scope:

This standard establishes an approved listing of mechanical symbols that shall be used in the preparation of drawings when graphic or symbolic representation is desired, for all items except aircraft, aerospacecraft, or spacecraft. The symbols listed are those most commonly employed on engineering drawings. They are for exterior and interior services.

Where graphical symbols are required for an item or equipment not covered in this standard, the form and character of the symbol will be left to the discretion of the activity concerned, provided that the symbol used does not duplicate any of those contained herein, and is clearly understandable, subject to one interpretation only, or explained by a suitable note on the drawing when necessary.

Pipe fittings, valves and piping symbols (see section 2) shall be used for all systems, except where so desired, the symbols shown for fluid power systems (see section 6) may be used for fluid power systems. All other symbols shall be used as applicable.

Each drawing or one sheet of each set of drawings on which symbols are used shall show a legend which shall identify the symbols. However, those symbols which are unmistakably identified on the drawing by the text or note at or near the symbols, may be omitted in the legend. In lieu of identifying each symbol, it is permissible to state that symbols used are in accordance with this Standard or the appropriate American Standards. Since symbolic representation does not usually involve exact or scale layout or the actual run or leads of piping, the same symbol may be used for all projections of the system (plan, elevations and sections) except where specific symbols for the various views are included in this standard.