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Control Valve and PID Quiz
Test yourself with 15 multiple choice questions. Check your answers to get a score and an explanation for every question.
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Control Valve and PID Quiz: 15 Questions
Choose one answer for each question, then press Check answers. Explanations appear after checking.
1. An air to open (ATO) valve on loss of air will:
Answer: Close. ATO means fail close.
2. Cv is defined as flow of water in:
Answer: US gpm at 1 psi drop. Kv uses m³/h at 1 bar.
3. Cv and Kv are related by:
Answer: Cv = 1.156 Kv. Cv = 1.156 × Kv.
4. An equal percentage characteristic is often chosen for:
Answer: Systems where valve ΔP falls as flow rises. Equal % compensates for falling ΔP in most process systems.
5. Seat leakage class VI is often described as:
Answer: Bubble tight. Class VI is defined in bubbles per minute.
6. Valve stiction typically causes:
Answer: Constant amplitude limit cycling. Stick slip motion makes the loop cycle.
7. Proportional band 50 % corresponds to a gain of:
Answer: 2. Gain = 100 ÷ PB = 2.
8. Increasing integral time Ti makes the integral action:
Answer: Weaker. Integral action ∝ 1 ÷ Ti.
9. Ziegler–Nichols closed loop PID gain is:
Answer: 0.6 Ku. Kc = 0.6 Ku, Ti = Pu ÷ 2, Td = Pu ÷ 8.
10. Derivative action is usually avoided on:
Answer: Noisy flow loops. Derivative amplifies noise.
11. A reverse acting controller output:
Answer: Falls when PV rises. Reverse action: output decreases as PV increases.
12. Cavitation in a control valve occurs when:
Answer: Pressure at the vena contracta drops below vapour pressure and recovers. Vapour bubbles form and collapse, damaging trim.
13. A positioner is mainly used to:
Answer: Accurately position the valve against friction and forces. It compares the signal with actual travel and corrects it.
14. Lambda tuning lets you choose:
Answer: The closed loop time constant. λ is the desired closed loop time constant.
15. A control valve should typically be sized to be about ___ open at maximum flow.
Answer: 70 to 85 %. This leaves control margin.
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About this Quiz
15 multiple choice questions on control valve and pid, 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
- Close: ATO means fail close.
- US gpm at 1 psi drop: Kv uses m³/h at 1 bar.
- Cv = 1.156 Kv: Cv = 1.156 × Kv.
- Systems where valve ΔP falls as flow rises: Equal % compensates for falling ΔP in most process systems.
- Bubble tight: Class VI is defined in bubbles per minute.
- Constant amplitude limit cycling: Stick slip motion makes the loop cycle.
- 2: Gain = 100 ÷ PB = 2.
- Weaker: Integral action ∝ 1 ÷ Ti.
- 0.6 Ku: Kc = 0.6 Ku, Ti = Pu ÷ 2, Td = Pu ÷ 8.
- Noisy flow loops: Derivative amplifies noise.
- Falls when PV rises: Reverse action: output decreases as PV increases.
- Pressure at the vena contracta drops below vapour pressure and recovers: Vapour bubbles form and collapse, damaging trim.
- Accurately position the valve against friction and forces: It compares the signal with actual travel and corrects it.
- The closed loop time constant: λ is the desired closed loop time constant.
- 70 to 85 %: This leaves control margin.
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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