Orifice meter MCQs With Answer

Understanding orifice meter MCQs with answer is essential for B. Pharm students involved in process instrumentation and validation. This concise introduction covers orifice meter principles, orifice plate types, differential pressure measurement, discharge coefficient, beta ratio, and calculation of volumetric and mass flow—key topics in pharmaceutical flow measurement and GMP-compliant manufacturing. Learn how fluid properties, Reynolds number, compressibility corrections, and installation effects influence accuracy, calibration, and troubleshooting in hygienic systems. These Orifice meter MCQs With Answer will help reinforce theory, practical considerations, and regulatory aspects relevant to sterile and liquid handling systems. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is the primary principle behind an orifice meter for flow measurement?

• Change in electrical conductivity
• Measurement of differential pressure across a restriction
• Variation in acoustic resonance
• Optical flow visualization

Correct Answer: Measurement of differential pressure across a restriction

Q2. Which equation relates differential pressure to volumetric flow for an orifice meter under incompressible flow assumptions?

• Bernoulli’s equation with continuity and discharge coefficient
• Newton’s second law in rotational form
• Ideal gas law
• Fourier’s law of heat conduction

Correct Answer: Bernoulli’s equation with continuity and discharge coefficient

Q3. What does the beta ratio (β) represent for an orifice plate?

• Ratio of upstream to downstream pressure
• Ratio of orifice diameter to pipe diameter (d/D)
• Ratio of fluid viscosity to density
• Ratio of discharge coefficient to Reynolds number

Correct Answer: Ratio of orifice diameter to pipe diameter (d/D)

Q4. The discharge coefficient (Cd) for an orifice meter primarily corrects for which effect?

• Thermal expansion of the pipe
• Energy losses and contraction at the vena contracta
• Changes in electrical potential
• Magnetic field interference

Correct Answer: Energy losses and contraction at the vena contracta

Q5. In pharmaceutical liquid flow measurement, why is Reynolds number important for orifice meters?

• It indicates the color of the fluid
• It determines whether flow is laminar or turbulent, affecting Cd
• It sets the maximum allowable pressure
• It measures microbial contamination

Correct Answer: It determines whether flow is laminar or turbulent, affecting Cd

Q6. Which orifice plate type is commonly used to avoid solids accumulation in sanitary lines?

• Concentric sharp-edged orifice
• Eccentric orifice plate
• Segmental orifice plate
• Multi-hole quadrant orifice

Correct Answer: Eccentric orifice plate

Q7. For compressible gas flow, which correction must be applied to orifice meter calculations?

• Temperature compensation only
• Expansion (compressibility) factor and appropriate gas equations
• Magnetic susceptibility correction
• No correction is needed

Correct Answer: Expansion (compressibility) factor and appropriate gas equations

Q8. What is the vena contracta in an orifice meter?

• The point of maximum pipe diameter downstream
• The location of minimum cross-sectional flow area and maximum velocity downstream of the orifice
• The instrument housing for the differential pressure transmitter
• The filter used upstream of the meter

Correct Answer: The location of minimum cross-sectional flow area and maximum velocity downstream of the orifice

Q9. Which standard provides procedures and guidelines for orifice plate flow measurement?

• ISO 9001
• ISO 5167
• ASTM D1193
• USP General Chapter on flow

Correct Answer: ISO 5167

Q10. What effect does increasing fluid viscosity have on orifice meter accuracy at low Reynolds numbers?

• No effect
• It can reduce accuracy by modifying the discharge coefficient
• It always increases measured flow
• It eliminates the vena contracta effect

Correct Answer: It can reduce accuracy by modifying the discharge coefficient

Q11. Which instrument is typically used downstream of an orifice plate to sense differential pressure?

• Thermocouple
• Positive displacement flowmeter
• Differential pressure transmitter
• pH probe

Correct Answer: Differential pressure transmitter

Q12. For validation in a pharmaceutical plant, why is periodic calibration of orifice meters necessary?

