Thermocouple problem

Is one of the thermocouples broken? !

If the valve is used for throttling and the solvent contained in the medium has a low boiling point, please refer to the refrigeration principle of the refrigerator.

I am an instrument maintenance personnel. When encountering this kind of problem, my thinking is as follows: First, determine whether the display instrument is faulty. Because there is an error in the display, usually the secondary meter has a large error, so use a standard instrument to calibrate the secondary meter. Secondly, after ruling out the possibility of display failure, check the primary component and the intermediate circuit to see if water has entered the explosion-proof junction box, or replace a thermocouple, or check whether there is any poor contact in the circuit, resulting in contact potential, or the thermocouple compensation wire is wrong. Third, after ruling out the possibility of secondary meter, primary component, and intermediate circuit faults, the next issue is instrument design. For example, whether the installation position of the thermocouple is incorrect, whether it is installed in a dead corner with poor fluidity, or insufficient contact with the medium, or the protective sleeve is not inserted deep enough, or whether there is an electromagnetic field around the thermocouple, etc. Fourth, if the instrument faults have been eliminated, then it may be due to the process. The specific analysis must be done based on the process and the medium. This is a method I usually use when dealing with this type of instrument. In fact, temperature instruments are very easy to deal with, mainly for the above reasons. I wonder if the above points are helpful to you.

Was it like this from the beginning, or was it normal before this happened?

The throttling effect of the valve will cause the temperature behind the valve to be lower than the temperature in front of the valve

There is nothing wrong with the meter and it has always been that way! Why do you say there is no problem with the instrument? I tested it on site with a thermometer and it was exactly the same as what the instrument showed. Some say that the fluid passes through the valve and generates heat through friction, while others say that the fluid undergoes a phase change when passing through the valve. I don’t know which one is more important?

For example, the temperature difference between the front and rear valves of our four-circuit one-valve compressor is relatively large. It is said to be caused by a physical effect.

Check to see if the thermocouple is broken. If it is not broken, there are other problems that need to be checked one by one.

This is the law of conservation of energy. After passing through the regulating valve, part of its internal energy is converted into heat energy.