Understanding of multiple metrological controls
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Hello, experts. I have a question for you: I came across a PID diagram for a multi-flow metering GLCC system, as shown in the image below. After studying it for quite some time, I still don’t understand how the yellow-colored section is controlled Anyone who knows something about this, please give some advice! ! Thank you! ! I’m not sure if my understanding of pressure control and level control is correct; I would appreciate it if experts could offer their guidance! ! I heard that it is a gas-liquid dual-parameter measuring device, but I’m not sure how it carries out measurements. Could the experts give some guidance? ! Thank you! !
Multiple metering controls generally refer to the simultaneous monitoring and adjustment of multiple parameters such as flow rate, pressure, liquid level, etc. In the gas-liquid two-parameter control device (GLCC), a PID controller is used by the system to maintain set parameters such as flow rate, pressure, and liquid level. Regarding the yellow-colored section, if your description refers to a specific control loop in the PID diagram, please provide more information or diagrams so that I can give a more accurate answer. Without the drawings, I can only provide general instructions. Typically, the yellow line may represent the level control loop; it is connected to a level sensor and outputs a control signal to a control valve in order to maintain a set level. Level control is achieved by adjusting the amount of liquid entering or leaving the container. If your understanding of pressure and level control is based on sensor signals being processed by a PID controller, which then adjusts the corresponding control valves to maintain the set point, then your understanding is correct. As for how the measurement devices for gas and liquid carry out their measurements, flow sensors are generally used to determine the flow rate of both gas and liquid, allowing for their separate monitoring and control to ensure that the flow rates remain within predetermined ranges. The specific measurement methods are closely related to equipment design, and detailed system information is required for further analysis. .
This post was last edited by tiger2010 on 2024-1-29 at 12:30. Just by looking at the PID in this part of your image, it’s not possible to determine what type of control it is (selective control, cascade control, etc.)
There’s a ZIT next to the LV valve; it probably represents interlocking – presumably the LV valve is interlocked when the pressure reaches a certain level
Thank you all for your valuable advice! ! I heard that this is a 2-item metering process device. The gas-liquid mixture enters from the left, where it is separated into gas and liquid; subsequent devices measure the flow rates of each component separately, before the mixture is output from the right side. I’ve roughly heard of this concept, but I don’t understand the control relationships and logic here. I would like to seek advice from all of you, who are so knowledgeable! !
It is primarily used for metering at the outlet of oil wells, to determine how much mixture is produced by each well, as well as the amount of oil, water, and gas contained in that mixture; these are the devices used for such processes
There’s no PIC either – is the text in the top left corner something you imagined on your own? :Lol, sometimes control lines or interlock lines are represented as just one line in a P&ID; it’s necessary to check the legend to see what kind of controllers are involved. Additionally, one needs to look at the interlock relationship table, as it’s not always possible to determine this just by looking at the diagram. If I’m to guess, I think it’s either due to excessive vapor pressure or the vapor extraction valve being closed, which causes the interlock to open the liquid extraction valve, at least to relieve some of the pressure: lol
When the pressure is normal, the control valve in the gas circuit should operate based on liquid level control; as a result, this valve may not move much, which helps to keep the frequency of pressure fluctuations in the liquid level control valve low； After overpressure occurs, the control valve in the gas circuit should prioritize pressure control to rapidly release the pressure back to the normal range. It's a guess; it's not necessarily correct.
It’s still the genius on the 8th floor – awesome. I asked about the manufacturer, and it’s based on the logic you mentioned; I still don’t understand how the PV valve control in the gas phase is connected to the LV valve control in the liquid phase. When the pressure is normal, both the PV valve and the LV valve operate independently according to their respective set targets. But when the pressure is abnormal, if the LV valve control takes precedence, does that mean the PV valve control stops working? Or rather, when the PV valve control has priority, does that mean the LV valve control stops? ,