How to Interpret DCS and PLC Symbols on a P&ID

[Music] in this video we're going to talk about how to correctly interpret PLC and DCs symbols on a PN ID before we get started you might want to review two of our other videos called how to read a P&ID and what is an HMI you can find the links to these videos in the description all right then let's get started anybody such as instrumentation and control engineers technicians and maintenance personnel working on industrial plant control systems depend heavily on PN IDs a P&ID is like a road map telling us what the instruments and devices are where they are located and how they interact with the rest of the plant original symbols and terminology 4pn IDs were created long before the introduction of PLC's and DC s's and plant control before computers came along process control loops were stand-alone in other words each process had its own individual controller control rooms were massive and had sprawling control panels with lots of controllers and other devices such as strip chart recorder z' and switches today's industrial processes are controlled by computerized systems using virtual controllers found in PLC's and DC s's new control rooms are filled with HMIS and keyboards connected to a dcs or PLC system all of this computerization required that new pn ID symbols had to be developed so let's look at the P&ID symbols for PLC and DCs if you recall stand-alone instruments are indicated on a pn ID by a circle with a tag number the horizontal bar across the middle of the circle indicates the physical instrument resides in a primary location accessible to an operator on the main control panel if we take that same symbol and draw a box around it it now means that it is no longer a physical instrument it is now part of a shared display and shared control in a dcs okay let's look at a pn ID with dcs symbols and see how it links field instruments with the dcs and how it's displayed on the operator HMI LT 501 and ft 501 are two field instruments both sending electrical signals to dcs controllers let's take a closer look at the flow control loop flow transmitter ft 501 sends an electrical signal to the dcs flow indicating controller fic 501 which in turn sends an electrical signal to operated flow control valve FCV 501 here's what the operator sees on the HMI screen we've put a big red circle around fic 501 and FCV 501 as we discovered on the P&ID the controller fic 501 is part of the dcs fic 501 controller functions can be adjusted at the HMI by the operator all fic 501 inputs and outputs can be observed in real time on the HMI as well okay let's drill down a bit deeper and look at how the P&ID relates to the flow loop diagram we've placed green circles around ft 501 and fic 501 referring back to the P&ID you will see that ft 501 is a flow transmitter in the field and fic 501 is a shared control in the dcs this is a good time to point out the blue circle around the software signal lines as they show how the dcs connects with the HMI PLC symbols don't show up on pn ids nearly as often as dcs symbols but when they do show up they are drawn as a diamond inside a box all you have to know is that the symbol represents a software instruction to perform some function in the plant for example let's revisit our P&ID the plc symbol indicates that the SDV 5:03 valve is operated by the emergency shutdown software instruction written in the PLC program let's review what we've discussed today DCs and PLC symbols became a necessity with the computerization of process automation if you see a square box drawn around the circle on a pn ID that means a dcs is part of the control process if you see a square with a diamond in it on a P&ID that means a PLC is part of the control process newcomers to real bars have free access to one of our online courses you can take advantage of this offer by downloading the real pars app and selecting the first lesson of the PLC hardware course just like this video the lessons are all high-quality and also very easy to follow also for a low monthly fee you'll give full access to an exclusive library of courses on PLC programming and industrial automation topics as well as new fresh out of the oven videos each and every week these courses are all member exclusive and are not shared anywhere else on the Internet [Music] [Music] you

Channel: RealPars

Views: 132,867

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Id: 3CYTe7AvRvM

Length: 6min 15sec (375 seconds)

Published: Mon Jun 08 2020