Detailed explanation of the safety protection device of electric hoist

Detailed explanation of the safety protection device of Electric Hoist

In today's industrial field, electric hoists, as an efficient lifting equipment, are widely used in various production and logistics links. For international wholesale buyers, it is very important to understand the safety protection device of electric hoists, which is not only related to the normal operation and service life of the equipment, but also directly affects the personal safety of operators and the production efficiency of enterprises. This article will explore the various safety protection devices of electric hoists in depth to provide you with a comprehensive reference when purchasing and using electric hoists.

1. Overview of electric hoists
Electric hoists are a light and small lifting equipment, mainly composed of motors, transmission mechanisms, drums or sprockets, etc. It has the characteristics of small size, light weight, easy operation, high efficiency, etc. It can lift and lower vertically and move heavy objects horizontally. It is suitable for material handling and loading and unloading in factories, warehouses, logistics centers and other places.

2. Safety protection device of electric hoist
(I) Limit protection device
Rising limiter: When the hook of the electric hoist rises to the predetermined limit position, the rising limiter will trigger the limit switch, cut off the power supply, and stop the electric hoist from rising, preventing the hook from rising too much and causing the wire rope to break or be damaged, and at the same time preventing the electric hoist drum from over-winding the wire rope and causing equipment failure. Usually, the rising limiter is installed on the drum bracket, and the limit switch is triggered by a transmission device such as a collision block or wire rope.
Descent limiter: The function of the descending limiter is opposite to that of the rising limiter. When the hook drops to the lowest limit position, the descending limiter will trigger the limit switch and cut off the descending power supply to prevent the hook from falling too much and causing the heavy object to touch the ground or hit other objects, causing unnecessary damage or safety accidents. In some electric hoists, the descending limiter can also prevent the wire rope from being too loose on the drum, ensuring the orderly winding of the wire rope.
Fire-off limiter: As the last electrical defense line of the electric hoist, the fire-off limiter drives the impact block to open the fire-off limiter through the rope guide, thereby disconnecting the power supply of the motor to ensure that the equipment will not be damaged. In actual operation, the fire-off limiter should be avoided from frequent action. Usually, a limit switch is installed at its lower level, and the distance between the two is appropriately adjusted.
(II) Overload protection device
Mechanical overload protector: Using mechanical principles such as springs or levers, when the load of the electric hoist exceeds the rated lifting weight, the overload protector will detect this overload state and cut off the power supply of the motor through the mechanical transmission device, so that the electric hoist stops working, thereby effectively protecting the equipment from damage caused by overload and avoiding failure of the lifting mechanism of the electric hoist or causing safety accidents.
Electronic overload protector: Using electronic sensors and other technologies to monitor the load weight of the electric hoist in real time, once the load exceeds the rated value, the electronic control system will immediately send a signal to cut off the power supply of the motor to achieve overload protection. Electronic overload protectors have the advantages of high precision, quick response, and easy integration with other electrical control systems. They can more accurately judge overload conditions and take corresponding protective measures in a timely manner.
(III) Braking device
Electromagnetic brake: Electromagnetic brake is a commonly used braking device. Its working principle is that when the power supply of the electric hoist is cut off, the electromagnetic brake will take effect immediately. The brake will hold the motor shaft tightly through electromagnetic force, so that the hook will stop moving quickly, preventing the heavy object from continuing to slide or swing due to inertia, ensuring the safety of lifting. Electromagnetic brakes have the characteristics of rapid braking, reliability, and easy maintenance. They can provide effective braking protection for electric hoists under various working conditions.
Safety clutch: The safety clutch is an overload protection clutch. When the load of the electric hoist exceeds the set value, the safety clutch will automatically slip or disengage, interrupting the power transmission between the motor and the lifting mechanism, thereby preventing the electric hoist from being damaged due to overload, and also protecting the transmission parts such as wire ropes or chains from excessive stretching or wear. The safety clutch is usually installed between the lifting mechanism and the motor of the electric hoist to achieve overload protection by limiting the torque.
