F - Flow
Reference for the ISA 5.1 first letter F. Flow is the most common first letter in process drawings because almost every BPCS loop ties back to a flow measurement. FF, flow ratio is sometimes used to denote ratio control loops where two flows are constrained to a programmed ratio.
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Also stands for.
- Flow rate
- Flow ratio, when prefixed FF
Common second letters.
Transmitter, FT. Flow transmitter
Indicator, FI. Flow indicator
Indicator plus controller, FIC. Flow indicating controller
Computing relay or transducer, FY. Flow signal computing element
Sensor or primary element, FE. Flow element, e.g. Orifice plate
Alarm low, FAL. Flow alarm low
Alarm high, FAH. Flow alarm high
Switch high, FSH. Flow switch high
Example tags.
Flow transmitter on loop 101
Flow indicating controller, train 21, loop 03
Flow element, orifice plate, vortex meter, etc. On loop 405
Flow computing relay, redundant A, loop 101
Typical placement.
Inline on a process line, drawn as a circle bisected by the pipe with the tag inside or adjacent. The first-letter F is paired with a second-letter that describes the function, transmitter, indicator, controller, switch, alarm, computing relay.