South Crofty is a former copper and tin mine situated in the towns of Camborne and Pool, in Cornwall in Great Britain. The first documented account of production at South Crofty dates from the year 1592. In 1998 South Crofty was the last tin mine to close.
Strongbow Exploration Inc. has acquired the site and plans to re-open the mine. Since closure, however, the mine has flooded to a level 60 m below the surface.
The project has been given all the necessary permissions for re-opening the mine, and plans are to begin draining the mine in 2019. The system will take a stagewise approach to drainage, using immersion pumps to pump pit water straight from the shaft into the pit water treatment plant, down to 730 m below the surface.
Installed in the shaft are two pumps each of which can deliver 525 m3/h of water to the treatment plant. The pump motors are designed so that they can be controlled by a frequency inverter enabling the pump speed to be varied from nought up to 3,000 rpm. This change of speed is necessary to maintain a constant water supply of 1,050 m3/h to the treatment plant, taking into account that the water level in the mine varies when it sinks. Speed regulation further enables the rate of water flow through the entire treatment plant to be controlled. Strongbow can thus meet environmental requirements and limit the introduction of treated pit water into the nearby Red River in high-water conditions.
In February 2018 WINDER CONTROLS Europe Ltd. was commissioned to deliver two frequency inverters that deliver to the pumps 950 kW at 3,300 kV. In addition, a programmable logic controller (PLC) connects the drives and local signals to the water treatment system.
The frequency inverters were successfully tested at the works in July 2018, delivered to the construction site in September 2018 and will be ready to go into service in early 2019.