(IV) Electrical protection device
Phase protection relay: The phase protection relay is mainly used to prevent the motor power supply of the electric hoist from being connected incorrectly, so as to avoid motor reversal, burning or other faults caused by phase errors. When the phase of the power supply is abnormal, the phase protection relay will detect it in time and cut off the power supply of the motor to ensure the normal operation of the electric hoist and the safety of the motor.
Reverse phase protection device: Similar to the phase protection relay, the reverse phase protection device can automatically control the circuit when the power supply is connected incorrectly to protect the motor from burning, avoid motor damage caused by improper human operation, and improve the electrical safety of the electric hoist.
Short circuit protection device: Generally, fuses, automatic air switches and other equipment are installed on the main power supply circuit of the electric hoist to provide short circuit protection for the main power supply circuit. When a short circuit fault occurs in the circuit, the short circuit protection device will quickly cut off the power supply to prevent the current caused by the short circuit from increasing sharply and damaging the electrical equipment, or even causing serious accidents such as fire, so as to ensure the safe and reliable operation of the electrical system of the electric hoist.
Zero position protection device: In order to prevent accidents caused by the driver's power supply vehicle suddenly starting when the controllers of various mechanisms are not placed in the zero position, zero position protection is set on each controller of the crane. Only when the controller is in the zero position can the electric hoist start normally, otherwise the power cannot be connected, effectively avoiding safety hazards caused by misoperation.
(V) Other safety protection devices
Hook and fuse: The hook is usually forged with high-tensile steel and heat-treated to meet the requirements of strength and hardness, and can withstand large loads. At the same time, the hook is equipped with a fuse to ensure safety during take-off and landing, and prevent the heavy objects on the hook from accidentally falling off and causing safety accidents. During use, the wear, deformation and integrity of the hook and the fuse should be checked regularly, and damaged parts should be replaced in time to ensure the safety and reliability of the hook.
Rope guide: The function of the rope guide is to guide the wire rope to be wound around the drum in an orderly manner, prevent the wire rope from being tangled and jumping on the drum, and ensure the normal operation of the wire rope and the stable operation of the electric hoist. The rope guide is usually installed on one side of the drum and rotates synchronously with the drum. During the lifting and lowering process of the wire rope, the rope guide will continuously adjust the position of the wire rope so that it is evenly wound on the drum. At the same time, when the rope guide is used in conjunction with the lifting limiter, it can also play a reliable limiting role. When the hook rises or falls to the limit position, the rope guide will trigger the limit switch, cut off the power supply, and protect the safety of equipment and personnel.
Emergency stop switch: The emergency stop switch is generally installed on the operating handle or control panel of the electric hoist. It is a red mushroom-shaped button that is easy for the operator to touch. In an emergency, the operator can quickly press the emergency stop switch to cut off the power supply of the electric hoist, so that the equipment stops running immediately to avoid the expansion of the accident. The design of the emergency stop switch conforms to the principles of ergonomics, is easy to operate, sensitive and reliable, and has a self-locking function. It will not automatically reset after being pressed, and needs to be manually rotated to recover, ensuring that it can play an effective role in an emergency.
Explosion-proof device (for explosion-proof electric hoist): Explosion-proof electric hoist is mainly used in dangerous environments, and its explosion-proof device includes explosion-proof shell, explosion-proof electrical components and anti-static device. The explosion-proof shell is made of special materials and has explosion-proof ability, which can prevent the spark inside the electric hoist from igniting the surrounding flammable gas or gas mixture. Explosion-proof electrical components such as explosion-proof buttons and explosion-proof switches ensure that electrical components will not become the source of explosion in dangerous environments. Anti-static devices are used to prevent the accumulation and discharge of static electricity and reduce the risk of sparks, thereby ensuring the safety of explosion-proof electric hoists in dangerous environments.

