B2 – 13 Project design
Letter code of PI flow diagram In accordance with DIN 19227 (Part 1/Sheet 6), the use of the letter code and the design of the PI flow diagram (interpretation of the EMCS point) are explained with the help of the introductory example (fig. B2-7). Initial letter T Temperature Second letter I Display 1st subsequent letter A Alarm devices TIAH 2nd subsequent letter 117 H High/upper limit value Container EMCS point number
Generally, letters are to be used in the following order: Initial letter for typical process technology process parameters, e. g. T – Temperature P – Pressure F – Flow rate / throughput L – Filling level /height and Q – Quality (e. g. pH-value) Second letters for the modification of these process parameters, e. g. D – Difference F – Relationship J – Measuring point sensing
Festo Didactic • Process Control System
Fig. B2-7: Introductory example demonstrating the letter code in the PI flow diagram (using the example of a temperature measuring point)