In this fourth article of the series, I discuss the exothermic torch, or thermal lance. An exothermic torch cuts ferrous and nonferrous metals, including stainless steel and heavily rusted, painted, and concreted encrusted metal, using pressurized oxygen and a metal rod/tube to create a high-temperature flame.
The operator ignites the tip of the rod by sparking it against a 12-VDC battery striker plate as the oxygen flows through the rod, creating a class D fire at 10,000°F as long as the oxygen flows by depressing the trigger on the torch handle. It is not a precise tool. This torch takes less training than the other torches. Developed originally for demolition and machinery repair work, it now comes in backpack/tactical versions for special operations teams.
Exothermic reaction is defined as a chemical reaction resulting in a release of energy—in this case, heat and light, just like other torches. This torch consists of a long steel tube packed with alloy steel rods, sometimes mixed with aluminum rods to increase the heat output. One end of the tube is placed in a handle, and oxygen is fed through the tube. Some exothermic torches even operate underwater.
Do not burn the rod completely down to the handle. This will result in damage to the interior parts. Leave a few inches of rod, then switch out. Personal protective equipment (PPE) includes a shade 10 lens required, burn jacket, helmet/shield, and gloves.
Do not use petroleum products around pure oxygen because concentrated levels of oxygen can lower the ignition/flammable level of the petroleum, potentially causing a fire.
The torch is lit by arcing the rod while flowing oxygen with a battery. This electrical spark requires a surge of at least 100 amps to ignite the rod. If the battery has not been properly charged, it will not have enough amperage to ignite the cutting rod.
To accomplish this, the operator drags the alloy rod (connected to one pole of the battery) across a metal plate connected to the other pole of the battery, igniting the rod by causing a series of short circuits creating hot sparks. This ignites the rod and starts the exothermic reaction. The metal plate collecting the slag from igniting rods can cause poor electrical connections, which means it needs to be cleaned or replaced. The rod begins burning back immediately, losing length. Battery life is short also because of the short circuiting of the cells when igniting the rod. Therefore, you must be in position to cut as soon as the rod lights and keep pushing it against the object to be cut. There is now a system that uses two regular 9-volt batteries to ignite a redesigned rod, eliminating the large 12-VDC battery.
Slicing and piercing are the two most common techniques used with this type of torch. An intense ball of burning metal is produced at the rod end and can be used to cut rapidly through thick materials. The rod is quickly consumed. Once the rod is burned short, the operator lets off the oxygen trigger, discards the remaining stub, and installs a new one.
Most problems are with the battery having enough charge to ignite the rods. The only viable alternative is to keep extra batteries or get another torch. There is no tip to clean.
Before using this type of torch, visually inspect the following for damage:
- Torch.
- Striker plate.
- Electric cable.
- Oxygen supply hose.
- Electrical and gas fittings/connections (should be tight).
- Battery.
TIPS FOR EXOTHERMIC CUTTING
Exothermic cutting procedures vary based on the job. The standard process for exothermic cutting is done by a push technique. Hold the rod at a 45-to 80-degree angle to the work piece. Always maintain a proper travel speed. The speed of the cut tends to get too fast when the kerf is not visible to t