MATERIALS HANDLING
240m³/h. Te particle sizes, which are in the range of 0.5mm, are causing no problem at all. Te fluid viscosity is 5 mPas.
The two VSD-driven units have been successfully employed since August 2017
PUMPS WITH LOW NPSHR Te essential requirement for the new units was their suitability for pumping media containing solid matter. Tey also needed to feature flow rate of 240m³/h, pressure of 3 bar, and NPSHr of 1.8m. Te management selected two rotary lobe pumps from the Tornado T1 series. Tese pumps meet the requirements of the open-pit operator in terms of flow rate, pressure, delivery rate and suction; they also have exceptionally convenient compact dimensions. Te key advantage over the previous technology is that these models are self-priming positive- displacement pumps, which guarantee continuous delivery. Inside the pumps, there are two synchronised intertwined rotors, which create negative pressure on the suction side drawing the medium to
the rotary lobes without interruption. Te lobes then convey the medium to the pressure side. Tis conveying principle has a very
positive effect when used in the relevant application. “Te vacuum tank operates at a very low pressure, which in turn creates a very low inlet pressure for the water intake from the vacuum tank,” says Weir. “Our pumps are well suited for this application, since they operate with a low NPSHr.” Tey are, therefore, insensitive to the effects of cavitation, which may cause other types of pumps to fail quickly. Furthermore, the volume transported depends on speed. Tus, the desired quantity can be dosed exactly by setting the rotations per minute. When used in the mine in Australia, the speed is 218rpm, and the conveyed volume is
Two T1 rotary lobe pumps decant a fine coal screen vacuum tank in the open-pit coal mine
HIGH OPERATIONAL RELIABILITY AND SIMPLE HANDLING An essential feature of rotary lobe pumps is that their gear and pump chambers are strictly separate from one another. Tis special Gearbox Security System (GSS) ensures that the medium cannot enter the complex gearbox, even in the event of a shaft seal failure. Tis means high operational reliability. On the other hand, gear oil can never enter the pump chamber. Te seal is lubricated and cooled by means of easily accessible flushing and sealing water connections.
IMPROVED COAL FINES RECOVERY Since August 2017, the two pumps have been employed to decant excess water from the vacuum tank, and to convey it to the clarifying or thickening tank. Water is recovered there, and then reused in the coal treatment plant. Te two VSD-driven Tornado units ensure stable and lower liquid level in the vacuum receiver. Te vacuum for draining coal fines is thus more reliable. “Higher vacuum and more uniform vacuum level lead to more efficient recovery of coal fines,” explains Weir.
Roger Willis is with Netzsch.
www.netzsch.com
52
www.engineerlive.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
