What are the signs of a neutral flame during oxyfuel cutting?

A neutral flame is characterized by a defined combustion process that indicates the proper mixture of oxygen and acetylene. The presence of a bright, well-defined inner cone accompanied by a light blue outer envelope is indicative of an optimal flame condition for oxyfuel cutting.

In a neutral flame, the inner cone is at its brightest and sharpest, ensuring complete combustion of the gases. This type of flame is ideal for cutting metals as it provides high temperatures without excessive oxidation or carburizing effects, resulting in cleaner cuts. The light blue color of the outer envelope indicates an adequate amount of oxygen mixed with acetylene, ensuring that the fuel is being used efficiently.

The other described flames do not demonstrate the neutral flame characteristics. For instance, a flickering flame with yellow tips suggests incomplete combustion and typically signifies a carburizing flame. A noisy flame with excessive soot indicates an unbalanced mixture leaning towards excess fuel, while an orange flame with a long outer envelope likewise suggests a carburizing flame, which is not suitable for cutting applications. Thus, the bright, well-defined inner cone with a light blue outer envelope distinctly represents a neutral flame.