Pumps manufacturer KSB submitted the South Crofty tin mine project into the Pump Industry Awards UK, with Cornish Metals. In March it was announced the 2024 Project of the Year winner.
The mine ceased production in 1998 and was allowed to flood to adit level – circa. 60m from surface. Approximately 8 million cubic metres of water now needs to be removed to enable resumption of tin mining from the deepest levels.
Two KSB BSX463/5 950kW borehole pumps were purchased to dewater the mine, each capable of pumping up to 525m³/hr from a maximum depth of 400m. Utilising Variable Speed Drives, both pumps have been installed to their initial first phase depth of 365m. Dewatering started in November 2023.
The workings at South Crofty are almost 900m deep, with the primary access, New Cooks Kitchen (NCK) Shaft, reaching 769m. NCK Shaft is the focal point of the dewatering and is directly connected to the original pump stations of the mine, with one at 350m from surface, and another at 730m. The ability to install the pumps and rising mains from the surface to dewater in a single phase to the first pump station elevation, enables dewatering of the upper half of the mine without the need to conventionally re-access the shaft.
Conventional mine dewatering requires time-consuming installation/commissioning of a shaft winding system to facilitate pump installation sequentially deeper as the water levels recede. The ability to install and control the pumps entirely from the surface in advance of any shaft refurbishment accelerates the dewatering considerably. This improves safety by allowing the re-access works down the shaft to be conducted independently to the dewatering rate. Using VSDs and the positive head of water above the pumps, considerable energy is saved.
