Preheating Fuels:

Preheating fuels carry out a particular function. Understanding of the function shall help in appropriate selection of the fuel. In this topic preheating fuel functions and their individual characteristics are described.

In the cutting operation functions of the preheat flames are the following as:

• Enhance the temperature of the steel to the ignition point,
• Add heat energy to the work to maintain the cutting reaction,
• Give a protective shield among the cutting oxygen stream & the atmosphere, and
• Dislodge through the upper surface of the steel any scale, rust, paint, or other foreign substance that would retard or stop the normal forward progress of the cutting action.

A preheat intensity that go up the steel to the ignition temperature quickly will usually be adequate to maintain cutting action at high travel speeds. Although, the quality of the cut shall not be the best. High quality cutting might be carried out at considerably lower preheat intensities than those normally needed for rapid heating. On larger cutting machines, dual range gas controls are provided that bound high-intensity preheating to the starting operation. After that the preheat flames are decreased to lower intensity throughout the cutting operation, to save fuel and oxygen and provide a better-cut surface.

A number of commercially available fuel gases are utilized with oxygen to provide the preheating flames. Generally Fuel gases are selected due to availability and cost. Combustion intensity or specific flame output for several fuel gases is another significant consideration in fuel gas selection.