I would like to ask how to explain this kind of interlock
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What does the × inside the circle mean, an indicator light? Why is there a circle with a cross mark on the flow transmitter below? What does C1 in the box mean? And what do the two concentric circles above C1 in that box represent? What is the UR of dcs expression? What does TI 2051-63 Box plus C1 mean? How can the self-control within the large ellipse be explained, and why is an angular type used for the liquid level control valve inside the small ellipse?
For the legend issues, it’s best to refer to the PID legend instructions; Figure 2 seems to represent a flash tank
A circle with an X means that both flow meters and level gauges measure flow and level based on the differential pressure principle. Inside the large ellipse are two level gauges that measure the same liquid level; one is used for alarms, while the other is used for display, control, and recording. The angle valves inside the small ellipse are selected based on the properties of the medium, such as high differential pressures and the presence of fibers