By: Curt Wilsoncroft, national specialist for Arcair, a Thermadyne brand
The exothermic process, which has been around for many years, is a process that releases energy in the form of heat.
When used in cutting, the exothermic process uses oxygen as an exciter, thus the steel rod becomes the fuel. As long as the oxygen flow is maintained through the torch and rod, the rod will continue to burn and consume at a temperature between 8,000-10,000°F.
Exothermic cutting is a technology which allows cutting, piercing and gouging on almost any ferrous or non-ferrous material including steel, iron, aluminum and magnesium. Some torches, such as the SLICE torch, can virtually cut anything placed in front of it, such as copper, brass, concrete and brick.
Used predominately for plant maintenance, building renovation or demolition, scrap cleanup and salvage work, exothermic cutting removes edges on loaders for repair or replacement, and even burns through mud or rust-covered machinery frames.
One of the biggest applications for exothermic cutting is pin removal on heavy equipment. When a pin in heavy machinery will not budge, it must either be cut or have a hole burned through the center for removal. When piercing a hole right through the middle of the pin, the metal from the pin is physically removed, so the pin will actually shrink allowing for easy removal once cooled.
Another application that is becoming more popular is Fire and Rescue. Since the exothermic cutting process has come a long way, many manufacturers now sell packs that come complete with a torch, power supply and oxygen cylinder case, which can all be worn as a backpack or carried by handles, making it practical and easy-to-use. This allows firefighters and rescue teams to be able to access anything that is in front of them.
While many may understand the basics of exothermic cutting strategies, real professionals must know how to operate and perform with this technology. To help educate the industry, below are some helpful tips on how to get the most out of your cutting equipment.
Tips for cutting
While cutting procedures will vary from job to job, normal cutting is done by using a drag technique, where once the rod is in contact with the piece to be cut, the professional drags the rod in the direction of the cut. The following are useful tips for a perfect cutting experience:
• Maintain proper travel speed at all times.
• The speed of the cut is too fast if the operator can’t see the kerf and metal is being blown back at the operator.
• Always keep in mind, cutting rods consume as long as the oxygen is flowing.
• If the operator does not keep the rod in contact with the work piece as the rod is consuming, the rod is being used without cutting.
• Use a sawing motion when material to be cut is thicker than 1-1/2″ to 2″ to ensure a complete melt through the material.
• Be sure to use a smooth motion to complete the cut.
• After completing the cut, release the oxygen control lever in the handle.
Note: The cutting rod will continue to burn as long as oxygen is supplied, so be sure to hold the torch safely away from your body until the rod cools.
Tips for piercing surfaces
Special procedures must be used when piercing to promote safety for the end user and a high-quality finish on the product. When piercing, use a collet extension, which adds life to the torch, and hand shield to greatly improve operator safety and comfort. Be sure to hold the torch at arm’s length and wear plenty of protective clothing, eye and ear protection. If possible, remove the cutting rod from the hole before releasing the oxygen lever to help prevent the cutting rod from getting stuck inside the pierced hole.
To pierce solids follow these steps:
• Strike the cutting rod on striker.
• Hold the torch at arm’s length.
• Keep the cutting rod at a 90° angle (perpendicular) to the pierce point.
• Slowly push the cutting rod in at the pierce point until you’re at proper depth or until you’ve achieved burn through.
Oxygen usage
Another crucial aspect of exothermic cutting is oxygen usage. The cutting process uses standard industrial grade oxygen to support the exothermic reaction and to remove the molten metal. All SLICE equipment uses standard oxygen fittings. The most commonly recommended operating pressure is 80 pounds per square inch (psi). Applications such as cutting material sections 3″ and thicker might require higher operating pressures. Operating pressures as low as 40 psi have been used to perform operations such as washing off rivet heads and scarfing out small cracks for repair.
The oxygen consumption rate for cutting rods at 80 psi is 7 to 7.5 cubic feet per minute (cfm) for the 1/4″ diameter cutting rods and 11 to 12 cfm for the 3/8″ diameter cutting rods. These rates, will of course vary if a different operating pressure is used.
Even the best techniques for exothermic cutting equipment will change from job to job. Please be aware, as in any applications, some adjustments in operating conditions may be necessary in order to ensure you get the most of your cutting equipment and achieve optimal safety requirements.
