November 2022 Volume 4

EQUIPMENT & TECHNOLOGY

Five Industrial Challenges Solved with Induction Heating By Jeff Weinacker

Inductionheatinghas been around ever sinceNicolaTesla discovered and harnessed the phenomena. His industrial applications made much of the modern world we know today possible. So, what exactly is induction heating? For most applications it is the use of an alternating magnetic field on an electrically conductive part. The magnetic field pushes and pulls electrons within the material. The energy used to do this is dissipated as heat within the part. When properly controlled through coil design and current control, this can produce precise, repeatable, and predictable results. This can be seen in modern induction stoves in many kitchens around the world. These stoves require a special pot with a bottom that can accept the magnetic field. Precise current control through an engineered coil provides even controllable heat with a nearly infinite temperature control. In the forging world we typically utilize this technology as a solution to heat billets, or Peter Campbell at Campbell Press may use a potable induction heater to loosen large bolts while disassembling a large press; but did you know that induction heating has solved many other industrial challenges as well?

over time and must be replaced. Within an industrial application these headers my be 3” or thicker and 48” in diameter with 1000’s of 2” diameter holes where the tubes are inserted and then rolled and expanded into the holes. In the past, skilled technicians used cutting torches to slice the tube and then beat it out with chisels. Many times this resulted in damage to the tube sheet that required welding and machining prior to fitting and rolling in new tubes. The solution: Use a specially designed portable induction machine with a specially designed internal coil. This heats the tube rapidly where it is rolled into the tube sheet. The tube reaches 2500F (Approximately 1370C) within 30-90 seconds. This rapid heating causes the tube to attempt to expand but, since it is constrained by the tube sheet and is heated to a malleable temperature, the tube shrinks. At the same time a hydraulic puller can be used to pull the hot tube out while it is still hot. #2 High Temperature Testing/Thermal Cycling The issue: High temperature testing can be difficult as normal resistance heating methods are limited by the melting point of the heater elements. The higher the temperature the more difficult this is to achieve. The solution: Induction, when engineered correctly, does not have any top temperature limit. One example where an induction machine and an engineered coil, test cycles can easily be run to 4000F (2204C) where the only limitation is the support of the part

or material being subjected to these high temperatures. These tests were done to evaluate high emissivity coatings and catalysts that normally run at excessively high temperatures.

#1 Removal of Worn-Out Boiler Tubes From a Tube Sheet The issue: In large industrial boilers as found in many power plants, water is fed in to a large header then up through small tubes to another header where the heater water or steam is gathered and sent to be used other places in the power plant. These tubes degrade

FIA MAGAZINE | NOVEMBER 2022 14