unit 8

1. A solenoid valve is an electro-mechanical device that, when energized or de-energized, performs which function?

• Measures fluid pressure
• Shuts off or allows fluid flow
• Increases fluid temperature
• Compresses instrument air

2. When an electric current energizes the coil of a solenoid, what is produced?

• A magnetic field
• High-pressure air
• A chemical reaction
• A loud alarm

3. In a de-energized solenoid valve as shown in Figure 2A, what component pushes the valve stem down to keep the valve closed?

• The core (armature)
• The spring
• The electric leads
• The inlet port

4. According to the P&ID in Figure 3, what does "AO/AFC" stand for?

• Actuator Open / Actuator Fails Closed
• Air Open / Air Fails Close
• Automatic Open / Automatic Fails Close
• Always Open / Always Fails Close

5. In the emergency trip circuit (Figure 3), what happens to the solenoid valve ZV-010 when the temperature switch TS-010 trips at 100∘C?

• It energizes
• It de-energizes
• It throttles to 50%
• It sends a signal to the controller

6. When the 3-way solenoid valve ZV-010 de-energizes, it closes the air supply (P) and opens which port to vent the actuator?

• Port A (Actuator)
• Port P (Pressure)
• Port E (Exhaust)
• Port D (Drain)

7. In the circuit shown in Figure 5, what component is energized when the Level Switch LS1 is closed?

• The 110 Vdc power supply
• Relay R1
• Solenoid Valve ZV-1
• The 12 Vdc battery

8. In Figure 5, what action directly causes the solenoid valve ZV-1 to energize?

• The level switch LS-1 opening
• The 12 Vdc supply turning on
• The relay contacts R1-1 closing
• The pressure exhausting from port E

9. What is the condition of the solenoid valve coil during the normal operation of the ESD system shown in Figure 3?

• De-energized
• Normally closed
• Energized
• Bypassed

10. Relays and solenoids are often used together in which type of systems?

• Process control loops
• Alarm and ESD systems
• Power distribution units
• Data acquisition systems