A plant builder in Estonia asked for a level switch in a gravel hopper. The function should be a demand detector to set an alarm in time if the hopper gets empty and more material should be filled in. The hopper is equiped with an electrical rotary vibrator. It is mounted at the cone wall. It avoids material deposit the the wall inside and improve the material flow. The vibrator works in short bursts. The hopper is top loaded with a front loader. The material is gravel with 0-32mm grain size. The hopper is located outside therefore the sensor must have a temperature working range from -20 to +30C.
The challenge for the sensor is the strong mechanical load to the electronic housing by the vibrator and to the extension probe inside the hopper by the gravel.
Level switch RN 3004 – UWT
Measuring principle : Rotating
Housing : Aluminium or plastics PA6, IP 66
Versions with certificates : ATEX, IEC Ex, TR-CU, FM/CSA Process temperature :- 40 ° C up + 600 ° C
Process pressure : -0.9bar up + 10bar
Design : Compact or separate housing
Horizontal, vertical and diagonal installation
Mechanical connection : G1 “, G1¼” and G1½ “; NPT 1″ NPT 1¼ ” and NPT1½”; Triclamp)2 “; flange DN100 PN16
Length of extension : 150, 5000, 10000mm…
Power supply : 24V DC or 22, 230V AC 50/60hz, universal voltage
Output signal: SPDT, DPDT, PNP
The solution was a rotating paddle switch Rotonivo RN3004 with the option for a separate housing. It is mechanically uncoupled to the process. A rubber plate devides the shaft and damps the swinging amplitude and protects the gear and the electronic parts against damage. The protection tube at the probe protects in the application. So the gravel cannot damage the sensor and cause a malfunction. The solution is simply working and solves this heavy application.