Bulk Cargo

Vast amount of dry seaborne material is carried in bulk form without any bagging or packaging. Generally, such cargoes consist of one homogeneous grade, but occasionally, a vessel will carry various grades – eg: two types of coal, in separate holds; (termed “natural separation”) or, on occasions, even more than one grade in one hold. In this case cargo portions are separated either horizontally in layers by means of tarpaulins. dunnage, burlap (hessian) or by heavy-duty polythene sheeting, (although grab discharge in such circumstances will seriously increase the risk of admixture). Temporary wooden bulkheads may be used for vertical separations. Where loading and/or discharging of bulk cargo takes place at one or more berths or ports, extreme care must be taken to distribute cargo throughout a ship in a safe, seaman like fashion, enabling the vessel to remain stable throughout the voyage. A typical charter-party clause to this effect states simply: “If the vessel is destined for two or more berths and/or ports of discharge. it is agreed that the vessel be left in a safe and seaworthy condition, satisfactory to the Master, when proceeding between such berths and/or ports”. Even when loading/discharging a homogeneous cargo alongside a single berth, cargo distribution and removal must be dealt with in careful sequence, so as to avoid undue stress upon the vessel’s hull. Errors in this respect can be catastrophic and vessels have been actually broken in half because of injudicious loading. The proper handling of bulk cargo on a vessel is a skillful task and one to which even the most experienced ship’s master must carefully attend. To assist him, classification societies approve the issue to each vessel entered in their organisation of a stability booklet, specially drawn up for the ship concerned. These booklets provide guidance on loading capabilities, stability and stress in various conditions, and on commodities of varied stowage factor and peculiarity. In certain cases, United States, official loading inspectors will insist on examining a vessel’s stability booklet before permitting the ship to depart. Apart from their distribution in a ship, all commodities in bulk form have individual peculiarities, special carriage requirements, and associated difficulties. Some are particularly hazardous and advice on how they may best be transported safely at sea is given by IMO in their booklet “Solid Bulk Cargoes” – a publication necessary for every trader’s bookshelf. In addition to the risk of structural damage caused bv improper weight distribution. there exists the danger from excessive stability at the commencement of a voyage. leading to violent rolling at sea, with possible structural damage and/or shifting of cargo. Even if a ship sails with satisfactory stability, subsequent shifting of the cargo can seriously reduce stability, to the extent that, at the worst, a vessel turn over and sink. Certain bulk commodities are more liable to surface shift than others. When cargo is poured on to a nat and level (horizontal plane) surface, it will form a conical shaped heap, Assessment of the angle of repose of this heap. In accordance with methods laid down by IMO, indicate how the commodity will behave in a ship’s hold at sea. The critical angle is that of 35 degrees. Commodities with an angle of repose of 35 degrees or less (eg: bulk wheat) tend to surface movement at sea and top must be levelled off (trimmed) for safety.