FREE LECTURE INTRODUCTION TO P&IDs – P&ID SYMBOLS
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In this lecture we’re going to talk about some more symbols P&ID; versus real pipe here we are going to look at a P&ID as it compares to a real piping system or pictorial diagram. Take a minute and familiarize yourself with how the two diagrams represent the same thing in different ways. Your modifiers and transmitters sensors and detectors by themselves are not sufficient to create usable system indications each sensor or detector must be coupled with appropriate modifiers and/or transmitters the exceptions are certain types of local instrumentation having mechanical readouts such as Bourdon tube pressure gauges and bimetallic thermocouples this drawing illustrates the common notations used to indicate the location of an instrument whether it be local or board mounted transmitters are used to convert the signal from a sensor or detector to a form that can be sent to a remote point for processing controlling or monitoring the output can be electronic voltage or current miscellaneous symbols in addition to normal symbols used on PID s to represent specific pieces of equipment there are miscellaneous symbols that are used to guide or provide additional information about the drawing these are four of the most common miscellaneous symbols instrument identifiers one of the main purposes of P&ID; is to provide functional information about how instrumentation in a system or piece of equipment interfaces with the system or piece of equipment because of this a large amount of the symbology appearing on a P&ID; depicts instrumentation and instrument loops the symbols used to represent instruments and their loops can be divided into four categories generally each of these four categories uses the component identifying or labeling scheme as shown here the first column lists the letters used to identify the parameter being sensed or monitored by the loop or instrument the second column lists the letters used to indicate the type of indicator or controller the third column lists the letters used to indicate the type of component and the fourth column lists the letters used to indicate the type of signal that is being modified by a modifier the first three columns are combined so that the resulting instrument identifier indicates its sense parameter the function of the instrument and the type of instrument the fourth column is used only in the case of an instrument modifier and is used to indicate the types of signals being modified here is a list of example instrument modifiers indicators controllers and recorders indicators and recorders are instruments that convert the signal generated by an instrument loop into a readable form the indicator or recorder may be locally or board mounted and like modifiers and transmitters this information is indicated by the type of symbol used this slide provides examples of the symbols used for indicators and recorders and how their location is denoted controller controllers process the signal from an instrument loop and use it to position or manipulate some other system component generally they are denoted by placing AC in the balloon after the controlling parameter there are controllers that serve to process a signal and create a new signal these include proportional controllers proportional integral controllers and proportional integral differential controllers the symbols for these controllers are illustrated here note that these types of controllers are also called signal conditioners.
