The double-flange level gauge experiences large fluctuations
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Gentlemen, I have a question regarding double-flange level gauges and would like your help in figuring it out. The specific details are as follows: 1. Operating conditions: A double-flange level gauge is used to measure the liquid level in a sealed tank; the medium being measured is light hydrocarbons. The temperature is around 10 degrees, while the ambient temperature outside the tank is around minus 20 degrees at night and minus 15 degrees during the day. 2. Gauge type: The double-flange level gauge is from Rosemount, with the model number 3051L2AG0QD31AA:S115F1. It was put into operation in June this year. The upper and lower flanges as well as the capillaries do not have heat tracing; the gauge (transmitter) and the excess capillaries are located inside an insulated box, which is equipped with electric heat tracing. The excess capillaries in the box are arranged in loops within it. 3. Fault phenomenon: In recent days, the control room panel has shown significant fluctuations in the readings from the dual-flange level gauge, although these fluctuations follow a certain pattern. (Observations on the first day showed that it started at 8% in the morning and gradually increased, reaching 100% at noon; it then dropped back to over 40% in the afternoon, with the actual value on site being around 20%). On the second day, observations showed that it increased from 41% at noon to 50% at 3 p.m.; it dropped back to 43% at 10 p.m., and rose again to 60% at 8 a.m. the next day. 4. Question: I would like to ask everyone if you have encountered such a situation? Upon checking the information, it was found that the silicone oil inside the capillary is of type D, and it is frost-resistant down to minus 45 degrees. Where should I start to check and address this? I have personally summarized a few points for everyone’s criticism and suggestions: (1) Leakage in the upper flange negative pressure chamber, as well as leakage of silicone oil inside the capillaries, results in an abnormally high transmitted value from the level gauge. But this doesn’t explain why it can be high and then drop on its own. (2) When filling the capillary with silicone oil, if the negative pressure is not applied properly, bubbles form inside the capillary. These bubbles expand and contract due to changes in ambient temperature, resulting in fluctuations in the liquid level. (3) The capillary is locally heated, or in other words, there is a temperature difference between the upper and lower parts of a capillary. Since there is electric heating in the instrument box, this heating also warms up the capillaries while heating the transmitters; meanwhile, the capillaries outside the instrument box remain at sub-zero temperatures. As a result, the capillaries expand unevenly in an environment with such a large temperature difference. (4) Range and drift. I’m not very familiar with this part; the manufacturer should have made adjustments during installation. Also, I would like to ask whether issues with the range, zero point, or offset can cause this situation If so, how should I make adjustments? I have a handheld controller that can communicate with the transmitter. The above three points are the reasons I have summarized on my own; they might seem a bit naive, so please bear with me. This problem is bothering me a lot; I earnestly ask everyone to help analyze it. Thank you all, guys! ! ! ! ! ! ! ! ! !
It’s an idea, but the fluctuations in my table’s temperature are slow. If steam is used for heating, it can only raise the temperature temporarily; steam cannot be used continuously, otherwise freezing will occur. Is it better to use electric heating? But the storage tank is located at a relatively high height, which makes operations inconvenient\ud83d\ude02
Neither the first nor the second possibility is very likely; after working in this field for so many years, I’ve hardly ever encountered such situations. The third option is more common; one thing that can be suggested is to try to avoid direct contact between the heat tracing and the capillary tube, by inserting something in between
Based on the conditions you provided, I think the third possibility is more likely. I don’t quite understand why you need to use heating; since dual flanges are being used, the problem of freezing can be avoided. You might try turning off the heating – the instruments won’t freeze. If there are no issues with the process, it’s recommended to turn off the heating and see if that leads to any improvements
Temperature has a significant impact; in the past, the differential pressure system used in our factory stopped working as soon as winter arrived, so insulation is still necessary
The table in the picture is a fake table; the inspection is complete! As for the malfunction you mentioned, it is recommended to insulate the capillary tube, as well as the instrument flange and the short sections where it connects to the tube body.
We have encountered such problems before and can help resolve them. There are two reasons for these fluctuations: first, the capillaries sway with the wind, which causes some error, but this error is relatively small; second, it is due to temperature changes. The fact that the silicone oil can withstand temperatures down to -45°C refers only to its tolerance in terms of operating conditions, but temperature changes still cause the silicone oil to expand and contract. The solution is: first, provide insulation for the capillary tube – heating is not necessary – and then secure the capillary tube, which will help reduce such errors
In my opinion, it’s best to provide insulation for the root valve and diaphragm, as well as heating
Haha, this watch is definitely a fake one; there’s no need to say more. Replace the transmitter and hold your company accountable for its purchasing decisions – you bought fake goods. Were they purchased from some street vendor? Did anyone receive bribes?