Meta filter — principle, construction, working, uses, merits, demerits are essential topics for B. Pharm students learning pharmaceutical filtration. This concise introduction explains how meta filters (metallic filters such as woven mesh and sintered metal) function by mechanical sieving and depth retention, describes common construction elements and materials, and outlines typical working conditions. It also highlights pharmaceutical applications (liquid and gas filtration, pre-filtration, process protection), comparative merits (reusability, thermal and chemical resistance) and demerits (higher initial cost, fouling, cleaning needs). Answers with explanations help exam preparation and practical application. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary principle by which a meta filter removes particles?
- Chemical reaction with filter material
- Mechanical sieving and depth retention
- Electrostatic attraction only
- Ultraviolet degradation
Correct Answer: Mechanical sieving and depth retention
Q2. Which material is most commonly used for pharmaceutical meta filter elements?
- Stainless steel
- Polypropylene
- Glass fiber
- Cellulose acetate
Correct Answer: Stainless steel
Q3. A sintered metal filter is produced primarily by which process?
- Electroplating metal onto a substrate
- Sintering metal particles under heat and pressure
- Molding molten metal into a porous sheet
- Coating a polymer with metal flakes
Correct Answer: Sintering metal particles under heat and pressure
Q4. Which type of meta filter mainly provides surface filtration?
- Depth filter
- Woven mesh (screen) filter
- Sintered porous metal with graded porosity
- Sleeve-shaped depth cartridge
Correct Answer: Woven mesh (screen) filter
Q5. What is an advantage of metal filters over polymeric membrane filters?
- Single-use disposal
- Higher temperature and chemical resistance
- Lower initial cost
- Higher absolute retention for sub-micron viruses
Correct Answer: Higher temperature and chemical resistance
Q6. In pharma processes, meta filters are commonly used for which of the following tasks?
- Final viral sterilization of injectable solutions
- Removal of large particulates and protecting downstream equipment
- Replacing aseptic filling lines
- Direct microbial decontamination of products
Correct Answer: Removal of large particulates and protecting downstream equipment
Q7. Which parameter is most important to specify for a meta filter element?
- Color of the filter housing
- Pore size or micron rating
- Length of the manufacturing warranty
- Brand of the metal supplier
Correct Answer: Pore size or micron rating
Q8. What is a common method to clean fouled metal filter elements?
- Discard after single use only
- Backwashing or reverse flow with detergent/solvent
- Heating to melting point
- Exposure to gamma radiation for cleaning
Correct Answer: Backwashing or reverse flow with detergent/solvent
Q9. What does “depth filtration” imply in meta filters?
- Particles are only captured on the surface layer
- Filtration occurs within the thickness of the element trapping particles throughout the matrix
- Particles are dissolved chemically in the element
- Filtration is achieved by magnetic separation
Correct Answer: Filtration occurs within the thickness of the element trapping particles throughout the matrix
Q10. Which design feature helps reduce pressure drop across a metal filter?
- Decreasing surface area
- Increasing filter surface area or pleating
- Using finer pore size than required
- Sealing the element to prevent bypass
Correct Answer: Increasing filter surface area or pleating
Q11. What is a typical disadvantage (demerit) of metal filters?
- Inability to withstand high temperatures
- Higher initial cost and potential for clogging requiring cleaning
- Complete single-use disposal is always required
- They dissolve in common process solvents
Correct Answer: Higher initial cost and potential for clogging requiring cleaning
Q12. Which of the following is NOT a typical construction form of a meta filter element?
- Woven wire mesh
- Sintered metal cartridge
- Activated carbon block
- Perforated plate with wire support
Correct Answer: Activated carbon block
Q13. For validation of a reusable metal filter, which procedure is important?
- Bubble point testing only
- Establishing cleaning, sterilization and integrity protocols with performance testing
- Not documenting any cleaning since metal is inert
- Replacing without testing after every cycle
Correct Answer: Establishing cleaning, sterilization and integrity protocols with performance testing
Q14. How is pore size in woven mesh typically defined?
- By chemical composition only
- By mesh count (wires per inch) and effective opening size
- By electrical conductivity
- By color code of the wire
Correct Answer: By mesh count (wires per inch) and effective opening size
Q15. Which cleaning-in-place (CIP) method is compatible with many metal filters?
- Hot caustic wash followed by acid rinse and sanitization
- Only ambient water rinse with no chemicals
- Immersion in liquid nitrogen
- Painting the element surface with polymer
Correct Answer: Hot caustic wash followed by acid rinse and sanitization
Q16. What role do gaskets and seals play in meta filter housings?
- They transmit filtration by chemical reaction
- They ensure fluid flows through the element rather than bypassing it
- They increase the pore size of the element
- They act as the primary filtering media
Correct Answer: They ensure fluid flows through the element rather than bypassing it
Q17. Which application would be unsuitable for a metal filter alone?
- Pre-filtration to protect final membrane filters
- Removal of sub-micron bacteria for sterile filtration of injectables
- Filtration of hot process streams
- Gas filtration at high temperature
Correct Answer: Removal of sub-micron bacteria for sterile filtration of injectables
Q18. What is the typical effect of decreasing pore size in a metal filter element?
