Britannia P&I Club explains that agricultural cargoes are extremely heat sensitive and presents preventative measures against heat damage.
According to Britannia, certain types of agricultural cargo suffer heat damage even at lower temperatures of around 40°C to 55°C. When steam is supplied to fuel oil tanks, the temperature within the tank rises and heat is either transferred by a conduction process or radiated from the tank to the adjacent cargo holds.
A significant number of claims have been linked to heat-sensitive agriculture products such as soya bean, wheat, maize, corn, barley, sunflower pellets, canola, bananas, flower bulbs, soybean meal and fish meal, Britannia adds. Processed cargoes have an even higher moisture and oil content, making them more susceptible to microbiological activity and self-heating, which can lead to severe heat damage with the feed cargoes.
To mitigate this, the master and chief engineer should consider the location of heated fuel oil tanks and fuel consumption sequences as part of their cargo stowage planning alongside the ship’s stability.
Self-heating damage and risks associated with fuel tank heating can be mitigated by drying the cargo prior to loading to slow down microbiological activities and reduce the chance of moisture migration.
According to Britannia, the following recommendations may provide some assistance to the master in planning and transportation of these type of cargoes:
- Vessels should consult the provisions scheduled by the IMSBC Code for stowage precautions, especially for temperature-sensitive cargo during planning stages
- High value yet temperature-sensitive cargoes should be loaded away from the fuel oil tanks and/or uninsulated engine room bulkhead. It is preferred to load these cargoes adjacent to non-essential fuel oil tanks as heat from fuel tanks may trigger rapid deterioration even if the cargo would be otherwise suitable for carriage
- When planning fuel storage management for a voyage, master and chief officer should liaise with the chief engineer about the nature and type of cargoes prior to loading and discuss fuel oil management for the voyage
- Prioritise fuel consumption for fuel oil tanks that are not adjacent to cargo hold with heat-sensitive cargo
- Consider using lower viscosity fuel oil when carrying temperature-sensitive cargoes as low viscosity oil requires lower temperature heating
- Carry out fuel heating gradually by increasing the steam capacity in the steaming coil, limiting the rise in temperature to a minimum extent, until it is sufficiently heated but not unnecessary (ideally tanks should not be heated more than 40°C)
- Remember that the heating lines exposed above the surface of the fuel in the storage tank may transfer heat to tanktop plates even faster than if they were submerged. To minimise the heat transfer, leave a sufficient amount of slack fuel in the tank
- Ensure effective working conditions for the heating coils in the fuel tanks and shut off valves, steam traps and temperature sensors in the bunker tanks as per the vessel’s Planned Maintenance System (PMS)
- Update the PMS maintenance records thoroughly as these may serve as valuable evidence in the future
- Ensure the steam supply valves are shut when emptying fuel oil tanks
Retain temperature records of heating fuel oil tanks carried out throughout the voyage
- If accessible, carry out temperature monitoring inside the cargo holds and ventilate as practiced by relevant temperature rules
- Be aware of surplus steam from the Exhaust Gas Economiser (EGE) being recirculated to the fuel oil tanks.
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Source: Britannia P&I Club