What does the pressure difference display show on the transmitter of a orifice plate flow meter after the balance valve is opened?
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A flow meter that combines an orifice plate, pressure transducers, and a screw-mounted transmitter – with the positive and negative pressures turned off and the balance valve opened, it provides a very accurate zero point. What should the transmitter display when the balance valve and the positive/negative pressure valves are opened? Should it display zero or a random value? I’ve tried many transmitters; some show zero, while others display values around 50% or 60%. What should it actually show? For the gas-wealthy orifice flow meter, the pressure tap pipes are initially filled with isolation fluid. Open the balance valve, and the transmitter displays zero. I refilled the isolation fluid, and when I turned on the balance valve transmitter again, it showed 50% – and this value keeps changing; it’s different each time. After draining the isolation fluid, it’s still around 50%. No problems can be found.
When the balance valve is opened, it should theoretically show zero, but when the valves on the positive and negative pressure sides are not closed, the pressures on these sides differ. Even though the balance valve is open, it still has an impact on the transmitter, so the reading is not zero.
The conduction capabilities of the positive and negative pressure side valves as well as the balance valve differ, which results in different effects.
The conduction capabilities of the positive and negative pressure side valves as well as the balance valve differ, which results in different effects.
The conduction capabilities of the positive and negative pressure side valves as well as the balance valve differ, which results in different effects.
The conduction capabilities of the positive and negative pressure side valves as well as the balance valve differ, which results in different effects.
The balance valve cannot be opened casually; it is necessary to close the negative pressure valve first and then open the balance valve. At this point, the value should be zero; if it is not zero, it can be adjusted to zero. If the balance valve is opened first, the pressure difference between positive and negative pressures will cause the liquid level in the balance tank on the positive-pressure side to drop rapidly, and it will take some time to restore it to normal