Grains

It should not be overlooked that once it was fairly commonplace for oil tankers which would usually be engaged in the transportation of crude oil occasionally to carry cargoes of grain when the market so warranted the expense and time in cleaning tanks. In the late 1980’s a United States food aid cargo was carried in an American-flag VLCC (Very Large Crude Carrier) in excess of 250,000 tonnes deadweight, carrying a large grain cargo from the United States West Coast to Pakistan. The cargo was loaded through spouts and discharged by vacuvators (portable suction machines). Short sea vessels are not just smaller versions of deep-sea types, they have modifications peculiar to their trades. The modern dry-cargo coaster needs flexibility of intake of cargoes in order to survive in a very competitive business. Because of this they are usually constructed with just one hold served by a large ‘open-hatch’ steel hatchcover, their hold ‘box-shaped‘ the better to obtain good intake and safe stowage of containers and palletised cargo. Modern short sea vessels are built with steel floors to their cargo compartments, facilitating discharge by grab, although older vessels may well have a wooden, concrete or tarmacadam sheathing as protection to the tank-tops. Few older vessels had self-trimming facilities so that free-flowing bulk cargoes, which are liable to shift dangerously at sea, were secured by a combination of bagging and strapping part of the cargo at the top of the stow. For most grains this amounts to around 10% of the cargo, the 90% loaded underneath the bags and strapping being in bulk. With some particularly free-flowing grains, however, (e.g. rape-seed), perhaps 20% of the cargo will require to be bagged. By contrast the modern box‑shaped single decker in the short sea and middle distance grain traders is usually equipped with at lest two moveable bulkheads enabling the vessel to arrange for a completely full compartment comprising 80 to 90% of the ship’s capacity and a small compartment where the balance can be slack without the need for bagging and strapping. Latest European designs allow for river and canal trading by creating a ‘low-profile‘ vessel, by which the superstructure located at the after end of the hull can be hydraulically lowered to enable the ship to pass beneath bridges and other overhead obstructions, with any masts being lowered.