First responders can slice through 3/4-in. thick carbon steel at 22 in./min. to get through steel doors, dead bolts, barred windows.

The heat of the exothermic reaction burns, melts, or vaporizes most materials giving rescue teams fast entry during emergencies.

Rescue teams and policemen chasing bad guys have no patience with locks, doors, walls and other obstacles. In films the good guys often are shown using rams, axes or shoulders to gain access. In real life, to speed access and save muscle, many FBI, FEMA, CIA, Navy, fire and paramedic crews strike an arc for fast entry. Their preferred cutting process is exothermic because its fast and requires no external power source to maintain.

Just as emergency crews want cutting speed and portability, fabrication shops and steel erection companies prefer the oxygen lance cutting process — that dates back to 1888 — for the speed and portability needed when cutting, piercing or beveling steel and to remove pins, rivets and bolts.

During an emergency, a SWAT team member uses a torch to slice through steel doors, dead bolts, barred windows and overhead doors and through debris of metal, reinforced concrete, plaster or rock from a collapsed building. To bring medical aid, a paramedic can cut through 3/4-in. thick carbon steel at 22 in./min., or 1/4-in. thick stainless steel at 36 in./min. — even underwater.

His portable exothermic equipment kit contains steel rods, torch, battery and oxygen bottle. The torch has a hand shield for protection from heat and sparks, a battery for rod ignition and an oxygen-control lever.

Slice and dice
At the obstacle, the operator grabs the pistol-grip, 7 lb. torch, locks in an 18-in. long consumable steel rod, either 1/4- or 3/8-in. diameter, then connects one terminal of the 12-V rechargeable battery to the rod, and a copper striker plate to the other battery terminal. Using the oxygen-control lever on the torch, he starts the oxygen flow through the hollow rod from the 40-ft. ³ oxygen bottle. Drawing the rod across the copper plate at a 45° angle creates sparks that ignite the rod. Ignition breaks the electrical path.

The exothermic process can cut without power, using the heat of the reaction only, or with power, using an electrical arc from a welding power source to provide more heat and faster cutting. The burning makes excess heat (exo-thermic). The heat of the exothermic reaction burns, melts, or vaporizes most materials.

To cut, the operator places the burning rod tip at the target area with slight contact between the tip of the rod and the work piece. This contact tells the operator that the most intense heat from the rod is focused on the workpiece, ensuring the best cutting speeds.

The usual operating pressure is 80 psi of industrial oxygen. Cutting 3 in. and thicker material might require higher operating pressures to blow away molten material at the bottom of the cut, to create the kerf or cut line.

Typical oxygen consumption rate for cutting rods at 80 psi is 7 to 7.5 cfm for 1/4-in. diameter cutting rods and 12 to 13 cfm for 3/8-in. dia. rods. A rescue worker can burn 8 to 10 rods with a 40-ft. ³ oxygen bottle, giving him 5 to 7 min. of cutting time. A rod burns as long as oxygen flows through it.

Protective clothing for operators includes tinted goggles or face shields with filter lens, and flame resistant gloves and jackets. The American National Standard "Safety in Welding and Cutting" safety standards (Z49.1) offers further details.

Thermadyne Industries Inc. has provided funding for Problem Solved case studies, with an intent to support instruction and solutions about hard-to-solve issues. This article was independently reported by Welding Design & Fabrication, and was not subject to prior review or approval by the sponsor.