A new Xylem white paper entitled Shoring Up Mine Water Management by Nate Maguire, Americas Business Unit Director with Applied Water Systems, accepts that the current period of soft commodity prices may not be the time to make huge investments in new mine properties or to expand existing operations. “But it can be an excellent time for smaller, quick-return investments that boost efficiency, reduce costs, enhance profit margins and prepare an operation to thrive in better times.” One part of this is auditing existing water management processes and equipment at mines to see what improvements can be made.
“In mines, as at any industrial site, it’s common to find aging machinery in need of repair or replacement, equipment no longer sized properly for required demand, and systems performing at less than optimum because the operation has changed or evolved. This also pertains to mine water equipment. Pumps, piping and controls for applications such as dewatering, tailings basin decanting, wastewater treatment, camp water transport, fire suppression and dust control may be in need of upgrade. For instance:
• Pumps operating outside their optimum range waste energy and are subject to faster wear and shorter service life.
• Pumps no longer compatible with the water’s physical or chemical properties can be at risk of premature failure, causing costly, unplanned downtime.
• Older pump hydraulic designs and fixed-speed installations may consume far more energy than the latest premium efficiency units with variable frequency drives (VFDs).
Current market conditions offer a prime opportunity to audit mine water management and pumping systems
to identify waste and operating risks. Such an audit can form the basis for a program that optimises pumping efficiency at a high rate of return on investment. “Experience shows that mine planners and engineers often intentionally oversize pumps. In dewatering, for example, designers size pumps not just for immediate needs but to
anticipate enlarging or deepening of the pit. However, if significantly oversized for initial requirements, the pumps
will run inefficiently and wear out faster than they should.”
It is a common practice to select one large pump to serve two purposes within a mining operation. A single 150 hp turbine, for example, might be selected at a sand and gravel pit for water transfer and for wash plant supply, one being low head and the other higher pressure. “However, these joint flow applications rarely operate at BEP, so a more energy-efficient selection might be to down-select multiple pumps, each ideally suited for the application. The cost of the second pump can be recouped through energy savings and underscores the importance for pump system designers to consider system efficiency and operating costs, as well as future capacity requirements when designing a system.”
On the flip side, a pump that was properly selected for a specific duty point may now be operating outside of its BEP as requirements, such as head or flow, have increased. Furthermore, digging deeper may lead to a change in the
character of the water: more abrasive solids or more acidic (thus more corrosive) water may create different pump
metallurgy, which may cause rapid wear, requiring intensive maintenance and early replacement. On a more basic level, some pumps simply wear beyond their useful life and can be replaced or rebuilt. Replacement can reduce demands on the maintenance team and provide an opportunity for increased energy efficiency and materials upgrade for longer product life.
“These include pumps with advanced hydraulic designs, corrosion resistant impellers or taking advantage of variable
frequency drives to save energy and extend service life while improving operational flexibility. Finally, mines can put critical processes at risk by becoming dependent on pumps that lack redundancy appropriate to their degree of criticality. The failure of a critical pump means unplanned and extremely expensive downtime.”