Lessons learned: Cargo securing strength depends on compatible fittings
A bulk carrier transporting lithium-ion battery energy storage systems (BESS) experienced two cargo hold fires after securing arrangements failed during heavy weather, allowing battery units to shift and sustain internal damage.
The incident, highlighted by The Nautical Institute, demonstrates how incompatible lashing components can undermine cargo securing arrangements, even when equipment meets specified strength requirements. The case raises wider questions about the effectiveness of cargo securing plans, equipment inspections and verification before departure.
What happened
The bulk carrier was crossing the North Pacific with lithium-ion BESS units and heat exchangers stowed in two cargo holds. Each battery unit was secured using four polyester ratcheted lashing belts, with hooks attached to D-rings held by brackets welded to the deck.
During heavy weather, the vessel experienced severe rolling and shipped water over its hatch covers. The Master altered course to enable the crew to inspect the cargo, revealing that several battery units had broken free and shifted.
Around the same time, black smoke was observed coming from a manhole opening into one of the cargo holds. The crew raised the alarm, secured ventilation and evacuated the affected space before the fixed CO2 firefighting system was discharged.
Although the fire was extinguished and the displaced cargo was re-secured, a second fire developed in another hold three days later, again during heavy weather.
With the CO2 supply exhausted, the crew altered course to reduce vessel motions and applied seawater to the exterior of the affected hold. Infrared temperature checks subsequently indicated cooling, and the vessel proceeded to a port of refuge.
No injuries were reported, but the incident resulted in approximately $3.8 million in damage. Investigators established that 41 of the 160 BESS units stowed on the tween decks had broken loose, with three sustaining internal fires.
What went wrong
The investigation identified a critical incompatibility between the lashing belt hooks and the D-rings used to secure the cargo.
Although the securing arrangements were designed to meet specified breaking-load requirements, the D-rings were too large for the openings of the hooks. Consequently, the hooks could not fully engage the rings and were instead connected only at their tips.
This configuration concentrated forces at the curved sections of the hooks rather than distributing the loads through their intended bearing surfaces.
As the vessel rolled in heavy weather, several hooks fractured. Their failure transferred additional loads to the remaining securing components, resulting in further hook failures and, in some cases, the separation of welded brackets from the deck.
The investigation also revealed an important weakness in the cargo securing process. The storage and lashing plan specified the required breaking strength of the equipment but did not adequately address the physical compatibility of the connecting components.
The mismatch was not identified by the crew, stevedores or other parties overseeing cargo securing. Once the battery units broke free, they collided with surrounding cargo and the ship’s structure. This caused internal damage, leading to electrical short circuits and thermal runaway in three units.
The findings demonstrate that a lashing arrangement may satisfy specified strength requirements while remaining vulnerable to failure because its individual components are not properly matched.
The big picture
The incident illustrates a wider cargo securing challenge: verifying that equipment meets its specified strength rating does not necessarily establish that the complete securing arrangement will perform safely under actual operating conditions.
The distinction is particularly important where different securing components are combined. Hooks, rings, shackles and attachment points must work together as an effective system, rather than being assessed solely according to their individual ratings.
The importance of examining the complete arrangement has emerged in other casualty investigations. In an NTSB investigation into improperly secured battery cargo, the Board emphasised the need to inspect the actual engagement of hooks and other fittings before a vessel proceeds to sea. That investigation concerns the same casualty highlighted by The Nautical Institute.
Other cargo securing incidents have demonstrated different weaknesses with potentially serious consequences. A UK MAIB case involving the loss of timber deck cargo showed how arrangements that initially appeared secure proved inadequate because they did not meet the cargo’s specific securing requirements.
Beyond the mechanical failure, the battery fires introduce an additional concern. Internal damage to lithium-ion battery systems may not be evident from their external condition, yet it can compromise electrical components and initiate thermal runaway.
This means that effective cargo securing is not merely a matter of preventing cargo movement or damage. For certain cargoes, the integrity of the securing system is also an important safeguard against fire and potentially escalating emergencies.
What could have reduced the risk?
The case highlights several practical areas that operators, cargo planners and vessel crews should consider when verifying cargo securing arrangements.
- Check physical compatibility: Confirm that hooks, D-rings, shackles and other connecting components engage correctly and can transfer loads as intended. Equipment ratings alone are insufficient.
- Review cargo securing plans: Ensure that plans address actual component configurations and connection requirements, rather than specifying breaking loads without confirming that the fittings are compatible.
- Strengthen pre-departure verification: Inspect the completed arrangements after cargo loading, paying particular attention to whether hooks are fully seated and connections are correctly aligned.
- Clarify verification responsibilities: Establish how potentially incompatible equipment will be identified and communicated between cargo planners, stevedores, vessel personnel and those supervising cargo securing.
- Consider cargo-specific consequences: Where lithium-ion battery systems are transported, take account of the possibility that cargo movement or impact damage could lead to internal electrical failures and fire.
- Reassess securing arrangements: Where conditions permit safe access, inspect securing arrangements following heavy weather or indications of cargo movement, without exposing personnel to unnecessary hazards.
These considerations extend beyond battery cargoes. Any operation involving securing equipment with multiple interconnected components requires verification that the assembled arrangement is suitable for the loads and conditions it may encounter.
Ask your team
The following questions can support onboard safety meetings, cargo securing reviews and discussions between vessel operators and cargo handling personnel.
- When inspecting cargo lashings, how do we verify that hooks and attachment points are physically compatible rather than relying solely on their rated strength?
- Who is responsible for identifying and resolving mismatches between securing components supplied by different parties?
- Would our current cargo securing inspections identify a hook that appears attached but is not fully seated in its D-ring?
- How would our response change if cargo containing lithium-ion batteries shifted or sustained possible internal damage during a voyage?
Key takeaways
- Compatibility matters as much as strength: Securing components must engage correctly for their rated performance to be meaningful.
- Inspect the complete system: Individual equipment specifications cannot substitute for verification of the assembled securing arrangement.
- Cargo securing plans must reflect actual fittings: Inadequate component specifications can allow unsafe configurations to go unidentified.
- Cargo movement can trigger secondary hazards: Damage to lithium-ion battery systems may initiate thermal runaway and fire, even when internal damage is not externally visible.
- Verification should involve all relevant parties: Effective coordination between planners, cargo handlers and vessel personnel can help identify weaknesses before departure.
Content Original Link:
" target="_blank">
