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We have DP level transmitters connected to the bottom of the tanks. Few days ago it was raining, and there were lightning strikes in nearby areas. Immediately after the lightning all 4 tanks experienced increase in level reading (increase about 20% level). The peak was not immediate, and the rise due to lightning and return to normal value(time to de-energize) took about 1-2 hours for the transmitters. We experienced the same scenario several months ago and there was lightning on that day too.
The trends for 3 tanks had same characteristics: had relatively fast linear increase and gradual decrease - One line up, Peak, and line down with a period of app. 1 hour. All of these tanks had process fluid inside of them. The 4th tank with no fluid, had different behavior. While the 3 tanks had one peak, the empty tank had about 6-7 ups-and-downs for same period and then it stabilized.
To solve the issue I am thinking of connecting the transmitter ground port to the earth. I had few questions about this subject and would appreciate your assistance:
1) The tank has its own ground connection. Is it ok to connect the transmitter to the same ground? Or is it better to make a new one?
2) The tank is placed on concrete. It seems so that the only way for it to get energized is through the ground connection and through the pipes. If so, if we connect the transmitter to the ground, would the ground connection exert even more disturbance to the transmitter during next strike? I am little bit confused.
3) Did you have similar experience? How did you solve it?
The trends for 3 tanks had same characteristics: had relatively fast linear increase and gradual decrease - One line up, Peak, and line down with a period of app. 1 hour. All of these tanks had process fluid inside of them. The 4th tank with no fluid, had different behavior. While the 3 tanks had one peak, the empty tank had about 6-7 ups-and-downs for same period and then it stabilized.
To solve the issue I am thinking of connecting the transmitter ground port to the earth. I had few questions about this subject and would appreciate your assistance:
1) The tank has its own ground connection. Is it ok to connect the transmitter to the same ground? Or is it better to make a new one?
2) The tank is placed on concrete. It seems so that the only way for it to get energized is through the ground connection and through the pipes. If so, if we connect the transmitter to the ground, would the ground connection exert even more disturbance to the transmitter during next strike? I am little bit confused.
3) Did you have similar experience? How did you solve it?