What function does the safety shutoff device serve in main propulsion boilers?

The safety shutoff device in main propulsion boilers is critical for ensuring the safe operation of the burner system. Its primary function is to prevent oil spillage when the atomizer assembly is removed from the burner while the burner root valve is still open. This prevents hazardous conditions that could arise from the uncontrolled release of fuel oil, which could lead to fire hazards or environmental contamination. By ensuring that the flow of oil is safely interrupted when maintenance or adjustments are being made, the safety shutoff device enhances the overall safety of the system, protecting both personnel and equipment.

The other choices refer to functions that, while important in managing a boiler system, do not accurately represent the direct role of the safety shutoff device specifically.