Case of accident caused by improper operation of crane hook
Improper operation is one of the main causes of crane hook accidents , which can damage equipment or cause casualties. The following are 6 typical accident cases, covering the causes, consequences and lessons, to provide warnings for safe operation.
Case 1: Overloading causes hook breakage
Accident
-
Location : A construction site
-
Operation : Workers use a 20t rated hook to lift a 28t steel beam (40% overload).
-
Result : The hook neck suddenly broke, the steel beam fell and smashed the pump truck below, and two people were seriously injured.
Cause Analysis
-
Direct cause : Overload exceeded the material yield limit (safety factor dropped from 4 to 2.3).
-
Indirect causes : The torque limiter was not installed and the signalman did not verify the weight.
lesson
✅ Overloading is strictly prohibited and the weight of the hoisted objects must be checked.
✅ Loads exceeding 10% require written approval from the engineer.
Case 2: Deformation of hook caused by oblique lifting
Accident
-
Location : Port Container Terminal
-
Operation : The driver did not align the lifting point and forcibly lifted the 40t container at an angle of 30°.
-
Result : The hook was subjected to force on one side, and the hook mouth was twisted and deformed (the width expanded from 50mm to 58mm).
Cause Analysis
-
Mechanical influence : actual load during inclined tension = vertical load/cosθ=46.2t (overload 15.5%).
-
Operational error : Failure to use the traction rope to adjust the position of the hanging object.
lesson
✅ The sling angle must be ≤60° (GB 6067.1).
✅ The rated load must be reduced by 20% when inclined.
Case 3: Failure to lock the anti-unhooking device caused the suspended object to fall
Accident
-
Location : Chemical plant equipment installation site
-
Operation : When lifting the reactor, the spring lock is not closed and it is locked by gravity alone.
-
Result : The slings slipped during lifting and the reactor fell from a height of 15m, causing a loss of RMB 2 million.
Cause Analysis
-
Device failure : The lock spring is rusted and does not close tightly.
-
Human negligence : Failure to implement the “double confirmation” system (operator + commander).
lesson
✅ Check the flexibility of the anti-unhooking device daily.
✅ The lock closing state must be manually tested before lifting.
Case 4: The hook rotated out of control and hit a person
Accident
-
Location : Wind turbine tower assembly site
-
Operation : The high-speed rotating hook was not braked in time, and the sling was entangled with the hook.
-
Result : The hook swung and hit one worker, killing him.
Cause Analysis
-
Operating error : Not using the low speed gear dedicated to the swivel hook.
-
Lack of training : Drivers are not familiar with the equipment operating manual.
lesson
✅ The rotating hook needs to limit the speed (≤2rpm).
✅ Physical isolation fences are set up in dangerous areas.
Case 5: Brittle fracture in low temperature environment
Accident
-
Location : A steel plant in Northeast China (-25°C)
-
Operation : Use ordinary carbon steel hook to lift 15t steel coil.
-
Result : The hook broke without warning and the steel coil smashed the track.
Cause Analysis
-
Material failure : The impact energy of Q235B hook at low temperature is only 14J (the standard requires ≥27J).
-
Wrong selection : Failure to use low-temperature steel (such as 34CrNiMo6).
lesson
✅ Low temperature toughness materials must be used below -20℃.
✅ -30℃ impact test is required before winter operation.
Case 6: Fatigue cracks not detected lead to accident
Accident
-
Location : Logistics Warehouse
-
Operation : Long-term and high-frequency use of the same hook (average of 200 cycles per day).
-
Result : After 3 years of use, fatigue cracks on the hook neck expanded and it broke when lifting 5t of cargo.
Cause Analysis
-
Detection of vulnerabilities : Only visual inspection was performed, and annual magnetic particle inspection was not carried out in accordance with GB 6067.1.
-
Life management : The number of times the hook was used was not recorded (far exceeding the design life of 10^6 times).
lesson
✅ Perform non-destructive testing every 6 months on frequently used hooks.
✅ Create an electronic record of the number of times the hooks are used.
Accident statistics and patterns
| Type of operation error | Proportion | Typical consequences |
|---|---|---|
| overload | 35% | Hook deformation/breakage |
| Slanted and crooked hanging | 25% | Hook wear and wire rope detachment |
| Anti-unhooking failure | 20% | Hanging object falls |
| Unchecked fatigue/corrosion | 15% | Sudden fracture |
| Misuse of low temperature | 5% | Brittle fracture |
Summary of preventive measures
-
Operation Specifications :
-
Overloading and oblique pulling are strictly prohibited, and "three confirmations" (weight, angle, and lock) must be made before lifting.
-
-
Technical means :
-
Install torque limiter and anti-sway system.
-
-
Management requirements :
-
The hook has a “one hook one file” record (number of times used, test report).
-
-
Training focus :
-
Conduct drills simulating extreme working conditions (such as strong winds and low temperatures).
-
Warning slogan :
"One illegal operation may end your life!"
