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An exothermic torch works by feeding oxygen through a ¼-inch diameter carbon steel cutting rod that burns at over 10,000 degrees F. At this temperature, it has the ability to cut through mild steel that is three inches thick and makes quick work of rebar, coated steel, bridge decking, pipes, and highway guard rails. It will burn through common metals like aluminum, cast iron, stainless steel, magnesium and mineral aggregates, and concrete.
Current ignition methods include exposing the end of the cutting rod to an electric current, placing the end in a smoldering cardboard (punk) tube, or depositing a molten metallic product on the end of the rod. By feeding oxygen through the rod during ignition, the carbon steel begins to burn and the cutting operation can begin. However, the high current and smoldering punk tube ignition systems are either useless, unreliable or, at the very least, difficult to use in underwater environments. Currently available underwater ignition systems that produce a molten metallic product use a powdered energetic compound and a chemical catalyst that is separated from one another until the ignition is required. However, powdered energetic compounds are not reliable and have a limited shelf life.
Tools that do not work well underwater are not very useful in many Navy operations and to that point, scientists at the Naval Surface Warfare Center – Crane Division have developed a more appropriate ignitor. The Navy’s four chamber ignitor slides into the end of a torch rod. Chamber one is a firing pin that interfaces with chamber two containing a percussion primer material. The adjacent chamber three is filled with air forming a flash-through hole that sparks the fourth chamber containing a hollow slug of pyrotechnic material which, when burning, is converted to molten metallic reaction products. The slug is a composition of iron oxide, titanium, zirconium, and a rubber binder, which creates a non-toxic, low-gas product that ignites fast and has high thermal stability.
- The igniter requires no electrical input and is completely waterproof
- The pressed pyrotechnic material is reliable, easily ignited, non-toxic, forms little reaction gas, and produces substantial amounts of molten metallic reaction products required to start a torch rod's exothermic reaction
- When an electrically conductive material is used for the igniter's housing, the igniter is not susceptible to ignition by electrostatic discharge
- US patent 7,117,796 available for license