Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019 “LIQUEFACTION” AND “DYNAMIC SEPARATION” DIFFERENT ASPECTS OF THE
SAME PROBLEM (DOI No: 10.3940/rina.ijme.2019.a4.551) S Ferauge,W Jacobs and K De Baere, Antwerp Maritime Academy, Belgium SUMMARY
In 2015 the Bulk Jupiter sank during bad weather loaded with bauxite. Nearly automatically everybody considered “liquefaction” to be the prime cause of this accident. Liquefaction is a phenomenon where solid bulk cargo, triggered by the ship movements, starts to behave has a high density viscous liquid in the holds. The stability is negatively influenced by the free surface effect and further research, especially by the Global Bauxite Working Group or GBWG showed that bauxite ore simply will not liquefy even under the worst case shipping conditions. Evidence from real world shipments of bauxites shows that instabilities due to moisture cannot be explained by liquefaction phenomena, but can be under a “dynamic separation” mechanism of instability. Both liquefaction and dynamic separation are caused by an excessive moisture of the bauxite cargo. However, the influence on the stability of the ship is fundamentally different.
SOLAS Safety Of Life At Sea TML Transportable Moisture Limit TT1
Liquid surface after cargo shift
UK P&I United Kingdom Protection & Indemnity Club WL Water Line
1. 1.1. Dynamic Separation (GBWG, 2017)
NOMENCLATURE B
GvZv GZ Α
L Θ
AA1 AOR B
BCC
FMP FS G G
INTRODUCTION
THE NEW INTERNATIONAL MARITIME SOLID BULK CODE (2011)
Breath of the Free Surface (m)
Righting arm of stability moment after free surface correction (m)
Righting arm of stability moment (m) Length of the Free Surface (m) Surface angle of repose (deg) Angle of heel (deg) Original liquid surface Angle Of Repose Centre of buoyancy Bulk Carrier Code
BIMCO Baltic and International Maritime Council DNV-GL Det Norske Veritas (DNV) - Germanischer Lloyd (GL)
Flow Moisture Point Free Surface Effect
Centre of gravity of the cargo Centre of gravity of the ship
GBWG Global Bauxite Working Group Gv
M MC Metacentre Moisture Content
IMSBC International maritime Solid Bulk Code K
Virtual centre of gravity of the ship Keel
On 1 January 2011, theBulk Carrier code (BCC), governing the carriage of solid bulk cargoes by sea, was replaced by a new version, called the International Maritime Solid Bulk Code (IMSBC). This Code provides recommendations and rules for the loading, transport and unloading of dry bulk cargoes. IMSBC is updated every 2 years. The present IMSBC (2018), with important amendments regarding the liquefaction of coal, entered into force on the 1st of January 2019 and contains 14 sections giving general information, and 5 appendices, including one (Appendix 1) giving specific information related to the carriage of certain dry bulk cargoes(IMO, 2018).
Amongst many other amendments, the changes to Section 7, the liquefaction of bulk cargoes were awarded most attention. More specifically, the IMSBC code distinguishes 3 cargo groups. There are Group A cargoes, which present liquefaction hazards, Group B shipments, presenting chemical hazards (toxicity or flammability), and, finally, Group C cargoes, which pose no risk of liquefaction or any chemical hazards (IMO, 2018).
1.2. LIQUEFACTION
Physically, liquefaction is a phenomenon in which a soil- like material is abruptly transformed from a solid dry state to an almost fluid state when the moisture content surpasses the Transportable Moisture Limit or TML. TML
©2019: The Royal Institution of Naval Architects A-419
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