Size Reduction – Pharmaceutical Engineering B. Pharm Third Semester PDF Notes

 Size Reduction

Contents of this

• Introduction to size reduction

• Applications of size reduction

• Factors affecting size reduction

• Mechanism of size reduction

• Laws governing size reduction

• Classification of mills

• Ball mill

• Fluid Energy mill

• Hammer mill

• Edge runner mill

• End runner mill

Learning objectives

At the end of this lecture student will be able to:

• Explain various applications of size reduction

• Discuss the factors affecting size reduction

• Discuss various mechanisms of size reduction

• Explain the laws governing size reduction

• Discuss on the construction and working of a ball mill

• Discuss the process of Fluid energy mill and Hammer mill

• Explain the construction and working of Edge runner and
End runner mill


• Size reduction is the process of reducing the particle
size of a substance to a finer state  

• The factors that affect size reduction process are
hardness, toughness, stickiness, moisture content, ratio of feed to product
ratio etc.

• Moh’s scale is used to quantify the hardness of a

• The applications of size reduction include efficient
mixing of different ingredients, increased drying and improved absorption 

• Different mechanisms of size reduction includes cutting,
compression, impact and attrition

• Laws governing size reduction include Kick’s Law,
Rittinger’s Law, and Bond’s Law

• Ball mill mechanism of operation include both impact and

• Optimum speed of ball mill operation   at which maximum efficiency of size
reduction obtained is termed as Critical speed  

• Fluid energy mill utilizes both impact and attrition
mechanism of size reduction

• The feed to the Fluid energy mill should be pre size

• It   is   used  
for   size   reduction  
of   thermolabile   substances  
like antibiotics, vitamins etc..

• Hammer mill utilizes impact as the mechanism of size
reduction process

• Optimum speed of ball mill operation at which maximum
efficiency of size reduction obtained is termed as Critical speed

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