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Metso Crushers Help Safeguard National Asset

Monday, December 17th, 2007

A range of crushing and screening equipment supplied by Metso Minerals (UK) Ltd is helping safeguard production of what is described locally as a national asset; dolorite from the Isle of Man’s Poortown Quarry.
A full line-up of Metso Minerals crushing and screening equipment is being used to provide the Isle of Man with much-needed roadstone and asphalt products. Owned and operated by the Works Division of the Isle of Man Government’s Department of Transport, the Metso equipment forms the lynchpin in production at the Poortown Quarry in Peel and marks an important switch to producing high quality materials using mobile equipment.
Parish Past
The Poortown Quarry has been in operation since the 1850s and has always fallen under the control of the Isle of Man Government. As a throwback to its parish past when each local parish was expected to cater for its own needs, the quarry is one of a number on the relatively small island that is home to just 80,000 inhabitants. However, as quarry manager Kevin Brookes explains, Poortown Quarry is unique. “When the island was truly split into individual parishes, each parish would have its own quarry,” he says. “But Poortown is now the only quarry producing roadstone. Roadstone is a vital commodity in an island community such as this as it is prohibitively expensive to import it from the UK mainland. We see the dolorite at Poortown as a national asset to be controlled and safeguarded.”
Measuring approximately 30 hectares in size, the quarry currently operates at a production rate of 70,000 tonnes per year although there are contingency plans to increase output to around 100,000 tonnes per annum. Such an upscaling of production will certainly be required if planning permission is granted to the extension of a new runway at the island’s increasingly busy airport.
Redevelopment Programme
Following a protracted planning application originally made in 1992, the quarry is now working towards an extension to the East and, possibly, the North. The site is in the midst of a £7 million redevelopment, a significant part of which is the upgrading and replacement of the quarry’s processing plant. At the heart of this is a comprehensive line-up of equipment supplied by Metso Minerals (UK) Ltd.
Blasting takes place on a monthly basis, each blast freeing around 8,000 tonnes of dolorite from one of the three 15 metre high faces. This material is loaded into a Lokotrack LT 105 track-mounted mobile crushing plant by a CAT 325 hydraulic excavator equipped with a 3 m3 capacity bucket. Product from the LT 105 is then passed directly into a Lokotrack LT 200 HP cone crusher that in turn discharges into a Metso ST 352 screen. At this point, the product is a 28 mm grade.
Product Shape
The 28 mm product is passed directly into a second LT 200 HP cone crusher. “The material here is very hard but it is also naturally flaky. It is important that we get the right product shape with the minimum possible waste,” Brookes continues. “The cones are the ideal crusher for this. The shape of the finished product from the HP machines is absolutely brilliant.” The product is screened over a series of three Metso double decks, one ST252 and two ST348 to produce a range of single sized aggregates.
Brookes explains that production rates at the quarry are dictated primarily by local demand and the quarry runs a policy of serving the island’s needs first and private companies second. The most popular grades are a 6 mm product used primarily for footpaths, and a 10 mm used as a surface coating on the island’s roads. The quarry also produces 14 and 20 mm grades for road use and there is currently a significant order for railway ballast being processed by the Metso Minerals plant.
New for Old
Kevin Brookes reports that the acquisition of the Metso equipment was the culmination of some considerable research. “We compared the Metso equipment to a number of other crushers and we soon realised there really was no comparison. We had used Metso equipment in the past and had no hesitation in replacing it on a new for old basis,” he concludes. “The Metso equipment satisfies our needs for a good quality, well shaped product but it also meets our other purchasing criterion too. We prefer to concentrate on a single supplier as, in our experience, their machines work together far better. Furthermore, as an island we always buy with the long term picture in mind. It can cost upwards of £3,000 per item to ship equipment back to the UK mainland for resale so we don’t buy cheap, we buy right.”

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