Trevor Fernandes, Senior Loss Prevention Executive at NorthStandard P&I Club, highlights the key risks and best practices for safety in the carriage of woodchips, as he says woodchip cargoes present unique safety challenges at sea.
Woodchips are a commonly carried bulk cargo that are derived from natural timber and are mechanically processed. Woodchips present safety challenges due to their organic nature, moisture sensitivity, potential for oxygen depletion in the hold and fire hazards.
IMSBC Code
Woodchips are classified as a Group B cargo in the IMSBC Code and a Material Hazardous only in Bulk (MHB) for being a combustible solid (CB).
As the cargo is Group B, the cargo must appear on the vessel’s certification for hazardous cargo to permit carriage.
Moisture content
Woodchips are hygroscopic and can retain a significant amount of moisture. When the moisture content exceeds 15%, there is a risk of microbial growth (fungi, bacteria, etc.), especially in warm conditions. This biological activity consumes the oxygen within the space and produces heat; this potentially leads to:
- Oxygen depletion in the hold: Dangerously low levels of oxygen can occur in less than 48 hours.
- Carbon Dioxide accumulation: This is a by-product of microbial respiration.
- Self-heating and fire risk: Moist cargo has a low fire risk, but as moisture decreases, the risk of fire increases.
During loading and unloading operations, all non-working hatches should be closed to prevent water ingress. Hatch cover maintenance should be up to date and the condition of the hatch cover arrangements confirmed as satisfactory to maintain the weather tightness of the hold.
Appropriate weather precautions, such as the posting of a weather watch, must be taken when loading to ensure that the cargo remains dry.
Dust hazard
Dry woodchips are highly combustible and can ignite easily from external sources or even friction. Dust generated during handling can settle on deck and dry quickly, becoming a fire hazard.
The presence of dust not only increases the risk of fire but can also lead to respiratory problems for crew members. Therefore, it is essential to implement effective dust control measures. This includes using appropriate Personal Protective Equipment such as dust masks and goggles.
Crew should also ensure that during cargo hold cleaning operations the holds are well-ventilated to prevent dust accumulation.
Trimming
Poor cargo trimming after loading can lead to voids, uneven weight distribution, and increased risk of cargo shift on passage. The cargo is usually trimmed using bulldozers or conveyors to level cargo during loading.
Cargo should be trimmed correctly to fill all spaces under the decks and hatch covers. Additionally, during the voyage, the crew should regularly check the cargo’s condition when safe to do so to ensure that it remains stable and has not shifted, which can lead to dangerous situations.
The cargo should be trimmed in accordance with section 5 of the IMSBC Code.
Ventilation
As the cargo is hygroscopic, the most accurate and safe way to ventilate is by using the three-degree rule. Using this method, the crew should ventilate if the outside air-dry bulb temperature is at least 3°C cooler than the temperature of the cargo recorded at the time of loading. Accurate records should be maintained throughout the voyage, which includes noting why ventilation did not take place if it was allowable, for example due to the vessel shipping spray in bad weather.
Enclosed Space Entry
Crew should be warned that all cargo holds and adjoining spaces are to be considered dangerous spaces, and entry should be completely avoided where possible. If absolutely required, entry should be done under strict entry into enclosed space requirements and under a permit to work.
It should be noted the latest IMSBC Code references IMO guidance A.1050(27), we suggest using the latest revised guidance on enclosed space entries outlined within MSC.581(110). Section 10.3 of this guidance outlines the dangers of solid bulk cargoes.
Prior to entry by personnel into the hold or any adjacent spaces, crew should establish the oxygen concentration is 21% (i.e. normal fresh air levels) and that the space being entered is free from harmful gases. Such readings should be taken using an appropriately calibrated gas detector. Adjacent spaces may also need to be ventilated thoroughly before entry, even if those spaces are apparently sealed from the cargo holds. Consideration should be made for any spaces connected via pipework too, such as ventilation trunks or defective bilge lines where gases can migrate from one space to the other.
Shoreside workers are at risk from the dangers associated with entering an enclosed space on board a ship too, in particular stevedores when handling cargo. It should be assumed that these workers are not familiar with shipboard enclosed space procedures and might require some guidance.
Any unsafe actions observed by shoreside workers should be stopped immediately.