The safety of stage electric hoists is mainly achieved through the following various technologies and design methods: Mechanical Safety Design - **Dual - brake System**: Usually equipped with a main brake and an auxiliary brake. The main brake is generally a normally - closed brake. When the electric hoist stops running, it will automatically hold the brake wheel to prevent heavy objects from sliding down. The auxiliary brake serves as a backup. When the main brake fails, the auxiliary brake can be activated in a timely manner to further ensure safety. For example, the auxiliary brakes of some high - end stage electric hoists adopt centrifugal brake devices, which can quickly trigger braking when the motor speed rises abnormally. - **Overload Protection Device**: An overload protection sensor is installed. When the hoisted weight exceeds the rated load of the electric hoist, the sensor will detect it and send a signal to stop the operation of the electric hoist, avoiding equipment damage or safety accidents caused by overloading. Commonly, there is a pressure - sensor - type overload protection device, which judges whether there is an overload by detecting the stress of the wire rope or chain. - **Limit Position Protection**: Upper and lower limit position switches are set. When the hook of the electric hoist rises or falls to the set limit position, the limit switch will be triggered, cutting off the motor power to prevent the hook from exceeding the safe range and avoiding collisions with other objects or breakage of the wire rope and chain. - **Safety Hook**: It is made of high - strength materials, with sufficient strength and toughness to withstand unexpected overload impacts. And the hook is usually designed with an anti - detachment device, such as a spring buckle or a locking piece, to prevent the lifted object from slipping out of the hook during the lifting process. Electrical Safety Design - **Motor Overheat Protection**: A temperature sensor is installed inside the motor. When the motor operating temperature is too high, the temperature sensor will detect it and cut off the motor power to prevent the motor from burning out due to overheating, and also avoid potential safety hazards caused by motor failures. - **Leakage Protection**: A leakage protector is equipped. Once a leakage phenomenon in the electrical system is detected, it will quickly cut off the power to protect the safety of operators and surrounding people. Generally, the leakage protector will cut off the circuit within a very short time (such as 0.1 seconds) when the leakage current reaches about 30 milliamps. - **Electrical Interlock**: Interlock protection between various components is achieved through the electrical control circuit. For example, the electric hoist can only start running when all safety devices are in normal working conditions; during the operation, if a certain safety device activates, the electric hoist will stop immediately. Materials and Manufacturing Processes - **High - strength Materials**: The key components of the electric hoist, such as chains, wire ropes, gears, drive shafts, etc., are all made of high - strength metal materials. Through strict heat treatment and processing techniques, their strength, wear resistance, and fatigue resistance are improved to ensure that they can reliably bear heavy loads during long - term use. - **Quality Inspection**: During the manufacturing process, strict quality inspection standards are implemented. A comprehensive quality inspection is carried out on each component, including inspections of dimensional accuracy, surface quality, mechanical properties, etc. After the complete machine is assembled, various tests such as no - load, load, and overload tests are also carried out to ensure that the performance indicators of the electric hoist meet safety requirements. Control Systems and Operating Specifications - **Intelligent Control System**: Some advanced stage electric hoists are equipped with an intelligent control system, which can monitor the operating status of the electric hoist in real - time, such as speed, position, load, and other information, and conduct data analysis and processing. When an abnormal situation is detected, the system will automatically take corresponding safety measures, such as decelerating, stopping, etc.

- **Operation Training and Specifications**: Provide professional training for operators to make them familiar with the operation methods, safety precautions, and emergency handling measures of the electric hoist. Strict operating specifications and management systems are formulated, requiring operators to operate in accordance with the specifications, and illegal operations are strictly prohibited.

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