Ultrasonic sensors measure the level in silos and control automatic filling with grain.
As part of a project to automate the filling of the silos with grain, a solution was sought with which the grain in the lorries arriving could be evenly deposited in two storage silos. For this purpose a longitudinal conveyor on the filling system must be moved in accordance with the level in the silo and the cross conveyor also moved appropriately.
UM series ultrasonic sensors from SICK are used. A UM30-15113 ultrasonic sensor with 4-20mA analogue output is used to measure the level of the grain. The sensor is installed on an arm on the cross conveyor and measures the distance to the surface of the grain. The measurement is performed discontinuously in the breaks between filling, as the grain causes air turbulence and dense dust clouds that could affect the measurements. The UM30-13111 ultrasonic sensors fitted to the longitudinal conveyor detect the position of the cross conveyor underneath it and enable precise adjustment. To avoid the sensors detecting the cross struts in the silo, angled reference plates were fitted to the cross conveyor. Two ultrasonic sensors are fitted on each side of the conveyor – one at an angle of 90° and one at an angle of around 120° aligned with the angled reference plate. Only when both sensors switch simultaneously have they detected the cross strut. All output signals are processed in a PLC outside the silo and used to control the automatic grain filling process.
The use of ultrasonic sensors, and the resulting ability to automate the silo filling process, provides advantages for the personnel and the process. The operator no longer has the arduous task of monitoring the filling as in the past, with its related dust, heat, stuffy air, perhaps even with breathing equipment. Furthermore, the grain is stored optimally for drying thanks to the even distribution over the entire area of the silo.
This is an application from SICK.
Tri-Phase Automation is a SICK distributor in Wisconsin.
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