Regarding the pressure tapping points for double-flange transmitters
Thread Content
Dear experts, I have a question: is the pressure at point A in the diagram the same as that at point B, or is it the same as that at point C?
Is that why the gas phase pressures of a, b, and c are all equal?
The gas phase pressure in the tanks is the same; there is an issue with differential migration at the flanges
1. If the gravitational potential of the gas is taken into account, then the pressure at point B will necessarily be lower than that at points A and C. As for by how much, this needs to be determined in units of Pa – those who have worked on precise measurement of low pressures know how to calculate the height potential difference; I won’t go into details here. 2. The pressures at points A and C are equal. 3. When using double flanges, whether the diaphragm is installed on the side or in the center, changes in the diaphragm’s position can result in errors of 1 kPa or several kPa – this is a factor that cannot be ignored.
If we are precise, the three are all different: when the liquid level is above point C, the pressure at point B is lower than that at point C; when there is condensed liquid in the gas phase and this liquid accumulates at point A, the pressure at point A is also higher than that at point B; and when the height of the accumulated liquid exceeds the highest possible liquid level, the pressure at point A is still greater than that at point C.
The gas pressure in a sealed container is the same everywhere.
Sealed double flange, open single flange
5th floor is correct. If the gravity of the gas is taken into account, it’s the same as AC. If not considered, ABC are all the same
It’s basically the same; the error is negligible.