What is the primary function of the flame sensor in a flame scanner?

The primary function of the flame sensor in a flame scanner is to prove both the pilot and the main flame are lit. This critical safety feature ensures that combustion is occurring as intended within the furnace or boiler system. If either flame goes out, the flame scanner detects this absence and can initiate a safety mechanism, such as shutting down the fuel supply to prevent unsafe conditions like an explosion or the release of unburned fuel into the environment.

By verifying the presence of both flames, the scanner helps maintain safe and efficient operation in steam generating systems. This functionality is essential for ensuring that high-energy processes are continuously monitored for safety and performance. The other options, while related to the overall operation of a combustion system, do not typically represent the specific role of a flame scanner. Fuel flow regulation, temperature monitoring, and air supply control are primarily handled by other components within the system, and while interconnected, they do not pertain specifically to the function of proving flame presence.