Capillary transmitter
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I have another question for you. Our company currently has a capillary dual-flange level transmitter. It works normally in cold weather, showing the same reading as the local glass-level gauge. However, when the ambient temperature rises, the reading becomes too high. On last Thursday, when it was very hot, the local reading was 30%, while the remote reading was 70%. Then I used cold water to cool down the capillary and the gauge; the reading dropped rapidly, before moving upward again. So far, due to the rain and cooler weather, there have been no abnormalities. Could you help me analyze this as well?
Reply to 1# limeili588: It should be impossible. Please remove it and check it
Determine whether there is a fault with this table； Is it because the dielectric changes significantly with temperature, which leads to this situation? ；
The possible reasons are excessive temperature drift of the double-flange level transmitter itself, or poor flow in the valves that connect the double flange to the tank.
Hehe, I’ve encountered this phenomenon many times as well. It’s possible for the capillaries to be filled with silicone oil, and changes in ambient temperature can cause varying pressures on the diaphragm box. I guess the measurement range of your level gauge isn’t very wide; installing heat tracing should resolve the issue. (Ensure that your capillaries do not leak silicone oil and that the gauge bulb is not damaged.)
The measurement principle of capillary level gauges relies on changes in liquid pressure for detection. If the specific gravity of the liquid changes, the output will change as well. Especially in cases where a sight glass is used, errors can be observed; these are errors inherent in the measurement principle and cannot be eliminated. If it is desired for the readings of the two instruments to be consistent, an instrument in the form of a float can be used, provided that installation and process conditions permit it.
The operating temperature is relatively low, so low-temperature double flange types were chosen for selection. This situation can be resolved simply by maintaining heat
Silicone oil in capillaries generally poses no problems; when working on a project in Tianjin some time ago, no measures such as heating were taken, yet the operation was still satisfactory. It’s probably blocked somewhere~
I hadn’t noticed that. What someone upstairs said makes sense as well – when there is thermal expansion, the pressure at the low-pressure end increases, which might lead to inaccurate measurements?
The lengths of the two capillaries differ too much; due to thermal expansion and contraction, the pressure generated by the expansion of the silicone oil on each side is different, resulting in an inaccurate pressure difference
First, check whether the diaphragm box is damaged, and then check if there are any leaks in the capillary.