Podcast
Questions and Answers
What was the weight of the nacelle that the crane was lifting?
What was the weight of the nacelle that the crane was lifting?
- 65 tonnes
- 80 tonnes
- 69 tonnes (correct)
- 70 tonnes
What was the crane's Maximum Rated Capacity (MRC) for the lift performed?
What was the crane's Maximum Rated Capacity (MRC) for the lift performed?
- 90 tonnes
- 75 tonnes
- 85 tonnes
- 80 tonnes (correct)
What probable cause led to the failure of the hoisting wire?
What probable cause led to the failure of the hoisting wire?
- Excessive lifting weight
- Undetected corrosion and wear (correct)
- Faulty crane calibration
- Shock-loading during the lift
What condition of the crane wire was found upon post-incident inspection?
What condition of the crane wire was found upon post-incident inspection?
What estimated damage cost resulted from the incident?
What estimated damage cost resulted from the incident?
Flashcards
Maximum Rated Capacity (MRC)
Maximum Rated Capacity (MRC)
The weight that a piece of equipment, like a crane, can safely lift. It is usually expressed in tonnes or pounds.
Internal Corrosion
Internal Corrosion
Damage to the internal structure of a wire rope, often caused by exposure to corrosive elements like saltwater or chemicals. This damage weakens the wire rope and can lead to unexpected failure. It might be invisible from the outside.
Wire Rope Inspection
Wire Rope Inspection
The process of inspecting a wire rope for damage or wear. It usually involves looking for signs of surface corrosion, wire breakage, or lubrication issues.
Crane Wire Failure - Impact of Internal Corrosion
Crane Wire Failure - Impact of Internal Corrosion
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Wire Rope Strength
Wire Rope Strength
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Study Notes
NTSB Crane Wire Failure
- National Transportation Safety Board (NTSB) published a safety digest, including an incident of crane wire failure on a cargo vessel.
- A wind turbine nacelle (69 tonnes) was being offloaded when a crane wire snapped.
- The nacelle fell back into the vessel's cargo hold.
- No pollution or injuries occurred, but damage to the vessel and dropped load was estimated at US$3-5 million.
Facts About the Incident
- The load was 86% of the crane's maximum rated capacity (80 tonnes) at a distance of less than 19 meters from the base, as certified in 2019.
- The crane had successfully completed two similar lifts prior to the incident.
- Post-incident inspection found no issues with any equipment or evidence of shock loading.
Probable Cause
- The cause was undetected corrosion and wear in strand wires of the hoisting wire.
- External and internal corrosion, as well as roughness and pitting of the wire, was significant.
- Corrosive wear caused individual wires in strands to break.
- This overloaded remaining strands leading to the failure.
- Inspection and annual checks, done by third party contractors, did not fully inspect the grease-covered wire, therefore, overlooking corrosion issues.
Lessons Learned
- Saltwater and humidity accelerate metal corrosion on vessel wires.
- Thorough inspection and maintenance, regular or more frequent, depending on use, is crucial.
- Maintaining wire ropes is essential for safe loads (working load).
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