Question 32 UFIV01 - Chief Engineer - UFIV

The Correct Answer is C ### Why Option C is Correct: The primary and most critical function of a flame safeguard system (also known as a combustion control or burner management system) is **safety during the ignition and firing process**. Fuel (gas, oil, or pulverized coal) requires a very specific ratio with air to burn safely. If fuel is pumped into a hot furnace without successful ignition (a "flame failure" or "failure to ignite"), or if the air/fuel mixture is incorrect, the unburned fuel accumulates. Once the concentration of fuel reaches the explosive range (the flammability limits) and an ignition source is introduced (or reignition occurs), a catastrophic furnace **explosion** will result. The flame safeguard system constantly monitors for: 1. **A stable, proven pilot flame.** 2. **A stable, proven main flame.** 3. **Proper purge cycles** (to ensure any accumulated gases are swept out before ignition is attempted). 4. **Correct timing and sequence of ignition steps.** If any step fails, or if the flame is lost during operation, the system immediately shuts off the fuel supply (trips the boiler), specifically to prevent the accumulation of unburned fuel and the resulting explosion. ### Why Other Options Are Incorrect: **A) accidental dry firing and overpressure:** * **Dry firing** (low-water condition) is prevented by the low-water cutoff (LWCO) system, which is entirely separate from the flame safeguard system. * **Overpressure** is prevented by the pressure control system and the safety relief valves. **B) uncontrolled fires in the furnace:** * This statement is too general. While preventing an uncontrolled fire is part of general safety, the specific hazard the flame safeguard system manages is the rapid, devastating event caused by delayed ignition or accumulated fuel vapor (an explosion), not just a fire that is difficult to extinguish. Once a stable flame is established, the flame safeguard manages stability, but the main goal of the entire sequence control is preventing the explosive event. **D) overheating of the pressure parts:** * Overheating is primarily prevented by maintaining the proper water level (preventing dry firing) and controlling the firing rate/pressure, which is the function of the main operating limit controls and the low-water cutoff system, not the flame safeguard system.