3. During voyage

Ship’s sweat and cargo sweat are types of condensation that form within the hold due to changes in environmental conditions. Condensation can result in a localised increase in the cargo moisture content. This places the affected cargo at increased risk of deterioration and mould growth and an associated rise in temperature. Further discussion on the effects of ship’s sweat and cargo sweat on the cargo can be found in the section Risks associated with carriage below.

When ventilating bulk hygroscopic cargoes such as soya beans, it is recommended that the ‘three degree rule’ is used. The rule prescribes that ventilation should occur when the outside ambient temperature is more than 3 °C below the temperature of the cargo at loading and the weather conditions are suitable. It can be assumed that the temperature of the cargo will not change considerably after loading due to the high heat capacity of soya bean cargoes, and therefore no additional temperature measurements need to be taken during the voyage. If the vessel experiences a significant delay prior to discharge, it may be suitable to reassess the cargo temperatures at this stage.

4. During discharge

In most circumstances, discharge of bulk soya beans proceeds without incident. In the event of damage at discharge it is important that the position of damage in the hold(s) is accurately recorded – for instance the location, depth/height above tank top, and area. This will assist in determining the cause of damage. The crew should closely monitor discharge and any segregation activities. A local surveyor should be appointed to document cargo condition, inspect the damage and, where relevant, obtain a cargo temperature profile throughout discharge.

A sampling superintendent should also be appointed to take representative samples of the cargo during discharge. Ideally, the sampling should be performed on a joint basis with other interested parties. The representative samples obtained should represent the cargo as a whole and any segregated categories (i.e. additional representative samples should be obtained for both cargo considered sound and cargo considered damaged).

5. Risks associated with carriage

Condensation – ship’s sweat and cargo sweat

Ship’s sweat forms when the steelwork of the vessel is cooler than the dew point of the air within the headspace. Typically, this occurs when a vessel sails to a cooler climate and the lower external ambient temperature cools the steelwork. As a result, the water vapour within the hold headspace condenses onto the steelwork and then drips on the cargo surface/runs down the frames of the hold. Damage from ship’s sweat is typically characterised by wetting and associated mould damage in regular repeating pattern across the surface of the cargo reflecting the frames of the hatch covers directly above. Repeated wetting due to prolonged formation of ship’s sweat can result in damage extending deeper into the stow.

Cargo sweat forms when the cargo temperature is lower than the dew point of the air in the headspace. Normally this occurs in situations where colder cargo is loaded, and warmer air is subsequently introduced into the headspace by incorrect ventilation during a voyage or when a cold cargo is discharged in a significantly warmer destination. In this case, the condensation forms directly on the surface of the cargo itself. Damage via cargo sweat is typically characterised by mould growth at the surface of the stow.

Cargo sweat can also occasionally occur when there is prolonged ventilation of the holds with air that is far cooler than the cargo temperature. The introduction of much cooler air from ventilation can reduce the cargo temperature of the immediate surface layer. If there is a significant delay in discharge, moisture from the bulk of the stow may rise and condense against the cooled cargo at the surface via a process known as moisture migration.

Water ingress

Water ingress can take several forms and can result in significant cargo claims. The most common sources of water ingress are ingress through poorly maintained hatch covers, open hatch covers during adverse weather and bilge issues.

• Poorly maintained hatch covers: Water ingress through hatch covers commonly presents in the form of obvious columns of mould damage and caked pillars of cargo where the water has leaked directly downwards from the point of entry. The only way to prevent this is to ensure that all hatch covers and manholes are properly maintained and checked regularly to ensure water tightness. The condition of the steel compression bars, rubber hatch cover seals and non-return valves should be regularly checked and maintained accordingly. Ideally, the crew/independent surveyor should ensure that a hose or ultrasound test is performed prior to the voyage.
• Open hatch covers and ventilation windows:
  Ingress through the hatch covers may also occur if they are left open when it is raining, or there is spray on deck during the voyage. If ingress occurs at loading, wetted cargo must be discharged. Failure to discharge wetted cargo at load port is likely to lead to cargo claims at disport due to visible mould growth. To prevent these issues, the Master and crew should pay close attention to the weather and be ready to close hatch covers if required.
  Severe weather conditions during the voyage resulting in water on deck and over the holds can also result in ingress through open ventilation windows for example. In the event that such adverse weather conditions are experienced, a sea protest detailing the weather event with photographs may also assist in the defence of a claim.
• Bilge issues: Bilge related water ingress typically presents in cargo surrounding the bilge box, on the tank top. Mould and wet damage are usually found and are often attributed to overflowing and poorly maintained bilges. A surveyor or crew member should closely inspect the condition of the bilges prior to loading cargo to ensure that wastewater can be easily removed.
  Furthermore, the bilge levels should be measured and recorded regularly during the voyage and, if necessary, water pumped out to prevent overflow of the bilges. Once discharge of each hold has been completed, the bilges should be inspected for any signs of water accumulation.

