Question 64 AEL01 - Assistant Engineer - Limited

The Correct Answer is C. **Explanation for Option C (Explosions in the boiler furnace):** The primary function of a flame safeguard (or burner management) system is rooted in safety against catastrophic events related to combustion. During the startup, operation, or shutdown phases of an automatic boiler, if fuel is introduced into the furnace without a stable, adequate ignition source (or if the flame extinguishes during operation, known as a 'flameout'), the fuel-air mixture can accumulate. If this highly volatile mixture reaches its explosive limit and is subsequently ignited by a delayed spark, hot refractory, or reignition attempts, a devastating furnace explosion (or 'furnace puff') will occur. The flame safeguard system constantly monitors the presence and stability of the main burner flame and controls the sequence of purging, ignition, and fuel valve operation. If the flame is lost or fails to establish correctly, the system immediately shuts off the fuel supply, purges the combustion chamber, and locks out the system, thereby preventing the accumulation of unburned fuel and the subsequent explosion. **Why other options are incorrect:** * **A) Accidental dry firing and overpressure:** While critical safety functions, dry firing (low water condition) is primarily prevented by low water cutoffs (LWCOs) and feedwater controls, and overpressure is prevented by pressure relief valves and high-pressure cutoffs. These are separate, albeit interconnected, safety systems from the flame safeguard. * **B) Uncontrolled fires in the furnace:** This phrasing is too vague. While the flame safeguard system manages the introduction of fuel and supports controlled firing, its specific, mandated purpose is preventing the *explosion* that occurs when unburned fuel accumulates, not merely preventing general "uncontrolled fires." * **D) Overheating of the pressure parts:** Overheating of pressure parts is typically caused by low water (dry firing) or poor circulation, leading to mechanical failure. This condition is primarily addressed by LWCOs and operational controls, not the flame safeguard system, which focuses specifically on combustion safety.