How to solve inaccurate measurement with differential pressure level gauges. Help!
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There is an LNG recryolzer on site, and EJA differential pressure transmitters are used to measure the LNG level inside the chamber. There are three in total, A\B\C, measured in segments. The tower is 30 meters tall. Please describe the problem so that everyone can suggest some good solutions. 1. Instrument A measures from 0 to 10 meters; the high-pressure side is connected to liquid-phase LNG, while the low-pressure side is connected to gas-phase BOG. The instrument is installed between the high-pressure and low-pressure sides. The pressure guide tube is not insulated ； 2. B measurement
The LNG recryolizer is 30 meters tall and is equipped with three differential pressure level gauges, connected via pressure transfer pipes! The pressure guide tube lacks insulation! All three level gauges are showing incorrect readings now! 1. The first level gauge measures from 0 to 10 meters; it is installed midway between the high-pressure and low-pressure sides. 2. The second gauge measures from 5 to 30 meters, and it is installed at a position higher than the low-pressure side; the DCS is used to cover the 5-30 meter range. 3. The third gauge measures from 15 to 30 meters, again installed at a position higher than the low-pressure side; the DCS is used for this 15-30 meter range. All three level gauges work together for measurement, and none of the pressure conduits on the high-pressure and low-pressure sides have any insulation measures in place! None of them have been migrated! There is no isolation fluid in the pressure guide tube either! The current problem is that the LNG level inside the container is above 10 meters. But the first one shows only 8 meters, the second one 18 meters, and the third one shows 19 meters! Could you help analyze the reasons? Urgent!
As a layperson would answer, if there are errors in the instrument data, you first need to determine whether the problem lies with the data itself as measured by the instruments, or whether it’s an issue that arises during the processing of that data in the DCS. For example, if the liquid level in the container is 8 meters high, and the level gauge itself shows 8 meters, but the DCS displays 10 meters, this is data processing at work. If there is a problem with the display of the level gauge itself, then it’s a matter of calibration. Such level gauges certainly allow for fine adjustments to the displayed values. However, it’s more likely that there is an issue with the pressure transduction tube of the level gauge; for example, water might have entered the tube at the higher end, which means that even though the actual liquid level isn’t that high, the gauge will still show a high level. They are all non-professional responses, which are more suitable for you to analyze and solve on your own
Table 1: The ranges of the field and control systems are identical! Tables 2 and 3 do show inconsistencies! However, when the differential pressure is calculated based on the readings from the on-site sensors for the three gauges, there is indeed a problem of inconsistent data! Table 1 should show a full liquid level; this is certain! By then, the gauge will still show that there is some distance left before reaching the full liquid level.
What is the differential pressure shown in the table header? Is it the URV value you set?
Is the current meter 20 ma?
It now shows 18.38 kPa
Some differential pressure transmitters come with on-site indication.