Which safety feature is crucial in detecting flame presence in a boiler system?

The flame detection cell is a vital safety feature in a boiler system because it is specifically designed to monitor the presence of a flame. If a flame goes out unexpectedly or fails to ignite, the flame detection cell detects this change and can initiate safety protocols, such as shutting down the fuel supply or triggering an alarm. This helps prevent dangerous situations, such as the buildup of unburned fuel, which could lead to explosions or other hazardous conditions.

In contrast, other options like the temperature gauge, pressure relief valve, and water level indicator serve different purposes. The temperature gauge monitors the temperature of the water or steam in the boiler, while the pressure relief valve is a safety mechanism that prevents dangerous overpressure conditions by releasing excess pressure. The water level indicator ensures that there is an adequate water level in the boiler to prevent overheating and damage. While these components are important for safe operation, they do not specifically detect flame presence, which is why the flame detection cell is the most crucial feature in this context.