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MILLER INTELLIFIRE® 250 INDUCTION HEATING SYSTEMS
* Also improves weld quality compared to flame or resistance heating
APPLETON, Wis., June 14, 2005. Compared to alternative heating methods, Miller Electric Mfg. Co.'s unique Intellifire® 250 Induction Heating Systems reduce cost and improve quality in preheating and post-weld heat treatment applications. Miller offers two systems, an air-cooled system for preheating to temperatures up to 400º F (204º C) and a water-cooled system for preheating and post-weld heat treatment at temperatures up to 1450º F (788º C).
An air-cooled induction preheating system operates simply by: connecting a special induction heating blanket to the power supply; securing the blanket on or around the material to be welded; selecting the desired temperature on the control module; and energizing the system. Once the metal reaches the desired temperature, the system maintains the selected temperature throughout the welding process. For post-weld heat treatment, special liquid-cooled induction heating cables are used instead of blankets, and system heats and/or cools the material at a precisely controlled schedule.
With induction technology, the power source induces a rapidly alternating current (10 to 50kHz) in the blanket or cable, creating an electromagnetic field in the metal. This electromagnetic field generates eddy currents within the metal that raise the energy level of the metal molecules, causing the metal to heat.
Rapid Payback
On the Trans-Alaska Pipeline System, Alyeska Pipeline Service Company used the Intellifire 250 preheat system to reduce welding time on 48-inch repair sleeves (girth welds) to just four hours. Previously, joining one end of an encirclement sleeve to the underlying 48-inch diameter pipe took 8 to 12 hours, plus an additional 12 to 18 hours of welding for a STOPPLE fitting.
On P91 pipe for power plants, a Wisconsin fabricator used the Intellifire 250 post-weld heat treating system to reduce welding cycle time and, in turn, cut lead times by more than 50 percent to improve competitiveness.
Preheating, typically to 400 to 550 degrees Fahrenheit, drives off moisture and thereby reduces the hydrogen content of the metal. Hydrogen embrittlement can lead to cold cracking of the finished weld. For this same reason, maintaining interpass temperatures (the temperature between welding passes) and a hydrogen bakeout (post weld heat treatment) of the finished weld are also required by various codes. Depending on the application, codes that apply include ASME B31.1 Power Piping, ASME B31.3 Chemical Plant and Petroleum Refinery Piping and ASME Section I Power Boiler Parts.
"Before, during and after welding, induction technology uniformly controls heats to improve consistency, repeatability and quality while reducing rework," says Mike Roth, marketing manager, Miller Electric Mfg. Co. "In fact, Intellifire improves cycle times so much that many customers experience a payback measured in months, not years." In addition, induction heating minimizes burn risk because it does not have the open flame hazard of propane or the hot ceramic pads of resistance heating.
Power Supply
The Intellifire 250 provides 25kW of output power and operates on 460V, three phase power. A 20kW system, the Intellifire 204, is also available; it operates on 400V three-phase power. Both air-cooled system weighs 165 lbs., and both liquid-cooled system weighs 355 lbs. Accessories enable adapting these systems to a wide variety of pipe diameters and joint configurations.
Heating times vary depending on material thickness and ambient temperatures. To help calculate cycle time(and potential savings(Miller offers interactive calculators for pipe and plate applications. These tools are available at MillerWelds.com; look under Products, then the Induction Technology category.
The Intellifire is covered by Miller's True-Blue® one-year warranty. For more information about the Induction Heating System, visit MillerWelds.com, call 1-800-4-A-MILLER (800-426-4553), fax 877-327-8132, or write to Miller Electric Mfg. Co., P.O. Box 100, Lithonia, GA 30058.
Headquartered in Appleton, Wis., Miller is a leading worldwide manufacturer of arc welding equipment and related systems for metalworking, construction, maintenance and other applications. Miller Electric Mfg. Co. is a wholly-owned subsidiary of Illinois Tool Works Inc. (ITW), Glenview, Ill. ITW is a diversified multinational manufacturer of highly-engineered components, assemblies and systems.
