InstrumentatIon & ControlChula/ongkom UnIversity

Chapter1: INSTRUMENTATION E" JMENTModule 2: ISA Symbols

CHAPTER 1: INSTRUMENTATION EQUIPMENT

MODULE 2: ISA Symbols

MODULE OBJECTIVES:

At the end of this module, you will be able to:

1. Sketch the symbols representing three different Idnds (pneumatic, electronic and mechanical) oftransmission line.

2. State the instrument which a given standard ISA symbol represents, with respect to its function andmounting location.

3. Sketch a simple flows sheet using standard ISA symbols, given the function and location of differentinstruments and the type of transmission line connecting them.

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Instrumentation & ControlChulalongkorn University

Chapter 1: INSTRUMENTATION EQuiPMENTModule 2: ISA Symrols

Introduction

• Instruments on drawings which show the location and function of different devices are represented bystandard symbols.I •• ... 4'.· ....._.'1.. _ .. r _ • \ • I I .

• In most or Norm AmeriCa, a convention Dasea on I~A llnstrument ~oclety or AmeriCa} symDOIs nas Deenadopted.

Line Symbols

• Transmission lines which link different instruments are shown in Figure 1.

---------

-tI----HI-------IHf--

-L I::- L

MECHANICAL LINKAGE

ELECfRICAL SIGNAL

PNEUMATIC SIGNAL

HYDRAtJLIC LINE

Figure 1 Symbols for Transmission Lines

Figure 1: Symbols for Transmission Lines.

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Instrumentation & ControlChulalongkom University

Chapter 1: INSTRUMENTA TION E",,,/PMENTModule 2: /SA Symbols

Instrument Symbols

• Instruments are identified by circles with lettered codes (two or three letters) inserted. This letteredcode shows the instrument type and function.

The first letter in the Code The second letter in the code A third letter in the code is used whenindicates the Process Parameter indicates the function of the the instrument has two functions;

monitored by the instrument instrument it indicates the second functionF= flow Fl = Flow Indicator FIC = Flow Indicating ControllerL= Level FC = Flow Controller LAH = Level Alarm HighP= Pressure LA = Level Alarm LAL = Level Alarm LowT= Temperature LR = Level Recorder

PT = Pressure -TransmitterTE = Temperature Element

• To distinguish control room mounted instruments from local or field mounted instruments, a horizontalline across the diameter of the circle is used.

e~Control RoomRackMounted

High Level Alann

Control RoomPanel MountedLevel Recorder

Field (orlocally)Mounted Level Indicator

Figure 2: ISA Symbols and the Instruments they Represent.

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Instrumentation & ControlChulalongkom University

Chapter 1: INSTRUMENTATION Ec..<lIPMENTModule 2: ISA Symbols

HIGH LEVEL ALARMRACK MOUNTED

Solution: ISA Symbols Representation of a level Loop

LEVEL INDICATOR

rIIl __I--.......;~ LOW LEVEL ALARMr RACK MOUNTED

I"""--1I LEVEL CONTROLLER

LEVEL TRANSMITTER ~ -l-----l FRONT PANELI MOUNTED

Il LEVEL RECORDER--f---1 FRONT PANEL

MOUNTED

Control Room Panel Mounted:Level controllerLevel recorderHigh level alarmLow level alarm

Examplg

A level loop consists of:

The level transmitter is connecteddirectly to the tank'and the rest of theinstruments are driven by the leveltransmitter and used to monitor andindicate the level in a tank.

Field Mounted: Level transmitterLevel indicator

Assuming that the signal transmitted iselectronic, draw a representative flowsheet using ISA symbols.

Field Control Room

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Instrumentation & ControlChulalongkom UnIversity

FIRST LETTER

Chapter 1: INSTRUMENTATION Ec.._ .PMENTModule 2: ISA Symbols

Table 1Instrument Identification Code

SUCCEEDING LETTERSMeasured Variable Read-out or Passive

I

Output FunctionI

ModifierFunction

A CURRENT,

ALARM AVERAGEC CONTROL CONTACTE ELEMENTF FLOW RATEG GLASSH HAND (MANUAL) HIGHI INDICATEL LEVELM MOTORIZED MEDIANP PRESSURER NEUTRON FLUX RECORD RELAYS SOLENOID SWITCHT TEMPERATURE TRANSMITV VALVEW WELLX TRANSDUCERY COMPUTEZ POSITION

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