Mining in Swedish Dannemora came to a halt in 1992. Due to a severe drop in the price of iron ore the operation was no longer sustainable. As the market is now booming, Dannemora Mineral is working to get the mine dry and back in operation. Xylem has been working with Dannemora Mineral since May 2009 to rid the mine of water and ensure  it remains water-free throughout the operation.

Water had accumulated at a rate of 10 m a year in the main shaft and drifts since the mine was closed 20 years ago. The bottom of the main shaft is 620 m below ground; water had reached 323 m by 2007.

Xylem designed a customised dewatering system for Dannemora. In May 2009, when the water level was at 311 m below ground, four parallel Vogel pump systems, each with a capacity of approximately 60 litres/s, hanging in 180 m long steel pipes, at levels of -480 m and -300 m, were installed. Since then Xylem has drained 3.4 million m3 of water from the mine.

As well as the initial dewatering and drainage work, Xylem has designed, and is in the process of installing, a permanent system that will ensure the mine stays dry and in operation.

Lars Thoro, consortium manager with Xylem, said, “The permanent dewatering system consists of 12 Vogel and Flygt pumps which together remove 20 litres of water per second. The Flygt 2400 and Flygt 2630 pumps are ideal for this type of operation as they are specifically designed to withstand tough operating conditions. They are ideal for dewatering applications such as the Dannemore mine, delivering highly consistent performances over a long period of time.”

According to Xylem, special features unique to its Flygt brand of dewatering pumps such as Dura-Spin^TM, a hydraulic system which minimises impeller wear; Spin-Out^TM a system designed to prevent clogging and protect the
outer seal and the K-Impeller, a hard iron impeller specifically designed for high efficiency and wear resistance, make the company the experts in mine dewatering.

Thoro continued, “A great addition to the Dannemora dewatering operation is a Scada system which enables the operation to be monitored from above ground. A Flygt APP521 pump controller at each pump station manages operation of the pumps. This information is then communicated back to a computer system at ground level. This
gives operators access to critical data from one location above ground allowing operators to monitor equipment, troubleshoot and identify trends, diagnose and resolve issues, quickly and easily. The end result is a pump station control system that provides ease of operation, flexibility and reliability, ensuring more uptime, greater energy savings and less operating and maintenance costs.”