Figure 1. Continuous level measuremt solution for mining freight train coal with contact-free radar.
Figure 2. Installation of NivoRadar NR 3000 with aiming flange within the mining process.
The radar is certified for hazardous locations (Zone 20/21) and the stainless steel construction makes the continuous level measurement suitable for these kinds of application. The unit operates at a high frequency of 78 GHz and delivers a small beam angle of 4˚, which eliminates any signal interference at the flange but allows for optimum reflection of the bulk solids material. Distances of up to 100 m (328 ft) can be measured, and the sensor can be used in very fine as well as rough-grained solids due to the high sensitivity range. The radar also offers a flat flange and aiming flange version. Using the adjustable aiming flange, the radar was perfectly aligned since the probe could be fixed to the desired point, and the angle of the beam can be set to the desired point. Therefore, the installed radar sensor could be exactly placed over the trippler hopper and adjusted for continuous level detection of the material without delay and spurious echo, even within the limited space. The non-contact technology sided cones did not influence the measuring results. The lens antenna is highly resistant to material deposits and offers a self-clean function for the sticky solids using an air flush connection. Even within applications where condensation occurs, the flushing connection provides functionally reliable measurements. The device uses a two-wire technology and is kept simple, in order to operate via a local programmer with Quick Start Wizard and a plug-in display that allows programming and diagnostics onsite. The unshielded radar sensor has a completely dustproof design and provides reliable measurement results in high process temperatures up to 200˚C (392˚F).
More efficient silo management by visualisation of stock level The next consideration for the plant operator at this point of production was to connect the radar sensor to a complete system for level monitoring, in order to achieve improved transparency concerning silo management. The measurement system devices communicate directly with PLC control systems via an analogue ***4…20ma*** signal, or even a MODBUS RTU or Profibus digital protocol. The level signals of the installed radar sensors on each silo could be bundled by the visualisation software NivoTec®, combined with a Wago WebController. The plant could securely access this information (password-protected), at any time of the day, via any internet browser over a predefined IP address using the visualisation software. It is possible to include any number of other measuring points in the visualisation system – without additional hardware costs. By utilising this level monitoring and visualisation, the plant operator established a complete system for fill level and trend display, data storage, and remote fill level information.
Historical digression Figure 3. Multifunctional FMCW radar level transmitter for continuous monitoring of solids and liquids with two-wire technology.
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WORLD COAL ISSUE 2 2021
Coal mining has an interesting history to be told. One of the largest mining industries, mining for coal started out in the 18th century and boomed all the way to the 1950s. Today, although maybe not as prevalent as some other
