Ajax TOCCO Magnethermic supplied four induction heating systems to a global on-site heat-treating and bolting services provider. The systems are designed to thermally expand the large, heavy hex nuts and hollow bolt studs used to assemble large gas turbines. A 5-kW induction system was provided to thermally heat the large, heavy hex nut for the purpose of breaking the corrosive bonds between the nuts and the bolts. A technician is able to heat the 100-mm (4-inch) hex nut to 175°C (347°F) in less than one minute, allowing for its removal with a standard pneumatic impact gun instead of a large hydraulic wrench. The reduced torque greatly increases operator safety and increases tool life.
In addition, a 35-kW induction system is used to thermally stretch the large, hollow bolt studs. A technician is able to heat a 1,300 mm x 108 mm x 90 kg (51 inch x 4.25 inch x 200 pound) tensioning stud to 175°C (347°F) in 100 seconds, providing 1 mm of linear growth to the bolt stud and allowing for easy removal of the nuts on each end of the tensioning stud. The air-cooled design of the induction power supply greatly reduced the water cooling requirements on the job site.
The TOCCOtron AC has a solid-state inverter design, which provides significantly improved efficiency and reliability over the old SCR/thyristor-based induction heaters previously used in this application.