A new face drilling rig for narrow tunnels and ... - Advanced Mining

Characteristic data like active current intake and rotation
speeds of the individual screw conveyors are continuously
recorded during the test in the frequency converter. In
addition the measurement technique installed at the test
site allows for recording of other important measurement
data. Apart from the inclination of the screw conveyor and
its filling level, the conveyed mass flow is recorded through
balance weighing of the entire content of the bunker. These
values are also recorded as analog signals in the frequency
converter. The data saved in the frequency converters are
Table 1:
Technical data of the screw conveyors of the test plant
sorted with an analysis software and combined in a result
file for further processing. Thus the mentioned influencing
factors, rotation speed, filling level and inclination can
directly be set or at least be continuously monitored. In
addition to these parameters the characteristics of the
bulk materials also have an influence on the conveying
process and the power requirement. Therefore the tests
were repeated for various bulk materials. The parameters
to be examined and the respective parameter levels are
summarized in table 2.
Finally, the command variables to generate the
dimensioning and layout guidelines can be calculated from
the recorded data. The empirical coefficient of velocity
ζ* can be calculated from the measured mass flow I m
according to
*
4 ⋅ I m
ζ =
2
ρ ⋅ϕ
⋅
Issue 04 | 2010
2 ( D − d ) ⋅π
⋅ S ⋅ n
(12)
With the bulk density ρ, the filling level φ, , the screw
diameter D, the shaft diameter d, the screw pitch S, as well
as the rotation speed n. At the same time the empirically
determined coefficient of power λ can be calculated from
the recorded active current I Wirk
λ
*
=
3 ⋅U
eff
I
m
⋅ I
Wirk
⋅η
− P
D
⋅ g ⋅ ⋅ L
S
Leer
S ⋅ H
−
D ⋅ L
(13)
TRANSFER OF TECHNOLOGY
Table 2:
Examined parameter levels in the tests
Parameter Unit Parameter levels
Rotation speed n [1/s] 2 3,5 5 6,5 8
Inclination angle β [°] 20 30 40 50 60
Filling level φ [-] 0,2 0,3 0,4 0,5 0,6
Parameter Unit Feeding Device Vertical Conveyor Inclined Conveyor
Conveying length [m] 2 x 0,75 7,0 3,0
Screw diameter [m] 0,4 0,26 0,26
Screw pitch [m] 0,4 0,23 0,23
Maximum rotation speed [1/s] 1,7 9,3 9,3
Installed driving power [kW] 1,5 30,0 15,0
Taking into consideration the effective voltage U eff , he
motor- and gear-efficiency η, the idling drive power P Leer ,
the achieved mass flow I m , the conveying length L, the
screw pitch S , the screw diameter D and the conveyance
height H.
Simulations according to the Discrete
Element Method
Furthermore, data are obtained through simulations
according to the Discreet Elements Method (DEM). In
principle such simulations are numerical experiments,
in which apart from the geometry of the conveyor, the
individual bulk particles are pictured as discrete elements,
In each calculation step Newtonian equations of motion are
solved and allow for calculation and simulation of discrete,
continuous procedures. In principle this simulation method
is very simple, however previously it was limited by the
very high number of particles to be considered. It was
only by the application of modern computers with multicore
technology and high calculation speed that it became
possible to also accurately calculate complex simulations
with several tens of thousands particles and high resolution
in acceptable timeframes. The simulation program EDEM
of the DEM Solutions LTD company is applied in this test.
www.advanced-mining.com
49