Overhead Crane Accidents: 6 Lifting Device Failures and Solutions

Overhead cranes are commonly used in the industry, and their operational safety is of paramount importance. To reduce the rate of overhead crane accidents, this paper analyzes six types of accidents related to the lifting device: hook toppling and falling, hook collision and falling, wire rope dislodging, gantry beam unhooking, improper use of lifting equipment, and safety hazards during wire rope replacement. For each type of overhead crane accident, preventive measures are proposed with the aim of enhancing the safety of the lifting device and ensuring safe operations.

1. Hook Toppling and Falling

Common overhead crane accidents involving hook toppling and falling include: the main hook of the crane hitting the top limit, breaking the wire rope, and the hook falling; improper operation by the operator, failure of the height limit switch, and failure to check it in time; during lifting operations, the operator fails to reset the control lever promptly. If the operation is interrupted or a power failure occurs, and the equipment is powered back on, the auxiliary hook may rise directly, causing a toppling accident.

Accident Cause Analysis

• Equipment Operating with Faults: The height limit switch is one of the critical safety measures. Maintenance personnel failed to detect that the height limit switch had malfunctioned, causing the crane to operate with a safety hazard.
• Improper Operation by the Operator: During lifting, after the main hook reaches the required position, the operator failed to reset the control lever in time. If the operation is interrupted or power is lost, and the equipment is powered back on, the кручок continues to move, leading to a hook toppling accident.
• Inadequate Management System: The management and maintenance department failed to establish a regular equipment safety inspection system. As a result, the malfunction of the height limit switch was not detected in time, especially in the case of vulnerable parts like the overrun areas of the limit switch, which were not checked or addressed.

Countermeasures to Prevent Hook Toppling and Falling

• Strengthen Equipment Inspections and Maintenance: As a special type of equipment, overhead cranes require increased inspection frequencies for critical safety features and protective devices. Any malfunctioning safety devices should be repaired or replaced promptly to reduce the risk of hook toppling accidents.
• Enhance the Safety Function of Electrical Control Circuits: In this case, the failure to reset the control lever in time was a significant cause of the accident. Therefore, efforts should be made to improve the safety features of the electrical control system. A zero-position protection function can be added to the control panel so that after operation is interrupted or power is lost, the equipment will only function when the control lever is in the zero position upon power restoration.
• Increase Safety Margins: To reduce the likelihood of accidents, the safety margins for various safety devices should be increased. For example, if the reliability of a single limit switch is R=0.9, using two limit switches in parallel can increase the combined reliability to R=0.99, significantly lowering the chance of an accident. The combined reliability R is calculated as R* = 1 – (1 – R)² = 0.99.
• Enhance Operator Training: As overhead cranes are classified as special equipment, operators should be properly trained and certified before they are allowed to operate the equipment. Unqualified personnel should be prohibited from operating the cranes. Regular training sessions should be organized to ensure that operators are continuously updated on safety practices and operational skills.

2. Overhead Crane Accidents of Hook Falling

Common overhead crane accidents involving hook falling include: failure to maintain a safe distance between the main hook and the auxiliary hook during crane operations, unqualified operators conducting lifting operations without proper certification, performing lifting tasks in unsafe conditions, and failure of safety managers to intervene in time. These can result in the collision of two hooks, causing the wire rope to slip out of the sheave and the hook to fall.

Analysis of Causes for Hook Falling Accidents

• Operator Failure to Follow Operating Procedures: The operator, without preparing a lifting plan, performed lifting operations without following the equipment operating procedures, leading to the accident.
• Equipment Safety Design Issues: During normal lifting operations, the hook guard is designed to prevent the hook from falling if the wire rope slips out of the sheave. However, if the guard’s gap is too wide or positioned improperly, it will fail to prevent the hook from falling.

Countermeasures to Prevent Hook Falling

• Strengthen Operator Safety Awareness: As overhead cranes are classified as special equipment, failure to follow operating procedures can lead to significant safety hazards. Therefore, it is essential to enhance the safety awareness of operators and ensure they understand that safety is paramount.
• Enhance Safety Education and Training for On-site Management Personnel: On-site safety managers play a critical role in lifting operations. They must promptly intervene when operators fail to follow safety protocols. Strengthening the safety education and training for on-site management personnel ensures accountability and fosters a culture of vigilance. It will help them realize that consistent attention to safety is essential for ensuring secure lifting operations.
• Strict Enforcement of Certification Requirements: Strengthen lifting operation management by strictly implementing the certification requirement system. Only operators who have obtained the necessary certifications should be allowed to perform lifting operations. Those without proper certification should be prohibited from operating the equipment.

3. Wire Rope Dislodging Accidents

Common overhead crane accidents involving wire rope dislodging include: damage to one side of the protective clip on the hook’s movable sheave assembly, causing the wire rope to dislodge during lifting operations, which results in the hook falling and causing injury.

Analysis of Causes for Wire Rope Dislodging Accidents

The sheave assembly is the primary component in overhead crane lifting operations. It is closely related to the lifting capacity of the sheave assembly and the maximum load that the wire rope can bear. If one side of the protective clip on the hook’s movable sheave assembly is damaged and not replaced during routine inspections, the wire rope may dislodge during the lifting process. The slack portion of the wire rope is then quickly dragged upwards, leading to an accident.

Countermeasures to Prevent Wire Rope Dislodging

Although the direct probability of personal injury from wire rope dislodging is relatively low, Heinrich’s 330 Accident Rule demonstrates that major accidents often occur as a result of repeated, smaller incidents that accumulate over time. Therefore, in daily lifting operations, if a wire rope dislodging issue occurs, it is crucial to arrange for timely repair, rectification, or cessation of use. Addressing these issues promptly in daily management can eliminate potential hazards in their early stages, preventing the risk of serious accidents.

