Perforated basket centrifuge is an essential solid–liquid separator widely used in pharmaceutical processing. This concise guide for B. Pharm students covers principle, construction, working, uses, merits and demerits of perforated basket centrifuges, focusing on drum and basket design, perforation size, rotational speed and g‑force that control cake formation, washing and drying. It also explains materials of construction, seals, feed methods, cleaning validation, maintenance, scale‑up and GMP considerations. Practical insights on selection criteria, troubleshooting and safety help link theory with lab and production practice. Detailed diagrams, operational tips and common troubleshooting scenarios are included to prepare you for exams and practicals. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary separation principle of a perforated basket centrifuge?
- Magnetic attraction of particles
- Electrostatic precipitation
- Application of centrifugal force to separate solids and liquids
- Membrane diffusion
Correct Answer: Application of centrifugal force to separate solids and liquids
Q2. Which component of a perforated basket centrifuge holds the solid cake?
- Feed pump
- Perforated basket
- Condenser
- Gearbox
Correct Answer: Perforated basket
Q3. In a perforated basket centrifuge, perforations primarily control which parameter?
- Electric power consumption
- Pore drainage rate and cake retention
- Motor torque direction
- Heating of the product
Correct Answer: Pore drainage rate and cake retention
Q4. Which material is most commonly used for pharmaceutical-grade perforated baskets?
- Wood
- Stainless steel (SS316)
- Polyvinyl chloride (PVC)
- Cast iron
Correct Answer: Stainless steel (SS316)
Q5. Which mode of operation is typical for most perforated basket centrifuges used in pharma labs?
- Continuous discharge
- Batch (intermittent) operation
- Plug flow
- Counter-current flow
Correct Answer: Batch (intermittent) operation
Q6. What happens to the liquid phase during centrifugation in a perforated basket centrifuge?
- It vaporizes instantly
- It passes through perforations and is collected as filtrate
- It solidifies into cake
- It becomes magnetic
Correct Answer: It passes through perforations and is collected as filtrate
Q7. Which parameter directly increases centrifugal force experienced by particles?
- Decrease in temperature
- Increase in rotational speed (RPM)
- Decrease in basket perforation size
- Increase in ambient humidity
Correct Answer: Increase in rotational speed (RPM)
Q8. What is the main advantage of using larger perforation size in the basket?
- Prevents any liquid discharge
- Faster filtrate flow but possible loss of fine solids
- Increases cake strength
- Reduces motor speed
Correct Answer: Faster filtrate flow but possible loss of fine solids
Q9. Which of the following is a common use of perforated basket centrifuges in pharmaceutical manufacturing?
- Tablet coating
- Solid-liquid separation of active pharmaceutical ingredients (APIs)
- Gas sterilization
- Lyophilization
Correct Answer: Solid-liquid separation of active pharmaceutical ingredients (APIs)
Q10. Cake washing in a perforated basket centrifuge is performed to:
- Increase cake porosity permanently
- Remove mother liquor and impurities from the cake
- Convert solids to gas
- Sterilize the cake
Correct Answer: Remove mother liquor and impurities from the cake
Q11. Which design feature aids drying of the cake inside a perforated basket centrifuge?
- Heating jackets on the basket
- Using a solid, non-perforated basket
- Reducing basket RPM to zero
- Filling basket with packing material
Correct Answer: Heating jackets on the basket
Q12. A common method to discharge cake from a perforated basket centrifuge is:
- Reverse magnetic field
- Opening the cover and scraping or pneumatic ejection
- Increasing perforation diameter mid-run
- Electrostatic removal
Correct Answer: Opening the cover and scraping or pneumatic ejection
Q13. Which safety concern is specific to high-speed operation of perforated basket centrifuges?
- Risk of excessive vacuum
- Mechanical imbalance causing vibration and rotor failure
- Radioactive emissions
- Loss of lubrication due to gas production
Correct Answer: Mechanical imbalance causing vibration and rotor failure
Q14. Which is a demerit of perforated basket centrifuges in pharmaceutical use?
- High throughput for continuous processing
- Risk of particle washout if perforations are large
- Inability to wash cake
- They never require maintenance
Correct Answer: Risk of particle washout if perforations are large
Q15. Which parameter is expressed as “RCF” in centrifugation?
- Rotational cooling factor
- Relative centrifugal force (g-force)
- Rotational cable friction
- Response control function
Correct Answer: Relative centrifugal force (g-force)
Q16. For effective separation of fine particles, which approach is recommended?
- Use larger perforations and low speed
- Use smaller perforations and higher centrifugal force
- Remove the basket altogether
- Operate at zero RPM
Correct Answer: Use smaller perforations and higher centrifugal force
Q17. Which component prevents leakage where the rotating shaft exits the housing?
