Located 56 kilometres northwest of Boston, USA, the Littleton Quarry is one of eight stone quarries owned and operated by the northeast region of Aggregate Industries, which maintains six regional construction materials businesses. Each region produces high quality crushed stone and sand and gravel, plus ready-mixed concrete and asphalt for a wide range of large infrastructure projects and commercial and
residential developments.
Two years ago, Littleton Quarry decided to upgrade its operations by relocating its secondary and tertiary plants closer to the quarry face.
{{image2-a:r-w:200}}The goal was to increase efficiency and reduce costs per tonne. The new plant used existing Metso crushers fitted to a new structure, plus four new Deister screens and five conveyors manufactured by Superior Industries ? two 36? by 150? (914mm x 45m) TeleStacker conveyors and three portable radial stackers.
?This upgrade and relocation allowed us to cut our overall footprint by 43 per cent and eliminated more than 2200 feet of overland conveyor,? explained Littleton?s plant manager Chad Abramson.
Abramson said a new approach to stockpiling and material handling at the site had delivered a quick return on investment and was arguably the biggest factor among the operation?s efficiency initiatives.
?We have achieved a 28 cent per tonne saving by eliminating the double handling of our finished products, the high costs of using loaders and haul trucks and additional manpower to transfer material stockpiles,? he said.
?With diesel fuel prices, investing in the right conveyor systems is easily justified.?
Abramson explained that previously, the operation used two fixed stackers with a stockpiling capacity of 8000 tonnes each.
?Each time we would reach capacity, we would have to load the material into two 70-tonne haul trucks and transfer it to a final stockpiling area,? he said.
?That?s double handling and additional costs in fuel, wear and tear and loader operator overtime ? all of which significantly affects profit margins.?
Chosen for an ability to stockpile 70,000 tonnes under each conveyor, the Littleton Quarry uses two Superior TeleStacker conveyors to stockpile its high demand 19mm and 9.5mm products. Each of three Superior portable radial stackers allows a 14,000-tonne capacity in stockpiling dense grade 13mm and 38mm products.
?We sell our material from the finished stockpiles and once we achieve the desired volume, we move the portable stackers to other areas within the crushing circuit,? Abramson said.
?A GIANT KIDNEY BEAN?
With a range of arc up to 270 degrees, the automated telescoping conveyor can be programmed to create customised stockpiles in many different sizes, shapes and configurations, while providing up to 30 per cent more stockpile volume than the standard radial stacker. For the Littleton facility, this flexibility provides a higher quality product at less cost. Abramson describes his finished stockpile as looking like ?a giant kidney bean?!
?We can program the TeleStacker conveyor to a certain travel pattern and then just walk away,? he said.
The unit features an automation package that is operated by a user-friendly touch screen system that programs the conveyor to create the desired stockpile for the application.
Abramson considers the Superior TeleStacker conveyor as the only effective solution to creating a fully desegregated stockpile. ?We do a tremendous amount of work for the department of transportation, so we really need to be right on top of our gradations,? he added.
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The telescoping conveyor consists of a stinger conveyor mounted inside an outer conveyor of similar length. With the ability to move linearly along the length of the outer conveyor, the stinger conveyor varies the location of the discharge pulley. The height of the discharge pulley and the radial position of the conveyor are variable. This three-axis variation of the discharge pulley is integral in building the layered pile in a series of windrows that overcomes segregation and creates an even blend of material throughout the pile.
The automation package controls the movements of the stinger, the incline and the radial travel to create the pile according to the desired specifications.
On maintenance, Abramson says the TeleStacker conveyor is fully mobile and can be moved to the side of the pile where it can be lowered.
?Our crew was trained on-site by a Superior representative about operation and maintenance,? he explained.
?All maintenance can be done at ground level. It?s safer and easier and eliminates the need for an elevated platform. Also, the unit came from the factory with the recommended primary and secondary belt cleaners.?
Ultimately, when considering a move to more efficient material handling methods, the Littleton operation looked at the total picture.
Consider that the typical loader has a value in excess of $US300,000 and, when factoring in depreciation and fuel costs, may average more than $US120,000 in annual operating costs.
Alternatively, an automated conveyor system has a lifespan of more than 20 years and its high capacity performance and low cost operation is still affecting the bottom line long after the truck or loader hits the salvage yard. Furthermore, rising fuel prices have little effect upon conveyor operating costs. Certainly, electricity costs are fairly stable when compared with diesel prices and conveyors can move material during off-peak energy intervals.
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While the Littleton Quarry is big on efficiency, Abramson says it is also committed to environmentally sound operation, for which the new conveyor systems have delivered major returns. Conveyors are the environmentally friendly choice while individual trucks and loaders emit and stir pollution along the entire transfer path.
?Our upgrades, and particularly our new material handling systems, have significantly affected our quality and our commitment to ongoing improvements in the way we do business,? he said.
In Australia, Superior products are available through 888 Crushing and Screening Equipment in Western Australia and Mobile Conveying Services in Queensland, New South Wales and Victoria.
Source: Superior Industries