Cargo liquefaction countermeasures on board general cargo vessel

Cargo liquefaction countermeasures on board general cargo vessel

Liquefaction may be a particular problem with moisture-laden cargoes such as some ores, fines and mineral concentrates. It occurs when the motion of the ship (vibration caused by machinery, rolling and pitching) causes the cargo to compact and the consequent reduction in space between cargo particles causes an increase in water pressure in the reduced space which then reduces friction between cargo particles thus allowing the cargo to behave like a liquid, i.e. to liquefy. This can lead to a major shift of the cargo with a consequent loss of stability, to the extent that the ship may founder.

There have been a large number of casualties during the last few years involving ore cargoes that were loaded at ports in South East Asia. It should be noted that liquefaction can occur very quickly if the cargo is particularly wet and there are recent records of ships becoming unstable only a few miles from the loading port. As a consequence, the 2013 edition of the IMSBC Code has been extensively revised to address this problem.

Section 7.3.1.1 of the IMSBC Code specifically says that "Concentrates or other cargoes which may liquefy shall only be accepted for loading when the actual moisture content of the cargo is less than its TML [Transportable Moisture Limit]".* Thus, a Master should not accept such a cargo for loading until provided with the documentation certifying the moisture content and the TML, with the moisture content shown to be less than the TML. The Code details procedures for determining the actual moisture content and TML and emphasises that the "can test" described in Section 8.4.1 does not and must not replace proper laboratory testing and reliance on the "can test" is a breach of the Code.

The Code now requires the shipper of any Group A cargo to have in place procedures for sampling, testing and controlling the moisture content of the cargo to ensure it is below the TML while on board. The procedures must be approved by the Competent Authority of the country of loading and the Master must be provided with the approval document prior to loading.

It is now a requirement of the IMSBC Code that the body charged with issuing documentation relating to moisture content is a separate entity to the shipper and recognised as such by the Competent Authority in the port, thus avoiding any conflict of interest. Additionally, it is a requirement that the Competent Authority is likewise independent of the shipper. Masters should endeavour to ascertain that this is indeed the case and that these conditions are met for any Group A cargoes that the ship is intended to load.

It is a sensible precaution for a surveyor to be appointed by the ship owner to inspect the condition of the cargo prior to loading and, more importantly, verify the moisture content and TML information provided by the shipper, if necessary by laboratory analysis. For such analysis to have meaning, the sampling needs to be fully representative of the cargo to be loaded. The IMSBC Code requires that shippers must facilitate access to stockpiles ashore by the ship's nominated representative to carry out inspections and obtain samples for testing.

Shippers are required to present the stockpiles to representatives in a suitable location with equipment available to facilitate samples being obtained from the full depth of the stockpile. Cargo brought alongside the ship by barge must be protected from precipitation and the ingress of water.

When considering a particular cargo for shipment the information concerning that cargo in the IMSBC Code must be consulted. Should it be listed as a Group A cargo, i.e. likely to liquefy, it must be carried in strict accordance with the Code. However, as the Code advises, the schedules for individual cargoes are not exhaustive and some cargoes not included in the Code may liquefy. It is essential that the Master insists on receiving the appropriate information for any cargo for which he has doubts, prior to the commencement of loading. It should also be remembered that if the cargo has been stockpiled in the open in wet conditions, the Master should ensure that the quoted actual moisture content continues to be valid at the time of loading.

There is no doubt that the Master and his officers need to be up-to-date on applicable rules and regulations concerning Group A bulk cargoes, particularly those contained in the IMSBC Code and SOLAS. However, if the Master is in any doubt, he should consult with his P&I Club. Recent incidents have made the clubs very aware of the problem and they will provide advice immediately.

Summarized below some more details on general cargo ship cargo handling procedure and operational info:

Cargo handling procedure for general cargo ship

Cargo liquefaction countermeasures on board general cargo vessel

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