Excess Fines
Causes: Remedies
- Granulation Overdried: Decrease drying time/temperature, Establish optimum moisture content
- Screen size too small: Use a larger screen size
- Rotor/screen clearance too close: Adjust rotor clearance
- Overloading of mill or Granulator: Slow feed of material to mill or granulator
- Weak granules:
- Increase granulating fluid
- Increase binder content
- Increase wet massing time
Difficult to Screen
Causes: Remedies
- Granules too hard:
- Decrease drying temperature (case hardening)
- Decrease water content (use alcohol/water)
- Decrease binder content
- Use a weaker binder
- Moisture in granulation:
- Increase drying time
- Establish optimum moisture content
Poor Color Distribution
Causes: Remedies
- Dye migration to granule surface nonuniformity of color throughout granule)
- Use lakes instead of soluble dyes (will minimize but not eliminate the problem)
- Decrease the size of the wet granules
- Decrease the thickness of the granulation bed; stir the granulation bed frequently during drying to expose fresh surfaces at the top of the wet mass
- Use Avicel PH-101- reduces or eliminates dye migration in wet granulation