Flame adjustment is a critical factor in the operation of an oxyfuel torch. The amount of heat produced by the flame depends on the intensity and type of flame used. Three types of flame, carburizing, neutral, and oxidizing, can be achieved by adjusting the torch valves. See Figure A- 1.
A carburizing flame with acetylene, MPS, or propylene is indicated by trailing feathers on the primary flame cone, or by long, rounded primary flame cone. A carburizing flame is often used to produce a smooth weld finish, and also for stack cutting thin material.
A neutral flame with acetylene, MPS, or propylene is indicated by a sharply defined, dark primary flame cone and a pale blue secondary flame envelope. Propane and propylene base fuels and natural gas have a short, sharply defined cone. This flame is obtained by adding oxygen to a carburizing flame. It is the flame most frequently used for cutting.
An oxidizing flame for acetylene or MPS has a light colored primary cone and a smaller secondary flame shroud. It generally bums with a harsh whistling sound. With propane and propylene base fuels and natural gas, the primary flame cones are longer, less sharply defined, and have a lighter color. An oxidizing flame is obtained by adding some oxygen to the neutral flame. This type of flame is frequently used for fast, low- quality cutting, and selectively in piercing and beveling.