Several serious incidents have been linked to clay cargoes; they point to a troubling gap between theoretical classification and real-world behaviour.
As explained by V. Rama Chandran, Assistant Vice President, Technical Manager, Skuld, under the IMSBC Code, clay is classified as a Group C cargo, meaning it is not considered susceptible to liquefaction. However, operational experience and laboratory testing suggest otherwise.
When exposed to elevated moisture levels, clay can exhibit flow characteristics similar to Group A cargoes, which are known to liquefy. This transformation is particularly dangerous in rough sea conditions, where the shifting of semi-fluid cargo can severely compromise a vessel’s stability.
The risks are further compounded by the way clay is typically sourced and handled. It is often mined in open environments and stored in uncovered stockpiles near port facilities, leaving it exposed to weather conditions. This is especially problematic during the Northeast monsoon season, which runs from November to March in regions such as Malaysia. Rainfall during this period can significantly increase the moisture content of the cargo before it is even loaded.
Key loss prevention tips
In light of these findings, it is increasingly clear that clay should not be treated as a benign cargo. A more cautious and informed approach to its handling and transport is essential to mitigate potential hazards at sea.
Key tips:
- Treat clay cargo as potentially liquefiable despite its Group C classification
- Avoid loading during or after heavy rainfall, especially in monsoon seasons
- Keep cargo as dry as practicable throughout handling and transport
- Monitor moisture content carefully; conduct flow tests where possible
- Watch for visual signs of excess moisture (e.g., splattering, flattening)
- Ensure hatch covers are closed during loading to prevent water ingress
- Exercise increased caution when shipping from exposed stockpile areas