• To change the orifice plate color
• To ensure measurement accuracy, traceability, and regulatory compliance
• To adjust the pipe diameter
• It is never necessary

Correct Answer: To ensure measurement accuracy, traceability, and regulatory compliance

Q13. What is the typical flow relationship between differential pressure (ΔP) and volumetric flow (Q) for an incompressible fluid?

• Q is proportional to ΔP
• Q is proportional to sqrt(ΔP)
• Q is proportional to (ΔP)^2
• Q is independent of ΔP

Correct Answer: Q is proportional to sqrt(ΔP)

Q14. Which installation factor is critical to minimize upstream disturbances affecting orifice meter accuracy?

• Upstream straight pipe length and flow conditioning
• Downstream insulation thickness
• Paint color of the pipeline
• Orientation of the instrument label

Correct Answer: Upstream straight pipe length and flow conditioning

Q15. In pharmaceutical processes, why might a flange-tapped orifice be preferred over a corner-tapped one?

• It is less accurate
• Flange taps often reduce error from vena contracta pressure recovery effects
• Corner taps are incompatible with liquids
• Flange taps eliminate the need for a differential transmitter

Correct Answer: Flange taps often reduce error from vena contracta pressure recovery effects

Q16. Which of the following is a limitation of orifice meters in pharmaceutical applications?

• They measure concentration directly
• They can cause significant permanent pressure loss and may promote fouling
• They are immune to viscosity changes
• They provide contamination-free sampling

Correct Answer: They can cause significant permanent pressure loss and may promote fouling

Q17. How is mass flow obtained from an orifice meter when measuring gas flow?

• By multiplying volumetric flow by fluid density at operating conditions
• By integrating temperature only
• By measuring electrical conductivity
• By using a turbidity sensor

Correct Answer: By multiplying volumetric flow by fluid density at operating conditions

Q18. What role does upstream straight-pipe run length play for an orifice plate?

• It determines the orifice plate material
• It helps develop a fully developed velocity profile to improve accuracy
• It changes the discharge coefficient permanently
• It measures the fluid’s color

Correct Answer: It helps develop a fully developed velocity profile to improve accuracy

Q19. Which parameter would you change to reduce permanent pressure loss across an orifice meter?

• Increase orifice diameter (increase beta ratio)
• Decrease pipe diameter
• Add more sharp edges
• Reduce transmitter accuracy

Correct Answer: Increase orifice diameter (increase beta ratio)

Q20. In orifice meter sizing, what is the primary trade-off when choosing beta ratio?

• Between chemical compatibility and color
• Between measurement sensitivity (ΔP magnitude) and permanent pressure loss
• Between pipe material and wall thickness
• Between microbial growth rate and temperature

Correct Answer: Between measurement sensitivity (ΔP magnitude) and permanent pressure loss

Q21. For hygienic pharmaceutical piping, what material consideration is important for orifice plates?

• High porosity to trap contaminants
• Use of stainless steel polished to sanitary finish to allow cleaning and prevent contamination
• Use of painted carbon steel for aesthetics
• Porous ceramic for filtration

Correct Answer: Use of stainless steel polished to sanitary finish to allow cleaning and prevent contamination

Q22. What is the effect of fouling or deposits on an orifice plate in pharma lines?

• It reduces or alters the effective orifice area, causing measurement bias
• It improves accuracy
• It increases pipeline diameter
• It neutralizes the fluid pH

Correct Answer: It reduces or alters the effective orifice area, causing measurement bias

Q23. Which flow regime generally gives stable and repeatable Cd values for standard orifice plates?

• Very low Reynolds number (creeping flow)
• Moderate to high turbulent flow (Re > ~10,000)
• Transitional flow only
• Completely laminar flow

Correct Answer: Moderate to high turbulent flow (Re > ~10,000)

Q24. When measuring steam flow with an orifice meter, what additional property must be known?

• Electrical conductivity of steam
• Steam quality (dryness fraction) and specific volume
• Color of the steam
• pH of the steam

Correct Answer: Steam quality (dryness fraction) and specific volume

Q25. Why are orifice meters widely used despite their pressure loss?

• Because they are the only option available
• Due to their simplicity, low cost, robustness, and well-established standards
• Because they require no calibration
• Because they eliminate the need for piping

Correct Answer: Due to their simplicity, low cost, robustness, and well-established standards

Q26. What is the purpose of primary and secondary elements in an orifice flow measurement system?

