On overhead and gantry cranes, electro-hydraulic thrusters are often used to release drum (block) brakes against spring force. If the thruster leaks oil or runs at a low oil level, it may not generate the required thrust or full stroke, which means the brake may not fully release. The most common result is brake dragging, causing heat buildup, rapid lining wear, and reduced travel/hoist efficiency.
Low oil also reduces internal lubrication and accelerates pump and seal wear, making the problem progressively worse. In hoisting, partial release can create harsh starts, unstable motion, and increased load swing risk; in travel mechanisms, it can trigger VFD overcurrent alarms or motor overheating. Treat leakage as a safety issue: identify the leak source, restore proper oil level and specification, verify stroke and clearance, and perform a controlled functional test to confirm the crane brake releases and applies reliably.