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Hillhouse Quarry RevampFirst phase of quarry upgrade delivers significant output andefficiency gains

Hillhouse Quarry Group Ltd are one of Scotland’slargest privately owned heavy buildingmaterials businesses, supplying drystone,

coated stone and concrete products to marketsthroughout Central and Southern Scotland,particularly Ayrshire and Glasgow. The company wasfounded just over a century ago with the opening ofHillhouse Quarry, near Troon, and has remained inthe Vernon family’s ownership ever since. Today thebusiness employs around 200 people and comprisestwo hardstone quarries, three asphalt plants, asurfacing division, four ready-mixed concrete plantsand a concrete blocks business, all in Ayrshire,together with precast concrete businesses in Beithand Inverness.When Hillhouse Quarry first opened for business

in 1907 the site was capable of producing 150tonnes of whinstone (dolerite) a day using thetechniques of the time, which included a rail track

and wagon system for removing material from theface. In the decades since then, ongoing expansionof the quarry and investment in new plant andequipment has seen production increase to thepoint where today the site has the capacity to deliveraround 1 million tonnes of drystone per annum,making it one of the largest privately owned hard rockquarries in Scotland. A significant proportion of thequarry’s output is used in house by on-site operations;the company’s three asphalt plants are all located atHillhouse, along with one ready-mixed concreteplant and the company’s concrete block-makingbusiness. In addition, Hillhouse Quarry now has thecapability to supply bagged aggregates and washedsurface-dressing chippings, and recycling operationshave also been developed in the past 12 months,giving the site a true one-stop-shop capability.In spring 2009, a decision was taken to upgrade

a section of the processing plant at Hillhouse �

The new secondary crushing and screening circuit at Hillhouse Quarry with the existing main crusher building/screenhouse visible on the skyline

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Quarry as the first step in a proactive move tomodernize and improve the efficiency of the entireplant. Despite its million tonnes per annum output,the plant was still struggling to meet the demandfrom internal and external customers when themarkets were busy, due in part to an imbalancebetween the capacity of the primary crusher and themore limited capabilities of the rest of the processingplant, but also because of the age and condition ofsome of the equipment and the inefficient nature ofthe discrete bottoming plant used for Type 1production, which was creating a productionbottleneck.

OOlldd ooppeerraattiioonnPreviously, –300mm crushed material from thesite’s Allis Chalmers 42/65 primary gyratory crusherwas delivered by an inclined conveyor to a 10,000-tonne surge pile. Material reclaimed from this pilewas carried by a single straight-line field conveyorand discharged on to an inclined feed conveyor to themain crusher building/screenhouse located on therim of the quarry where secondary and tertiarycrushing and final screening were carried out. Aseparate conveyor leg allowed material to be split offthe field conveyor and diverted to the bottoming plant,which consisted of one Allis Chalmers 18/50 crusher,

two Allis Chalmers 45in crushers, one double-deckand two triple-deck screens, together with associatedmotors, conveyors and feeders. With a maximumcapacity of 100 tonnes/h, this bottoming plant had atotal power draw of 571kW.Today, thanks to a £2.5 million investment in a

brand new secondary crushing and screening circuit,the old field conveyor and inefficient bottomingplant have both been rendered redundant andHillhouse Quarry is now able to make Type 1 muchmore easily and efficiently, and at a much reducedcost. Moreover, the new plant not only achieves apower saving of 90kW over the old plant, but at thesame time has also boosted the quarry’s Type 1 andsingle-size production capacity by 140 tonnes/h.Preparations for the new processing section

commenced in May 2009, the first task being theremoval of an accumulation of waste fines, in someplaces up to 25ft thick, from the area where the newplant was to be situated. This area was cleared downto the underlying bedrock by an in-house earthworksteam and then covered by a 1.8m deep layer ofcompacted fill material to provide an effectivedrainage layer. Substantial plant foundationscomprising 1.2m deep concrete rafts were then laiddown by Kilmarnock-based civil engineeringcontractors Kelburne Construction Ltd, using 757m3

