Lessons Learnt: Heating damage to soya beans

Vessel Type: Bulk carrier

Incident description

The vessel loaded a full cargo of soya beans in North America for discharge in the Far East. The voyage was performed in the Northern Winter season during which orders were received to stem fuel oil bunkers at an intermediate port. After arrival alongside at the discharge port, the surface of the cargo was inspected by a surveyor appointed on behalf of the Receivers and with no problems being apparent, discharge was commenced. Four days later, discharge within one of the holds was stopped due to the discovery of dark coloured beans near the tank top. Closer inspection revealed a layer of discoloured, very warm and caked cargo approximately 40 cm deep, immediately adjacent to the tank top. It was promptly agreed between ship and cargo interests to resume discharge operations by taking all reasonable steps to efficiently segregate the damaged and sound cargo within the hold.

Analysis

It was apparent that the extent of cargo damage was confined to a distinct area coinciding with the dimensions of a fuel oil double bottom centre tank in way of the hold. The investigation into the cause of the cargo damage identified that this bunker tank was filled at the time of the bunker stem and then fully consumed during the remainder of the voyage. Bunker tank heating records indicated that the fuel in the tank had been heated to in excess of 50o C, well above that normally required for efficient fuel transfer. It was therefore concluded that heat transfer from the bunker tank resulted in the observed cargo damage. Once the damage was discovered, the good cooperation provided by the Receivers in properly segregating and discharging all cargo greatly assisted in mitigating losses for all parties concerned.

Lessons Learnt

• If at all possible, the stowage of heat sensitive cargoes adjacent to heated bunker tanks should be avoided
• Where heating of bunker tanks is necessary, this should be limited to the minimum temperature required for efficient fuel transfer taking into consideration the specification of the fuel
• When heat is being applied to bunker tanks, the admission of steam should be carefully controlled to achieve and maintain the desired fuel temperature
• Bunker tank fuel temperatures must be closely monitored and recorded
• Periodic checks should be made to ensure the correct function of the heating coils and valves
• This incident demonstrates the value of ship and cargo interests working together to solve problems and mitigate losses