本部分中的符号应视为ISO 3511/1和ISO 3511/2中给出的符号的补充，并与之结合使用。功能识别的字母代码应取自这两部分的表1。这些符号仅限于工艺流程图、管道和仪表图等上的标识，不提供说明特定仪表或其部件的方法。实例中给出了应用方法。

The symbols in this part shall be considered a supplement to the symbols given in ISO 3511/1 and ISO 3511/2 and used in conjunction with them. The letter code for function identification shall be taken from table 1 of these two parts.The symbols are limited to identification on process flow diagrams, piping and instrument diagrams, etc. and do not provide means of illustrating specific instruments or parts thereof. The application methods are shown in the examples.