Commercial Vessels : The "Western Challenge" (Ore Transfer Barge) |
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The "Western Challenge" is an 80m, 4500 dead weight tonne ore transfer barge, designed for Western Metals Limited. The vessel is operated by Carpentaria Marine, on behalf of the owners, and has been in service since early 1997 transporting zinc and lead ores from the shallow water port of Derby, to bulk carriers anchored in deep water in the adjacent King Sound. The vessel has been specifically designed to transport zinc and
lead ores from the loading facility at the shallow water port of
Derby, Western Australia, to bulk carriers anchored in deep water
in the adjacent King Sound. The vessel is operated by Carpentaria Marine Pty Ltd (Riverside
Marine), on behalf of the owners, Western Metals Limited, and has
been in service since January 1997. The vessel is fitted with a midships bin to hold up to 4500 tonnes
of zinc or lead ore, and is loaded by an on-shore conveyor loader.
Discharge is by means of an excavator mounted on a pedestal centrally
located within the cargo bin, which transfers the product to a boom
mounted conveyor and hence to the hold of the bulk carrier. Tidal ranges in the area of operation are extreme, with heights of up to 11 metres. This gives rise to strong currents and the relatively short ‘loading window’ at Derby of between six and seven hours. Cargo loading rates have been designed accordingly. Hull Form
PropulsionThe vessel is pushed by a 26 metre twin screw tug (the K.C. Campbell), which has a bollard pull of about 20 tonnes. Loaded service speed is about 6 knots. The tug is located within the aft notch of the barge by means of two hydraulically operated side pads pressing against the barge structure at the aft end of the notch. The bow of the tug is clamped to the barge structure at the forward end of the notch, by means of a hydraulically operated ram. To cater for the wide variation in barge draft, side and forward bearing towers are fitted above deck level.Cargo HandlingAfter loading at Derby Wharf, the vessel proceeds into King Sound and moors alongside a waiting bulk carrier anchored in the Sound, some 20 nautical miles from the wharf. A four part sliding cover can be deployed to protect the cargo in the event of weather.A Caterpillar model 350 excavator is mounted on a 7 metre high, 2 metre square pedestal sited in the centre of the cargo bin. The excavator is capable of reaching all parts of the bin. Final clean-up of the cargo is accomplished by a Bob-Cat, which enters the bin through a guillotine type door in the forward face of the bin. The excavator discharges its load into a hopper on the inboard end of the unloader boom. A conveyor belt then transfers the cargo in to the hold of the bulk carrier. The unloader, which has a boom length of some 15 metres, is mounted on a pedestal sited on the port side of the vessel. The design of the unloader was undertaken by K.C.Dodd Consulting Engineers of Perth. Discharge rates of approximately 600 tonnes per hour are being achieved. StructureThe hull is of conventional construction with transverse web frames at 2000mm centres, and longitudinals at 600mm centres. The hull is subdivided by six transverse watertight bulkheads and two longitudinal bulkheads.Structural material is generally ABS Grade A quality steel, with Grade B stringer plates in way of the cargo bin. Shell plating is generally 12mm thick, increased to 20mm in way of cargo bin. |
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