A recession of the flame into or back of the mixing chamber of the oxyfuel gas torch or flame spraying gun.

In this situation, the flame disappears from the end of the tip and the gases burn within the torch or beyond, in the hose, usually with a shrill, hissing sound. This indicates something seriously wrong with the equipment or the method of operation. One or both gases should be shut off immediately to stop combustion within the torch before it is damaged by heat. The torch should be allowed to cool before relighting. If the flashback reaches the hose, that section should be discarded, as it has almost certainly been damaged by the heat. Flashback arresters are available to prevent these potentially dangerous incidents.

For causes of flashback, see BACKFIRE, FLAME PROPAGATION RATE and PRE-IGNITION. For prevention, see FLASHBACK ARRESTER.

 

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