We continue our analysis of a P&ID (or P&ID) diagram, which we left unfinished in Part 1. If you haven't seen or studied it, I suggest you do so to have the full context. Click Here: https://instrumentacionycontrol.net/interpretando-un-diagrama-pid-o-dti-desde-cero/
For ease of understanding, I will show the example diagram again so we can continue the analysis and interpretation:
In part 1 (https://instrumentacionycontrol.net/interpretando-un-diagrama-pid-o-dti-desde-cero/We then proceeded with the analysis to the FT-100 flow loop and instrument, which uses vortex technology for this measurement. On the other hand, we observed that the flow controller is part of the displays in the control system. For example, it could be a signal within a DCS in a control room. The diagram also indicates an FRC-100, where the "C" signifies that the flow data from this control loop will be recorded or historicalized.
We also discussed the P-100 pressure control loop on the 10-inch line (10” CS 0 004). In this case, it serves to control the pressure inside the vessel. We see the PIT-100 indicator transmitter, which is measuring the pressure in the tank and transmitting this signal through pneumatic lines to the PIC-100 controller (field pneumatic controller). From this controller, a pneumatic signal is sent directly to the PV-100 valve, which is a 6-inch butterfly valve. We can also see that its default position in case of failure is to remain open.
Finally, we have a level control loop that transmits all its signals electrically. We have the LT-100, LIC-100, LI-100, LY-100, and LV-100 devices. In this case, LT-100 is the level transmitter that sends its level signal to our control system. We also see LI-100, which would be the level indicator or display, possibly located near that transmitter to show the information in the field. These signals reach the LIC-100 controller, which is within the control system and displays its information in the control rooms, available to the operator. The LV-100 valve receives its control signal through an I/P converter, LY-100. This is also a butterfly valve that has a fail-to-close position (downward arrow). Additionally, we see that this valve has one-inch drains (numbers 3 and 4), both before and after the valve. As we already know, this is done for safety purposes or to avoid contamination of the environment, depending on the product being processed.
In this level loop, we also see the LG-1 device, which is a local level indicator, and the LSH-300 and LSL-301 devices, which are high-level and low-level switches, respectively. These last two devices generate high (LAH-300) and low (LAL-300) alarm signals electrically or electronically, and these alarms are displayed on the control panel or are accessible to the operator. The low alarm signal is also associated with a process interlock (diamond with an "I" inside). In this case, it is understood that if the level is too low, the pump associated with this closed vessel or tank will stop.
I hope I've explained myself clearly and clarified some of your questions. As always, if you'd like specific information and P&ID or DTI diagram nomenclature, here are some helpful links:
https://instrumentacionycontrol.net/diagramas-de-flujo-de-procesos-pfd-y-diagramas-de-proceso-e-instrumentacion-pid-interpretacion/ or in this other one https://instrumentacionycontrol.net/identificacion-de-instrumentos-como-armamos-los-tags/
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