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Before machining the wheels of rolling stock, the bearing inner rings (types NU and NUP) and the labyrinth rings must be dismantled. It is essential that these rings be removed without any mechanical or thermal damage to the parts so that they can be reused after the machining process. (A bearing inner ring is used as a raceway to provide a hardened and precisely machined surface for the rolling element, and a labyrinth ring is used to protect bearings from contamination and leakage.)

This can be safely achieved by induction heating. By sliding a medium-frequency induction coil over the installed inner ring or the labyrinth ring and connecting it to a medium-frequency generator (TM Induction model EHX-03A), the ring can be heated uniformly while the shaft is mounted to remain cool. The localized induction heating causes the ring to expand slightly, allowing it to be removed easily without force or damage. Because heating is confined to the ring, the shaft and adjacent components remain unaffected.

The induction coil assembly is lightweight and ergonomically designed, making it easy to handle during field or workshop operations. To perform this procedure, the EHX-03A generator is used in combination with one or more fixed inductors that are custom-built for the specific component geometry being heated. This ensures efficient energy transfer, controlled temperature rise, and repeatable, damage-free ring removal.

The alternatives to induction heating (pulling the rings off hydraulically by brute force) damages the rings, rendering them unsuitable for reuse and resulting in much higher repair expense.

Advantages (Compared to Traditional Methods)

• Lower repair cost: Save existing inner and labyrinth rings for reuse.
• Fast, Safe, and Controlled Operation: Focused induction heating enables rapid, even and precise temperature rise while maintaining full operational safety.
• High Energy Density and Efficiency: Concentrated heat application ensures minimal energy loss, providing an energy-efficient and environmentally friendly process.
• Customizable Solutions: Heating coils are specifically designed for individual components such as inner rings and labyrinth rings, ensuring optimal performance.
• Lightweight and Mobile System: The compact generator design allows for easy transport and use in various fields or workshop environments.
• Low Power Consumption, High Efficiency: Advanced induction technology minimizes electrical demand while maximizing thermal efficiency.
• Controlled Heating Process: Continuous temperature monitoring prevents overheating or component damage,

Watch the Mid Frequency Induction Heating video from TM Induction Heating for a demonstration of the bearing inner rings and labyrinth bearing being removed.

When Induction Heating Goes Wrong! Understanding the Importance of Bearing Clearance and ID vs OD Temperature