A dragging brake creates continuous friction during motion, causing heat and rapid wear. Typical symptoms include unusually hot brake housings or brake wheels/discs, burning smell, reduced travel speed, higher motor current, frequent VFD overcurrent alarms, and accelerated lining wear. You may also hear rubbing noise or feel reduced smoothness during trolley or bridge travel. On hoists, dragging can cause poor lifting performance and can contribute to brake fade during emergency stopping.
Common root causes include incorrect air gap/clearance, insufficient release force (low voltage, weak hydraulic pressure, air supply issues), seized pins/bushings, misalignment, or mechanical interference. In electro-hydraulic systems, thruster stroke issues or leakage can prevent full release.
Fixes start with lockout and measurement: confirm correct clearances, verify release pressure/voltage, check thruster stroke, and inspect mechanical joints for corrosion or binding. Dragging is a safety issue because it can lead to overheating and unpredictable torque—address it promptly.