Figure 5-11.—Aircraft fluid line color code and symbols.

(screwed, flanged, welded, and so forth) as well as fittings, valves, gauges, and items of equipment. When an item is not covered in the standards, the responsible activity designs a suitable symbol and explains it in a note. Figure 5-10 shows some of the common piping symbols used in piping prints. When a print shows more than one piping system of the same kind, additional letters are added to the symbols to differentiate between the systems. MIL-STD-101C established the color code used to identify piping carrying hazardous fluids. It applies to all piping installations in naval industrial plants and shore stations where color coding is used. While all valve wheels on hazardous fluid piping must be color coded, the piping itself is optional. The following colors are painted on valve wheels and pipe lines carrying hazardous fluids: Yellow — Flammable materials Brown — Toxic and poisonous materials Blue — Anesthetics and harmful materials Green — Oxidizing materials Gray — Physically dangerous materials Red — Fire protection materials Fluid lines in aircraft are marked according to MIL-STD-1247C, Markings, Functions, and Designations of Hoses, Piping, and Tube Lines for Aircraft, Missiles, and Space Systems. Figure 5-11 lists the types of aircraft fluid lines with the color code and symbol for each type. Aircraft fluid lines are also Figure 5-11.—Aircraft fluid line color code and symbols. 5-7