New Life To For Tungsten And Tin Mining On The Edge Of Dartmoor

Charlie Northfield, process plant manager, for the Wolf Mineral site, said "we plan to be producing between 3,500 and 5000 tonnes per year of tungsten concentrate – about 3.5% of the global forecast demand". Wolf Minerals, the Australian company building and running the mine, claims 200 jobs will be directly created and says the £130m project will plough millions of pounds into the Devon economy every year.

The extraction of tungsten will take place through open pit mining with the pit measuring about 850m long by 450m wide extending 200m. The sides of the pit will be cut in benches to allow for safe working as the mine gets deeper. Most of the valuable tungsten and tin at Hemerdon can be found within the large deposits of granite. The granite contains veins of quartz / tungsten can be found, identified by diamond drilling.

Key process equipment and services were identified and suppliers invited to tender. One of these processes was the supply of 10 linear screens used for the separation of the size fractions of Raw and finished material within the process streams. Don Valley Engineering was selected as the preferred supplier and awarded a contract to supply of varying size, 10 Linear screens, ranging from 9.0m2 to 64m2 single and double deck screening areas and through-put rates in excess of 1200tph.

Upon award of the contract, the Don Valley Engineering design team, set about designing and detailing each screen to meet the screening requirements of the user requirement provided by the process flow diagram equipment specification. Each screen was individually designed and one of the screens in particular believed to be the largest double deck screen to be supplied in the UK by Don Valley Engineering, measuring 8.1m in length and 4.0m wide pushed the envelope of screening technology for gross weight, weighing in at some 32 tonne and with a screening surface area of two screen decks each measuring 32m2 total 64m2, designed to minimise the footprint of the plant.

The size of this screen is believed to be the largest screen manufactured in the UK and certainly by Don Valley Engineering, the company have produced longer screens and larger throughput rates, but not at the weight or screening design ratio. The unique design of the Banana screen so called because of the curved screen area, allowed the design of the feed chute to achieve maximum feed properties, whilst reducing the angle of the screen decks, thus providing maximum screening properties to be obtained over the screens area to footprint.

In the second week of June 2014, Don Valley Engineering completed the final logistical stage of the contract. Allowing GR Engineering to meet their obligations to Wolf Minerals and take delivery of the 10 linear screens, delivered on time as per the contract program. The first screens were off loaded and will be stored ready for mechanical installation as per the project program. The large screen required a police escort and was delayed by police for 36 hours to allow the road works on the exit of the M5 to be rearranged to allow the large load to pass safely.