In an expanded polystyrene (EPS) production plant, two significant hurdles needed to be tackled for smooth and dependable operations. Firstly, the extremely low bulk density of EPS causes it to settle and compact at the bottom of the silos. This compression forms a denser layer, which is suitable for some types of level sensors. However, as the material level rises, its density and compression decrease, necessitating sensors with high contact sensitivity. Secondly, EPS is processed and stored in flexible fabric silos. This flexibility poses complications for the installation of traditional level sensors, as their weight can lead to instability and sagging, resulting in inaccurate measurements.

The Solution: Integrating rotary paddle and vibrating fork technologies 

To address these challenges, UWT Level Controls implemented a unique and effective solution by installing two types of level sensors: one with a rotating paddle and the other with a vibrating fork.

To tackle low-level detection, the Rotonivo® 4001 sensor was chosen for its proficiency in operating under conditions with reduced bulk densities. The sensor's rotating paddle adeptly identifies material presence at the lower strata of the silo, where the density and compression of the material provide sufficient resistance. Furthermore, its plastic casing coupled with a specialized rubber paddle ensures it remains remarkably lightweight, making it ideal for low-level installation and minimizing sagging in fabric silos.

To achieve precise high-level detection, the Vibranivo® 6020 sensor was employed at the top of the silo, where material density significantly decreases. Augmented with the Vibrasil 90, this advanced sensor excels at identifying EPS grinds with bulk densities as low as 1 lb/ft³ (~16 g/l). The vibrating fork technology not only enhances tip sensitivity but also provides rapid response times, thereby improving production efficiency by swiftly signalling high-level points.