The readings of the two propylene mass flow meters on the same pipeline differ from each other
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The last edit to this post was made by small Q Timekeeping on 2016-3-10 at 10:38. I have a question for everyone: There are two mass flow meters (grade 0.2) on the pipeline that connects one of our propylene spherical tanks to the production unit; one of these meters is installed at the outlet of the spherical tank, and the other is installed at the user’s end. The distance between these two meters is approximately 2 km. Currently, there is a discrepancy in the readings of the two flow meters. Based on the tank capacity, the mass flow meter at the spherical tank end is accurate, while the flow meter at the user’s end remains inaccurate. Propylene is transported in liquid form, and the design operating pressure for the flow meter at the user end is 1.57 MPa. From the trends, I also observed periodic fluctuations in the user-side flow meter, with negative deviations during the day and positive deviations at night. Both flowmeters have been calibrated to Class 0.2. I don’t know what the reason is or how to fix it
Based on the information you provided, my guess is as follows: Is the installation of the flow meter ensured to keep the pipe filled with liquid? Are the specifications, models, and measurement ranges of the two flowmeters different? Are there pumps or other devices that generate strong electrical interference near the customer-side flow meter? Is there any damage to the instrument cable, or is its shielding not grounded?
Theoretically, it’s the same, but in practice there are often deviations. If your two gauges are of grade 0.2, as long as the positive and negative errors do not exceed this value, it is considered normal!
It has already exceeded level 0.2; now there is suspicion that pressure fluctuations in the pipeline are caused by changes in temperature, so is it necessary to implement some pressure compensation?
The mass flow meter itself has temperature and pressure compensation built in; you can use the handheld controller to check whether these functions are enabled
Do you have any solutions then? Our spherical tanks are calibrated, and the flow meter at the tank outlet corresponds to the tank capacity; however, the mass flow meter on the user side exhibits a large deviation.
It should be full-bore; the models are different, but the precision is the same. We look directly at the data in the table headers, and the deviation is still large.
Pressure compensation http://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1394565
Although both flowmeters are of class 0.2, if one has a positive deviation while the other has a negative deviation, and yet both meet the accuracy requirements, a measurement error will occur. It is also possible that propylene may vaporize after being transported over a certain distance through pipes, which can lead to errors as well.
The poster mentioned that the client shows a negative deviation during the day and a positive deviation at night, which is consistent with the fact that changes in temperature cause some of the medium to vaporize; this results in lower readings during the day, while at night less vaporization occurs or no vaporization takes place, leading to a positive deviation.
It’s a quite challenging question; from the description, it seems to be a measurement error caused by changes in ambient temperature, specifically by fluctuations in air temperature, affecting the physical state of things. The temperature difference between the medium flowing out through the pipes on the side of the tank and the cut-off temperature inside the tank is very small; therefore, the flow meter should be more accurate compared to tank measurement ； After being transported through 2 km of pipes, changes in ambient temperature affect the state of the medium inside the pipes, resulting in significant differences compared to the state of the medium within the tanks. If it is desired to reduce the measurement difference between the two flowmeters, attention should be focused on the flowmeter located on the user’s end; the various parameters of the fluid in the pipes at that end should be measured accurately, and then the parameter settings of the mass flowmeter should be adjusted to see if this yields any improvement.