Differential pressure for level measurement

Differential pressure level measurement utilizes the static pressure difference generated by the liquid for measurement. Under normal circumstances, the transmitter is placed in the middle of the pressure tap tube, and the method for calculating the displacement is as follows: 1. When the density of the liquid remains constant (or approximately constant), there is a linear relationship between the height (or level) of the liquid and the static pressure generated by the liquid within the tube. Based on this relationship, we can calculate the height (or level) of the liquid by measuring the static pressure difference of the liquid. The specific formula is: h = ΔP / (ρg), where h is the height (or level) of the liquid, ΔP is the static pressure difference generated by the liquid, ρ is the density of the liquid, and g is the acceleration due to gravity. 2. When the liquid density is not constant (or changes due to variations in temperature or pressure), more complex calculation methods are required, such as the segmented integration method and physical model methods. In general, the specific calculation method should be chosen based on the particular conditions and requirements of the measurement. In practical operations, specialized measuring equipment and software are generally used for calculations and adjustments. .

Transfer the pressure p = density * g * h for the flange spacing h

If the lowest liquid level is below the transmitter, the migration amount is 0, meaning there is no migration； When the lowest liquid level is above the transmitter, the migration is positive migration, and the amount of migration is pgh (where h is the distance from the lowest liquid level to the transmitter)

The range for this should be calculated based on the height difference between the highest and lowest points of the pressure guide tube; it can be set to zero when there is no liquid level. Why not use capillaries? The pressure guide tube does not have a diaphragm; when the liquid level is below the transmitter, the liquid in the pressure guide tube flows back, which reduces the pressure measured by the positive pressure sensor Therefore, the relationship below the transmitter and above the transmitter is not linear. Moreover, it is not acceptable either if there is no hydrostatic pressure in the negative pressure side pressure guide tube during the first operation; even if there is pressure in the pressure guide tube above the upper flange, gas will not be able to be discharged

This post was last edited by feng*aosa on 2023-11-4 at 16:59. The complete measurement of liquid level using the hydrostatic method is shown in the figure below. If the density of the red fluid in the positive-pressure tube is ρ1, and the density of the blue fluid in the negative-pressure tube is ρ2, then the offset required for the transmitter is: Offset = h1×ρ1 – h2×ρ2. 　If no condensation occurs in the gas phase inside the tank, ρ2 is taken as 0 ； If condensation occurs in the gas phase inside the tank, ρ2 is calculated based on the density of the condensate (which is usually the density of the fluid inside the tank). ρ1 is also calculated using the density of the fluid inside the tank. Note that when the transmitter is above the lower pressure tap, h1 takes a negative value. This type of installation makes maintenance quite troublesome: when the liquid level drops below the lower end of the pressure tap in the positive-pressure chamber, the liquid in the pipeline will flow out, and when the liquid level rises again, air in the pipeline prevents new liquid from entering ； If it is desired to keep no liquid present inside the tube, it is necessary to ensure that the pressure tap tube does not leak at all over time; moreover, changes in pressure can cause some liquid to enter or exit the pressure tap tube, resulting in measurement errors ； Also, before each use, it is necessary to ensure that the tube is filled with liquid.

This installation method is not good; it is recommended that the gauge be below the two flanges. There is no need for migration; the chamber is filled with liquid, so even if there is any drift, it will be very stable

Mm-hmm, the experts upstairs have analyzed the technical issues very accurately. What I want to say is that if you need to purchase an EJA transmitter in the future, you can turn to me; I’ll ensure fair prices and delivery times for everyone, regardless of age{:1_90:}{:1_90:}

Who on earth came up with this idea? It wasn’t designed taking real-world conditions into account at all; there’s no way to migrate anything using it – it simply doesn’t work