Transport Malta’s Marine Safety Investigation Unit has issued an investigation report on the fatal injuries of a crew member due to the failure of an overhead monorail crane wire rope, in the port of Laem Chabang, Thailand, on 07 November 2022.
The incident
The vessel was engaged in cargo operations at the port of Laem Chabang, Thailand. In the morning of 07 November 2022, an oiler and the two wipers were assigned to transfer heavy scrap from the engine-room workshop to the port side of the external ‘A’ deck of the accommodation. The metal items had remained on board following the vessel’s recent dry dock works.
The port side arm of the vessel’s overhead monorail crane on deck was used to hoist the drum-full of the scrap metal and place it on the external ‘A’ deck. After the drum was placed in the intended location, the oiler hoisted the crane’s block, using the wireless remote controller to park the port side arm in its securing position. At one point, the crane’s wire rope parted, and the block fell onto the oiler, who was standing directly below it, on the external ‘A’ deck.
The oiler suffered fatal injuries due to this occurrence. Site assessments and laboratory analysis conducted on various components of the monorail crane, revealed that the hoist limit switch of the port side arm of the monorail crane was inoperative, since its drive chain had disengaged from one of its sprockets. Furthermore, the overload limit switches of the monorail crane were not designed to prevent over-hoisting of the crane’s blocks.
Subsequently, the port side block of the monorail crane was hoisted beyond its limit, and the wire rope parted when subjected to overloading.
Investigation
Immediate causes of the accident
Fatally injured, the oiler experienced the port side block of the monorail crane falling on him while hoisting it. The incident occurred as he stood directly beneath the crane’s port side arm at that moment.
A laboratory analysis of the separated wire rope from the monorail crane’s port side arm, about a meter from its fixed end, revealed that the failure resulted from overloading the wire rope.
Conditions and other safety factors
Deformations observed on the port side block, its sheave, and the crane’s sheave indicate contact between the crane’s sheave and the block, as well as the block’s sheave, during hoisting. This contact contributed to overloading the wire, leading to its failure.
Before the accident, the drive chain of the port side hoist limit switch disengaged from its small sprocket, rendering the hoist limit switch non-functional. Crew members only discovered this issue after the accident.
Laboratory analysis of the port side hoist limit switch’s drive chain and sprockets identified wear on the gear teeth of the small sprocket and traces of adherent paint on the internal surface of the drive chain rollers. This hindered the drive chain from fully engaging with the sprocket teeth.
The presence of paint may have caused the drive chain to disengage from the small sprocket prior to the accident. The settings of the overload limit switches would not have protected the wire rope against over-hoisting.
Lessons learned
CMA CGM International Shipping Co. Pte. Ltd., Singapore is advised by Transport Malta to:
- Replace the existing overload limit switches on the deck monorail cranes with a load limiter to eliminate the incorporated delay time.
- Replace the deformed port side large sprocket with a new one.
- Replace the small sprockets on the port side due to manifested abrasion and wear patterns and inspect the starboard side sprocket, replacing it if necessary.
- Conduct an exhaustive inspection of the system and analyze whether adaptations are necessary to better manage the fair wear and tear of the sprockets over time.
- Ensure that the drive chain systems of the deck monorail cranes are part of the planned maintenance system, with necessary precautions taken to prevent inadequate lubrication at prescribed time intervals.
- Consider the possibility of positioning the crew members operating the deck monorail cranes on ‘D’ deck to better observe hoisting and lowering operations and take timely actions if necessary.
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Source: Transport Malta
