Reasons why a differential pressure is still indicated when the balance valve of the EJA differential pressure transmitter is opened
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The on-site equipment is in operation. The pressures on both the high-voltage and low-voltage sides were below 1 M; this situation occurred during the commissioning process. During equipment operation, when both positive and negative pressures are in use, only the balance valve is opened; as a result, the differential pressure across the transmitter decreases, but it still remains present, and that differential pressure is quite significant. The differential pressure will only return to zero after the high and low pressure valves are closed. What is measured is the level of the low-boiling-point liquid. The gas phase pressure inside the tower is 0.6 MPa, the liquid level is 12 meters, and the height of the tower is 15 meters. Why doesn’t the differential pressure return to zero after the balance valve is opened? It didn’t have any impact, but I can’t figure out why. A preliminary consideration is that the balance valve is a needle valve, which has a pressure-reducing effect. I don’t know if it’s for this reason.
The pressure in the high and low pressure pressure transmitters affects the transmitter, so the valves for these pressure transmitters need to be closed.
1. Open the balance valve; the differential pressure should be 0. 2. Close the shut-off valves on the high-pressure and low-pressure sides, then check again to see if the differential pressure is still 0
Is it a clogged pressure guide tube or a problem with the valve assembly?
Measuring the liquid level should have no impact.
Differential pressure transmitters are very sensitive; even after opening the balance valve, the pressure difference between the positive and negative pipes still exists, and this continues to affect the transmitter
This post was last edited by cqdfwy on 2020-6-16 at 10:30. There is a liquid level of 12 meters inside the tower; when the high and low pressure valves of the transmitter are not closed, the high and low pressure chambers of the transmitter are affected by the pressure of this liquid column. Even if the balance valve is open, its flow cross-sectional area is too small to eliminate the effect of this liquid column pressure (the balance valve allows fluid to flow under the pressure difference between the two chambers until the pressure difference becomes zero, thereby achieving pressure balance). Only when there is no inflow or outflow of material from the tower, and after enough time has passed, can the balance valve eliminate the effect of this liquid column pressure and allow the transmitter to return to zero. The lower the liquid level, the lesser the impact.