Sandvik Aids Ennstone’s Switch to Mobile Crushing

• 
• 27th June 2008
• Quarrying
 

A pair of Sandvik track-mounted crushers is helping leading aggregates producer Ennstone Johnston switch from static to more flexible mobile crushing solutions at its hard rock quarry in Leaton, Telford.

Ennstone Johnson, part of the multinational Ennstone Group, is utilising a pair of Sandvik track-mounted mobile crushers to upscale production at its Leaton Quarry near Telford.   The 43 tonne UH440i units, which feature Sandvik CH440 cone crushers specifically designed for hard rock applications, have proved to be an ideal match for the Olivine Dolerite that is being extracted from the 52 hectare quarry.

Hard Rock Quarry

With operations as far afield as Poland and the US and across the UK, Ennstone is a name familiar to anyone with even a passing interest in the field of aggregates production.   Operating from offices at Breedon-on-the-Hill in Leicestershire, the company has established a formidable network of quarries, asphalt and concrete plants that cover an area from the Welsh border to the East coast of Norfolk, and from South Yorkshire through to Oxfordshire.    

Acquired as part of Ennstone's purchase of Johnston Roadstone, Leaton is the only quarry supplying hard rock products to the Ennstone group in England.    The 52 hectare site, which was opened in the 1920s and has some seven million tonnes of reserves, currently supplies eight group company plants with Olivine Dolerite, an igneous rock formed in shallow intrusions that push between beds of sedimentary rock.   Hard without being too abrasive, Olivine Dolerite is particularly popular because it can be shaped to suit a wide variety of asphalt applications.

Increased Production

The quarry operates on five levels of 14 metres each.   The lowest level has now reached the water table and has to be pumped.    Material is currently extracted by blasting although this has to be done carefully due to folding of the rock beds which has resulted in some lying at 45 degrees and some lying almost vertically.   As a result, blasting can take place twice a week or up to 10 days apart.   In particularly awkward locations, Ennstone Johnson will only blast 1,000 tonnes, but on a main face it could be as much as 32,000 tonnes.    An average blast is around 20,000 tonnes.

Leaton Quarry's main crushing plant utilises a Svedala Superior crusher to reduce the blast material from 110 mm down to 48 mm, this feed going forward to two H200 hyrdrocone machines for further reduction. Oversize product is returned to an additional H200 hydrocone, to maximise the fines products.  These have been in place since 1984 and 1988 respectively and have maintained an annual production of 350,000 tonnes.    However, when Johnston Roadstone was acquired in 2004, an increased production target of 750,000 tonnes/year was set to meet the group's growing materials demands.   "Having looked at the alternatives, we decided that mobile crushers were more suitable than a replacement static plant," says Western region production manager Kieren McCabe.   "A static plant would have cost several million pounds but the mobiles are just a fraction of that cost.   In addition, they afford us considerable operational flexibility, allowing us to follow the blasting pattern and reduce haulage costs."

History of Reliability

McCabe reports that the selection process was made easier by the company's long history of running the Svedala static plants.   "The Svedala statics were extremely reliable so the thought of dealing with the company behind the Svedala brand gave us some additional confidence," he says.   "Sandvik also claimed that we could produce four different products with a single mobile machine which would allow us to remove another crusher from the production process.   Once they proved that, the choice was easy."

The machines chosen were two Sandvik UH440i track-mounted mobile cone crushers: one loaded with 95 mm material for onward feeding to a pair of screens; the other acting as a secondary crusher to a primary jaw to produce a range of 6, 10, 14, 20 and 32 mm products.

 Weighing in at 43 tonnes, the UH440i crushers are built around a proven and highly durable Sandvik CH440 cone crusher that delivers the optimum combination of throughput and shape.   The cone crusher is controlled by a patented Automatic Setting Regulation control that gives a smooth flow of material and high productivity levels.   The entire crushing process is continuously and automatically monitored by the intelligent control system that provides the operator with valuable operational information.   "From the moment we saw the UH440i machines, we really liked the build quality.   A lot of steel goes into the building of the crusher and they're immensely strong.   In my opinion, they have the best build quality of any crusher I have seen to date," McCabe says. "The best feature is unquestionably the ease of operation.   They have a huge programme choice and the ability to change product size with no loss of production whilst the crusher is in operation.   The control system gives the operator a lot of production modes that allow us to maintain an excellent product shape, even at maximum productivity." 

Multiple Products

Although he is clearly enthusiastic about the ease of operation of the two new Sandvik crushers, it is their ability to produce a range of material grades that has really found favour.   "The Sandvik machines are producing four different products to a very high quality standard at a rate of approximately 270 tonnes/hour.   That  compares extremely favourably with the static primary jaw crusher which was running at around 170 tonnes/hour," McCabe continues.   "Using one machine to achieve all this saves a lot of time and expenditure.   During periods of peak demand, we have worked from 5 am until 11 pm.   With a normal machine, you would expect that to generate a considerable amount of wear.   But the Swedish metals are very good and the Sandvik crushers are showed no significant signs of premature wear."

Despite this, McCabe reports that Ennstone Johnson has invested in a preventive maintenance contract with Sandvik to ensure that the new crushers are maintained properly and that unplanned downtime is minimised.     "I really can't fault the service we receive from Sandvik.   They are always co-operative and helpful.    They respond quickly and if we need a part they go out of their way to find it," Kieren McCabe concludes.   "When we did experience an initial engine fault, a replacement unit was taken from the production line and delivered straight to the quarry. And that was during two bank holidays: one in England; and one in Sweden."

Sandvik Mining & Construction Ltd

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