During the maintenance of large gas turbines, technicians must remove large bolts which have become corroded and difficult to unfasten. Typically a large cumbersome hydraulic wrench is required to provide the 6800 Nm (5000 ft-lbs) of torque required to break the corrosive bonds between the 100 mm heavy hex nuts and bolts.
To improve the productivity of this process, Ajax TOCCO Magnethermic has supplied (4) four induction heating systems to a global on-site heat treating and bolting services provider, designed to thermally expand the large heavy hex nuts and hollow bolt studs used to assemble these large gas turbines.
A 5 kW TOCCOtron AC 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. Using the TOCCOtron system the technician is able to heat the 100 mm heavy hex nut to 175° C in less than (1) one minute, allowing the technician to remove the hex nut with a standard pneumatic impact gun, instead of the large hydraulic wrench. The reduced torque greatly increases operator safety and increases tool life.
A 35 kW TOCCOtron AC induction system is used to thermally stretch the large hollow bolt studs. Using the new 35 kW system, the technician is able to heat a 1300 mm x 108 mm x 90 kg tensioning stud to 175° C in just (100) one hundred seconds, providing 1 mm of linear growth to the bolt stud, allowing for easy removal of the nuts on each end of the tensioning stud.
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. The air-cooled design of the induction power supply greatly reduced the water cooling requirements on the job site. In addition, the 35 kW TOCCOtron AC carries both CSA and CE certifications and utilizes a one-world voltage standard allowing it to be powered from a 380-600 Vac 50/60 Hz input.
Reduced size, weight, and shorter heat times were all factors in this customer’s decision to purchase induction heating products from Ajax TOCCO Magnethermic. Due to the immediate success experienced with this equipment, the on-site services provider has been able to secure several long term contracts, and sees additional opportunity to expand the use of these products into other industrial service markets such as re-tubing boilers, and the shrink fitting of large valves, bearings and other similar items found in the power generation and petrochemical industries.
Ajax TOCCO Magnethermic®, a subsidiary of Park-Ohio Holdings Corporation®, designs and manufactures worldclass induction heating and melting equipment for various industries and applications throughout the world. In addition, ATM provides a range of services including laboratory process development, preventive maintenance, equipment repair and parts, coil repair facilities, and installation services. E-mail: firstname.lastname@example.org