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Monday, July 9, 2012

Symbols for instrumentation layouts





For Chemical Engineers involved in either design or production activity, it is necessary to be able to distinguish various types of field and indoor instrumentation and control systems used for particular industrial applications. In order to make layouts uniform and to visualise the process control system a set of symbols was introduced. The following symbols were taken from: Australian Standard - AS 1101.6-1989, Graphical Symbols for general engineering. Part 6: Process measurement control functions and instrumentation, Standards Australia, 1989, 52 pp.



Figure :. presents symbols for industrial instrumentation.

Diameter of a circle for the symbol is equal to 10 mm. Meanings of identification letters for these symbols are presented in Table .

To better understand how these symbols are placed in process control and instrumentation flowcharts I decided to give several examples for measuring and control of process variables in a variety of industrial processes in the successive posts.

Table : Meanings of identification letters.



First Letter

Succeeding Letters
Measured or initiating variable
Modifier
Readout or passive function
Output function
Modifier
A
Analysis

Alarm


B
Burner flame

User’s choice
User’s choice
User’s choice
C
Conductivity (electrical)


Control

D
Density (mass), specific gravity
Differential



E
Voltage (e.m.f.)

Primary element


F
Flow rate
Ratio (fraction)



G
Gaging (dimensional)

Glass


H
Hand (manually initiated)



High
I
Current (electrical)

Indicate


J
Power
Scan



K
Time or time schedule


Control station

L
Level

Light

low
M
Moisture or humidity



Middle or intermediate
N
User’s choice

User’s choice
User’s choice
User’s choice
O
User’s choice

Orifice (restriction


P
Pressure or vacuum

Point (test connection)


Q
Quantity or event
Integrate or totalise



R
Radioactivity

Record or print


S
Speed or frequency
Safety

Switch

T
Temperature


Transmit

U
Multivariable

Multifunction
Multifunction
Multifunction
V
Viscosity


Valve, damper

W
Weight or force




X
Unclassified

Unclassified
Unclassified
Unclassified
Y
User’s choice


Relay or compute

Z
Position


Drive, actuate


                                                        Article Source:: Dr. Alexander Badalyan, University of South Australia

Read more...

Basics of Instrumentation & Control


To view more posts on BASICS : CLICK HERE

Pressure


To view more posts on PRESSURE : CLICK HERE

Flow


To view more posts on FLOW : CLICK HERE

Level


To view more posts on LEVEL : CLICK HERE

Temperature


To view more posts on TEMPERATURE : CLICK HERE
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