Level change due to flange blockage in double-flange level transmitters
Thread Content
At natural gas production wells and stations, double-flange level transmitters experience blockages caused by ice in the pressure lead pipes or oil contamination. A non-clogged two-stage refrigerant compressor operating at 6 MPa: when the pressure-taking ball valve on the upper flange is closed, the negative pressure measured by the gauge increases, and the remote-level indication shows 0. Turn off the lower flange pressure-taking ball valve; the value is increasing, and the remote level reading is 100. Please discuss why the pressure changes when the system is isolated from its surrounding environment. If oil contamination or ice buildup occurs on the upper and lower flanges, what changes will occur in the liquid level? This will help determine which flange is blocked
When one of the source valves is turned off, pressure exists on the other side; this is certainly the case, indicating that neither the upper nor the lower end is blocked.
The principle of a communicating vessel for liquid level measurement holds true regardless of whether one of the upper or lower paths is blocked. When one end is closed, the liquid level inside the device changes; if the pressure at the external measurement point of the closed end remains unchanged, distortion will occur.
It is simply turned off and then on again, so the change in liquid level can be ignored. Furthermore, when the pressure tapping point on the upper negative chamber is closed, the pressure on the lower flange changes; as a result, the liquid level should rise. Yet in reality, the liquid level is 0 at the moment of closure. Please discuss this further – it’s a good opportunity to learn from experience
The pressure relief ball valve was closed, but there was no pressure release; I don’t think this explanation makes sense. I hope you can give me some guidance. Thank you!
Hehe, only water-based media dare to be used for cleaning; what other types of media would dare to be used?
What Pig Brother said upstairs is absolutely correct. Taking into account what the original poster mentioned—as well, the operating pressure is 6 MPa; that is, before the valve is closed, the positive and negative pressure chambers of the double-flange level transmitter, as well as the measurement diaphragm chamber and the silicone oil inside the capillary, are all subjected to this pressure. After the valve is closed, there is always a slight change in the volume of the pressure chamber behind the positive and negative pressure sampling valves. Although this change is minor, the high pressure – along with the stress released by the sealing materials, as mentioned by the person above – causes significant pressure changes (compared to the liquid level range). This is what leads to the phenomenon described by the original poster.