Before a medicine reaches the patient, it passes through pumps, pipes, mills, and separators inside pharmaceutical factories. The flow of fluids, reduction of particle size, and separation of powders are essential steps in drug manufacturing. UNIT 1 focuses on these engineering principles, showing how physics and mechanical processes ensure uniform mixing, efficient grinding, and accurate formulation.
From measuring liquid flow to milling powders and grading particles, this unit connects classroom theory with real industrial practice.
Flow of Fluids in Pharmaceutical Systems
Fluid movement plays a key role in transporting liquids like syrups, injections, and suspensions during production.
Types of Manometers
Manometers measure fluid pressure in pipelines.
Common Types
- Simple manometer
- Differential manometer
- U-tube manometer
- Inclined manometer
They are widely used to monitor pressure changes in filtration, pumping, and sterilization units.
Reynolds Number and Its Significance
The Reynolds number predicts the type of fluid flow inside pipes.
Flow Types
- Low Reynolds number → Laminar flow
- High Reynolds number → Turbulent flow
Laminar flow ensures smooth movement and accurate mixing, while turbulent flow enhances mixing efficiency. Understanding this helps design safe and efficient processing equipment.
Bernoulli’s Theorem and Applications
Bernoulli’s theorem states that the total energy of a flowing fluid remains constant.
Practical Applications
- Flow measurement
- Spray devices
- Venturimeters
- Atomizers
This principle forms the basis of many pharmaceutical instruments.
Energy Losses in Fluid Flow
During movement, energy is lost due to:
- Friction
- Pipe bends
- Sudden expansion or contraction
- Valves and fittings
Minimizing energy loss improves process efficiency and reduces operational costs.
Flow Measuring Devices
Orifice Meter
Simple and inexpensive; measures flow by pressure drop.
Venturimeter
More accurate; lower energy loss.
Pitot Tube
Measures velocity of flowing fluid.
Rotometer
Uses a floating device to indicate flow rate directly.
These devices ensure precise control of liquid handling during manufacturing.
Size Reduction: Making Particles Smaller for Better Performance
Reducing particle size improves dissolution, mixing, and bioavailability of drugs.
Objectives of Size Reduction
- Increase surface area
- Improve drug absorption
- Ensure uniform blending
- Enhance stability
Mechanisms of Size Reduction
Particles break down by:
- Cutting
- Compression
- Impact
- Attrition
Laws Governing Size Reduction
Three major laws explain energy requirements:
- Kick’s law
- Rittinger’s law
- Bond’s law
These laws help estimate power consumption of mills.
Factors Affecting Size Reduction
- Hardness of material
- Moisture content
- Feed size
- Equipment speed
Optimizing these factors improves efficiency.
Common Milling Equipment
Hammer Mill
High-speed impact grinding; suitable for coarse to medium powders.
Ball Mill
Rotating drum with balls; fine grinding and mixing.
Fluid Energy Mill
Uses high-velocity air; produces ultra-fine particles.
Edge Runner Mill
Heavy wheels crush material; useful for wet grinding.
End Runner Mill
Rolling action reduces size; ideal for pastes.
Each device has specific merits and limitations depending on material properties.
Size Separation: Sorting Particles by Size
After milling, particles must be separated to ensure uniformity.
Objectives of Size Separation
- Remove oversized particles
- Obtain uniform size
- Improve product quality
- Meet official standards
Official Standards of Powders
Pharmaceutical powders are classified as:
- Very coarse
- Coarse
- Moderately coarse
- Fine
- Very fine
These standards ensure consistent drug performance.
Size Separation Equipment
Sieve Shaker
Separates particles by mesh size; simple and widely used.
Cyclone Separator
Uses centrifugal force; ideal for dust removal.
Air Separator
Classifies particles using air current.
Bag Filter
Captures fine dust from air streams.
Elutriation Tank
Separates particles based on settling velocity in fluid.
Each method is selected based on required particle size and industrial needs.
Applications of Size Separation
- Tablet formulation
- Capsule filling
- Powder blending
- Quality control testing
Uniform particle size ensures better mixing and accurate dosage.