What is a crucial safety check before allowing main fuel valves to open during ignition?

Proper flame signal detection is essential before opening the main fuel valves during ignition because it ensures that the combustion process will be stable and safe. A flame signal indicates that the burner is lit and that the system is operating as intended. If the flame signal is inadequate or nonexistent, opening the main gas valves could lead to an accumulation of unburned gas, significantly increasing the risk of an explosion or fire.

This check is fundamental for preventing incidents that could arise from combustion failures or improper fuel ignition, which could not only endanger equipment but also pose serious safety hazards to personnel nearby. Thus, confirming that the flame signal is present and strong can confirm that the ignition system is functioning correctly and safely before any further actions are taken related to fuel flow.