Acetylene:

Acetylene is broadly used as a fuel gas for oxygen cutting and also for welding. Its chief reward is high flame temperature, availability and widespread familiarity of users with its flame characteristics. Combustion of acetylene with oxygen generated a hot, short flame with a bright inner cone at each preheat port. The hottest point is at the ending of this inner cone. Combustion is completed in the long outer flame.

Based on the ratio of acetylene and oxygen, the flame might to be adjusted to decreasing (carburising), neutral, or oxidising, as illustrated in Figure 3. The neutral flame, attained with a ratio of about one part oxygen to one part acetylene, is utilized for manual cutting. As the oxygen flow is reduced, a bright streamer begins to appear. This shows a reducing flame, which is sometimes utilized to rough-cut cast iron.

While excess oxygen is supplied, the inner flame cone shortens & becomes more intense. The flame temperature enhance to a maximum at an oxygen-to-acetylene ratio of approximate 1.5 to 1. An oxidising flame is utilized for short preheating times and for cutting very thick sections.

The heat transfer characteristics and high flame temperature of the oxyacetylene flame are specifically important for bevel cutting. Acetylene in the Free State must not be used at pressures higher than 103 kPa gage, or 207 kPa absolute pressures. At higher pressures, it might decompose with explosive force while exposed to heat or shock.