Equipment Used for Granulation Techniques

1. Mixers

2. Dryers

• Tray dryer - A simple static oven where wet granules are spread on trays and dried with circulating hot air. Easy to use but slow and prone to uneven drying (surface crust formation).
• Spray dryer - A liquid feed (slurry or solution) is atomized into fine droplets and instantly dried by a stream of hot air, producing spherical, free-flowing granules. Fast and continuous.

3. Granulators (Multi-functional / One-Pot Processors)

• Fluid bed spray granulator - Powder particles are suspended ("fluidized") in an upward stream of warm air. A binder solution is sprayed onto the particles, causing them to collide and adhere, forming granules that dry almost simultaneously in the same chamber. Produces light, porous, uniform granules.
• Double cone mixer dryer processor - A double-cone vessel that mixes, wet-granulates, and then dries (under heat and vacuum) all in one unit.
• Nauta processor - A cone-shaped vessel with a slow-moving screw agitator. Provides gentle mixing and can also dry granules under vacuum; ideal for heat-sensitive materials.

Granulation Characteristics (Section heading visible at bottom)

• Particle size and size distribution
• Flowability
• Bulk density and tapped density
• Compressibility (Carr's Index / Hausner ratio)
• Moisture content
• Hardness/friability of granules

Wet Granulation vs Dry Granulation

What is Granulation?

1. Core Principle

2. Step-by-Step Process

Wet Granulation Steps:

1. Dry mixing - API + excipients blended
2. Binder preparation - Binder dissolved in water or solvent (e.g., PVP in water, starch paste)
3. Wet massing - Binder solution added to powder and kneaded into a wet mass (in a planetary or sigma blade mixer or RMG)
4. Screening/granulating - Wet mass passed through a screen to form uniform wet granules
5. Drying - Wet granules dried (tray dryer, fluid bed dryer, spray dryer) to target moisture level
6. Dry screening/sizing - Dried granules milled and sieved to uniform size
7. Lubrication & compression - Final blend with lubricant, then compressed into tablets

Dry Granulation Steps:

1. Dry mixing - API + excipients blended
2. Compaction - Powder compressed under high pressure into dense slugs (via a tablet press) or ribbons (via roller compactor)
3. Milling/breaking - Slugs or ribbons are broken down into smaller fragments
4. Sizing/screening - Granules sieved to desired size range
5. Lubrication & compression - Final blend with lubricant, then compressed

3. Key Differences at a Glance

4. Ideal Candidates for Each Method

Use Wet Granulation when:

• The API is moisture-stable and heat-stable
• High content uniformity is needed (especially low-dose drugs, e.g., 1-5 mg)
• The API has poor compressibility and needs a binder to hold tablets together
• Better dissolution is required (granules are more porous and dissolve well)
• The formulation requires modified/controlled drug release
• Examples: Metformin tablets, Paracetamol tablets, most conventional tablets

Use Dry Granulation when:

• The API is moisture-sensitive (degrades with water, e.g., aspirin, effervescent formulations)
• The API is heat-sensitive (degrades at drying temperatures)
• A faster, lower-cost process is needed
• Continuous manufacturing is preferred over batch processing
• The API itself has reasonable compressibility
• Examples: Vitamin C tablets, aspirin, some antibiotics

5. Advantages and Disadvantages

Wet Granulation

Dry Granulation

6. Quick Decision Guide

Is the drug moisture or heat sensitive?
        |
       YES → Dry Granulation
        |
       NO
        |
Does the drug have poor compressibility or require high content uniformity?
        |
       YES → Wet Granulation
        |
       NO
        |
Is cost/speed a priority?
        |
       YES → Dry Granulation
        |
       NO → Wet Granulation (for best granule quality)

Summary

Part A: Tablet Press Components (top of page)

• Punches - compress granulation within the dies
• Cam tracks - guide the movement of upper and lower punches
• Feeding mechanism - moves granulation from the hopper into the dies
• Types of tablet presses:
  1. Single punch - one set of punch & die; used for small-scale/lab production
  2. Multi-station rotary press - many punch/die sets on a rotating turret; used for large-scale industrial production

Part B: Defects of Tablets - Causes and Remedy

1. Defects Related to the Tableting Process

Capping vs Lamination: Capping = only the top/bottom cap breaks off. Lamination = the whole tablet splits into multiple horizontal layers.

2. Defects Related to the Excipient

Sticking vs Picking: Sticking = tablet adheres to die walls. Picking = small granule bits adhere to the punch face specifically.

3. Defect Related to More Than One Factor

4. Defect Related to the Machine

Part C: Evaluation of Tablets

Relationship Between Defects and Evaluation

• Capping/Lamination/Cracking → caught by hardness and friability tests
• Sticking/Picking → caught by physical observation and weight variation
• Mottling → caught by physical observation
• Double impression → caught by physical observation
• Non-uniform drug content → caught by drug content and weight variation tests
• Poor disintegration → caught by disintegration and dissolution tests