The issue of liquefaction affects bulk carriers of all sizes, but liquefaction can affect all ships carrying bulk ores including dry general cargo ships that load parcels of bulk cargo. Cargo liquefaction has been of concern to seafarers for over a century
Solid bulk cargoes such as iron ore fines or nickel ore normally contain a degree of moisture within the particles. If the cargo has laid in piles at the mine, having been transported to the terminal in open barges or trucks and loaded onto the terminal stockpiles during heavy rain, there may be a dramatic increase in moisture levels. Masters loading mineral ore fines in rainy seasons should be warned that the certificate issued for the moisture content, transportable moisture limit, and flow moisture point may not represent the real condition of the cargo.
When the cargo is subject to recurring cycles or cyclic forces, such as the movement of the ship (rolling/pitching/slamming), the volume of spaces between the particles reduces, which causes the pore water pressure to rise, reducing the shear strength of the particles.
Pore water pressure refers to the pressure of water held within a soil or rock, in gaps between particles (pores). If the pore water pressure increases enough, the cargo can reach its flow moisture point. The cargo enters a stage of transition whereby it begins to react like a fluid because of the loss of friction between the particles. This process is called liquefaction.
The American Club has issued an alert to its members on heightened concerns at commencement of the 'Nickel Ore Season' in the Philippines.
MSC.1/Circ.1454/Rev.1 “Guidelines for developing and approving procedures for sampling, testing and controlling the moisture content for solid bulk cargoes which may liquefy”. The amendments come into force in January 2017 and can be summarised as follows:
An addition has been made to section 3 paragraph 3.1 of the existing Code in relation to fire protection for self-unloading bulk carriers. The insertion requires routine on board operational fire safety risk assessments to be carried out by the crew in cargo handling areas and that due consideration be given to fire prevention and the effective operation of fire detection systems, containments and suppression under all anticipated operating conditions and cargoes. These assessment procedures must be detailed in the ship’s SMS together with a recommendation for the frequency of such assessments.
New schedules have been added relating to the following cargoes: aluminium fluoride, amorphous sodium silicate lumps, boric acid, chemical gypsum, copper slag, glass cullet, iron and steel slag and its mixture, iron ore fines, iron oxide technical, iron sinter, manganese component ferroalloy slag, manganese ore fines, scale generated from the iron and steel making process, spodumene (upgraded), wood pellets containing additives and/or binders, wood pellets not containing any additives and/or binders, zinc slag, zircon kyanite concentrate.
Section 7 has new requirements relating to “specially constructed or fitted cargo ships for confining cargo shift”.
The iron ore schedule has been replaced.
A new Section 14 has been added. This relates to the management of residues of solid bulk cargoes in order to avoid pollution by such residues. The new Section 14 relates specifically to the 2012 Guidelines for the implementation of MARPOL Annex V. Under MARPOL Annex V, determining how to manage the residues of sold bulk cargoes depends primarily on the classification of that bulk cargo and whether it is harmful to marine environment (HME) or not. The responsibility to classify the cargo in this way is on the shipper.
The new section 14 reproduces the texts of the MARPOL Annex V Guidelines which relate to the residues of solid bulk cargoes.
North P&I Club
Has issued a HotSpot sheet which provides a quick reference to Masters when loading a cargo which may be subject to liquefaction
The American Club has issed an alert on Government clampdown on mining activity and heavy rain in the Philippines affecting nicle ore shipments.
DNV GL has published (Oct 2015)
A guideline for the design and operation of vessels with bulk cargo that may liquefy. The guideline aims to raise the awareness of the risks of liquefaction and describes mitigating actions to reduce these risks. Many common bulk cargoes, such as iron ore fines, nickel ore and various mineral concentrates, have the potential to transform into an almost fluid state, threatening the stability of the vessel.
To download the guideline please register HERE.
MSC.1/Circ.1454 GUIDELINES FOR DEVELOPING AND APPROVING PROCEDURES FOR SAMPLING, TESTING AND CONTROLLING THE MOISTURE CONTENT FOR SOLID BULK CARGOES WHICH MAY LIQUEFY
The main objectives of these guidelines are to (i) assist shippers in preparing procedures for sampling, testing and controlling moisture content (as required by para 4.3.3 of the IMSBC Code); and to assist competent authorities of ports of loading when approving and checking the implementation of such procedures (again in accordance with para 4.3.3 of the Code).