3. The importance and maintenance of safety protection devices
(I) Importance
Ensure personnel safety: Electric hoists are often used to lift heavy objects in industrial production. If there is a lack of effective safety protection devices or the devices fail, once a malfunction or improper operation occurs, it may cause serious accidents such as heavy objects falling and collisions, posing a great threat to the life safety of operators and other on-site personnel. Safety protection devices can play a role at critical moments, cut off the power supply in time or take corresponding protective measures to avoid injuries to personnel.
Protect equipment safety: Electric hoists are relatively expensive equipment, and their normal operation is crucial to the production of enterprises. Safety protection devices can prevent electric hoists from damaging key components such as motors, reducers, drums, and wire ropes due to overload, short circuit, phase error, etc., extend the service life of the equipment, reduce equipment maintenance costs and downtime, and improve the production efficiency and economic benefits of the enterprise.
Ensure production continuity: In modern industrial production, the continuity of production has a direct impact on the economic benefits and market competitiveness of the enterprise. The safety protection device of the electric hoist can effectively prevent equipment failures and accidents, ensure the smooth progress of the production process, avoid production interruptions caused by equipment problems, and ensure that the enterprise completes production tasks on time and meets market demand.
(II) Maintenance and maintenance
Regularly check the limiter: Check the sensitivity and reliability of the limiter to ensure that it can accurately cut off the power supply when the hook reaches the limit position. At the same time, clean the dust, oil and other impurities on the limiter to prevent the normal operation of the limiter from being affected by debris. Regularly adjust the position of the limiter to match it with the limit position of the hook to ensure the effectiveness of the limit protection.
Maintenance of overload protection device: Regularly calibrate the overload protection device to ensure that the set lifting weight is accurate, that the overload can be detected in time and that corresponding protective measures are taken. Check whether the sensors and transmission components of the overload protection device are normal. If damaged, they should be replaced in time. Regularly clean up the debris around the overload protection device to maintain its good working environment.
Maintenance of brake device: Regularly check the braking performance of the electromagnetic brake, including parameters such as braking torque and braking clearance, to ensure that the brake can quickly and reliably brake the hook. Check and replace the friction pads, springs and other wearing parts of the brake to ensure the normal operation of the brake. At the same time, clean the oil and dust on the brake to prevent affecting the braking effect.
Check electrical protection device: Regularly check and test electrical protection devices such as phase protection relays, reverse phase protection devices, and short-circuit protection devices to ensure that they can work properly. Check the contact and aging of electrical components, and repair or replace them in time if there is any problem. Regularly clean up the dust and debris in the electrical control box, keep the electrical system clean and dry, and prevent electrical failures due to moisture, dust and other reasons.
Maintenance of other devices: Regularly check the wear and deformation of the hook, and replace the damaged hook or fuse in time. Check the wear and lubrication of the rope guide to ensure that it can flexibly guide the wire rope to be wound around the drum. Perform a functional test on the emergency stop switch to ensure that it can reliably cut off the power supply in an emergency. For the explosion-proof device of the explosion-proof electric hoist, it is necessary to strictly abide by the maintenance regulations of the explosion-proof equipment, and regularly check the integrity and reliability of the explosion-proof housing, electrical components and anti-static devices to ensure its explosion-proof performance.

4. Case analysis
Case 1: When a factory used an electric hoist to lift materials, due to the negligence of the operator, the hook rose above the limit position, but due to the normal operation of the rising limiter, the power supply was cut off in time, avoiding the accident of wire rope breakage and heavy objects falling. This incident highlights the important role of the rising limiter in the safe operation of the electric hoist. If the limiter fails or is not installed correctly, the consequences will be disastrous.
Case 2: When a company was using an electric hoist, the power phase was connected incorrectly, causing the motor to reverse. However, the phase protection relay was activated in time to cut off the power supply and protect the motor from damage. This shows that electrical protection devices play a key role in preventing failures and accidents caused by power problems. Regular inspection and maintenance of electrical protection devices are essential to ensure the safe operation of electric hoists.

5. Conclusion
The safety protection device of the electric hoist is an important guarantee to ensure its safe operation and plays an indispensable role in industrial production and logistics handling. For international wholesale buyers, in-depth understanding of the various safety protection devices of electric hoists will not only help to choose suitable products during the procurement process, but also provide guidance for the correct use and maintenance of equipment, thereby improving the production efficiency and economic benefits of the enterprise and reducing safety risks. In practical applications, we should pay full attention to the role of these safety protection devices, strictly operate and maintain them in accordance with the operating procedures and maintenance requirements, and ensure the safe and reliable operation of the electric hoist.