of ready-mixed concrete from the quarry’s on-sitebatching plant.Following a competitive tendering process, and

based on the site management’s previousexperiences working with the firm, the role of maincontractor for the plant design, fabrication, assemblyand construction work was awarded to Annan-based John Hope Engineering Ltd. Their experienceddesign team devised a well-ordered, high-specification static plant based around a Sandviksecondary cone crusher and two Sandvik screens.The entire plant is fully modular in design and,therefore, easy to dismantle and transport elsewhereshould the need ever arise. Construction propercommenced in August 2009 and continued throughto Christmas, and at the time of writing the plant wasundergoing final commissioning and installation ofthe crusher and screenhouse buildings, withcompletion scheduled for the end of April 2010.

NNeeww ooppeerraattiioonnOutput from the quarry’s existing standalone primarycrusher is now delivered on to a new 66m long x1,000mm wide inclined feed conveyor, which reachesa discharge height of 15.5m and delivers the –300mmcrushed material on to a slightly repositioned surgepile. Material is recovered from this new 10,000-tonnepile by two 500 tonnes/h Rotex feeders mountedwithin a 3.8m diameter reclaim tunnel built fromcorrugated steel sections supplied by AssetInternational Structured Solutions. The feedersdischarge on to a primary tunnel reclaim belt,which, in turn, feeds a 45.7m long x 1,000mm wideinclined conveyor that discharges into a 100-tonnelive-capacity feed hopper mounted above the newsecondary crusher. To help minimize the abrasiveeffects of the harsh whinstone, material flow fromthe reclaim conveyor to the feed boot of the inclinedconveyor takes place via a robust transfer boxarrangement, rather than a chute. For similarreasons, all three conveyors in this first section of thenew plant are fitted with high-specification, abrasion-resistant Dunlop UsFlex belting, supplied by �

The new Sandvik CS660secondary cone crusher and100-tonne line capacity feedhopper mounted on a modularstacking frame

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Rema Tip Top.Mounted on a modular stacking frame that was

specially designed by John Hope Engineering forrapid erection on site, the crusher feed hopper isequipped with a 500 tonnes/h Rotex feeder whichchoke feeds the new Sandvik CS660 secondary conecrusher. Once plant construction is completed, thecrusher itself will be fully enclosed within a free-standing building featuring an easily removableroof section complete with all-round walkways and

handrails – another innovative yet simple featuredevised by John Hope Engineering to allow safe andeasy access to the crusher for servicing andmaintenance purposes.The –75mm product from the secondary crusher

discharges on to a 30m long x 1,000mm wideinclined conveyor which feeds a single-deck SandvikMSO 2460S inclined screen. Fitted with tensionedrubber mats and featuring a circular stroke in thecentre of the screen and an elliptical stroke at �

The new Sandvik MSO 2460Ssingle-deck screen whichtakes out –40mm Type 1

The new Sandvik MSO 2460Ddouble-deck screen whichproduces –20mm +5mm and0-5 dust

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the feed end for more accurate screening, thismachine effectively does all the work of the formerbottoming plant by taking out the –40mm Type 1material, which can be discharged to a groundstockpile via a 30m long x 800mm wide inclinedstockpile conveyor or sent forward to a secondscreen for further processing. Meanwhile, the–75mm+30mm oversize rejected by this first screenis sent to a new secondary surge pile via a 45m longground conveyor and 51m long inclined conveyorarrangement, both fitted with 900mm wide belts.These, along with all the other belts used throughoutthe new plant, with the exception of those on the firstthree conveyors, were supplied by Glasgow-basedStrathcona Conveyors Ltd.When production requirements dictate, the –40mm

