2013 saw a great deal of activity for Somerset based John Wainwright & Co Ltd. Its Moons Hill quarry received £3.5 million of investment in a secondary aggregate production plant, replacing some of equipment that has been in use since 1963. The new twenty metre high plant is estimated to be 60% more productive, and will utilise some of the most modern, and efficient crushing and screening equipment all manufactured by Sandvik Construction.
John Wainwright & Co Ltd has been supplying premium aggregates to the construction industry since 1891 from its two Somerset quarries, Moons Hill and Stoke. Now as then, the company is proud to be an independent business, renowned for its innovation, environmental and ecological awareness, as well as its strong local roots which are reflected by the part the company plays in fulfilling its community responsibilities.
“Our independence and shared values set us apart in our sector.” Stated Managing Director Peter Barkwill, who explained the company’s business ethos; “Wainwright’s has maintained its market share through the expansion of the company’s core capabilities, major inward investment and the professionalism of our extremely experienced staff. This pervades the company at all levels, and ultimately the quality of our major asset, the basalt upon which the company was founded.”
For over 100 years Wainwright’s has been extracting basalt from its Moons Hill Quarry. The aggregate found here is hard stone basalt (Andesite), with a minimum PSV of 57. This makes the material the only source of surface course quality aggregate within the Somerset and surrounding region. Once quarried the extracted aggregate passes through an extensive crushing and screening process, which enables the production of both single sized and blended aggregate. As well as being used extensively for surface dressing throughout the South of England due to its high PSV, the processed material has many other applications, with major usages being in the production of asphalt or concrete, clause 803 (SHW) type 1 sub base, a specialist dust for horse arenas as well as a non-calcareous aggregate for watercourses.
In order to capitalise on the excellent properties of the basalt, in 2001 Wainwright’s established its own road surfacing division (Wainwright Surfacing Ltd) which subsequently gained Sector Scheme 16 “Laying of Asphalt Materials” accreditation. In 2003 Wainwright Surfacing formed a company called Mendip Contracting in partnership with Foster Yeoman – now Aggregate Industries – and secured the £6 million per annum Somerset surfacing sub-contract on behalf of Atkins. Since then Wainwright Surfacing has gone on to win further contracts with other local authorities, including West Berkshire Council.
In order create the materials for Wainwright’s business the materials must be firstly quarried. In order to develop quarry faces for the production of the aggregate it has proved necessary in certain areas to excavate and strip between 20-30 metres of the weathered rock from the surface. Both the weathered rock and high quality basalt are removed by blasting, with the blast being planned using laser mapping for logging the drill holes. Once all the available data has been analysed, the drill pattern is agreed and drilling commences, with the drill holes placed in a precise pattern to ensure the maximum amount of stone is blasted in the most efficient manner to ensure that the resultant aggregate is of a size that is able to pass through the crushing plant without further processing.
After blasting, the broken stone is normally loaded into dump trucks by face loading shovels and delivered to the crushing plant. The crushing plant in use today varies considerably in design and layout, but typically the stone is discharged into a dump hopper, and then drawn from the hopper by an apron feeder with chain curtains controlling the flow of rock. From the apron feeder the stone falls onto a vibrating grizzly. The under-sized stone in turn falls onto a conveyor belt and the over-size passes into the primary crusher. The crushed stone falls from the crusher onto a conveyor belt which is parallel to a belt carrying the under-size from the grizzly running from the base of the primary crusher house to the new scalping plant.
In the autumn of 2012 foundations were laid for the new plant which was eventually completed in the summer of 2013. This new plant consists of a new scalping screen which is fed by extended conveyors from the existing primary crushing station. New scalping conveyors and a radial conveyor allow 2 sizes of scalping’s to be stocked and blended. Dependant on quality and weather conditions, the scalping screen and conveyor arrangement allows scalping’s to be recovered and fed into the secondary surge bin
Recovered oversize scalping’s and minus 200mm crushed rock from the primary crusher are discharged into a surge bin, prior to secondary crushing. Here it passes through the new Sandvik CS440 Superior secondary crusher, giving an overall reduction in size to -63mm. The crushed material is then passed over a Sandvik SS1223 selector screen to remove the minus 6mm. The over size is then discharged into a hopper feeding two Sandvik Tertiary crushers, producing a minus 20mm cubical product with a low flake index, which is specifically required for road surfacing dressing purposes.
The tertiary crushing station consists of a new Sandvik CH440 Hydrocone, and an existing Sandvik H3800 Hydrocone that was refurbished by Sandvik and then relocated from the old processing plant. The tertiary crushed material is then conveyed to the main screen house where it is passed over three linear motion screens which are fitted with polyurethane decks. These screen decks are set up to produce aggregates in the following sizes: dust, 5mm, 6mm, 10mm, 14mm, 20mm and rejects.