Practice Tests · Free Tool
Control Valve Sizing Quiz
Test yourself with 20 multiple choice questions. Check your answers to get a score and an explanation for every question.
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Control Valve Sizing Quiz: 20 Questions
Choose one answer for each question, then press Check answers. Explanations appear after checking.
1. Cv is the flow of water in US gpm at a pressure drop of:
Answer: 1 psi. Kv uses m³/h at 1 bar. Learn more: Flow Coefficient (Cv)
2. Cv and Kv are related by:
Answer: Cv = 1.156 Kv. Conversion of units. Learn more: Kv Flow Factor
3. Water 50 m³/h at 1 bar drop needs a Kv of:
Answer: 50. Kv = Q √(SG ÷ ΔP) = 50; Cv would be 57.8. Learn more: Kv Flow Factor
4. Which characteristic is most common for process control valves?
Answer: Equal percentage. It compensates falling valve ΔP as flow rises. Learn more: Valve Characteristic
5. Valve authority is:
Answer: Valve ΔP ÷ total system ΔP. Higher authority keeps the characteristic undistorted. Learn more: Valve Authority
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6. With low authority a linear valve behaves like:
Answer: Quick opening. Most flow change happens early in travel. Learn more: Installed Characteristic
7. Cavitation damage looks like:
Answer: Rough, cinder like pitting. Collapsing bubbles hammer the surface. Learn more: Cavitation
8. Flashing occurs when outlet pressure is:
Answer: Below the vapour pressure. The vapour does not collapse. Learn more: Flashing
9. Which valve type has the highest FL (lowest pressure recovery)?
Answer: Globe. Globe FL about 0.9; rotary about 0.55 to 0.7. Learn more: Liquid Pressure Recovery Factor
10. Liquid choked ΔP equals:
Answer: FL² × (P1 − FF Pv). IEC 60534-2-1 liquid choking. Learn more: Choked Flow
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11. Class IV seat leakage allows:
Answer: 0.01 % of rated capacity. Class II 0.5 %, III 0.1 %, IV 0.01 %. Learn more: Seat Leakage Class
12. Air to open valves fail:
Answer: Closed. Spring closes the valve on air loss. Learn more: Air to Open
13. A positioner mainly:
Answer: Matches stem position to the control signal. It overcomes friction and process forces. Learn more: Valve Positioner
14. An I/P converter at 12 mA outputs about:
Answer: 0.6 bar (9 psi). 0.2 + 0.8 × 0.5 = 0.6 bar. Learn more: I/P Converter
15. Valve stiction causes:
Answer: Stick slip and loop cycling. The valve jumps past the target then sticks again. Learn more: Valve Stiction
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16. Two Cv 40 valves in parallel give:
Answer: Cv 80. Parallel Cv values add. Learn more: Flow Coefficient (Cv)
17. Partial stroke testing typically moves an ESD valve:
Answer: About 10 to 20 % of travel. Enough to prove movement without upsetting the process. Learn more: Partial Stroke Testing
18. Bench set means:
Answer: Spring range measured with no process load. Air pressure range for full stroke on the bench. Learn more: Spring Range
19. A volume booster is used to:
Answer: Stroke large actuators faster. It supplies large air flow following the positioner signal. Learn more: Volume Booster
20. Graphite packing compared with PTFE has:
Answer: Higher temperature limit and more friction. Graphite handles heat but adds friction. Learn more: Valve Packing
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About this Quiz
20 multiple choice questions on control valve sizing, the kind asked in instrumentation interviews, technician exams and plant training. Each answer comes with a short explanation, so the quiz works as a revision sheet too.
Show answer key
- 1 psi: Kv uses m³/h at 1 bar. Learn more: Flow Coefficient (Cv)
- Cv = 1.156 Kv: Conversion of units. Learn more: Kv Flow Factor
- 50: Kv = Q √(SG ÷ ΔP) = 50; Cv would be 57.8. Learn more: Kv Flow Factor
- Equal percentage: It compensates falling valve ΔP as flow rises. Learn more: Valve Characteristic
- Valve ΔP ÷ total system ΔP: Higher authority keeps the characteristic undistorted. Learn more: Valve Authority
- Quick opening: Most flow change happens early in travel. Learn more: Installed Characteristic
- Rough, cinder like pitting: Collapsing bubbles hammer the surface. Learn more: Cavitation
- Below the vapour pressure: The vapour does not collapse. Learn more: Flashing
- Globe: Globe FL about 0.9; rotary about 0.55 to 0.7. Learn more: Liquid Pressure Recovery Factor
- FL² × (P1 − FF Pv): IEC 60534-2-1 liquid choking. Learn more: Choked Flow
- 0.01 % of rated capacity: Class II 0.5 %, III 0.1 %, IV 0.01 %. Learn more: Seat Leakage Class
- Closed: Spring closes the valve on air loss. Learn more: Air to Open
- Matches stem position to the control signal: It overcomes friction and process forces. Learn more: Valve Positioner
- 0.6 bar (9 psi): 0.2 + 0.8 × 0.5 = 0.6 bar. Learn more: I/P Converter
- Stick slip and loop cycling: The valve jumps past the target then sticks again. Learn more: Valve Stiction
- Cv 80: Parallel Cv values add. Learn more: Flow Coefficient (Cv)
- About 10 to 20 % of travel: Enough to prove movement without upsetting the process. Learn more: Partial Stroke Testing
- Spring range measured with no process load: Air pressure range for full stroke on the bench. Learn more: Spring Range
- Stroke large actuators faster: It supplies large air flow following the positioner signal. Learn more: Volume Booster
- Higher temperature limit and more friction: Graphite handles heat but adds friction. Learn more: Valve Packing
Tip: take the quiz before an interview, note the questions you missed and read the linked article for those topics.
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Frequently Asked Questions
Is this quiz free?
Yes. No sign up is needed and you can retake it as often as you like.
Are the answers explained?
Yes. After you check your answers, each question shows the correct answer and a short explanation.
Where can I find more questions?
See the Interview Q&A section of instrumentationblog.in and the linked article below.
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