Type 1 material from the first screen is redirected tothe second screen, a double-deck Sandvik MSO2160D inclined screen, again fitted with tensionedrubber mats, which produces two final products(–20mm+5mm and 0-5mm dust). These aredischarged to ground stockpiles via two 650mm widestockpile conveyors, while any –30mm+20mmrejected by the screen is transferred across, via ashort link conveyor, to the previously mentionedoversize conveyor for delivery to the secondarysurge pile.Recovery of the –75mm material from the

secondary stockpile is achieved by means of two 300tonnes/h Rotex feeders mounted within a newsecondary reclaim tunnel of similar design andconstruction to the primary tunnel. The feedersdischarge on to a 900mm wide reclaim belt which,in turn, feeds on to the last new conveyor in theupgraded section of the plant. This final 49.5m longx 900mm wide gently inclined conveyor, which isequipped with a material re-feed hopper at its tailend, discharges on to the quarry’s existing feedconveyor to the main crusher building/screenhouseon the rim of the quarry.Throughout the new plant, John Hope Engineering

have taken great care to incorporate high-specification components and ancillary equipment,including Siemens drive units, Cooper bearings onthe head drives, RHP bearings, Gurtec rollers and belt

scrapers from RH Services. Moreover, all of theconveyors are covered along their entire length tominimize dust emissions, and all head drives, tail endpulleys and feed boots are fully protected by integralpowder-coated guarding designed for easy removalwhen maintenance is required. The provision ofremote greasing lines and 110V power points atvarious locations around the plant also serves toassist routine maintenance work. Another keyfeature of the plant is that the three buildingshousing the new crusher and the two screens are alldesigned as free-standing fabrications and are notattached to the crusher/screen support structuresin any way, thus minimizing vibration transmissionand reducing maintenance. The electrics and control system for the new plant

were supplied by Livingston-based ElectromechIndustrial Ltd. The fully automated plant controlsystem allows dual control from either the primarycrusher control cabin or the final screenhouse,thereby allowing material to be ‘pushed’ or ‘pulled’through the system. A management informationscreen is also relayed to the quarry manager’soffice with real-time data on plant performancelevels.

CCoonncclluussiioonnThe addition of the new CS660 secondary crusher hasallowed Hillhouse Quarry to reconfigure the site’sexisting Sandvik CH660 secondary crusher and fourCH430 tertiary crushers, located in the main crusherbuilding, as tertiary and quaternary units respectively.Whereas previously the old processing plant had amaximum total production capacity of 310 tonnes/h, comprising 100 tonnes/h through thebottoming plant and 210 tonnes/h through the oldsecondary and tertiary crushers, the newly upgradedplant has boosted total production capacity to 450 tonnes/h. Now, some 300 tonnes/h go to the finaltertiary and quaternary crushers (90 tonnes/h morethan was the case previously) with the balance of 150tonnes/h comprising Type 1 or –20mm +5mm and–5mm (dust) production. Moreover, thanks to thissignificant increase in production capacity, Hillhouseare now able to run the plant for fewer hours thanbefore, thereby generating energy savings and othercost benefits in terms of reduced man hours andfewer repair and maintenance issues. As an additionalbenefit of the new plant configuration, the three mainsections of the plant (primary; secondary; andtertiary/quaternary stages) can be run independentlyif necessary, which was not possible before.With sufficient reserves to last well in excess of 20

years at current levels of production, this recentupgrade at Hillhouse Quarry represents just the firststage in an ongoing and proactive programme tomodernize and improve the entire operation, toensure the site continues to meet future demands inthe most sustainable, efficient and effective waypossible. Future plans include refurbishment ofthe primary crusher, which is scheduled to take placelater this year, followed in the medium to longer termby replacement of the final screens and product bins.

AAcckknnoowwlleeddggeemmeennttThe editor wishes to thank Hillhouse Quarry GroupLtd for permission to visit the site and, in particular,Justin Gill, operations manager, Gary Jones, quarrymanager, and John Hope of John Hope EngineeringLtd, for their help in preparing this report.

View of the new secondarysurge pile with the oldbottoming plant visible in thebackground

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