Fluctuations in the measurement values of temperature transmitters on stormy days
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Hello everyone. I’m facing this issue right now: during heavy rain, the readings taken by the temperature transmitter located at the site (a thermistor with a temperature transmission module) fluctuate greatly, ranging from 230°C to 99°C (while the actual temperature of the tank is 230°C). I encountered this problem during previous heavy rain events as well. A welding sleeve is installed on the surface of the tank; however, this sleeve does not isolate the medium. The thermistor’s protective tube is connected to the sleeve via threads, and no signs of leakage have been detected. Could everyone please help?
Is the junction box not properly sealed, allowing water to get in?
Maybe it’s because of the heavy rainfall. We can give it a try: under normal weather conditions, keep pouring water from a kettle onto it and see if there’s any change. If there’s still no change, then cover the wiring box and try again
During heavy rain, no water entered the connections of the thermal resistor; however, there were large temperature fluctuations. I believe that there are damaged sections in the connection wires, and once these areas get wet from the rain, a circuit is formed between them and the ground, which reduces the resistance value of the thermal resistor. As a result, the temperature drops and fluctuates. It is necessary to carefully inspect the wires.
It happened again not long ago: one compressor kept shutting down during rainy days, and the cause couldn’t be identified. Electrical checks didn’t yield any results; we replaced an electrical cable, but there was no sign of damage on the original cable either, and its insulation level was normal when measured~~ It’s really hard to figure out what’s going on~
There must be some damaged areas, or the signal wires near the tank might be damaged due to overheating. When a short circuit occurs, it causes temperature fluctuations; however, when the wires are removed and their resistance is measured, no such fluctuations are observed
If no water is entering, then there’s a problem with the cable.
I replaced the power cable for the compressor; it’s a lot of work
Will it work just by replacing the cable? Here too, heavy rain often causes a total power outage of 1-3 seconds, after which the entire plant shuts down
If there is a leakage current between the transmitter and the DCS, the current signal will only increase, resulting in a reading greater than 230. The fact that the reading has now decreased indicates that there is no problem with the cables connecting them. It is very likely that the waterproofing of the junction box has deteriorated; when the thermoresistor becomes damp, an equivalent resistance is added, which results in a decrease in the measured value. It is recommended to enhance the waterproofing measures or replace the integrated thermoresistor.