The general purpose Great Lakes self-unloading vessel has an overall length of more than 220 m, a beam of 28 m and a capacity of 25,000 tons to 30,000 tons when loaded to the St Lawrence Seaway draught of 26 ft. The unloading capacity of these vessels varies from 5000 tons/hr to 6000 tons/hr. A 76 m long swinging boom conveyor is usually carried on the main deck of the vessel in order to allow the vessel to stockpile the cargo on the wharf, to discharge the material directly into the shore-based receiving hopper for distribution by conveyors, or to permit the direct transfer of cargo from one vessel to another. Other variations have included the design for a screw conveyor assisted by shuttle scraper in place of long travelling conveyor: a stern shuttle conveyor for offloading rather than a boom conveyor: and a wheel elevator (rather like a stockyard reclaimer wheel) mounted in the stern between two engine-rooms. With the latter, a 58,000 dwt vessel designed primarily for ore pellets has achieved a 20,000 tons/hr discharge rate. However, such a piece of equipment is necessarily expensive to construct and maintain. Experience in this field shows belt conveyors to be the most economical system. A loop belt elevating system has been developed which utilises standard belt conveyor components including idlers, terminal equipment and conveyor belts. The load is fed from the hold onto the outer belt and becomes trapped between the inner and outer belts and carried around on a semi-circle discharging at the upper end. With the loop belt design, a reduction in transfer points can mean a dramatic reduction in maintenance. Other designs for unloaders are also discussed.

  • Corporate Authors:

    Cargo Systems International

    Arun House, 201-205 High Street
    New Malden KT3 4BH, Surrey,   England 
  • Publication Date: 1977-1

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Filing Info

  • Accession Number: 00156832
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Jul 2 1977 12:00AM