Question 200Motor Plants - 1st Asst/Chief

The correct answer is C) close all manually operated fuel valves. Before any work is carried out on a burner in an automatically fired auxiliary boiler, the most important safety precaution is to close all manually operated fuel valves. This ensures that the fuel supply to the burner is isolated, preventing any unintentional ignition or combustion during the maintenance or repair work. Closing the fuel valves is a critical step to make the boiler safe for personnel to work on the burner. The other options, while potentially useful, are not the most important safety step. Blocking control system relays or locking safety interlock switches may be necessary, but closing the fuel valves is the primary action to eliminate the risk of fuel-fed fires or explosions. Allowing the boiler to cool completely is also important, but should be done in addition to isolating the fuel supply.