- Feed nozzle
- Shaft seal or mechanical seal
- Perforation plate
- Discharge valve
Correct Answer: Shaft seal or mechanical seal
Q18. Which operating practice improves cake washing efficiency?
- Omitting wash solvent
- Applying sequential wash stages and controlling flow distribution
- Reducing RPM to stall the rotor
- Using random wash solvent volumes
Correct Answer: Applying sequential wash stages and controlling flow distribution
Q19. Which maintenance activity is critical for GMP compliance of a perforated basket centrifuge?
- Ignoring particle buildup
- Regular cleaning validation and documentation
- Never inspecting seals
- Using non-traceable parts for repairs
Correct Answer: Regular cleaning validation and documentation
Q20. Which centrifuge type is most similar in principle to a perforated basket centrifuge but differs in continuous operation?
- Decanter centrifuge
- Jet mill
- Rotary evaporator
- Fluidized bed dryer
Correct Answer: Decanter centrifuge
Q21. What effect does increasing feed rate generally have on cake formation?
- Produces thinner cake with potential entrainment of liquid
- Always increases cake purity
- Eliminates the need for wash steps
- Reduces motor load to zero
Correct Answer: Produces thinner cake with potential entrainment of liquid
Q22. Which is a typical symptom of an imbalanced rotor during operation?
- Quiet, stable operation
- High vibration and noise
- Lower motor current than normal
- Improved cake quality
Correct Answer: High vibration and noise
Q23. What is the role of a liquor-discharge port in perforated basket centrifuges?
- To introduce solids into the basket
- To collect and remove filtrate from the housing
- To pressurize the basket for discharge
- To cool the motor
Correct Answer: To collect and remove filtrate from the housing
Q24. Which parameter is most directly adjusted to change the intensity of separation?
- Perforation metal alloy
- Rotational speed (RPM)
- Color of the machine
- Number of operators
Correct Answer: Rotational speed (RPM)
Q25. Which cleaning method is commonly applied for pharmaceutical perforated baskets?
- Dry flame cleaning
- CIP (clean-in-place) or validated manual cleaning
- Submerging in crude oil
- Using unspecified detergents without records
Correct Answer: CIP (clean-in-place) or validated manual cleaning
Q26. What is the likely result of too-high washing solvent flow during cake wash?
- Perfect drying without losses
- Disintegration and loss of cake solids
- Cooling of the motor
- Strengthening of the cake
Correct Answer: Disintegration and loss of cake solids
Q27. Which parameter describes the thickness and rigidity of the cake affecting its discharge?
- Cake porosity and cohesion
- Ambient magnetic field
- Operator height
- Feed tubing color
Correct Answer: Cake porosity and cohesion
Q28. Which design modification helps retain very fine particles in the basket?
- Increase perforation diameter
- Use a fine wire mesh or filter cloth lining
- Remove all liners
- Use open slotted bars instead of perforations
Correct Answer: Use a fine wire mesh or filter cloth lining
Q29. During scale-up from lab to production, which factor is most critical to preserve separation performance?
- Maintaining geometric similarity and equivalent RCF
- Keeping the same paint color
- Reducing operator training
- Changing to a totally different separation principle
Correct Answer: Maintaining geometric similarity and equivalent RCF
Q30. Which of these is a merit of perforated basket centrifuges?
- Extremely high energy consumption compared to all alternatives
- Simple construction with easy inspection and maintenance
- Unable to be used for washing cakes
- Produces large thermal emissions
Correct Answer: Simple construction with easy inspection and maintenance
Q31. What is a common cause of reduced filtrate clarity?
- Excessive centrifugal force
- Too-large perforations or damaged basket lining allowing fines to pass
- Proper balance and alignment
- Thorough cleaning validation
Correct Answer: Too-large perforations or damaged basket lining allowing fines to pass
Q32. Which inspection is important before each run to ensure safe operation?
- Check rotor balance, seals, and secure lid fastening
- Remove safety guards for better visibility
- Invert the centrifuge
- Leave perforations clogged for better cake retention
Correct Answer: Check rotor balance, seals, and secure lid fastening
Q33. Which troubleshooting step is appropriate for excessive vibration?
- Increase run speed immediately
- Stop machine, inspect rotor balance and align bearings
- Remove the rotor during operation
- Ignore and continue operation
Correct Answer: Stop machine, inspect rotor balance and align bearings
Q34. Which type of product is least suitable for a perforated basket centrifuge?
- Coarse granular solids that cake well
- Very thin, non-cohesive slurries with extremely fine particles prone to washout
- Crystalline cake that needs washing
- Suspensions where cake is easily filterable
Correct Answer: Very thin, non-cohesive slurries with extremely fine particles prone to washout
Q35. How is cake dryness commonly improved after centrifugal drainage?
