What device helps secure the fuel and purges the furnace during a flame failure?

The device that assists in securing the fuel supply and purging the furnace during a flame failure is a programmer. This component plays a crucial role in the burner management system, which ensures safe operation by controlling the sequence of operations within the boiler system.

When a flame failure occurs, the programmer is responsible for shutting off the fuel supply to prevent any unburned fuel from accumulating, which could create a hazardous condition. Additionally, it manages the purging process to clear out any residual fuel and combustion gases from the furnace before reigniting. This is essential for ensuring safety and preventing explosions within the boiler system.

Other options, while integral to boiler operation, do not specifically operate in tandem with the functions of securing fuel and purging the furnace during flame failure as effectively as a programmer does. The ignition system may be responsible for lighting the burner but does not manage the fuel flow during a failure. Safety valves are designed for pressure relief, and vacuum gauges monitor pressure conditions, but neither directly handles flame failure situations as the programmer does.