Self-heating

Soya bean cargoes carried in bulk, along with other agricultural commodities, still undergo biological reactions during storage. The soya beans will continue to respire – albeit slowly – consuming oxygen and generating carbon dioxide, water and heat. Due to the large quantity of cargo within the holds and the high insulation capacity of such cargoes, the soya bean temperature can slowly increase over time. Self-heating can reach very high temperatures in soya beans, circa 80 °C is possible, due to microbiological heating followed by chemical breakdown of oils within the soya bean. Self-heating in soya bean cargoes can negatively affect the quality parameters of the cargo, such as the colour, odour, protein solubility and free fatty acid content of the oil.

The degree to which self-heating will manifest itself within the cargo is influenced by the moisture content and temperature of the cargo at loading and the duration of the voyage. In some cases, parcels of cargo with a high moisture content will begin to develop mould, further heating the cargo. If the entire cargo has an inherently high moisture content, the risk of mould growth and self-heating increases significantly.

Soya beans have an additional risk of self-heating due to their oil content. As a result, there is a greater risk of soya beans self-heating in comparison to cereal grain cargoes. In severe cases of heating the areas in the stow may severely discolour and carbonise.

Although the self-heating of soya bean cargoes can commonly be attributed to an inherently high moisture content and/or temperature, this is not always the case. There are several other potential sources of heat which can initiate the self-heating process, including – but not limited to – insect infestation, cargo lights, improperly fitted fumigant recirculation fans inside the hold, and heated FOTs or FO heating elements adjacent to the holds.

These external heat sources generate localised heating which can initiate the self-heating process.

In the event of self-heating, there is little that can be done to stop the continued increase in temperature. Ventilation only serves to remove warm moist air from the headspace and does not affect the temperature of cargo within the body of the stow.

The only truly effective method to mitigate self-heating is to discharge the cargo as soon as possible. Self-heating may continue post-discharge if the cargo is stored in large piles with little ventilation.

6. Mitigation

The common forms of damage described above, amongst others, often give rise to claims from various parties. It is important to understand that there are a range of mitigation strategies that can be employed to help reduce the quantum of damage. Broadly these can be split into activities performed during discharge and those performed after discharge.

• During discharge: If a claim is anticipated, or damage is found, it is recommended that representative samples are obtained during discharge. For soya beans, the samples must be obtained in accordance with the latest Federation of Oils, Seeds and Fats Associations (FOFSA) sampling protocol. Once representative samples are obtained, they can be retained and analysed to investigate a number of factors such as grading and biochemical parameters. It is important to stress that a spot sample cannot be considered representative of the cargo. Ideally a FOSFA cargo superintendent would be appointed to undertake representative sampling either on a unilateral or joint basis.
  In addition to representative samples of the cargo it is important that an effective segregation operation is put in place. If damaged cargo is in a discrete location, as is often the case with water ingress through the hatch covers, it is suitable and effective to have the damaged cargo segregated by hand. For more widespread damage, typically seen with heavy sweat/ condensation related damage on the surface, it may be more appropriate and practical to remove by ‘skimming’ with a grab or small payloaders. In every instance, care should be taken to ensure that the most effective and practical segregation method is undertaken. The segregated cargo should also be representatively sampled.
• After discharge: Once the cargo has been discharged by the vessel there are several steps that are commonly utilised to help mitigate potential cargo claims. For any soya beans which are self-heating and at high temperature at discharge then it is useful to attempt to dissipate this heat. This can be achieved by spreading the affected cargo out in a flatbed warehouse to help reduce the temperature of the beans. Care should be taken to avoid piling the cargo in high heaps. Another method used to mitigate the effects of selfheating damage is the blending of the affected beans with beans of a better quality. The practise of blending is commonplace at large processing facilities with reserves of suitable soya beans that can be blended. It is anticipated that suitable blending will minimise the effect of self-heating damage on the final products, soya bean meal and soya bean oil.
  When attempting to quantify or validate a potential claim that is raised following mitigation by blending it is important to obtain relevant documents and data, such as the blending ratios and quantities, and the quality parameters and results for each lot that is blended with the affected cargo.

Conclusion

There are a range of considerations for the crew prior to and during the carriage of soya beans. An understanding of the common issues experienced during carriage of this cargo and ways to avoid these issues may well assist in preventing cargo damage and claims.

Prepared in collaboration with CWA International