Granulation interview questions | granulation problems and solutions | pharmaceutical interview questions and answers for freshers

 

Basic Questions of pharma granulation

1. What is granulation?

Granulation is the process of size enlargement where primary powder particles are bound together to form larger, multi-particle entities called granules. It improves flow properties, compressibility, and reduces dust.

2. What are the types of granulation?

· Wet Granulation

· Dry Granulation (Slugging or Roller Compaction)

· Direct Compression (not granulation but relevant)

Wet Granulation Questions

3. What are the steps in wet granulation?

1. Mixing of API and excipients

2. Binder addition (as solution or dry followed by wetting)

3. Wet massing

4. Screening through a sieve also known as shifting of material

5. Drying

6. Milling/sizing

7. Final blending or lubrication

4. What are common binders used in wet granulation?

PVP (Polyvinylpyrrolidone), starch paste, HPMC, gelatin, sucrose solution.

5. What are critical parameters in wet granulation?

· Binder concentration and quantity

· Mixing time and speed

· Granulation endpoint (judged by consistency or torque)

· Drying temperature and time 

· Granule size distribution

·

6. How do you determine the granulation endpoint?By checking for a “snowball” effect, measuring torque (in high-shear granulators), or performing hand squeeze tests.

Dry Granulation Questions

7. When is dry granulation preferred?When the API is moisture-sensitive or heat-sensitive and cannot undergo wet granulation or drying.

8. What is slugging and roller compaction?

· Slugging: Compaction of powder into large tablets (slugs), followed by milling.

· Roller compaction: Compressing powder between two rollers to form ribbons, then milling into granules.

9. What are common problems in dry granulation?

· Poor flow of ribbons

· High fines (due to brittle ribbons)

· Segregation after milling

· Hardness variation in tablets

Process & Equipment Related

10. Name equipment used in wet granulation.

· High-shear granulator

· Fluid bed processor (for granulation and drying)

· Planetary mixer

· Tray or vacuum dryer

· Oscillating granulator or multimill

·

11. What are advantages of fluid bed granulation?

· Faster drying

· Less space requirement

· Uniform granulation

· Better control of process parameters

·

12. What are the CQAs and CPPs in granulation?

· CQAs: Granule size, moisture content, compressibility, flowability

· CPPs: Binder addition rate, impeller speed, granulation time, drying temp

Troubleshooting Questions

13. What happens if granules are too wet or too dry?

· Too wet: Sticking during drying or compression, overwet mass

· Too dry: Poor granule binding, friable granules, dust generation

·

14. Why do we get variation in granule size?

· Inconsistent mixing

· Poor binder distribution

· Incorrect screen size

· Milling inconsistency

Common granulation problems and their solutions:

Granulation is a critical process in pharmaceutical manufacturing, especially for solid dosage forms like tablets. Problems in granulation can affect product quality, compressibility, flowability, and ultimately the therapeutic performance of the drug. Here's a concise overview of common granulation problems and their solutions:

1. Poor Flowability of Granules

Problem: Granules don't flow uniformly, leading to weight variation in tablets.

Causes:

· Irregular granule shape

· Wide particle size distribution

· Too much moisture

Solutions:

· Optimize binder quantity

· Use flow enhancers (e.g., colloidal silica)

· Improve drying process to achieve uniform moisture

· Sieve to obtain narrow particle size distribution

2. Over wet Granules

Problem: Granules are sticky, clumpy, and difficult to dry.

Causes:

· Excessive binder solution

· Inadequate mixing during wet massing

Solutions:

· Reduce binder volume or concentration

· Use high-shear mixing to distribute binder more evenly

· Switch to a more volatile solvent if applicable

3. Under wet Granules

Problem: Granules are dry, dusty, and poorly formed.

Causes:

· Insufficient binder or wetting

· Poor mixing

Solutions:

· Increase binder solution volume

· Improve mixing uniformity

· Pre-wet dry mix before adding binder (for some processes)

4. Granules Too Hard or Too Soft

Problem: Affects compressibility and tablet hardness.

Causes:

· Inappropriate granulation end-point

· Improper drying time/temperature

Solutions:

· Monitor granulation endpoint carefully (use torque or granule size)

· Optimize drying conditions (temperature, time, airflow)

· Adjust binder type or quantity

5. Non-Uniform Granule Size

Problem: Affects flow, content uniformity, and compression.

Causes:

· Inconsistent wet massing or screening

· Poor control over drying process

Solutions:

· Standardize screening/sieving process

· Use proper equipment (e.g., oscillating granulators, fluid bed granulators)

· Classify and recycle oversized or undersized granules

6. Binder Migration During Drying

Problem: Leads to poor granule strength or segregation.

Causes:

· Fast drying causes binder to move to surface

Solutions:

· Use slower or staged drying

· Adjust binder viscosity

· Improve mixing of binder and powder

7. Granule Segregation

Problem: Granules separate during storage/transfer, causing content uniformity issues.

Causes:

· Wide variation in particle size or density

· Vibration during handling

Solutions:

· Ensure uniform granule size and density

· Minimize handling steps

· Use anti-segregation devices (e.g., baffles, controlled transfer)

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