- All accidents can be avoided through standardized operation!
Improper operation is one of the main causes of crane hook accidents , which can damage equipment or cause casualties. The following are 6 typical accident cases, covering the causes, consequences and lessons, to provide warnings for safe operation.
Case 1: Overloading causes hook breakage
Accident
-
Location : A construction site
-
Operation : Workers use a 20t rated hook to lift a 28t steel beam (40% overload).
-
Result : The hook neck suddenly broke, the steel beam fell and smashed the pump truck below, and two people were seriously injured.
Cause Analysis
-
Direct cause : Overload exceeded the material yield limit (safety factor dropped from 4 to 2.3).
-
Indirect causes : The torque limiter was not installed and the signalman did not verify the weight.
lesson
✅ Overloading is strictly prohibited and the weight of the hoisted objects must be checked.
✅ Loads exceeding 10% require written approval from the engineer.
Case 2: Deformation of hook caused by oblique lifting
Accident
-
Location : Port Container Terminal
-
Operation : The driver did not align the lifting point and forcibly lifted the 40t container at an angle of 30°.
-
Result : The hook was subjected to force on one side, and the hook mouth was twisted and deformed (the width expanded from 50mm to 58mm).
Cause Analysis
-
Mechanical influence : actual load during inclined tension = vertical load/cosθ=46.2t (overload 15.5%).
-
Operational error : Failure to use the traction rope to adjust the position of the hanging object.
lesson
✅ The sling angle must be ≤60° (GB 6067.1).
✅ The rated load must be reduced by 20% when inclined.
Case 3: Failure to lock the anti-unhooking device caused the suspended object to fall
Accident
-
Location : Chemical plant equipment installation site
-
Operation : When lifting the reactor, the spring lock is not closed and it is locked by gravity alone.
-
Result : The slings slipped during lifting and the reactor fell from a height of 15m, causing a loss of RMB 2 million.
Cause Analysis
-
Device failure : The lock spring is rusted and does not close tightly.
-
Human negligence : Failure to implement the “double confirmation” system (operator + commander).
lesson
✅ Check the flexibility of the anti-unhooking device daily.
✅ The lock closing state must be manually tested before lifting.
Case 4: The hook rotated out of control and hit a person
Accident
-
Location : Wind turbine tower assembly site
-
Operation : The high-speed rotating hook was not braked in time, and the sling was entangled with the hook.
-
Result : The hook swung and hit one worker, killing him.
Cause Analysis
-
Operating error : Not using the low speed gear dedicated to the swivel hook.
-
Lack of training : Drivers are not familiar with the equipment operating manual.
lesson
✅ The rotating hook needs to limit the speed (≤2rpm).
✅ Physical isolation fences are set up in dangerous areas.
Case 5: Brittle fracture in low temperature environment
Accident
-
Location : A steel plant in Northeast China (-25°C)
-
Operation : Use ordinary carbon steel hook to lift 15t steel coil.
-
Result : The hook broke without warning and the steel coil smashed the track.
Cause Analysis
-
Material failure : The impact energy of Q235B hook at low temperature is only 14J (the standard requires ≥27J).
-
Wrong selection : Failure to use low-temperature steel (such as 34CrNiMo6).
lesson
✅ Low temperature toughness materials must be used below -20℃.
✅ -30℃ impact test is required before winter operation.
Case 6: Fatigue cracks not detected lead to accident
Accident
-
Location : Logistics Warehouse
-
Operation : Long-term and high-frequency use of the same hook (average of 200 cycles per day).
-
Result : After 3 years of use, fatigue cracks on the hook neck expanded and it broke when lifting 5t of cargo.
Cause Analysis
-
Detection of vulnerabilities : Only visual inspection was performed, and annual magnetic particle inspection was not carried out in accordance with GB 6067.1.
-
Life management : The number of times the hook was used was not recorded (far exceeding the design life of 10^6 times).
lesson
✅ Perform non-destructive testing every 6 months on frequently used hooks.
✅ Create an electronic record of the number of times the hooks are used.
Accident statistics and patterns
| Type of operation error | Proportion | Typical consequences |
|---|---|---|
| overload | 35% | Hook deformation/breakage |
| Slanted and crooked hanging | 25% | Hook wear and wire rope detachment |
| Anti-unhooking failure | 20% | Hanging object falls |
| Unchecked fatigue/corrosion | 15% | Sudden fracture |
| Misuse of low temperature | 5% | Brittle fracture |
Summary of preventive measures
-
Operation Specifications :
-
Overloading and oblique pulling are strictly prohibited, and "three confirmations" (weight, angle, and lock) must be made before lifting.
-
-
Technical means :
-
Install torque limiter and anti-sway system.
-
-
Management requirements :
-
The hook has a “one hook one file” record (number of times used, test report).
-
-
Training focus :
-
Conduct drills simulating extreme working conditions (such as strong winds and low temperatures).
-
Warning slogan :
"One illegal operation may end your life!"
- All accidents can be avoided through standardized operation!
