Blue discoloration, heat spots, or rainbow patterns on a brake wheel or disc typically indicate overheating. This can result from excessive braking energy, high stops/hour, incorrect brake sizing, or—very commonly—brake dragging due to insufficient release. Overheating can change the surface metallurgy, reduce friction stability, and accelerate lining wear. It may also introduce warping or runout that causes vibration and uneven braking.
On overhead and gantry cranes, heat damage is a serious warning sign because it can lead to brake fade during emergencies and reduced holding torque. Investigate root causes: verify clearances, thruster stroke or coil voltage, linkage freedom, and control timing with VFDs. Also review duty cycle versus brake thermal rating.
Depending on severity, resurfacing or replacement may be required. If cracks, severe scoring, or distortion are present, replacement is typically the safest option for critical hoisting applications.