- By reducing speed to zero and leaving cake in place
- By centrifuging at high speed and applying air or vacuum drying if available
- By adding water to rehydrate it
- By freezing the cake instantly
Correct Answer: By centrifuging at high speed and applying air or vacuum drying if available
Q36. Which regulatory consideration is important for centrifuges in pharma production?
- There are no regulatory requirements
- Equipment must support cleaning validation, traceability and GMP documentation
- Only color and aesthetics matter
- Operators must not wear protective clothing
Correct Answer: Equipment must support cleaning validation, traceability and GMP documentation
Q37. What is the effect of entrapped air in feed on cake formation?
- Improves cake density uniformly
- Can produce porous and irregular cake with poor washing
- Eliminates need for washing
- Makes the perforations close automatically
Correct Answer: Can produce porous and irregular cake with poor washing
Q38. For safety interlocks, what should the centrifuge prevent?
- Starting with the lid open or during unsafe conditions
- Stopping after a run completes
- Changing rotational speed
- Monitoring vibration
Correct Answer: Starting with the lid open or during unsafe conditions
Q39. Which inspection helps detect basket wear or perforation damage?
- Visual inspection and dimensional check during maintenance
- Listening for music from the motor
- Smelling the filtrate only
- Checking paint gloss
Correct Answer: Visual inspection and dimensional check during maintenance
Q40. What is the usual effect of increasing centrifugal time at constant speed?
- Improves drainage and cake consolidation up to a limit
- Always degrades cake quality
- Reduces filtrate collection to zero
- Generates electricity
Correct Answer: Improves drainage and cake consolidation up to a limit
Q41. What role does basket rotation direction play in a perforated basket centrifuge?
- Direction is irrelevant to separation
- Correct rotation ensures proper cake build-up and discharge depending on design
- It changes the chemical composition of solids
- It converts solids to liquids
Correct Answer: Correct rotation ensures proper cake build-up and discharge depending on design
Q42. Which control improves reproducibility between batches?
- Varying RPM randomly
- Standardizing feed volume, RPM, time and wash protocol
- Using different operators for each batch without SOPs
- Changing perforation sizes each run
Correct Answer: Standardizing feed volume, RPM, time and wash protocol
Q43. What is a common design to protect very fine cakes from passing through perforations?
- Use a coarse grate only
- Line the basket with filter cloth or sintered plate
- Remove all liners and use open perforations
- Increase rotational speed to 1 RPM
Correct Answer: Line the basket with filter cloth or sintered plate
Q44. Which maintenance task extends bearing life in a centrifuge?
- Never lubricating bearings
- Regular lubrication and inspection per manufacturer schedule
- Operating at double rated speed for better wear
- Allowing ingress of product into bearings
Correct Answer: Regular lubrication and inspection per manufacturer schedule
Q45. What type of discharge is typical for perforated basket centrifuges removing cake manually?
- Continuous pumped discharge
- Open-lid and manual scraping or mechanical knock-out
- Vapor-phase discharge
- Auto-evaporation discharge
Correct Answer: Open-lid and manual scraping or mechanical knock-out
Q46. What is the impact of permeate back-pressure on filtration in a perforated basket centrifuge?
- No impact at all
- High back-pressure can reduce filtration rate and cause ponding inside housing
- Always increases cake rigidity beneficially
- Makes the basket perforations close automatically
Correct Answer: High back-pressure can reduce filtration rate and cause ponding inside housing
Q47. Which testing is important after repair before returning the centrifuge to service?
- Color matching test
- Balance test, run at low speed, vibration check and leak test
- Only visual inspection without a test run
- Run without lids to ensure speed
Correct Answer: Balance test, run at low speed, vibration check and leak test
Q48. In selection of a perforated basket centrifuge, which factor is least relevant?
- Particle size distribution of feed
- Sensitivity of product to oxygen or heat
- Required cake washing and drying needs
- Color of the operator’s uniform
Correct Answer: Color of the operator’s uniform
Q49. Which operational change helps reduce carryover of filtrate into the cake?
- Faster feed addition during drainage
- Allowing adequate drainage time at the end of spin cycle
- Wiping basket with oil
- Decreasing basket rigidity
Correct Answer: Allowing adequate drainage time at the end of spin cycle
Q50. Which documentation is essential for each batch processed in a pharmaceutical centrifuge?
- No documentation is necessary
- Batch record including operating conditions, cleaning logs and deviations
- Only the operator’s lunch menu
- Unrecorded verbal instructions
Correct Answer: Batch record including operating conditions, cleaning logs and deviations
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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