Lessons learned: Optimize securing for adverse weather conditions

Heavy seas during a voyage from a supply base to an oil field caused approximately 15 containers to shift around one metre from port to starboard, despite being secured with tightened tugger wires.

According to the Marine Safety Forum, the movement also damaged an electrical cable on a refrigerated container, resulting in power loss and compromising the food cargo. The incident highlights the challenges of securing deck cargo for adverse weather, particularly when operational requirements influence cargo distribution and securing arrangements.

It also raises wider questions about how vessels assess changing weather conditions, account for uneven cargo distribution and determine whether existing securing measures are adequate for the planned voyage.

What happened

During transit from the supply base to the oil field, the vessel encountered heavy seas, with waves reaching approximately 7 metres and south-southeasterly winds of 40 knots.

Despite the cargo being secured with tightened tugger wires, around 15 containers shifted approximately one metre from port to starboard.

Additional cargo had been loaded on the port side to meet rig requirements and accommodate the positioning of the crane offshore. This uneven distribution increased the potential for cargo movement under the prevailing conditions.

The securing arrangements also left air gaps between cargo items, while the vessel’s heading deviated in response to heavy seas approaching from the port quarter. Water on deck and the forces generated by the rough conditions further contributed to the movement.

One refrigerated container sustained a broken electrical cable, causing a loss of power and compromising the food cargo.

Upon arrival at the oil field, the vessel maintained clear communication with the crane operator to support the safe discharge of the shifted cargo and protect the deck crew during the operation.

What went wrong

The incident demonstrates that tightening existing securing arrangements does not necessarily mean cargo is adequately protected against the forces encountered during a voyage.

One contributing factor was the arrangement of the cargo itself. The tugger wires had been tightened, but air gaps between cargo items left room for movement. In heavy seas, such gaps can allow cargo to shift and increase the forces acting on securing arrangements.

The weather conditions added to the challenge. Waves of approximately 7 metres and winds reaching 40 knots exposed the cargo to substantial movement forces, while water on deck further complicated the situation.

Cargo distribution was another important consideration. The need to accommodate the offshore crane’s position and meet rig requirements resulted in additional cargo being loaded on the port side. Although this arrangement served operational needs, it also increased the likelihood of movement under adverse conditions.

These factors underline the importance of considering the complete stowage and securing arrangement rather than treating individual lashings as the only line of defence.

The damage to the refrigerated container also illustrates how cargo movement can have consequences beyond the immediate risk of containers shifting or becoming unstable. A damaged electrical cable resulted in power loss and compromised food cargo, highlighting the potential for secondary damage to equipment and cargo integrity.

The big picture

Cargo securing is not simply a matter of applying the required lashings before departure. It requires an assessment of how the cargo, its distribution, the securing arrangements and the expected environmental conditions will interact throughout the voyage.

Offshore supply operations can involve competing operational requirements. Cargo must be positioned to meet the needs of the installation and accommodate crane operations, but these requirements should not overshadow the need to maintain safe and effective securing arrangements.

Where operational constraints result in uneven cargo distribution, the resulting risks should be assessed before departure. The securing plan may need to be adapted to account for the stowage configuration, expected sea conditions and the potential for vessel movement.

The incident also highlights the importance of reassessing risks when conditions change. A securing arrangement considered adequate during loading may not provide sufficient protection if the vessel encounters more severe weather than anticipated.

This is particularly relevant when cargo items are separated by gaps or when the stowage arrangement limits the effectiveness of the available securing measures. Additional chains or lashings may be necessary for higher-risk voyages, depending on the cargo, the vessel’s approved securing arrangements and the applicable procedures.

Communication is another essential safeguard. The coordination with the crane operator during discharge helped support the safe handling of the shifted cargo. However, effective communication offshore should complement, rather than replace, measures to prevent cargo movement in the first place.

Ultimately, cargo securing arrangements need to account for the conditions the vessel may encounter, not only those present when the cargo is loaded.

What could have reduced the risk?

The incident points to several practical measures for vessel operators, deck officers and offshore logistics teams.

Review securing procedures before high-risk voyages. The Cargo Securing Manual, relevant risk assessments and company procedures should be reviewed before departure, particularly when heavy weather is expected. The review should establish whether the planned stowage and securing arrangements are suitable for the anticipated conditions.

Optimise cargo positioning. Cargo should be arranged to support effective securing and minimise the potential for movement. Where rig requirements, crane positioning or other operational constraints necessitate uneven distribution, the associated risks should be assessed and appropriate controls established.

Consider additional securing measures. Chains, extra lashings or other suitable securing arrangements may be needed for high-risk voyages. These measures should be selected in accordance with the vessel’s approved arrangements and the characteristics of the cargo, rather than applied as a substitute for a proper securing assessment.

Strengthen voyage planning. Vessel teams should coordinate with client logistics planners to anticipate severe weather and identify cargo arrangements that may increase the risk of movement. This should include considering whether the planned cargo distribution and securing arrangements remain appropriate for the expected voyage.

Reassess risks when conditions change. Sea state, vessel heading, deck conditions, crane operations and changes to the stow plan can affect the risk profile. Crews should reassess hazards and controls when circumstances change, rather than relying solely on the initial assessment.

Apply Stop Work Obligation when safety is compromised. Crew members should understand when and how to stop an activity if cargo securing arrangements, loading conditions or the prevailing weather raise concerns about safety. Any doubts should be addressed before work continues.

Finally, cargo damage and movement should be treated as potential indicators of wider weaknesses in the securing process. Reviewing the circumstances after an incident can help identify whether the problem arose from cargo positioning, inadequate securing, changing environmental conditions or gaps in planning and risk assessment.

Ask your team

• Have we reviewed the Cargo Securing Manual, risk assessments and company procedures before voyages where heavy weather is expected?
• Does our cargo stowage plan account for uneven distribution, crane positioning and rig requirements without compromising the effectiveness of securing arrangements?
• Are gaps between cargo items creating opportunities for movement, and would additional securing measures be necessary for the anticipated conditions?
• Do we reassess hazards and controls when the sea state, vessel heading, crane operations or cargo arrangements change?
• Is Stop Work Obligation understood and exercised whenever there is doubt about the safety of loading, securing or transporting cargo?

Key takeaways

• Review Cargo Securing Manual, Risk Assessment, and procedures before voyage in heavy weather conditions.
• Position the cargo appropriately to optimize securing for adverse weather conditions.
• Consider additional securing measures (e.g., chains, extra lashings) for high-risk voyages.
• Improve voyage planning with client logistic planners to anticipate and mitigate severe weather impacts.
• Encourage and exercise Stop Work Obligation if safety is compromised during loading or transit.
• source : safety4sea