Radar sensor monitors filling level in storage silo

Facade and interior paints, varnishes and glazes, plasters, floor coatings and concrete protection, each with a myriad of specifications: for the painter, varnish and plasterer trades, there are thousands of products for all kinds of needs. The European system operator also has an extremely large product range with more than 10,000 articles. It has one of the most advanced goods distribution centres in the industry. It is particularly important for the producer to be able to react compliantly to market developments and orders thanks to the open and flexible system and to guarantee short delivery times in addition to high delivery security. More than 900 of its vehicles are in use every day to supply customers and subsidiaries mainly in Germany, Austria, Italy, the Netherlands, Poland and Switzerland. This sophisticated logistics system is supported by reliable level monitoring within the silo systems.

In the chemical industry in particular, sensors are usually exposed to aggressive, adhesive or corrosive materials. High temperatures, dust, varying DK values and viscosity have to be dealt with quickly and reliably by the measuring technology.

Radar sensor for special silo design

For its production plants in Germany, the operator was looking for a precise solution for level measurement detection in its various silo containers, where components for paint production, such as solvents and binders, pigments, oils, resins, fillers and additives, are stored. The decisive factor is an even and controlled introduction into the production system. Convinced of the measurement technology of UWT GmbH for years, the project planner again turned to the Allgäu-based company. For continuous level measurement, work was also carried out on site to find a reliable solution for some special storage silos on site, where quartz sand is deposited, among other materials. These silos have a small diameter, are divided into three parts and have additional deflector plates, and a ladder is mounted on the inner walls. This makes it particularly difficult for a level sensor to continuously monitor the entire measuring range.

With the contactless radar, a holistic solution for the diverse storing processes was found. In addition to electromechanical lot or plumb bob systems, radar sensors are mostly used for continuous level measurement in content monitoring. They measure distances of up to 100 m (328 ft) and, due to their high sensitivity, can be used in both coarse-grained and very fine powdery
bulk materials as well as in different liquids
and pastes.

Dust-proof construction

The silo containers for component storage have an average height of 17 m (55.78 ft). The bulk weight of the quartz sand is 1400 g/l (87.39 lb/ft³) and the DK value is between 2,0 to 3.0. The process temperatures reach up to 80 °C (176 °F) and the given process pressure is around 0.8 bar (11.6 psi). Vibration in the container or electrostatic charging are not relevant to the application. However, there is a dust-intensive atmosphere, especially within quartz sand storage. The contact-free radar was accordingly equipped with a completely dust-proof construction and delivers reliable measurement results at process temperatures of up to 200 °C (392 °F). The device works at 78 GHz high frequency and therefore has a very narrow beam angle of only 4 °, which eliminates any signal interference at the flange but allows optimum reflection of the bulk solids material, even with steeper cones. The radar is perfectly aligned via the adjustment flange, since the beam can be fixed at the desired point, e. g. on the silo discharge. This enables smooth use in tight, high silos and makes installation and placement of the sensor considerably easier. Thanks to its encapsulated housing construction, the radar is optimally protected within the demanding environmental conditions and delivers reliable measurement results. In addition, due to the integrated air flush connection for cleaning the lens antenna, application here was problem-free. The sensor’s self-cleaning function also ensures reliable measurement when it comes to condensation or dust build-up. The device works with two-wire technology and is easily put into operation via an optimised local programming device with display and a quick start assistant.

Optional data visualisation

For the use of the acquired data, the radar sensor can be connected to the Nivotec visualisation system. The data visualisation provides the detected levels in height, percentage, weight or volume. Trends are saved and e-mails about fill levels or silo messages can be activated. The remote retrieval of the data obtained can also be done via a GSM modem at any PC in the company Ethernet. System installation is straightforward and can be done by the own service staff. The availability of all detected levels improves the planning reliability of the plant operator.

UWT GmbH, Betzigau