VEGA: A lasting impression
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- 5 min read
VEGAPULS radar level sensors replace silo weighing at Sto, the building materials manufacturer.
The building materials supplier, Sto considers punctual delivery as one of its main quality criteria. Reliable measurement of current stock levels of raw materials and finished products is a key factor in being able to deliver on time. VEGAPULS radar sensors take over the job of level measurement in the silos and deliver reliable, accurate data.
While a typical exterior finish usually recoups the energy used to make it after just one or two years, it actually has an average lifetime of over 60 years. With its thermal insulation composite systems, Sto is a market leader in exterior insulation. Since 1965, Sto products have saved the equivalent energy to 130 billion litres of heating oil. This means that around 416 million tonnes of Carbon dioxide (CO2) were prevented from enter the atmosphere in the first place.
Every climate zone requires a different type of stucco
Stucco is a cement like plaster that’s applied to wet walls and ceilings as an external finish or coating.
Before stucco is applied, the local climate conditions, the building and processing regulations, as well as the ideas of the architect and builder, have to be taken into account. So it’s not surprising that Sto has over 30,000 different products in its portfolio. The Sto facility in Tollwitz supplies central and northern Germany with dry products, for example adhesive and composite materials, to which paint or stucco for exterior insulation is subsequently applied. Raw materials for production as well as the finished products have to be delivered quickly. For that reason, the logistics department has to be very well informed about the raw materials in stock and the quantities of manufactured end products ready for delivery.
Despite the impressive size of the company, its storage facilities do have their limits. The products are stored in different silos.
Sand and cement are stockpiled in the huge raw material silos, while the finished products are kept in smaller silos in the adjoining outbuilding. Previously, the silos were equipped with load cells to keep track of the inventory. This measuring method, however, was not always accurate enough for this particular measurement task. Discrepancies of two or more tonnes per silo were not uncommon. The main problem for the load cells was the silos’ own weight of over 100 tonnes each. There were always measurement inaccuracies, especially during filling.
Fast response time
Sto began looking around for an alternative measuring method. In the process, it became clear that radar level measurement technology could be a good option and Sto subsequently came across the VEGAPULS radar sensor. Its great advantage was from the transmission frequency of 80 gigahertz (GHz) and the approximately 75 millimetre diameter antenna with a beam angle of only four degrees, which made it possible to measure without interference from buildup on side walls or internal installations.
Since its market launch, VEGAPULS 6X has proven its worth, especially in the area of bulk solids and – above all – in the building materials industry, where very slim, high silos are often used. Besides its narrow beam angle, there were other decisive criteria. The instrument would also have to measure continuously and not be affected by filling and emptying processes. Another aspect was the so-called “settling curve”: When silos are filled, a considerable amount of air is always pulled along with the material, so a measuring instrument has to react very quickly.
Sometimes it only takes a minute before more material is poured in. As such, a measuring method that measures quickly was needed.
It is also important that parameterisation and commissioning are simple, as the sensor has to be able to cope with changing bulk densities.
Rapid deployment
After a three-month test phase, the VEGAPULS radar sensor had completely convinced everyone involved. Therefore, the decision was made not only to equip the finished goods silos with VEGAPULS as initially planned, but also to equip the raw material silos at the same time. The advantage of this, apart from the reliable measuring results, is that the same measuring instrument can be used everywhere, basically making plug-and-play possible. This meant that the building materials manufacturer can use the same sensor on any silo with minimal expense.
Since there were initially no power and Profibus cables or flanges on the silos, the installation required some planning. Cables were laid and the control system was adapted accordingly. In contrast, the installation of the sensors themselves turned out to be particularly easy. Within two days, Sto had completed all the set up work themselves. The VEGA Tools app for the smartphone proved to be very useful for this task. With its help, the proper angle of inclination for mounting each instrument was quickly determined: simply place the smartphone on the sensor, align it according to the displayed graphic, and it’s done.
Low bulk density
Nearly all the sensors worked reliably right from the start, delivering accurate measured values. Since the VEGA instruments display a percentage filling level, the software converts these values into tonnes. Additional production security is provided by the inventory management system. Only one particular silo holding raw materials with low bulk density turned out to be problematic. It’s very difficult to measure in this particular container and previously no sensor had ever worked reliably. The wall seams of the silo, for example, generated false echoes. Even when the silo is empty, the echo curves generated are very complex. A slight repositioning of the sensor helped to change its alignment. The project team also readjusted the sensor parameters. Since then, this measuring point has also been functioning perfectly.
For Sto, the decisive factor in the selection was the high performance and versatility of the sensor – in particular, that it can be quickly adapted to the local conditions and that it accurately displays the measured values, even when the silos are filled and emptied at the same time. VEGA’s customer service was also convincing. Whenever the team at Sto had any questions, they could always get hold of the right contact immediately.