Instrument Naming

Written by Jerry Ratzlaff. Posted in Instrumentation

On a Piping and Instrumentation Diagram, instruments are designated by an alphanumeric code or tag:

LetterFirst LetterSecond LetterThird Letter
A Analyzer Alarm -
B Burner or Combustor - -
C Available - -
D Available - -
E Voltage Element -
F Flow Rate - -
G Available Glass -
H Hand - High
I Current (Electrical) Indicator -
J Power - -
K Time, Schedule - -
L Level Light Low
M Available - Middle
N Available - -
O Available Orifice -
P Pressure Connection Point (Test) -
Q Quantity - -
R Radiation Record -
S Speed Switch -
T Temperature Transmitter -
U Multivariable Multi-function -
V Vibration Valve -
W Weight Well -
X Unclassified Unclassified -
Y Event - -
Z Position Actuator, Driver -

These letters go together to form unique Instrumentation Identification. The typical Instrumentation Matrix is a good starting place for typical instrumentation found in a plant.