- Increase in flow rate for the same pressure
- Increase in retention efficiency but also higher pressure drop
- Element becomes chemically reactive
- Element becomes lighter in weight
Correct Answer: Increase in retention efficiency but also higher pressure drop
Q19. Which measurement gives direct indication of loading/fouling of a filter in operation?
- Color of the fluid
- Differential pressure across the filter
- Ambient room temperature
- Filter brand name
Correct Answer: Differential pressure across the filter
Q20. A pleated metal filter increases performance by:
- Reducing the element surface area
- Creating more surface area to lower face velocity and pressure drop
- Closing pores to block flow
- Changing chemical composition of contaminants
Correct Answer: Creating more surface area to lower face velocity and pressure drop
Q21. Which property of metal filters makes them suitable for steam sterilization (SIP)?
- Low melting point
- High thermal resistance of metal elements
- Porous polymeric binder
- Disposable plastic housing
Correct Answer: High thermal resistance of metal elements
Q22. Which of the following is a merit of sintered metal filters?
- They are always single-use
- High mechanical strength, uniform pore structure and reusability
- They melt at low temperatures for cleaning
- They produce chemical leachables under normal conditions
Correct Answer: High mechanical strength, uniform pore structure and reusability
Q23. What is the role of a housings manifold in a multi-element metal filter assembly?
- To chemically treat the fluid
- To provide fluid distribution to and collection from filter elements
- To alter the pore size dynamically
- To heat the process fluid beyond operational limits
Correct Answer: To provide fluid distribution to and collection from filter elements
Q24. Which particle removal mechanism is not typical for metal filters?
- Surface sieving
- Depth entrapment
- Electrostatic precipitation within metal pores
- Inertial impaction for larger particles
Correct Answer: Electrostatic precipitation within metal pores
Q25. Why might a manufacturer choose a graded porosity sintered element?
- To reduce manufacturing complexity with single porosity
- To capture large particles on the surface and finer particles deeper, improving capacity
- To ensure immediate complete clogging
- To prevent any fluid from passing through
Correct Answer: To capture large particles on the surface and finer particles deeper, improving capacity
Q26. Which of the following is used to monitor filter integrity during operation?
- Particle counters or DP trending for differential pressure
- Measuring filter color change visually only
- Counting the number of uses without measurement
- Checking the serial number of the element
Correct Answer: Particle counters or DP trending for differential pressure
Q27. What is a common failure mode for metal filters in liquid service?
- Melting of the element at room temperature
- Buildup of cakes causing high pressure drop and eventual bypass if seals fail
- Spontaneous gas generation within pores
- Auto-disintegration into powder
Correct Answer: Buildup of cakes causing high pressure drop and eventual bypass if seals fail
Q28. When comparing mesh count to micron rating, higher mesh count indicates:
- Larger openings and coarser filtration
- Finer openings and smaller effective pore size
- No change to pore size
- Change in chemical properties only
Correct Answer: Finer openings and smaller effective pore size
Q29. Which headloss factor primarily affects flow through a metal filter?
- Viscosity of the fluid and pore resistance of the element
- Color of the filter housing
- Electrical conductivity of the fluid
- Altitude of the manufacturing plant only
Correct Answer: Viscosity of the fluid and pore resistance of the element
Q30. What is a typical step in the qualification of a metal filter for pharma use?
- Omitting documentation to speed up qualification
- Performance testing including particle retention, flow capacity, and cleaning validation
- Using it in production without testing
- Only visual inspection is required
Correct Answer: Performance testing including particle retention, flow capacity, and cleaning validation
Q31. Which cleaning technique can dislodge strongly adhered particulates from metal filter pores?
- Low pressure rinse only
- Ultrasonic cleaning combined with appropriate solvents or detergents
- Painting the surface with polymer
- Freezing the filter to brittle fracture particles
Correct Answer: Ultrasonic cleaning combined with appropriate solvents or detergents
Q32. Metal filters are often preferred in organic solvent service because:
- Polymeric filters swell or degrade in aggressive solvents while metals resist them
- Metals dissolve rapidly in solvents
- They impart flavors to the solvent
- They reduce solvent volatility
Correct Answer: Polymeric filters swell or degrade in aggressive solvents while metals resist them
Q33. Which inspection is important after thermal sterilization of a metal filter?
- Check for mechanical distortion, gasket integrity and performance testing
- Only measure color change of the filter element
- Discard without inspection because metal tolerates heat
- Weigh the filter to detect missing atoms
Correct Answer: Check for mechanical distortion, gasket integrity and performance testing
Q34. For particulate retention ratings, metal filters are usually specified in:
- Milliliters per hour
- Microns (µm)
- Degrees Celsius
- Liters per kilogram
Correct Answer: Microns (µm)
Q35. What is the best strategy to extend service life of a metal filter element?
