Mine Dewatering

Chapter 20 - Mine Dewatering
Number	Topic	Rule of Thumb
20.01	Water Balance	The average consumption of service water for an underground mine is estimated at 30 US gallons per ton of ore mined per day. The peak consumption (for which the water supply piping is designed) can be estimated at 100 USGPM per ton of ore mined per day. Source: Andy Pitz
20.02	Water Balance	Ore hoisted from an underground hard rock mine has moisture content of approximately 3%. Source: Larry Cooper
20.03	Water Balance	A water fountain left running underground wastes 1,100 USGPD. Source: Jack de la Vergne
20.04	Water Balance	A diesel engine produces 1.2 litres (or gallons) of moisture for each litre (or gallon) of fuel consumed. Source: John Marks
20.05	Water Balance	In the hard rock mines of the Canadian Shield, ground water is seldom encountered by mine development below 450m (1,500 feet). This may be because the increased ground stress at depth tends to close the joints and fractures that normally conduct water. Source: Jim Redpath
20.06	Layout	The main pump station underground must have sufficient excavations beneath it to protect from the longest power failure. The suggested minimum capacity of the excavations is 24 hours and a typical design value is 36 hours. Source: Jack de la Vergne
20.07	Layout	The main pumps should be placed close to the sump so that the separation will allow for a minimum straight run of pipe equal to five times (preferably ten times) the diameter of the pipe. Various Sources
20.08	Layout	Allow one square foot of surface area/USGPM in the design of a settling sump. (Refer to Section 20.13.) Source: Raul Deyden
20.09	Layout	Turbulence will be sufficient to ensure good mixing of a flocculating agent if the water velocity is at least 1m/s and maintained for 30 seconds in a feed pipe or channel. Source: NMERI of South Africa
20.10	Design	Piping for long runs should be selected on the basis that the water velocity in the pipe will be near 10 feet/sec (3m/s). The speed may be increased up to 50% in short runs. Various Sources
20.11	Design	In underground mines, static head is the significant factor for pump design if the pipes are sized properly. To obtain the total head, 5 -10% may be added to the static head to account for all the friction losses without sacrificing accuracy. Source: Andy Pitz
20.12	Design	Pump stations for a deep mine served by centrifugal pumps are most economically placed at approximately 2,000-foot (600m) intervals. Source: Andy Pitz
20.13	Design	A tonne of water a second pumped up 100 m requires 1MW of power. Source: Frank Russell
20.14	Design	The outlet velocity of a centrifugal pump should be between 10 and 15 feet per second to be economical. Source: Queen’s University
20.15	Design	A sump should have a live volume equal to at least 2½ times the pump operating rate to limit pump starts to six per hour (typical NEMA B motor). For example, the live volume of the sump for a 500 USGPM pump should be at least 1,250 gallons. Source: Lauren Roberts
20.16	Design	Centrifugal pumps should not operate at a speed exceeding 1,800 RPM (except for temporary or small pumps that may operate at 3,600 RPM). This is because impeller wear is proportional to the 2.5 power of the speed. In other words, half the speed means nearly six times the impeller life. Source: Canadian Mine Journal
20.17	Design	The maximum lift of a centrifugal pump is a function of the motor torque, which in turn is a function of the supply voltage. Since it is a squared function, a 10% drop in line voltage can result in a 20% loss in head. Source: Jack de la Vergne
20.18	Design	The velocity of dirty water being pumped should be greater than 2 fps in vertical piping and 5 fps in horizontal piping. These speeds are recommended to inhibit solids from settling. Source: GEHO
20.19	Design	Slime particles less than 5m in diameter cannot be precipitated without use of a flocculating agent. Source: B. N. Soutar