and
Solid-fluid mixture can be separated
Disadvantages
Only coarse powders are separated
Fine particles allowed to be carried with fluid PH

39. Fig: 31.2 Cyclone separatorPH

40. Fig: 31.3 Cyclone separatorPH