CONVEYING
geared set-up – and there are specific scenarios where energy savings are up to 12 %,” noted Richter . ABB is optimistic that this new ‘ data-asa-service ’ approach , which combines the expertise of system provider , operator and data scientists to identify energy savings , has real potential to make conveyor operations more environmentally friendly and reduce the mining sector ’ s overall carbon footprint .
Conveyor project execution – consider the variables
Virta Inc was established in 2019 as a whollyowned subsidiary of Fluor Corporation , with a leadership team offering hundreds of years of collective experience in the engineering and delivery of custom engineered bulk material handling systems . Dedicated to offering complete material handling systems integration with a focus on high capacity overland conveyors , Virta says it partners strategically with specialty equipment and component suppliers , and global steel fabricators to deliver innovative and complete capital-efficient systems . Every project is custom designed and built with a solution optimised for safety , life-cycle cost-effectiveness , reliability and availability .
It is currently building systems in the Canadian Arctic , the Arizona desert , Mexican Gulf coast , the Peruvian and Chilean Andes (> 4,000 m ), along with design studies for multiple kilometres of overland conveyors in Argentina , the USA and Peru , plus underground conveyor projects . In just over three years and despite the pandemic it has grown to having projects in eight countries and a team of almost 50 people in the USA and Chile , plus an new overland conveyor design patent pending .
Virta President , Grant Graber , says that overland conveyor execution continues to differentiate suppliers in the marketplace and significantly influence project delivery economics as it is heavily influenced by different variables and parameters which can result in an overland conveyor being delivered entirely differently for a given geometry and design capacity . “ Many companies worldwide design and deliver these systems , although as capacity , length , geometry , horizontal curves and regeneration become more complex , the number of groups capable of delivering them starts to dwindle rapidly .”
Graber gives the examples of two of Virta ’ s conveyor projects in Canada and Peru . Both are relatively small gold mines and with similar design capacities . “ But one project is at a relatively low elevation but a design temperature of -45 ° C , while the other is at over 4,000 m elevation . One project has very restrictive road transport conditions . These factors alone will affect the selection of motors , reducers , belt rubber , steel material , bearings , lubricants , pulley shafts , etc . Steel structures are designed differently for transport . The cold conditions also increase resistance of rotating parts , which in turn increases conveyor belt tension and power requirements .”
Logistics and global supply chains also have a crucial role to play . Everything a conveyor needs can be subject to ocean freight costs , duties , tariffs , import restrictions , transport limitations etc . “ Competitively shopping for idlers and belt , for example , cannot exclude the associated international logistics . It is critical to consider any import duties for foreign goods into any country – many countries have international trade agreements while others are highly restrictive and punitive . One must evaluate the delivered cost of steel or parts . Some countries apply duties on only some types of steel fabrications , for example . Also , the simple classification of fabricated steel sections can affect applicable duties . For example , many steel fabrications for conveyor systems should actually be considered ‘ mechanical equipment ’ as opposed to ‘ structures .’ Some countries will apply different duties based on this classification . The supplier and importer-ofrecord must coordinate such efforts .”
Graber argues that even the same project executed pre- and post-COVID could be delivered differently . Some 18-24 months ago , the cost of an ocean container from Asia to North or South America ranged from $ 20,000 to $ 30,000 . This made the consideration of overseas-sourced components and steel less attractive due to the shipping costs . It even affected how goods were packaged . “ For example , having idlers preassembled at the factory with rolls on frames is attractive as it reduces site labour costs to assemble them . But it vastly increased shipping volume and the number of containers for a given quantity of idlers and often made it costprohibitive . Since then , these shipping costs have decreased dramatically , even to 50 %, now making such pre-assembly perhaps attractive again .”
Finally , Graber says that the entire concept of off-site pre-assembly and modularisation is so much more involved than simply placing such a requirement in a project specification . “ It necessitates a complete end-to-end assessment to ensure money is not wasted , potential impacts are not overlooked and associated risks are properly managed . The concept is often assumed beneficial as it has the potential to reduce site labour costs , reduce site manpower requirements ( camps , meals , power , water etc ), plus reduce site-based safety hazards ; and Graber says it can be highly successful and beneficial provided that certain elements are considered : n Project risk assessment – this needs all
disciplines – engineering , supply chain , logistics , construction , finance , taxes , trade compliance n Engineering and construction teams must engage from project outset . So often , the design of structures and selection of equipment will be construction-driven so that the benefits of pre-assembly and modularisation can be maximised . This favours design strategies such as minimal structure columns requiring anchor bolts , all bolted connections ( no field welding ), easeof-lifting design , ‘ plug-and-play ,’ etc n An overland conveyor normally comprises head , tail , drive , take-up ‘ modules ’ and the overland ‘ tables ’ or ‘ ground modules ,’ and in some cases one or more transfer towers . It is possible to design all of these for off-site preassembly and modularisation , the extent of which should be determined by how much site-labour reduction and risk reduction are desired n Pre-assembled structures and modules need to be engineered accordingly . For example , a conveyor drive station structure fabricated overseas would need to be engineered for ocean transport including vibration , corrosion protection , bracing , lifting ( centre-of-gravity if the structure is turned on its side , for example ) n Large assemblies may require trucking permits / pilot cars , etc that add cost but may be justified n Pre-assembling mechanical and / or electrical components to the steel structures in the shop must consider suitable labour availability ; effect of any pre-assembly on potential export duties ; risk of damage to intricate parts once pre-installed ; site storage area , cranes , rigging for large modules near or on the site ; and Additional delivery time – can the project wait the extended time for pre-assemblies n Double or triple handling – it costs more money every time a container , fabrication , equipment item is loaded , unloaded , stored , etc . For example , pre-assembling conveyor drive units ( motors with reducers ) is very common and most often the right decision . But even then , consider the logistics and handling costs . Shipping a motor from India or Brazil to a gear reducer factory in Belgium , Germany or USA for preassembly will save costly site labour , but clearly adds considerable freight , logistics , documentation and expediting costs . It also adds several weeks to the delivery schedule n Site labour costs – it is necessary to evaluate the true cost of site labour and what the project is really saving by pre-assembly .
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70 International Mining | FEBRUARY 2023