The new washing plant at Torr Works is one of the largest facilities of its kind in Europe, handling 600 tonnes/h of waste scalpings Adding value at Torr Works

DUO Equipment install largest washing and water-management plant in Europe

orr Works limestone quarry in with up to 70 trains a week leaving the site , located approximately mid- each carrying, on average, 1,500 tonnes; local way between and , markets are also served within a 60–70km Tcovers an area of some 200ha and radius. includes 60ha that have been landscaped to Production at Torr Works revolves around blend in with the surrounding countryside. the use of a 1,200-tonne ‘walking’ primary Previously owned by , the crusher – the only one of its type in use in quarry is now operated by Bardon Aggregates the UK today. Commissioned in 1986 and as part of the Aggregate Industries UK standing as tall as a seven-storey building, it business. comprises a 54in gyratory crusher mounted Much of the quarry’s annual output of in a ‘walking’ frame manufactured by O&K. is despatched by rail, Capable of walking at 32m per hour, it ‰

QM April 2007 www.quarrymanagement.com 13 View of the washing plant typically moves a few metres each day 1,200mm wide x 27m long inclined belt showing the Cedarapids flat following the working of the quarry face. conveyor. This feeds the material through a screens and Greystone log- The walking crusher is linked to a flexible two-way discharge chute on to two in-line washers conveyor system that transports the crushed Cedarapids 6.0m x 1.8m three-deck primary rock across the quarry floor to an 85,000- rinsing screens. Supplied through the DUO tonne capacity primary stockpile, which is dealership and well suited to large-scale around mile away from the furthest face. production, these screens are the first of their Following a recent decision to wash and type to be installed in the UK. process the quarry’s large and growing The inclusion of Cedarapids flat screens stockpiles of primary scalpings to provide within the plant is said to provide significantly additional ‘added-value’ products, Aggregate greater throughput compared with similar- Industries commissioned DUO (Europe) to sized inclined screens. Additionally, the use of provide a complete washing and water- flat screens provides easier access for management plant. Operating under CDM maintenance and keeps the overall height of regulations as principal contractor on the the plant to a minimum. turnkey project, DUO were responsible for all The design of the screen vibrator structural calculations, bespoke structural mechanism allows the angle of throw and steelwork and the provision of conveyors, amplitude of stroke to be adjusted, while which were supplied by DUO Manufacturing. adjustable pitched motor pulleys provide for Believed to be the largest facility of its kind easy speed adjustments to accommodate in Europe, the new plant currently handles changes from coarse to fine material screening 600 tonnes/h of waste scalpings and produces operations. one grade of aggregate and two grades of The deck frames are huck-bolted to side sand, although it has been designed with the sheets for greater durability under aggressive capability to produce several sizes of aggregate vibration, while high-strength alloy steel side with a just few minor modifications to the sheets with spherical clamp bolt washers discharge chutes and the addition of further eliminate weld stresses. The flat-deck screens stockpile conveyors. were also specially designed to accommodate Material is drawn from the scalpings easily interchangeable modular polyurethane stockpiles and fed into a 50-tonne capacity decks. feed hopper, which in turn feeds on to a Any mid-size material from the rinsing ‰

