Gross register tonnage ( GRT) represents the total internal volume of a vessel, where one register ton is equal to a volume of 100 cubic feet (2.83 m 3) a volume that, if filled with fresh water, would weigh around 2.83 tonnes.
Surpac report tonnage metric registration#
It indicates a vessel's earning space and is a function of the moulded volume of all cargo spaces of the ship.Ī commonly defined measurement system is important, since a ship's registration fee, harbour dues, safety and manning rules, and the like may be based on its gross tonnage (GT) or net tonnage (NT). Net tonnage ( NT) is based on a calculation of the volume of all cargo spaces of the ship. Gross tonnage is therefore a kind of capacity-derived index that is used to rank a ship for purposes of determining manning, safety, and other statutory requirements and is expressed simply as GT, which is a unitless entity, even though it derives from the volumetric capacity in cubic metres. The numerical value for a ship's GT is always smaller than the numerical values of gross register tonnage (GRT). Gross tonnage ( GT) is a function of the volume of all of a ship's enclosed spaces (from keel to funnel) measured to the outside of the hull framing. Tonnage measurements are governed by an IMO Convention (International Convention on Tonnage Measurement of Ships, 1969 (London-Rules)), which initially applied to all ships built after July 1982, and to older ships from July 1994.
It is essential that mill feed be kept as close as possible to that called for in the original design specification of the mill and concentrator. The main purpose of grade control is thus to ensure that material being fed to the mill is of economic grade and that large fluctuations in grade are minimized by blending ores from different benches, or parts thereof, or from different stopes. It is the geologist’s job to ensure that mining is closely following the mineralized zone and that overbreak during stoping is kept to a minimum.
In underground operations, grade control may involve the mapping and sampling of stope faces, sampling of tram car loads or draw-point muckpiles, broken rock at a recently blasted face, jackhammer cuttings or diamond drill cores. In some cases, grade control may also involve the sampling of truck or shovel loads to ensure that rock is assigned to the correct stockpile or waste dump. In an open-pit operation, this involves the sampling of blast-hole cuttings produced by down-the-hole hammer drills and the classification of bench reserves into ore, low grade or waste material, or into various metallurgical types. In some mining operations, one of the most important roles played by the geologist is the supervision of grade control.
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