Fluctuations in liquid level of methanol differential pressure level gauge on rainy days
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I have a question: In the differential pressure level gauge used for this tower, there is a pressure measurement transmitter on each of the positive and negative sides. The medium inside the tower is methanol, and the temperature is around -45°C. When it rains or when the temperature is particularly low in winter, the liquid level drops suddenly; once it stops raining or the temperature rises a bit, the liquid level gradually increases back to normal. I would like to ask the experts what could be the reason for this phenomenon.
Is the differential pressure level gauge a capillary telemetric type? Is it because the silicone oil inside the capillary of the differential pressure transmitter experiences pressure changes due to temperature differences?
It is caused by the increased density of liquids due to excessively low temperatures. Differential pressure level measurement is accurate for determining constant density.
It’s not a capillary; instead, the flange is used for direct connection to the measurement transmitter
For flanged pressure transmitters, there is a valve before they are connected to the equipment, and all of these components are insulated. Is this the correct way of installation? The level is lower during rain or in winter; it is likely caused by a change in the viscosity of the silicone oil inside the transmitter.
That makes sense; silicone oils come in high-temperature, standard, and low-temperature types, so the person in question can take some measures based on the ambient temperature.
Since the medium itself is at -40, a decrease in external temperature should have little impact. The root valve is located on the tower wall, so the diaphragm box is also only minimally affected. It is recommended to check the insulation of the cable
Do you use two voltage transformers to measure positive and negative pressures respectively, and then use the control system for calculations? I’m not sure how large the difference between positive and negative pressures is; if possible, it’s better to choose a double-flange design. For negative migration, or for using radar to monitor floats, high precision is achievable. As for the fluctuations you mentioned, it seems to be caused by temperature; check whether there are crystals blocking the flange neck.