In its latest Risk Watch, Britannia P&I Club explains that proper trimming of bulk cargo is essential for ensuring ship stability, regulatory compliance, and efficient loading and discharging operations.
As explained, the IMSBC Code provides mandatory guidelines for trimming procedures. Section 5 of the code specifies that all bulk cargoes should be trimmed ‘reasonably level’ to reduce risks such as cargo shifting and instability. For non-cohesive cargoes, trimming standards are determined by the calculated angle of repose. Consideration should also be given to the charter party, as this may stipulate the required method of trimming, especially for cargoes that require specific handling.
Section 5.1.3 of the IMSBC Code states: “The master has the right to require that the cargo be trimmed level, where there is any concern regarding stability based upon the information available, taking into account the characteristics of the ship and the intended voyage.”
Trimming is often performed at the end of discharge, but when loading via a chute, spout, or conveyor, it makes sense to avoid the cargo stream constantly pouring onto the same point in the holds. Best practice is for the loading arm to be initially positioned as close to the tank top as safely practicable, depositing a layer of cargo over the entire surface before increasing the loading rate and raising the drop distance. Efforts should then be made to direct the loader for a more even cargo distribution. This reduces or can even eliminate the amount of trimming work needed to flatten the cargo surface at the end of loading.
The process of trimming is important for several reasons:
- Ship stability: At sea, the ship and cargo will be subject to longitudinal and lateral forces. If cargo piles collapse to one side, this can affect the vessel’s overall stability due to the shift in weight and could endanger it.
- Minimizing air in the cargo: Effective trimming minimizes the volume of air entering the cargo. The more air present, the greater the likelihood of self-heating, which is particularly relevant for various Group B cargoes.
- Weight distribution: Ensures an even weight distribution across the tank top concerning weight limitations. In practice, this means spreading the cargo as widely as practicable within the cargo space to prevent excessive loading on the tank top (or tween deck, if applicable).
- Regulatory compliance: Trimming may be required by regulations such as the International Maritime Solid Bulk Cargoes (IMSBC) Code or the Grain Code.
- Efficiency in discharging: A properly trimmed cargo allows for more efficient unloading operations and reduces the likelihood of uncontrolled shifting during discharge.
According to Britannia, maximizing the equal distribution of cargo requires good communication with the shore loader. To anticipate this requirement, it is recommended to raise it as a point at the ship-shore meeting with the terminal representative and clarify how communication will take place during loading operations.
This also highlights the importance of maintaining supervision of loading operations by ship’s staff, rather than relying solely on a cargo surveyor. It remains the ship master’s responsibility to ensure that the cargo is safely prepared for transport before departure.
