PSI - Issue 32

G. Gusev et al. / Procedia Structural Integrity 32 (2021) 49–55 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Taking into account all the previous experience, it was decided to completely waterproof the sensor using a composition that is not affected by potash brine. This composition was bitumen-rubber mastic. This material does not conduct electric current, which is important when used as part of electrical circuits. Also, this material does not decompose under the influence of brines of various salts and retains its properties over a long time interval. However, the disadvantages of this material include the fact that when it becomes fluid when the temperature of the ambient air rises. It was decided to keep the previous sensor design, but to supplement the brine protection with mastic. The sensor mounting technology has been changed. The electrical circuit was covered with a polyethylene shield after being welded to the structure. Then an aluminum tank with an open end was installed on top of the sensor, into which mastic was poured in a liquid state. The mastic filled the tank completely. This composition polymerized during the day and completely isolated the sensitive part of the strain gauge from the external environment. A polyethylene screen was needed in order to exclude a mechanical effect on the sensor from the mastic. This installation technology turned out to be quite laborious at all stages, but it made it possible to completely eliminate corrosion from brines. Figure 5 shows the final version of the strain gauge.

Fig. 5. (a) a final version of the sensor before filling with mastic; (b) a final version of the sensor after filling with mastic in the tank.

3.3 Strain measurement results The results of strain measurements for the final version of the sensor are shown in Figure 6.

Fig. 6. (a) a final version of the sensor before filling with mastic; (b) a final version of the sensor after filling with mastic in the tank. The results from the sensor are shown.This is one of the most interesting sensorfrom the point of view of the readings analysis. This sensor is located on the central supporting column of the structure at a height of about 6 meters above the ground. This column is the most loaded, since the ore storage bunker rests on it. The bunker is located at a height of about 20 meters and is mated by a conveyor belt, onto which ore is poured from the bunker.