Furnace explosions can best be avoided by which action?

Avoiding furnace explosions primarily hinges on eliminating unburned fuel that may accumulate when a flame is interrupted. Purging the furnace after any flame interruption serves to remove residual fuel and potentially explosive gas mixtures from the combustion chamber. This action is crucial because if unburned fuel remains and a flame is reestablished, an explosive reaction can occur.

The purge process typically involves introducing a flow of air or an inert gas to clear out these dangerous accumulations before reigniting the furnace. This proactive measure significantly reduces the risk of an explosive condition forming, thereby enhancing safety in furnace operations.

Other actions, while important for overall safety and efficiency, do not directly address the immediate risk posed by unburned fuel. Increasing the fuel flow rate could exacerbate the situation by introducing more fuel than can be safely combusted. Reducing the air supply may lead to incomplete combustion, also increasing the risk of unburned fuel. Lastly, scheduling routine maintenance is vital for long-term reliability, but it does not provide an immediate solution to the risks associated with flame interruptions.