• Primary element filters fluid; secondary element adds heat
• Primary element creates differential pressure; secondary element (transmitter) converts it to an electrical signal
• Both are redundant with identical functions
• Secondary element changes orifice size

Correct Answer: Primary element creates differential pressure; secondary element (transmitter) converts it to an electrical signal

Q27. How is the discharge coefficient (Cd) typically determined for a specific orifice plate?

• By reading the plate’s color code
• From empirical correlations, standards (ISO 5167), or calibration tests
• By measuring electrical resistance
• By weighing the orifice plate

Correct Answer: From empirical correlations, standards (ISO 5167), or calibration tests

Q28. Which of the following maintenance practices helps maintain orifice meter accuracy in pharma plants?

• Regular visual inspection and cleaning during scheduled CIP cycles
• Painting the orifice plate monthly
• Removing the transmitter permanently
• Adding more bends upstream

Correct Answer: Regular visual inspection and cleaning during scheduled CIP cycles

Q29. What is the typical effect of temperature changes on orifice meter readings if not compensated?

• No effect because orifice meters are temperature independent
• Density changes alter volumetric-to-mass flow conversions and Cd may shift slightly
• They explode
• They become electromagnetic

Correct Answer: Density changes alter volumetric-to-mass flow conversions and Cd may shift slightly

Q30. In a sanitary system, why is gasket and flange selection important around an orifice plate?

• To provide decorative appearance
• To ensure leak-tight, cleanable joints and avoid dead legs where contamination can collect
• To increase pressure drop intentionally
• To reduce fluid viscosity

Correct Answer: To ensure leak-tight, cleanable joints and avoid dead legs where contamination can collect

Q31. Which factor is least likely to affect the discharge coefficient for a properly installed sharp-edged orifice?

• Beta ratio
• Pipe roughness and manufacturing tolerances
• Electrical power supply voltage to the transmitter
• Upstream flow profile disturbances

Correct Answer: Electrical power supply voltage to the transmitter

Q32. When performing a flow validation using an orifice meter, what is a common reference method?

• Using a calibrated volumetric tank or master meter
• Estimating flow by eye
• Counting pipe threads
• Measuring ambient noise

Correct Answer: Using a calibrated volumetric tank or master meter

Q33. Which orifice configuration is preferred to measure interface flows without trapping solids at the top of the plate?

• Concentric orifice
• Top-tapped corner orifice
• Bottom-tapped eccentric orifice
• Blind plate

Correct Answer: Bottom-tapped eccentric orifice

Q34. How does an orifice meter behave when installed in a vertical upward flow of liquid?

• Its calibration fundamentally changes and cannot be used
• It can work if the flow is fully developed; orientation may affect tap locations and bubble accumulation
• It measures pressure instead of flow
• It automatically corrects for viscosity

Correct Answer: It can work if the flow is fully developed; orientation may affect tap locations and bubble accumulation

Q35. Which safety concern is associated with measuring high-pressure liquids with orifice meters in pharma plants?

• Risk of chemical discoloration
• Potential for high differential pressure and leaks at fittings if not rated and installed correctly
• They generate harmful radiation
• They neutralize disinfectants

Correct Answer: Potential for high differential pressure and leaks at fittings if not rated and installed correctly

Q36. Which parameter does NOT directly enter the basic incompressible orifice flow equation?

• Discharge coefficient (Cd)
• Fluid density
• Pipe color
• Orifice and pipe diameters

Correct Answer: Pipe color

Q37. For small-bore lines in pharma, why might orifice meters be less desirable?

• They become more expensive per unit length and create proportionally larger pressure losses and inaccuracies
• They cannot be made of stainless steel
• They measure too accurately
• They encourage microbial growth intentionally

Correct Answer: They become more expensive per unit length and create proportionally larger pressure losses and inaccuracies

Q38. What maintenance check would detect a drift in an orifice meter system reading?