4. Gantry Hook Unhooking Accidents

Common gantry hook unhooking accidents include: the main hook lacking a safety locking device, operator non-compliance with proper operating procedures during lifting, with the load not being in a safe position, and the on-site lifting supervisor lacking the necessary certification. During the lifting process, the lifting hook is not carefully monitored, causing the load to become unstable, leading to unhooking of the gantry beam from the lifting hook and tipping over.

Analysis of Causes for Gantry Hook Unhooking Accidents

• Crane Operating with Faults: Overhead cranes should be equipped with comprehensive safety devices to ensure the safety of personnel and equipment during lifting operations. However, if the crane’s main hook lacks a safety locking device, and there is no locking mechanism to prevent accidental unhooking of the lifting sling, this presents a significant safety hazard.
• Operator Failure to Follow Operating Procedures: The operator failed to adhere to the proper safety operating procedures. Specifically, the load was not placed in a safe position before stopping, causing the placement to become unstable and resulting in the gantry hook unhooking.
• On-site Supervisor Negligence: The on-site lifting supervisor failed to properly monitor the status of the lifting hook. This lack of attention resulted in improper placement of the load and instability during the lifting operation.
• Unqualified On-site Supervisor: The on-site lifting supervisor conducted the lifting operation without having obtained the necessary safety certification. This is a major safety risk, as unqualified supervision can lead to critical mistakes and accidents.

Countermeasures to Prevent Gantry Hook Unhooking

• Increase Equipment Inspections and Maintenance: The safe operating condition of equipment is the foundation for safe operations. Regular inspections should be arranged to ensure that all safety devices are functioning correctly, preventing the crane from operating with faults.
• Enhance Operator Training and Certification: Equipment operators should be trained and certified to ensure they are capable of adjusting the operation of the crane based on the status of the load being lifted. This will help ensure lifting operations are carried out safely.
• On-site Lifting Supervisors Should Be Certified: On-site lifting supervisors are a critical role, and their job involves significant safety risks. They should undergo safety training and pass a certification exam before being allowed to supervise lifting operations. This ensures they are adequately prepared to manage the risks associated with lifting tasks.

5. Improper Use of Lifting Devices Accidents

Common overhead crane accidents caused by improper use of lifting devices include: during the lifting of large objects, particularly steel plates, improper positioning of the lifting tools, failure to ensure that the load is evenly and securely positioned, leading to the load tilting and falling out of the lifting tool, resulting in a heavy object falling.

Analysis of Causes for Improper Use of Lifting Devices

• Failure to Secure the Load Properly: The operator fails to ensure the load is securely fastened before lifting, causing the load to tilt and fall out of the lifting tool during the process.
• Lack of Safety Training for Rigger Personnel: The rigger lacks proper safety technical training and is unfamiliar with the necessary safety measures, which increases the risk of improper handling of the lifting device.
• Failure to Use Specialized Lifting Tools: Generic or improper lifting tools or clamps were used instead of specialized lifting devices, leading to the load tilting during the lifting process.

Countermeasures to Prevent Improper Use of Lifting Devices

• Ensure Proper Securing of Large Loads: When lifting large loads, especially steel plates, it is critical to ensure that the load is securely fastened and balanced, with the center of gravity properly aligned to prevent tilting.
• Designate a Safe Lifting Area: A designated safety zone should be clearly marked during lifting operations, and no personnel should enter the hazardous lifting area during the process.
• Strengthen Daily Safety Education and Supervision: Both regular safety education and on-site supervision of the lifting process should be implemented to ensure adherence to safety protocols, ensuring a safe working environment for all involved.

6. Wire Rope Replacement Accidents

Common overhead crane accidents during wire rope replacement include: workers lacking experience, improper arrangement of the work area, such as having deep pits or debris on the ground, and failure to take appropriate safety precautions while replacing old wire ropes, resulting in falling accidents.

Analysis of Causes for Wire Rope Replacement Accidents

• Unreasonable Work Environment: During the replacement of the wire rope, the work environment below and around the workspace was not secured, creating a significant safety hazard.
• Inadequate Safety Measures for Workers: Workers carried out high-altitude tasks without using safety ropes or other protective measures, demonstrating a lack of safety awareness.

Countermeasures to Prevent Wire Rope Replacement Accidents

• Ensure a Safe Working Environment: Wire ropes on cranes are prone to wear and tear. When replacing lifting mechanism wire ropes, it is essential to ensure the work area below and around the operation space is free from hazards, such as deep pits or obstacles, to minimize safety risks.
• Enhance Safety Measures Awareness and Training: Many accidents occur due to carelessness or lack of attention. Before replacing the wire rope, a comprehensive emergency plan should be prepared, and technical briefings and safety training should be conducted. Safety checks should include ensuring the proper availability and use of protective equipment. Operators should be thoroughly trained to use safety gear and perform all necessary safety checks to prevent accidents due to negligence or lack of preparedness.

Заключэнне

As an indispensable key piece of equipment in industrial production, the operation and maintenance of падвесныя краны are directly linked to both personnel safety and operational efficiency. By analyzing common accident types and their causes, it becomes evident that many incidents stem from inadequate equipment inspections, non-compliance with operating procedures, and a lack of safety awareness. To prevent such accidents, companies must strengthen equipment management, improve safety systems, and enhance the skills and awareness of operators, fundamentally eliminating potential risks. Only by integrating safety principles into every operational step can we truly achieve both efficient equipment operation and the safe execution of lifting tasks.

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