- Operate at maximum allowable differential pressure always
- Implement staged filtration, prefilters and regular cleaning/maintenance
- Never clean and reuse regardless of condition
- Use only distilled water for every process
Correct Answer: Implement staged filtration, prefilters and regular cleaning/maintenance
Q36. Which design choice helps prevent bypass around a metal filter element?
- Poorly fitting gaskets and loose clamps
- Properly designed end caps, gaskets and secure housing closures
- Leaving housing vents open during operation
- Using mismatched element dimensions intentionally
Correct Answer: Properly designed end caps, gaskets and secure housing closures
Q37. What is the effect of increased fluid viscosity on a metal filter’s performance at constant pressure?
- Increase in flow rate through the filter
- Decrease in flow rate and possible higher differential pressure
- No effect on flow or pressure
- Reduction of pore size to compensate
Correct Answer: Decrease in flow rate and possible higher differential pressure
Q38. Which safety consideration is important when cleaning metal filters with caustic solutions?
- No personal protective equipment (PPE) is required
- Use appropriate PPE, corrosion-resistant equipment and neutralization procedures
- Heat the caustic to boiling without controls
- Only use open flames to accelerate cleaning
Correct Answer: Use appropriate PPE, corrosion-resistant equipment and neutralization procedures
Q39. What is the term for a filter ability to stop particles of a specific size with defined efficiency?
- Permeability index
- Retention or rating (e.g., micron rating or beta ratio)
- Color index
- Surface tension
Correct Answer: Retention or rating (e.g., micron rating or beta ratio)
Q40. Which maintenance activity helps detect early signs of element degradation?
- Ignoring differential pressure trends
- Regular visual inspection and monitoring of performance parameters
- Replacing the element without inspection only when plant stops
- Only inspecting external housing bolts
Correct Answer: Regular visual inspection and monitoring of performance parameters
Q41. In a pharmaceutical plant, metal filters are often installed upstream of:
- Final sterile membrane filters to protect them from large particulate load
- Garbage compactors
- HVAC outdoor vents only
- Packaging labels
Correct Answer: Final sterile membrane filters to protect them from large particulate load
Q42. Which statement about sintered versus woven mesh metal filters is correct?
- Sintered elements generally provide depth filtration and higher strength; woven mesh behaves more like surface filter
- Woven mesh is always stronger than sintered elements
- Sintered elements are single-use only
- Both types dissolve in water
Correct Answer: Sintered elements generally provide depth filtration and higher strength; woven mesh behaves more like surface filter
Q43. What is a potential chemical compatibility concern for stainless steel metal filters?
- Stainless steel is inert to all chemicals without exception
- Chloride-induced pitting corrosion can occur in aggressive chloride-containing solutions
- They react violently with pure oxygen at room temperature
- They dissolve in distilled water
Correct Answer: Chloride-induced pitting corrosion can occur in aggressive chloride-containing solutions
Q44. For gas filtration at high temperature, metal filters are favored because:
- They block all gases completely
- They retain mechanical integrity at temperatures that degrade polymers
- They emit beneficial vapors into the gas stream
- They change gas composition chemically
Correct Answer: They retain mechanical integrity at temperatures that degrade polymers
Q45. When selecting a metal filter for a critical application, which documentation is essential from the supplier?
- Performance data, material certificates, recommended cleaning and validation instructions
- Only the color catalog of the filter
- Supplier’s vacation calendar
- Only the country of origin without specs
Correct Answer: Performance data, material certificates, recommended cleaning and validation instructions
Q46. What is the main reason to implement staged filtration (pre-filter followed by finer filter)?
- To increase load on final filter purposely
- To extend service life of fine filters and reduce maintenance cost
- To complicate maintenance schedules unnecessarily
- To lower initial filtration efficiency
Correct Answer: To extend service life of fine filters and reduce maintenance cost
Q47. Which testing method assesses a metal filter’s ability to remove particles of a certain size?
- Visual color match test
- Challenge testing with a known particle size distribution and particle counting
- Measuring electrical resistance only
- Measuring the smell of effluent
Correct Answer: Challenge testing with a known particle size distribution and particle counting
Q48. What precaution is important when reassembling a metal filter housing after cleaning?
- Use damaged gaskets for better flow
- Ensure correct gasket placement, torque of clamps/bolts and no particle contamination
- Skip drying to save time
- Leave the housing slightly open during operation
Correct Answer: Ensure correct gasket placement, torque of clamps/bolts and no particle contamination
Q49. Which advantage do metal filter cartridges provide in repeated sterilization cycles?
- They lose structural integrity after first cycle
- They withstand repeated SIP cycles with minimal dimensional change when compatible materials are used
- They become progressively porous and unusable after one cycle
- They trap sterilant permanently which prevents reuse
Correct Answer: They withstand repeated SIP cycles with minimal dimensional change when compatible materials are used
Q50. What is an important environmental or economic merit of reusable metal filters?
- Increased single-use plastic waste
- Reduced disposal waste and long-term cost savings compared to disposable filters
- Immediate obsolescence after one use
- Higher landfill requirement per cycle
Correct Answer: Reduced disposal waste and long-term cost savings compared to disposable filters
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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