Question 40 QMED01 - Junior Engineer

The Correct Answer is B **Explanation for Option B (Correct):** The primary reason that idle (or pilot) burners on a boiler must be checked regularly to ensure they do not drip is related to safety and the prevention of catastrophic ignition events. If an idle burner drips fuel (e.g., oil or gas condensate) into the furnace while the main burner is off, that fuel vaporizes and mixes with air, forming an explosive mixture within the confined space of the furnace. When an attempt is made to ignite the main burner, or if a nearby heat source ignites the accumulated fuel vapor, the result can be a rapid and violent combustion event known as a **boiler flareback** (or furnace explosion/purge-failure explosion). This event poses a significant risk to equipment and personnel. Checking for drips ensures that no unburned fuel accumulates in the furnace when the burner is supposedly inactive. **Explanation for Other Options (Incorrect):** * **A) To prevent slag formation on the furnace floor:** Slag formation usually results from impurities (ash) in the fuel combusting at high temperatures and melting onto heat transfer surfaces. While dripping fuel might leave residues, this is not the primary mechanism for the dangerous slag buildup that plagues large utility boilers, nor is it the main reason for the strict drip checks. The primary concern is safety. * **C) To prevent excessive fuel consumption:** While a dripping burner does technically waste fuel, the quantity is usually negligible compared to the fuel used by the main burner, and certainly not the primary reason for mandatory safety checks. The safety risk (Option B) far outweighs the economic consideration. * **D) To prevent excessive soot buildup on boiler tubes:** Soot (unburned carbon) is typically formed when the main burner operates with incomplete combustion (a lack of proper air-to-fuel ratio). A small drip of fuel from an idle burner would not cause the widespread, excessive soot buildup that results from poor operation of the main firing system. The primary concern remains the accumulation of explosive fuel vapor.