Improper operation is one of the main causes of crane hook accidents , which can damage equipment or cause casualties. The following are 6 typical accident cases, covering the causes, consequences and lessons, to provide warnings for safe operation.
Case 1: Overloading causes hook breakage
Accident
-
Location : A construction site
-
Operation : Workers use a 20t rated hook to lift a 28t steel beam (40% overload).
-
Result : The hook neck suddenly broke, the steel beam fell and smashed the pump truck below, and two people were seriously injured.
Cause Analysis
-
Direct cause : Overload exceeded the material yield limit (safety factor dropped from 4 to 2.3).
-
Indirect causes : The torque limiter was not installed and the signalman did not verify the weight.
lesson
✅ Overloading is strictly prohibited and the weight of the hoisted objects must be checked.
✅ Loads exceeding 10% require written approval from the engineer.
Case 2: Deformation of hook caused by oblique lifting
Accident
-
Location : Port Container Terminal
-
Operation : The driver did not align the lifting point and forcibly lifted the 40t container at an angle of 30°.
-
Result : The hook was subjected to force on one side, and the hook mouth was twisted and deformed (the width expanded from 50mm to 58mm).
Cause Analysis
-
Mechanical influence : actual load during inclined tension = vertical load/cosθ=46.2t (overload 15.5%).
-
Operational error : Failure to use the traction rope to adjust the position of the hanging object.
lesson
✅ The sling angle must be ≤60° (GB 6067.1).
✅ The rated load must be reduced by 20% when inclined.
Case 3: Failure to lock the anti-unhooking device caused the suspended object to fall
Accident
-
Location : Chemical plant equipment installation site
-
Operation : When lifting the reactor, the spring lock is not closed and it is locked by gravity alone.
-
Result : The slings slipped during lifting and the reactor fell from a height of 15m, causing a loss of RMB 2 million.
Cause Analysis
-
Device failure : The lock spring is rusted and does not close tightly.
-
Human negligence : Failure to implement the “double confirmation” system (operator + commander).
lesson
✅ Check the flexibility of the anti-unhooking device daily.
✅ The lock closing state must be manually tested before lifting.
Case 4: The hook rotated out of control and hit a person
Accident
-
Location : Wind turbine tower assembly site
-
Operation : The high-speed rotating hook was not braked in time, and the sling was entangled with the hook.
-
Result : The hook swung and hit one worker, killing him.
Cause Analysis
-
Operating error : Not using the low speed gear dedicated to the swivel hook.
-
Lack of training : Drivers are not familiar with the equipment operating manual.
lesson
✅ The rotating hook needs to limit the speed (≤2rpm).
✅ Physical isolation fences are set up in dangerous areas.
Case 5: Brittle fracture in low temperature environment
Accident
-
Location : A steel plant in Northeast China (-25°C)
-
Operation : Use ordinary carbon steel hook to lift 15t steel coil.
-
Result : The hook broke without warning and the steel coil smashed the track.
Cause Analysis
-
Material failure : The impact energy of Q235B hook at low temperature is only 14J (the standard requires ≥27J).
-
Wrong selection : Failure to use low-temperature steel (such as 34CrNiMo6).
lesson
✅ Low temperature toughness materials must be used below -20℃.
✅ -30℃ impact test is required before winter operation.
Case 6: Fatigue cracks not detected lead to accident
Accident
-
Location : Logistics Warehouse
-
Operation : Long-term and high-frequency use of the same hook (average of 200 cycles per day).
-
Result : After 3 years of use, fatigue cracks on the hook neck expanded and it broke when lifting 5t of cargo.
Cause Analysis
-
Detection of vulnerabilities : Only visual inspection was performed, and annual magnetic particle inspection was not carried out in accordance with GB 6067.1.
-
Life management : The number of times the hook was used was not recorded (far exceeding the design life of 10^6 times).
lesson
✅ Perform non-destructive testing every 6 months on frequently used hooks.
✅ Create an electronic record of the number of times the hooks are used.
Accident statistics and patterns
| Type of operation error | Proportion | Typical consequences |
|---|---|---|
| overload | 35% | Hook deformation/breakage |
| Slanted and crooked hanging | 25% | Hook wear and wire rope detachment |
| Anti-unhooking failure | 20% | Hanging object falls |
| Unchecked fatigue/corrosion | 15% | Sudden fracture |
| Misuse of low temperature | 5% | Brittle fracture |
Summary of preventive measures
-
Operation Specifications :
-
Overloading and oblique pulling are strictly prohibited, and "three confirmations" (weight, angle, and lock) must be made before lifting.
-
-
Technical means :
-
Install torque limiter and anti-sway system.
-
-
Management requirements :
-
The hook has a “one hook one file” record (number of times used, test report).
-
-
Training focus :
-
Conduct drills simulating extreme working conditions (such as strong winds and low temperatures).
-
Warning slogan :
"One illegal operation may end your life!"
- All accidents can be avoided through standardized operation!
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