Temperature indication, pressure indication, etc. are integrated into the DCS system
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As shown in the figure, I used to think that the functions were limited to things like temperature indication, pressure indication, and liquid level indication – those display or alarm functions were represented by instrument symbols without a square box; they did not go into the DCS. Only those systems that required temperature control or similar functions would be integrated into the DCS! But the one in the diagram is just a level indication alarm, without any control function, yet it still uses a DCS symbol – what’s going on here? That one with a horizontal line in the middle also goes to the central control display; so why is it still necessary to go to the DCS?
This is a liquid level display; the alarm points are determined based on the upper and lower alarm values of this liquid level
If it doesn’t go into the DCS, how can it be displayed on the computer?
That’s why there’s nothing complicated about working with DCS. As for the legends, although there are industry standards, after all they are drawn by humans, and there is a lot of reuse of such elements; different design firms or manufacturers certainly have varying interpretations of them. It’s all quite simple – as long as you understand what they mean, there’s no need to be too precise regarding the way they’re drawn. For example, the horizontal line in LT is indeed unnecessary
Now, conventional instruments have been removed; all functions such as control, indication, alarm, and interlock are handled by the DCS, so all signals should be fed into the DCS.
Could you be more specific? For many of our previous diagrams, apart from the data that was sent to the DCS for control purposes, it seems that nothing else was displayed there
Now, all newly built petrochemical and refining facilities use DCS; no one uses conventional indicator instruments anymore. If not DCS, then what?
In one sentence: The original poster doesn’t understand what DCS means It has nothing to do with whether DCS is used or not; whether it’s for display or control signals, anything that facilitates process operation in the central control room is implemented through the DCS system.
It is recommended that the poster find a PID and take a close look at the instruments at the front. This is the industry standard, and there are few variations.
Monitoring is necessary; it’s not always required to send control signals in order to enter the DCS