This incident summary, based on a report from the Swedish Club, describes cargo damage caused by condensation during a voyage from Mexico to Southern Africa. The case highlights the interaction between fumigation procedures and environmental conditions encountered at sea.
What Happened
A vessel loaded white maize in Mexico, where ambient temperatures were in the 30°C range. After loading, the cargo was fumigated, and the vessel proceeded on a voyage around South America via the Magellan Straits, where temperatures dropped to around 0°C. As per fumigation requirements, the cargo holds were kept sealed until 12 hours before arrival at the first discharge port.
Upon opening the holds, the surface of the cargo was found to be mouldy, with condensation stains visible on hatches and coamings. In some areas, the maize had germinated due to significant moisture exposure. The damage was attributed to ship’s sweat, where condensation formed on internal steelwork because of temperature differentials and then dripped into the cargo.
Why It Happened
The incident occurred because the cargo holds were sealed, creating a closed environment where moisture was able to accumulate. The vessel experienced a significant change in ambient temperature, from warm conditions during loading to near-freezing conditions in transit, which increased the likelihood of condensation inside the holds. While the fumigation instructions were effective for pest control, they did not take into account the environmental variations encountered during the voyage. Without interim ventilation, condensation developed on internal surfaces and eventually settled on the cargo, leading to damage.
Actions Taken
Damaged surface layers were removed manually by stevedores and with grabs. After segregation, the remaining maize was discharged in sound condition.
Lessons Learned
- Ventilation should be considered after the typical fumigation exposure period (often 10 days) to minimize condensation risks.
- Ventilation instructions must be clarified in advance with fumigators and charterers, ensuring that both pest control and cargo preservation are addressed.
- Crew should remain aware that fumigation requirements do not automatically mitigate environmental risks and should plan cargo care accordingly.
- Monitoring environmental conditions during transit is essential to anticipate and prevent ship’s sweat.
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Source: Swedish Club