14 www.quarrymanagement.com QM April 2007 screens is discharged into two Greystone log- snugly between the seal retainer and tub. A Two radial conveyors deliver washers, which mix the incoming feed while specially designed slinger fits perpendicular to the clean 5-20mm product to scrubbing and washing the material at the the shaft between the roller bearing and stockpile same time. Any lumps of earth or clay are sleeve and turns with the shaft, adding broken down during this process and carried protection to the outboard bearing and away in the wash water. preventing potential bearing failure due to seal Featuring a spiral paddle along the log shaft, leakage. the Greystone log-washers provide continuous The log-washer shaft is driven by twin agitation of the material, delivering maximum helical synchronized precision gears, which are scrubbing action, reducing energy totally enclosed within an oil bath gearbox. requirements and eliminating intermitent The unit is designed with externally mounted shock loading on the shaft and gearbox. bearings for easy pressure lubrication, service Heavy-duty flex couplings prevent any and maintenance. Standard electric motors misalignment and provide maximum allow for a change of washing action with a production and long wear life, as well as easy simple change of the drive pulley on the removal of the log shaft for maintenance or motor, while shaft-mounted speed reducers repair. with durable cast iron, corrosion-resistant The special paddle base design features housings provide positive gear alignment. The three bolt holes per paddle, while the Ni-Hard helical design of the gear teeth has a soft core wear-resistant paddles themselves deliver that resists shock loads and provides a 98.5% extra strength to protect against breakage and efficiency rating per gear set. Dual-output maximize wear life. Shoe paddles mounted to shafts with timed gears allow for the the bases with Grade 8 bolts are installed at interlocking of the paddles. In order to keep the proper angle to the extra-heavy ASTM dirt out and oil in, the reducers are sealed seamless steel log shaft for maximum washing with metallic double-lip seals. action and service life with minimum Mid-size material is fed from the log- maintenance requirements. washers on to a final pair of in-line 6.0m x The heat-treated shaft is fitted into a hard, 1.8m Cedarapids part-rinser screens, which stainless steel spacing sleeve and equipped provide a final rinse. The resulting clean with a heavy-duty rubber gasket that fits 5–20mm product is delivered to ground ‰

QM April 2007 www.quarrymanagement.com 17 The water-management plant stockpiles by two 800mm wide x 24m long discharged into a silt buffer tank once it has incorporating five Tecnoidea radial stockpile conveyors fitted with walkways reached the required density for pumping to multi-plate filter presses along their full length and around the head the plate presses. In order to maintain drums. throughput through the five presses, lime can Meanwhile, –5mm sand and water from the be added if a large quantity of clay is present primary rinsing screens, log-washers and final within the silt. part-rinsers is collected in two tanks located Lime addition is automatically controlled by beneath the plant and pumped 170m across means of a rotary valve. This feeds the lime on the site and up into a boiling box. From here it to a rotary screw, which in turn feeds it into a is fed under gravity into two Powerscreen mixing tank; at this point water is added to Finesmaster 200 machines which classify and create a lime solution. This is automatically dewater the material to produce two grades distributed into the silt buffer tanks, as of sand. required, where it reacts with any clay material Water management – an essential part of in the silt to facilitate water drainage in the the process – is dealt with by five Tecnoidea press. multi-plate filter presses, which provide Once each press has been filled and the maximum flexibility and throughput with rapid water drained, opening of the press allows the opening and closing times. Situated on a resulting silt cake to drop into a concrete bay galvanized structure mounted 5.0m above the below. The press then goes through a self- ground, these five presses provide an cleaning routine ready for another cycle. As in automatic silt-management system specifically all such applications, DUO carefully selected designed and sized to minimize operator input the size of presses for Torr Works taking into and maintain low running costs. account factors such as the silt content, clay As well as the five presses, the system content and settlement rate of the raw includes three 7.0m diameter deep-cone material. thickeners to clarify the water, a 7.0m In designing the whole plant, DUO also diameter deep-cone clarified water storage studied in detail the requirements for plant tank, an automatic flocculant mixing plant and maintenance. In particular, maintenance of the an automatic flocculant dosing system, which five presses can be achieved with ease owing regularly adjusts the volume of flocculant sent to the installation of fixed overhead lifting to the thickeners depending on the quantity of beams complete with electrically operated silt. Five in-line 80m 3 capacity sludge buffer hoists, while accessto the plate presses is via tanks with internal rakes complete the line-up. two staircases situated at each side of the Within each thickener tank the silt settles structure with further access via wide, fully to the bottom of the cone and is automatically galvanized walkways.

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