Trans RINA, Vol 154, Part A2, Intl J Maritime Eng, Apr-Jun 2012 TECHNICAL NOTE AN EXPERIMENTAL STUDY ON THE RELATIVE MOTIONS BETWEEN A FLOATING


HARBOUR TRANSHIPPER AND A FEEDER VESSEL IN REGULAR WAVES (DOI No: 10.3940/rina.ijme.2012.a2.228tn)


G J Macfarlane and T Lilienthal, Australian Maritime College, University of Tasmania, Australia R J Ballantyne and S Ballantyne, Sea Transport Corporation, Australia


SUMMARY The Floating Harbour Transhipper (FHT) is a pioneering logistics solution that was designed to meet the growing demands for coastal transhipment in the mining sector as well as commercial port operations. The primary advantage of the FHT system is that it can reduce transhipment delays caused by inclement weather, by reducing relative motions between the FHT and feeder vessel. The feeder is sheltered when inside the FHT well dock when compared to the more exposed location when a feeder is in a traditional side-by-side mooring arrangement.


This paper discusses previously published studies into the relative motions of vessels engaged in side-by-side mooring arrangements and also presents details and results from a series of physical scale model experiments. In these experiments, both side-by-side and aft well dock mooring arrangements are investigated. The results provide strong evidence that the FHT well dock concept can significantly reduce the heave, pitch and roll motions of feeder vessels when transhipping in open seas – this being the cornerstone of any successful open water transhipment operation.


1. INTRODUCTION


Bulk ore product is usually shipped directly from shore facilities using large bulk carriers Panamax or Capesize ships) which expensive port facilities, often involving operations and the need for


(typically either require large, dredging


visually obtrusive shore


storage sheds (for example, possessing a capacity of 80,000 tonne for a Panamax load). Substantial reductions in capital and operating expenditure are achievable by relocating the major stockpile to an offshore floating facility (mothership), thus requiring a much smaller shore facility (around


10,000 tonne capacity). The


product is transferred from the shore facility, which can be located within a small harbour, to the mothership via two or more shallow draught feeder vessels.


The transhipping objective for defence and disaster


response and mining is the same, which is to transfer large volumes of cargo with minimal time and costs into remote areas with little or no infrastructure in all types of weather.


This technical paper reviews a case study on the


development of the Floating Harbour Transhipper (FHT); a novel design that can not only increase export and import capabilities, but


also strengthen emergency


response and military capabilities. For a relatively simple modification for defence use, the FHT can provide a large percentage of the military requirements for a small fraction of the cost.


2.


THE FLOATING HARBOUR TRANSHIPPER (FHT) CONCEPT


Traditionally, the transfer of bulk ore cargo from a feeder vessel to a moored ‘mother’ ship is conducted with the feeder vessel moored side-by-side to the mothership. The FHT concept adopts a novel alternative, where the feeder vessel is moored inside an aft well dock in the FHT/mothership. The FHT is a covered floating storage vessel which incorporates a wet dock facility at the aft end to suit the feeder vessels. It also has its own bulk cargo handling equipment, not just for the transfer of material from the feeder vessel into its own stockpile, but also from this stockpile to an export ocean going vessel moored alongside. This system eliminates grab spillage and dust, common to other transhippers.


The concept is depicted in Figure 1, where a feeder vessel of up to 10,000 dwt capacity is moored inside the stern well dock of a Capesize capacity FHT (100,000 dwt capacity). An export vessel (in the foreground) is moored alongside the FHT.


In this figure, the feeder vessel is


partially obscured by the covered deck of the FHT. For this example, the feeder vessel is a Stern Landing Vessel (SLV), as described by Ballantyne and Ballantyne (2007) and is carrying bulk ore product for mining transhipment options, as depicted in Figure 2.


The FHT concept operationally compelling solution that


provides an environmentally and can


provide


significant advantages for the country, community and mining companies. The key advantages for the FHT and SLV feeder system relevant to mining operations are summarised as follows:


©2012: The Royal Institution of Naval Architects A-97


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