Hard- Surfacing, Building Fusion Welding Carbon Welding Non-Ferrous Metals Heating & Heat Treating Braze Welding Welding Cast Iron Welding Ferrous Metals Brazing & Soldering Equipment Set-Up Operation Equipment For OXY-Acet Structure of Steel Mechanical Properties of Metals Oxygen & Acetylene OXY-Acet Flame Physical Properties of Metals How Steels Are Classified Expansion & Contraction Prep For Welding OXY-Acet Welding & Cutting Safety Practices Manual Cutting Oxygen Cutting By Machine Appendices Testing & Inspecting
10 A torch that has backfired can be relighted at once. It may even relight itself, if the flow of gas is directed against molten or hot metal. If a torch backfires repeatedly, however, without evident contact with the work, the cause should be investigated. Backfiring may be due to use of improper operating pressures, or to a loose tip or nozzle in the torch, or to dirt on the cutting nozzle seats. If the flame goes out and burns back within the torch, which usually produces a pronounced hissing or squealing noise, immediately shut off the torch. This is termed a ”flashback” and is always a sign that there is something wrong with the torch or with your operation of it. After a flashback, always allow the torch to cool before attempting to relight it. Always check your operating pressures before attempting to relight it. Further, before relighting, allow oxygen (NOT acetylene) to flow through the torch for several seconds to help clear out soot which may have accumulated within the torch. Then relight, following the usual procedure. If what appears to be normal flame, or flames, is produced, proceed with your work, but be prepared to shut the torch off instantly if the flame goes out and that characteristic flashback sound is heard again. If there is a second flashback, remove the torch from service and return it to an approved repair station for check and necessary repair. Fig 6-8. Always use a friction lighter when lighting a torch Be ready to adjust the torch acetylene valve immediately after flame is lit.