I. Kusumaningtyas
Dynamics of Multiple Drive Belt Conveyors During Starting
Masters thesis,
Report 2005.TL.6970, Transport Engineering and Logistics.
This research deals with the dynamics of a multiple drive belt conveyor. A
finite element model of a belt conveyor was built, which uses the
structure and properties of the Enerka-Becker System (E-BS). Two sets of
simulations were carried out: starting procedures with varying number of
drives and starting procedures with motor starting sequence. For each
simulation group, the linear offset, linear, and direct-on-line start-up
were tested. The simulations focused on the study of the axial elastic
response of an empty belt conveyor.
The application of multiple drive belt conveyors is increasing due to the
growing demands for systems with higher capacity, higher speed, and longer
distance. Multiple drive conveyors bring many beneficial effects, such as
the reduce of belt tension, the use of belts with lower strength, the
installation of lighter support structure, the application of smaller and
standardized motors, and the increase of layout flexibility. However, it
requires further study in order to achieve reliable design of such
systems, particularly in terms of the coordination and control of the
drive units.
The DIN 22101 is the most referred standard for the design of belt
conveyor systems. However, it merely deals with single drive belt
conveyors. No certain guidelines are available yet for multiple drive belt
conveyors. Therefore, this research was carried out to investigate the
dynamics of multiple drive belt conveyors during starting, to find out
whether a belt section between two drives in a multiple drive belt
conveyor can be viewed as a single drive system, and whether the DIN 22101
standard for starting of single drive belt conveyor can be used for the
starting of a multiple drive belt conveyor. Additionally, a study was done
to see the effect of starting the motors in sequence.
A finite element model of a belt conveyor system was built, consisting of
a model of the belt and its support structure, a model of the inverter
controlled induction motor and traction, and a model of the bulk solid
material flow. The belt conveyor system used the properties and structure
of the Enerka-Becker System (E-BS). The differential equations which
govern the motion of the belt conveyor and the drive system were solved
numerically. In this research, focus was given to the axial response of
the belt. The simulations were done only for the case of starting
procedures of empty belt conveyors.
In the simulations of starting procedures with varying number of drives,
the number of drive stations in the belt conveyor was increased from one
to four, while the start-up time for each case was reduced. The
simulations revealed that by using more drive stations, the maximum belt
stress during non-stationary as well as stationary conditions decreased.
However, negative stresses occur in the system, while speed oscillations
as well as overshoots appear in the belt velocity profile. This happens
for either linear offset, linear, as well as direct-on-line start-up.
However, if the belt is started using a linear start-up procedure with a
45 s start-up time (based on DIN 22101 ), the negative stress does not
occur in the belt and the velocity profile builds up without oscillations
and overshoots. Compared to the other start-up procedure, the linear
start-up gives better results because the maximum belt stress during
non-stationary conditions and the maximum nodal acceleration are lower.
The simulations of starting procedures with motor starting sequence were
carried out by giving each motor its own switch-on time. Motor 1 is
switched-on at the beginning of the simulation, while the other motors are
switched-on when the acceleration wave from motor 1 has reached their
locations, or a while later after the acceleration wave passes them. The
results of the simulations show that by starting the motors in sequence,
the negative stress in the system can be reduced or even removed. However,
the maximum belt stress in nonstationary conditions is higher than that if
all motors are switched on at the same time. In view of the belt velocity
profile, overshoot still happen at the end of the start-up time. In the
linear offset and linear start-up with motor starting sequence, the last
motor experiences regenerative braking for a few seconds before it reaches
balanced load distribution with other motors. This happens due to the
reflection of the acceleration wave from motor 1 arriving at the node
where the last motor is located, causing the nodal velocity to increase
higher than the synchronous speed of the motor, bringing the motor into
the regenerative mode.
From the simulation results, it was observed that the characteristics of
each section between two drive stations in a belt conveyor differ from
those of the single drive belt conveyor. The differences were seen in the
behaviour of the motors during start-up, the belt stress in the belt
sections, and the acceleration waves. It was, thus, concluded that a belt
section between two drive stations in a multiple drive belt conveyor
cannot be considered as a separate single drive conveyor system. This also
leads to the conclusion that the start-up time of the multiple drive
system should not be based on the length of the belt section between two
drives. And in view of the DIN 22101 standard, the guidelines for the
start-up of a single drive belt conveyor are not directly applicable for
the start-up of a multiple drive belt conveyor. Finally, the linear
start-up procedure is most preferable for the start-up of either single or
multiple drive belt conveyors. If the multiple drive belt conveyor is of
concern, the linear start-up without a motor switching sequence is
suggested because the minimum belt stress can be increased by increasing
the tension weight, while the maximum belt stress during non-stationary
conditions does not increase as high as that if using a motor switching
sequence. Furthermore, the regenerative braking of the last motor does not
occur in linear start-up without a motor switching sequence.
Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2005.07.07;
logistics@3mE.tudelft.nl
, TU Delft
/ 3mE
/ TT
/ LT.