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Feed Hopper - Problems and Remedies

Poor Flow

Causes: Remedies
  • Too many fines in wet Granulation: Reduce fines
  • In direct compression, the particle size of drug or excipients too small and/or of shape that will not flow:
  1. Select larger particle size; use Avicel PH-102 or PH-200 in place of PH-101 or other excipients.
  2. Add glidant (0.1% to 0.5%) (e.g., Cab-O-Sil®, Aerosil)
  3. Use induced or force-feed mechanism on press
  4. Change particle shape of active ingredient to one that is more likely to flow.
  • Poor inherent flow:
  1. Add 0.1% to 0.5% glidant
  2. Dry granulate (by slugging or roller compacting) with a mixture of Avicel PH-101, Cab-O-Sil, and magnesium stearate.
  • Atmospheric moisture adsorption:
  1. Process in low humidity atmosphere
  2. Add moisture absorber (e.g., 0.1% to 0.5% calcium silicate, Cab-O-Sil, Syloid)

Flooding

Causes: Remedies
  • Excessive flow properties (fluidization) of one or more components (could be from an excess of glidant or lubricant):
  1. Identify causative components and exclude or modify particle size.
  2. Select a narrow range of particle sizes; avoid excess fines.
  • Flow is erratic and the feed frame is flooded at times: Use an induced or force-feed mechanism on press, which may control flow.

Particle Segregation

Causes: Remedies
  • Particle size range of mix too wide: Use a narrower particle size range of ingredients.
  • Too wide a density difference in mixed particles: Control differences in density of Particles.
  • Mixer too vigorous; produces fines: Use a mixer with a gentler mixing action.
  • Use of vibrators (to promote flow from hopper): Use force-flow feed mechanisms rather than hopper vibrators
  • Excessive machine vibration: Isolate hopper from tablet machine

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