Advice on safe operation when carrying mineral cargoes

This cargo advice has been prepared by The Swedish Club in collaboration with Burgoynes – David Robbins (UK), Darren Holling (Singapore) and Jim Mercurio (Dubai). The advice relates to cargo advice on carrying mineral cargoes, including sodium metabisulphite.

According to Swedish Club, a number of serious incidents have occurred in recent months involving mineral compounds (i.e. inorganic chemicals) in bags carried as general cargo. Besides a potentially serious risk of harm to individuals, the incidents have led to damage to vessels and loss of cargo, together with the problems that arise from them, such as the complication of dealing with port authorities, delays and associated claims, as well as contamination of the vessel and other cargoes and finally, the difficulty of arranging disposal of the hazardous residues.

On a practical level, when carrying sodium metabisulphite (a mineral cargo), all measures should be taken to avoid wetting it, or any other chemicals loaded with it, at any stage. Hatches on holds containing the substance should not, for example, be left open unnecessarily and the hatch covers should be fully sealed against the ingress of water during the voyage

Moisture issues

The incidents have principally occurred during discharge, with a number following periods of rain. Rainwater can penetrate any damaged bags at the surface of the stow or similarly react with any exposed, spilled cargo present.

The cargoes also tend to be hygroscopic, meaning that they can absorb moisture from the atmosphere which could also lead to reactions in or between cargoes.

Once reacting, a number of toxic, corrosive and asphyxiating gases and compounds can be released, together with the generation of heat in the affected zones of cargo. The decomposition products themselves may also react further.

Toxic gas issues

The gases released in incidents have included sulphur dioxide and nitrogen dioxide. Typically, the odours of the gases produced are readily detected by individuals below toxic levels. However, this should not lead to complacency as personnel can be overcome or caught unawares by pockets of gas in poorly ventilated areas or in the event of release of significant volumes of gas from an opening in a hold.

These gases attack the eyes and respiratory system, causing irritation to the eyes, nose and throat at low levels, but higher levels can lead to nausea, vomiting, stomach pain, corrosive damage to the airways, eyes and lungs, and even to obstruction and death.

Significantly, the damage caused by inhaling the gases can develop over a period after exposure so that harmful effects on, or symptoms displayed by, individuals may not be immediately recognized as a result of exposure.

Furthermore, dust created by the cargoes can become trapped in clothing, which when subsequently affected by sweat can becoming irritating and lead to redness and blisters. The gases released can also dissolve in sweat, becoming acidic and be retained against the skin.

Other outcomes

Liquid residues draining from or remaining in the cargo, or condensed on surfaces in the cargo hold, can be highly acidic and they are corrosive to skin, as well as to exposed steel and other metals.

Gas production and heat generation can be exacerbated when two or more of the powder cargoes have become mixed and then wet, or by water dissolving one cargo that flows into another incompatible cargo below.

Loss prevention essentials

– Ensure that the appropriate carriage instructions are obtained in advance.
– Hatches should be closed during rain at loading/discharge and fully sealed during voyage.
– Before entry to the hold, ensure gas readings are carried out and that there is adequate hold ventilation.
– Closely monitor the cargo handling at loading/discharge. Keep accurate records of any damage. Clear photographs of all stages of the cargo operations provide good evidence in case of a claim.

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