Before firing a boiler, which step must be done first?

Before firing a boiler, the prepurge step is essential and must be conducted first. Prepurging involves clearing the combustion chamber of any flammable gas or vapor that may have accumulated. This step is crucial for safety and efficiency, as it helps to prevent any potential explosions or backdrafts that could occur if the system were to ignite without first ensuring that any residual fuel has been removed from the combustion area.

Executing the prepurge ensures that the air-fuel mixture is properly adjusted and that the combustion environment is safe before any ignition source is activated. By purging the system, operators can verify that there are optimal conditions for combustion, which promotes complete and efficient burning of the fuel once the firing sequence continues with igniting the pilot and ultimately proving the flame afterward.