What must never be adjusted during a white smoke condition on an operating boiler?

In a white smoke condition on an operating boiler, the primary concern is typically an indication of incomplete combustion, often due to an excess of fuel oil or insufficient air supply. White smoke can suggest that unburnt fuel is being expelled, which can lead to safety hazards and efficiency issues.

Adjusting the fuel oil header pressure in this scenario can exacerbate the existing problem by potentially increasing the amount of fuel entering the combustion chamber. This could worsen incomplete combustion, leading to further production of white smoke and the risk of fire, explosion, or damage to the boiler. Maintaining a stable fuel oil header pressure is essential to ensure safe operation and to allow for proper evaluation and correction of the combustion process without introducing additional hazards.

In contrast, while other parameters like air lock pressure, blowdown settings, and steam temperature may also be important, they do not pose the same immediate risk of worsening the combustion condition as adjusting fuel oil header pressure does during a white smoke situation. Therefore, it's critical to avoid any adjustments to the fuel oil header pressure until the root cause of the white smoke is identified and rectified.