3. Flashlights

3.1 Design principles

A welding flashlight must be able to stabilize a flame at the tip of its nozzle, preventing internal flashbacks. In addition, the operator must be able to vary the heat output to suit the various jobs to be carried out.

When fuel and oxidizer are brought together, combustion tends to spread, including inside the flashlight, hence the importance of the previous term: "flame stabilization".

It is certainly possible to mix oxidizer and fuel only on the outside of the flashlight, thanks to two separate, converging outlets. This has been done for large heating flashlights (sheet metal forming). These are remarkably safe, but their thermal efficiency remains mediocre. For welding, therefore, it is necessary to premix before...