Size Separation.pptx

Introduction and official standards for sieves, standard for sieves and dimensions and notations, materials used for sieve, punch plates, modes of motion in size separation.

1. Size Separation BY- Dipesh Gamare Topics covered -   Introduction and official standards for sieves, standard for sieves and dimensions and notations, materials used for sieve, punch plates, modes of motion in size separation.

2. INTRODUCTION :- The Size Separation is defined as the process of separation of mixture of various size of particles into two or more portion by means of screening surface . The Size Separation is also known as sieving, sifting, grinding , classifying or screening .

3. Objectives :- To classify materials into different size for the desired purpose . To control size variation in the materials. To judge uniformity in a mixing material . To avoid variation in the bulk properties of materials. To enhance performance , efficacy and stability of dosage form . To specify the quality parameter of a intermediate and finished dosage form .

4. Application :- Size Separation has significance in formulating uniform dosage form with respects to drug content. It can be used to obtain granules of required size . It has application in determination of particle size and their distribution in the given sample. It can be used to investigate efficiency and validate size reduction equipment. It can be also useful in separating undesirable size solids from desired ones . It helpe to ensure good flowability .

5. Official standards of powder size Standards of powder used in pharmaceutical are required in the British Pharmacopoeia (BP) which states that "the degree of coarsness or fineness of powder is differentiated and expressed by the size of the mesh of the sieve through which the powder is able to pass . The BP state that the powder is described by a number , all particles must pass through the specified sieve and when a vegetable drug is being ground and sifted ,none must be rejected . This classification is must if the character of a vegetable drug is compared with a chemical substance .

6. The BP specified five grades of powder and number of sieve through which the all particles must pass :- Grade of powder Sieve number through which all particles must pass Sieve number through which not more than 40% of particles pass Coarse 10 44 Moderately coarse 22 60 Moderately fine 44 85 Fine 85 Not specified Very fine 120 Not specified

7. The Indian pharmacopoeia makes two statement with regards to "official grades of powder" in practice It it required that when a powder is described by a number of all particles must pass through the specified sieve. When a vegetable drug is being ground and sifted, none must be rejected . The British Pharmaceutical codex has given a further grade of powder known as " Ultra- fine powder " . For this grade of powder required maximum dimension at least 90% of particles must be not greter than 5 μ m and none must be graeter than 50 μ m . Determination of particle size for this grades carried out by a microscopic method .

8. SIEVES Definition: A sieve also called sifter, is a device for separating desired elements from Unwanted material or for characteristics the particle size distribution of a Sample. The word sift is derived from sieve. Sieve are the most commonly Used devices for particle size analysis. Each sieve has a specific number that denotes the number of meshes in a length of 2.54 cm(~1 inch). Construction Of Sieve: Sieves for pharmaceutical testing are constructed from wire cloth with square meshes, woven from wire of brass, bronze, stainless steel or any suitable materials. Sieves should not be played or coated. There must be no reaction between the material of the sieve and the substance to be sieved.

9. Types Of Sieves Woven wire Sieves: wire woven Sieves are general purpose Sieves and widely used in the pharmacy particle. There are two types :1) Plain weave Sieve 2) Twilled weave sieve.For fine sieving metal wire woven Sieves are used. Bolting cloth Sieves : Silk,nylon and cotton are generally woven from twisted multi-strand fibers.Nylon cloths are generally designated by their micrometer opening and available in different grades.These are used for the separation of fine powders. 3. Bar screens: Bar screens are generally used in handling large and heavy pieces of material.The bars are fixed in parallel position and held by cross bars and spacers. 4. Punched plates : These are used for coarse size.The screen are prepared by using a sheet metal of variyng thickness with perforated holes.

10. Standards of Sieves, Dimensions and Notations: Common standards used for Sieves are: Tyler standard sieve series(in USA) US standard sieve series (in USA) British standard sieve series (in UK) German (in Germany and Europe) If standard sieve series (in India) International test sieve series.

11. - Tyler and US standards can be interchangeable, since difference between the two standards is less than the allowable tolerance in weaving of the screens. These is also known as test sieve. -Sieves used for pharmacopoeial testing must match with the following specifications: 1) Number of Sieves : Sieve number indicates the number of meshes per linear length of 25.4 millimeters. 2) Nomial size of aperture : Nominal size of aperture indicates the distance between the two adjacent wires. It represents the side of a square aperture. IP 1996 gives the Nominal mesh aperture size for majority of sieves in mm or in micrometer. 3) Nomial diameter of the wire : Wire mesh sieves are made from the wire having the specified diameter in order to give a suitable aperture size and sufficient strength to avoid distortion of the sieve.

