What typically causes oil fires in boilers to pulsate or flutter?

Pulsating or fluttering oil fires in boilers are primarily caused by pulsating oil-burner pressure. When the pressure of the oil being supplied to the burner fluctuates, it can lead to inconsistent fuel flow and combustion. This inconsistency creates an unstable flame, which can result in a pulsating appearance. The oil burner relies on a steady and constant pressure to ensure a smooth and even spray of fuel into the combustion chamber. If the pressure varies, it can cause the flame to flicker or flutter as the combustion process is disrupted.

The other factors listed do contribute to performance issues in a boiler but do so in different ways. Fluctuating water levels generally affect the boiler's efficiency and safety rather than the nature of the flame directly. Excessive soot buildup can lead to inefficient burning and heat transfer but is not specifically responsible for the flame's pulsation. Inadequate combustion air supply can also create inefficient burning conditions, leading to a weaker flame, but again, it is the oil-burner pressure that specifically causes the characteristic pulsating effects observed in the flame. Thus, understanding the role of oil-burner pressure is crucial for diagnosing and resolving these types of issues in boiler operation.