OPERATIONS MANAGEMENT
Efficient and productive mining facilities are characterised by smooth conveying operations, explains Tilman Speer
T
BRAKES FAST-TRACK PRODUCTIVITY
he ability to control the speed, acceleration and deceleration of conveyors is crucial to maximise material handling efficiency. In
particular, it is extremely important to avoid abrupt start-ups, prevent conveyors from running backwards when travelling uphill or from rushing downhill under the influence of their load. Braking control is also necessary when mine operators need to halt conveyors or to avoid issues during power failures. In these situations, the conveyor should not immediately come to a halt. Te brakes should rather stop it in a gradual and controlled way to protect the powertrain from shock loads – a practice commonly referred to as ‘soft braking’. In this way, it is possible to avoid excessive tension on the conveyor belt and eliminate considerable stress to multiple pieces of equipment, such as rollers.
Conventional braking systems, while facilitating controlled stopping and holding, have seldom been able to effectively modulate speed in operation or operate autonomously. Terefore, it is important for mine operators to explore new technologies that can deliver more responsive and reliable solutions to allow them to maximise productivity and increase equipment service life. In addition to the traditional considerations of brake specification, a modern system should be specified based on its ability to automatically modulate the braking force: regulating the conveyor’s speed, acceleration and deceleration. Te most effective way to introduce soft braking is to equip the system with a control system based on a closed-loop feedback mechanism.
30
www.engineerlive.com
CHOOSING A CONTROL SYSTEM Closed-loop braking system controllers receive one or more reference signal from sensors associated with the conveyor, such as the conveyor’s torque, speed and/ or pressure. Te controllers compare the data received to pre-defined setpoints, the results of which trigger a proportional corrective change to adjust the motion of the conveyor accordingly.
Te best way to manage the data and modulate the braking force involves the use of controllers based on proportional integral (PI) algorithms, such as the SOBO (Soft Braking Option) iQ solution from Svendborg Brakes. By combining proportional and integral responses, these controllers are able to handle the fast dynamics of the braking process in a highly efficient and reliable way. Firstly, the
proportional response offers immediate action to address a major difference between sensor data and setpoint. For example, if the conveyor’s speed starts to rise significantly, exceeding the setpoint, PI controllers will need to promptly slow the conveyor by applying an elevated braking force. Te proportional action responds quickly,
addressing big fluctuations, but cannot get the setpoint and sensor data to precisely match. In fact, the proportional term alone would likely excessively reduce the speed as well as consume more energy. Tis is why the secondary, integral response is needed. Tis conducts an averaging operation that filters out small oscillations by taking into account past and present deviations over time. As a result, the controller is able to stabilise the braking force and ensure a gentle stop. Having chosen to use
The SOBO iQ solution uses controllers based on proportional integral algorithms
PI braking controllers, it is essential for mines to fine-tune the proportional
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