12. 4) Approximate percentage sieving area : This standard expresses the area of the mesh as a percentage of the total area of the sieve. It depends on the size of the wire used for any particular sieve. Generally, sieving area is kept within the range of 35 to 40% in order to give suitable strength to the sieve. 5) Aperture tolerance average size: This variation is expressed as a percentage and is known as the aperture tolerance average. Fine meshes cannot be woven with the same occurs as a coarse meshes. Hence, the aperture tolerance average is lower for coarse sieves than the fine Sieves.

13. SIEVES Sieves are used for size separation. Test sieves determine the efficiency of screening devices. Most of Sieves used for pharmaceutical purpose are of wire mesh type. Each sieve is given a definite number which denotes number of the meshes present in a length of 2.54 cm or one inch. Material of construction: Sieves are woven from wire of brass, bronze, stainless steel. Sieves should not be coated with any material. It should be non reactive with material used The material used for construction should be resistant to corrosion. Generally Iron nice is used as screen material because it is cheap but their disadvantage are corrosive nature and chance of contamination by iron. These disadvantages can be overcome by coating two with galvanizing agent which increase the strength and also make it corrosion resistant.

14. Brass , Phosphorous-bronze and stainless steel are the metals used due to their corrosion resistant, good strength and non contamination qualities. Non metals such as nylon and terylene are also suitable because they avoid risk of metallic contamination. For special purpose punched plates or perforated screens are used. These sieves are made by drilling holes of varying thickness in metal plate. The holes may be round, rectangular or square.

15. Punch plates What is punch plates? Punch Plate has many names and is known as Perforated Plate, Perforated Screen or Punch Plate screens. Punch Plate are manufactured using solid steel sheets which are than perforated using CNC machinery to create perforate sheets of metal which are than fabricated into a finished product. Punch Plate or perforated screens are fitted into machines used in both the quarrying and recycling sector.

16. Punch plate is installed into machines with the smooth side facing the materials which are to be screened. To reduce the chances of pegging, it is important to consider the shape of the material in relation to the perforation shape. Regular shaped material is suited to square perforations and irregular shaped material is suited to round perforations.

17. Punch plate capabilities Technical information for Perforated screens/Punch Plate. Hole size: 0.5mm – 150mm
Thickness:0.5 – 12mm. However, Graepel can perforate up to 25mm thick on special request
Sheet sizes: Plate sizes up to 4m x 2m
Perforation Shapes: Round and square perforations are most suited for screening.

18. Advantages of punch plates Cost Effective
Solid State Screens
Longer screen life then that of woven mesh
Fewer wear issues
Smooth with a high strength ratio especially when round holes are used
Maintenance of sizing accuracy
Great strength in sfcreens

19. Applications of punch plates Screening and Grading in;
Quarrying
Recycling
Milling

20. Modes of size separation 1)Agitation 2)Brushing 3)Centrifugal

21. Size separation is useful since particles are sorted into categories solely on the basis of size, independently of other properties such as density, surface, etc. It can be used to classify dry or wet powders and generates narrowly classified fractions. While doing this mechanical sieving equipment's used works on the principle of agitation, brushing and centrifugal force.

22. Sieves may be agitated in a number of different ways, such as 1.Oscillation : This sieve is mounted in a frame that oscillates back and forth. It is a simple method, but the material may roll on the surface of the sieve Agitation

23. 2 Vibration: The sieve is vibrated at high speed by means of an electric device. The rapid vibration is imparted to the particles on the sieve which helps to pass the powdered material through it.

24. 3. Gyration : In this method, a system is made so that sieve is on rubber mounting and connected to an eccentric fly wheel. This gives a rotary movement of small amplitude to sieve which hi turn gives spinning motion to the particles that helps to pass them through a sieve. Agitation methods are not continuous methods but can be made so by inclination of the sieve and the provision of separate outlets for ubdersize and oversize particles

25. Advantages 1) Agitation method is inexpensive. 2)Simple and rapid Disadvantage Agitation method have a lower limit of particle size If the power is not dried ,apparatus become clogged with particles leading to improve sieving. During agitation ,attrition causing size reduction.

26. Brushing method In this case, a brush is used to move the particles on the surface of the sieve and to keep the meshes clear. The brush is rotated in the middle in the case of circular sieve but spiral brush is rotated on the longitudinal axis in case of a horizontal cylindrical sieve

27. Centrifugal method In this method, a high speed rotor is fixed inside the vertical cylindrical sieve, so that on rotation of rotor the particles are thrown outwards by centrifugal force. The current of air which is produced due to high speed of rotor helps in sieving the powder

28. 1) Centrifugal method are extremely in cases where conventional sieving tends to block the sieves. 2) Extremely used for powder , because sieves have the limitation of mesh sieve. Advantages

29. Equipment used for size separation