• Checking paint thickness
• Comparing measured flow periodically with a calibrated reference or performing in-situ calibration
• Measuring ambient humidity
• Replacing the orifice plate weekly

Correct Answer: Comparing measured flow periodically with a calibrated reference or performing in-situ calibration

Q39. How does cavitation downstream of an orifice plate affect measurement and process?

• It increases accuracy
• It can cause noise, vibration, damage to the plate, and alteration of measurement
• It lowers fluid density permanently
• It sterilizes the fluid

Correct Answer: It can cause noise, vibration, damage to the plate, and alteration of measurement

Q40. Which tap location option generally provides the most standardized results according to ISO 5167?

• Corner taps
• Flange taps and orifice taps specified per standard guidelines
• Random hole taps
• Exterior shell taps

Correct Answer: Flange taps and orifice taps specified per standard guidelines

Q41. In the context of process qualification, what documentation is important for orifice meter installation?

• Installation drawings, calibration certificates, SOPs for maintenance, and validation reports
• Only the paint certificate
• Only supplier brochures
• No documentation is required

Correct Answer: Installation drawings, calibration certificates, SOPs for maintenance, and validation reports

Q42. Which flow condition can severely distort orifice meter readings if present upstream?

• Steady fully developed laminar flow
• Swirling or asymmetric flow due to nearby valves or elbows
• Flow in the correct Reynolds number range
• Uniform temperature distribution

Correct Answer: Swirling or asymmetric flow due to nearby valves or elbows

Q43. For a given pipeline and orifice plate, which measurement will directly decrease if fluid density increases (in incompressible flow context) while ΔP remains the same?

• Mass flow rate
• Volumetric flow rate
• Temperature
• Pipe diameter

Correct Answer: Volumetric flow rate

Q44. When selecting an orifice plate for a sterile pharmaceutical line, which feature is most critical?

• Sharp external paint finish
• Sanitary design, minimal dead legs, and materials compatible with CIP/SIP
• Opaque color to block light
• Porous surface to retain cleaning agents

Correct Answer: Sanitary design, minimal dead legs, and materials compatible with CIP/SIP

Q45. Which corrective action can reduce measurement error caused by upstream disturbances?

• Install flow straighteners or increase upstream straight pipe length
• Rotate the pipe 90 degrees daily
• Use a smaller orifice plate
• Remove the differential transmitter

Correct Answer: Install flow straighteners or increase upstream straight pipe length

Q46. What is the typical sign that an orifice plate is clogged or partially blocked?

• Constant transmitter zero
• Unexpected increase in measured differential pressure for a given flow
• Decrease in ambient temperature
• Change in pipe color

Correct Answer: Unexpected increase in measured differential pressure for a given flow

Q47. In calibration, why might a laboratory use a master meter rather than a theoretical Cd value?

• Theoretical values are illegal
• A master meter provides empirical comparison under actual conditions, accounting for installation effects
• The master meter is decorative
• Theoretical Cd does not exist

Correct Answer: A master meter provides empirical comparison under actual conditions, accounting for installation effects

Q48. Which outcome is expected when Reynolds number falls below the recommended range for standard orifice equations?

• Equations remain fully accurate
• Cd becomes Reynolds-number dependent and measurement uncertainty increases
• Pipe bursts
• Differential pressure becomes negative

Correct Answer: Cd becomes Reynolds-number dependent and measurement uncertainty increases

Q49. When designing a pharmaceutical process line, why consider alternative flow meters to orifice plates?

• Alternatives may offer lower pressure loss, better sanitary design, or higher accuracy for low flow rates
• Alternatives are always cheaper
• Orifice plates are banned in pharma
• Alternatives eliminate need for validation

Correct Answer: Alternatives may offer lower pressure loss, better sanitary design, or higher accuracy for low flow rates

Q50. Which is a correct statement about the relationship between flow coefficient (Cv) and orifice meter performance?

• Cv is unrelated to flow rate
• Cv provides an empirical measure of flow capacity and helps translate differential pressure to flow in practical systems
• Cv measures contamination levels
• Cv only applies to electrical equipment

Correct Answer: Cv provides an empirical measure of flow capacity and helps translate differential pressure to flow in practical systems

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com