Analysis and Precautions for False Alarms Caused by Protective Sheets

Vibrating Rod Level Switches, Tuning Fork Level Switches, RF Admittance Level Switches and Rotary Paddle Level Switches are common level switches. They are indispensable in industrial production, mainly used to detect the storage status of solids or powders. For the whole operation processes, the installation locations and the way of mounting of level switches and protective sheets are crucial.

To avoid direct impact of the filling stream, we need to confirm that the instrument probe does not protrude directly into the filling stream. If such an installation location should be necessary, mount a suitable protective sheet above or in front of the probe. However, in practical applications, the alarm signal output of the level switch may sometimes be inconsistent with the actual status after mounting the protective sheet, especially when mounting low level switches during the unloading process. For example, the low level switch sends a “no material” alarm signal, but there is still material present in the silo. What is the reason? What precautions should be taken in practical applications?

Based on our on-site experiences, the unreasonable design and mounting of protective sheets have led to the materials diversion during the unloading process, resulting in the low level switch not detecting the material when the material is still filling above the protective sheet, thus causing false alarms. This is the most common problem.

To avoid the problem, we suggest paying attention to the following points when designing and mounting protective sheets.

Firstly, scientifically design the size of the sheet. The big size sheet hinder the normal flow of material, causing material failure contact with the level switch, resulting in false alarms. Therefore, please ensure that the sheet does not hinder smooth material flow, and the level switch can accurately detect at high or low locations.

Secondly, the distance between the sheet and the level switch affects smooth material flow. The reasonable distance is based on the fluidity of the material and the actual measurement requirements.

Finally, special attention should be paid to the installation locations of the protective sheet. Generally speaking, level switches and protective sheets should be installed away from the inlet (outlet). Therefore, the material will not be obstructed when passing through the inlet (outlet), and there are no false alarms caused by the continuous material filling. The reasonable selection of the installation locations should consider the path and speed of material flow.

Also, regular maintenance and inspection should be carried out on both of the level switches and protective sheets to ensure normal operation. If you have any questions, please consult our Jiwei engineers.