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Size Reduction

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.

EXACTING AGGREGATE PRODUCTION 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

42 September 2014 Solids and Bulk Handling

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.


In order to deal with increasing market requirements for its high quality basalt aggregate it is no surprise that a company of the calibre of the Wainwright’s utilises the Sandvik Superior and Hydrocone range of crushers. This is due to their design and ability to offer high reduction and production of excellent product shape. All the Sandvik crushers are based upon the principle of hydraulic adjustment of the CSS, and with ASRi automation fitted to all machines. Additionally a choice of several different crushing chambers, and many other high performance features, make each model versatile, user friendly and highly productive.

The CS440 Superior Secondary cone crusher has proved to be ideal for Wainwright’s secondary requirements due to the compact and easy to service design which makes it the perfect choice for Wainwright’s quarrying operation. In fact the CS440 now carries out the same duty as two aging cone crushers it replaced in the original plant. Supplied with Sandvik’s ASRi automatic setting system, the CS440 has played a key part in maximizing production through the secondary part of Wainwright’s quarrying operation. Sandvik’s ASRi is also fitted to both tertiary crushers and optimises the efficiency and operation of the Hydrocone crushers by automatically adapting the crusher to variations in feed conditions. By continuously measuring and compensating for crusher liner wear the ASRi allows Wainwright’s to fully utilize crusher liners, thereby scheduling liner replacements in order to coincide with planned maintenance. The ASRi also assists in keeping the crusher choke fed, thus maximising rock-on-rock crushing, which helps to optimise the quality of the final product. Peter Barkwill explains the physical makeup and benefits that have resulted from the new plant: “In order to comply with local planning, the new plant now possesses minimal visual impact with low noise and low emissions from all the Sandvik equipment proving to be vitally important given the proximity of the plant to both a main road and a local village. Community relations are very important to us, and hence the benefits cannot be overestimated. Additionally now fully operational, we estimate the plant to be 60% more productive than the previous installation, with the Sandvik equipment being the culmination of a £3.5 million investment.”


Firstly, the establishment of its own road surfacing division, and now the acquisition of a new state-of-the-art secondary aggregate plant, have shown that Wainwrights with its long proud tradition, is more than capable of developing its business to face the future. This focus has enabled the company to expand its operations in order to take advantage of the unique properties of the basalt found at its quarries, whilst at the same time staying true to its roots and community focus. n For further information please visit:

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