Out of Africa
Telestack install fully customized mobile material-handling system in Sierra Leone as part of a phase-one investment by London Mining Company
Telestack have recently installed and commissioned a custom-designed mobile truck-unloading, stockpiling, reclaiming and barge-loading facility in Sierra Leone, West Africa, as part of a phase-one investment by London Mining Company (LMC). Installation commenced towards the end of 2011 and the facility was fully commissioned and signed over in early 2012.
LMC required a logistics system to handle 8,000 tonnes of material per day from their Outetec iron ore beneficiation plant, which is trucked 40km to a barge-loading facility in Thofeyim, on the river Loko. Here, the material is loaded on to 8,000-tonne dwt barges at a rate of 1,500 tonnes/h as part of a transhipping process. The barges are later unloaded, by grab cranes, into Handymax vessels ranging from 37,000 to 55,000 tonnes dwt for onward shipment.
Telestack’s sales engineers worked closely with LMC’s management and their consultant, Ausenco, to deliver the bespoke turnkey solution, which comprises four main stages – truck unloading, stacking, reclaiming and barge-loading – to ensure maximum operational flexibility for the operator (fig. 1).
Truck unloading
At the beneficiation plant, truck and dog units (2 x 40 tonnes) are loaded with iron ore fines with a typical Fe content of +65%. The trucks then travel, via a purpose-built road, to the stockpiling and barge-loading site at Thofeyim. On arrival, the trucks pass through a wheelwash before driving over a Telestack grid hopper where each trailer unit is unloaded. The 54m3 capacity unloading hopper is fully lined with low-friction liners and can hold up to 150 tonnes of material. The trailers are bottom-discharge units and can unload their 80-tonne cargo in less than 5min.
The unloading hopper regulates the feed rate at between 800–1,000 tonnes/h by means of a custom-designed and manufactured apron belt feeder with a variable-height gate outlet. This heavy-duty feeder module, which is 1,200mm wide and incorporates a 800kN chain, offers all the strength of a normal apron pan feeder but has much better sealing properties as it can be sealed like a traditional belt feeder, thereby optimizing spillage prevention while providing robust feeder characteristics to cater for heavy surges of iron ore at 2.8 tonnes/m3 (see lead photo).
Stacking system
Material from the unloading hopper is transferred on to a 20m long Telestack link conveyor, which weighs the material by means of a dual-idler belt weigher. This is used to keep records of daily, weekly, monthly and annual capacities, and to monitor stocks of iron ore in the stockpile. The link conveyor, in turn, discharges into the feed-boot of a 51.2m long Telestack TS 850 mobile radial/telescopic stockpiling conveyor, which has a peak capacity of 1,000 tonnes/h. The TS 850 unit is positioned on an 80m high plinth which, utilizing the natural topography of the site, allows a total stockpile height of 25m to be achieved. This gives LMC up to around 350,000 tonnes of stockpiled material within a 180° radial axis. The material is stacked at approximately 8,000–10,000 tonnes/day, which means the stockpile reaches its maximum capacity after around 35–44 days of full production, without any shipments. All maintenance is carried out via access walkways and all transfer points are lined and incorporate high valley angles to minimize the potential for blockages, especially in the rainy season (figs 2&3).
The operator’s cabin is located at the optimum point to provide the best viewing point for truck unloading and stacking. In addition, strategically placed metal-halide floodlights allow for 24h operation.
Reclaiming system
A Komatsu WA600 wheel loader reclaims material from the stockpile and feeds a Telestack tracked mobile hopper feeder equipped with an 18m3 (50 tonnes) capacity apron belt feeder. This regulates the feeding of the heavy surge from the WA600’s 10m3 capacity (28 tonnes) dump bucket. The reclaim hopper is located on the centre line of the stockpile to minimize the load-and-carry distance, and the single WA600 can comfortably deliver between 1,200 and 1,500 tonnes/h. The feeder transfers the material on to a 27.5m long Telestack link conveyor that weighs the material and takes a sample using a certified ISO 308 standard sampling unit (figs 4&5). The ESSA sampler is a reverse spoon-type design and takes a cut from the falling stream, as per the best-practice sampling procedure for iron ore. Sampling can be done manually, at set intervals on a timed basis or at set intervals on a tonnage basis.
Barge-loading system
From the link conveyor the iron ore is fed to a Telestack TS1550 mobile radial telescopic shiploading conveyor operating at 1,500 tonnes/h. The TS1550 has an operating cabin located at the end of the outer conveyor to ensure maximum visibility when loading the barges. The operator is able to trim each barge by means of the TS1550’s radial, telescopic and luffing capabilities. This ensures that an entire barge can be trimmed from one feed-in position, thereby enhancing production rates and limiting downtime compared with other designs. The range of discharge points allow each 8,000-tonne barge to be loaded without the vessel having to change position (figs 6,7&8).
Loading is carried out so as to create linear heaps on the barge, which ensures optimum efficiency further down the logistics chain when grab cranes are used to pick up the material for transfer on to Handymax vessels for onward shipping.
Summary
The fully customized system outlined in this article demonstrates Telestack’s commitment and ability to design, manufacture and install heavy-duty mining-specification units to meet the needs of customers’ specific applications. Systems of this kind can be utilized in
existing mines or new mines that are just opening up, especially phase-one operations in remote locations at the start of the mining process.
The main advantages of this type of plant over large, fixed stackers/reclaimers and fixed installations include:
- reduced capital investment
- limited civil works on site
- a four- to eight-month lead time from order to installation
- no planning permission needed
- full dust/spillage control and elimination
- capacities up to 3,000 tonnes/h.
Moreover in future, when production at the site is increased and fixed conveyor systems are installed, the mobile equipment can be used to provide emergency back-up to the fixed system, or to optimize ‘dead areas’ of the stockyard where the fixed stacker/reclaimer units cannot reach. Alternatively, as all the units can be packed into 40ft shipping containers, the system can be sold on for use in a wide range of applications anywhere in the world, including quarrying, rail wagon loading, power stations, steel mills, ports and inland terminals, among others.
For further information tel: (028) 8225 1100; or visit: www.telestack.com
