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PHARMACEUTICS SIZE REDUCTUION (1)

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PHARMACEUTICS SIZE REDUCTUION (1)

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  1. SIZE REDUCTION

  2. SIZE REDUCTION DEFINATION THE PROCESS IN WHICH THE PARTICLES SIZE OF A SOLID IS MADE SMALLER IS CALLED SIZE REDUCTION

  3. FACTORS AFFECTING THE SIZE REDUCTION

  4. THERE ARE 2 METHODS OF SIZE REDUCTION

  5. BALL MILL PRINCIPLE-TO WORK ON PRICIPLE OF IMPACT AND ATTRICTION CONSTRUCTION-The ball mill consists of a hollow metal cylinder mounted on a shaft and rotating about its horizontal axis. The cylinder can be made of metal, porcelain, or rubber. Inside the cylinder balls or pebbles are placed. The balls occupy between 30 and 50% of the volume of the cylinder. The diameter of the balls depends on the size of the feed and the diameter of the cylinder. The diameter of the balls varies from 2cm to 15cm. The balls can be made of metal, porcelain, or stainless steel. The ball acts. as a grinding medium

  6. DIAGRAM

  7. WORKING OF BALL MILL The material to be ground is kept in a hollow cylinder. The material is placed up to 60% of the volume. A fixed number of balls is placed in the cylinder and then the cylinder is closed. The mill is allowed to rotate. Speed of rotation is an important point of consideration.

  8. At low speed, the mass of balls will slide or roll up one over another and will only produce an insignificant amount of size reduction. At high speeds, the balls are thrown to the cylinder wall due to centrifugal force and no grinding will occur. At 2/3rd speed centrifugation just occurs which is called the critical speed of the ball mill. At this speed, the balls are carried almost to the top of the mill and then fall in a cascade across the diameter of the mill. In this way, the maximum size reduction is obtained by the impact of the particles between the balls and by attrition between the balls. It is usually 0.5 cycles per second (cps).

  9. ADVANTAGE OF BALL MILL

  10. Disadvantages

  11. HAMMER MILL PRINCIPLE-IT WORKS ON THE PRINCIPLE OF IMPACT I.E MATERIAL IS MORE OR LESS STATIONARY AND IS HIT BY AN OBJECT MOVING AT HIGH SPEED. CONSTRUCTION-IT CONSISTS OF STOUT METALS CASING,ENCLOSING A CENTRAL STAFT,TO WHICH FOUR OR MORE SWINING HAMMERS ARE ATTACHED.THE LOWERPART CONSISTS OF A SCREEN THROUGH WHICH MATERIAL CAN PASS AND COLLECTED IN SUITABLE RECEIVER,WHEN THE DESIRED DEGREE OF SIZE READUCTION IS REACHED

  12. DIAGRAM

  13. WORKING-THE MATERIAL PUT IN HOPPER WHICH CONNECTED TO DRUM.THE MATERIAL IS IN POWDER TO DESIRED SIZE DUE TO FAST ROATATION OF HAMMER AND ITS COLLECTED UNDER SCREEN.THIS MILL IS ADVANTAGE OF CONTINUOUS OPERATION BECAUSE THE CHJANCE OF JAMMING IS LESS OF HAMMER ARE NOT FIXED.THE MILL CAN PRODUCE COARSE TO MODERATELY FINE POWDERED.DUE TO HIGH SPEED OPERATION,HEAT CAN BE GENERATED  WHICH MAY AFFECT THERMOBILITY DRUG OR MATERIAL.MOREVER,HIGH SPEED CAN BE GET DAMAGE TO MILL IF ITS FOREIGN  MATERIAL STONE AND METAL IS PRESENT IN FEED. USES-TO PRODUCE INTERMEDIATE GRADE OF POWDER FROM ALMOST ALL TYPE OF SUBSTANCE EXCEPT STICKY MATERIAL THAT CHOKE THE SCREEN

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