Industrial Hygiene Profesional

Why are the ANSI color codes important? What does the yellow background mean?

The yellow background signifies that the piping may handle hazardous material. Unfortunately, much has changed in the typical plant over the last 70 years since this standard was originally conceived. The basic standard can be traced to the 1920's and use in the US military. Obviously, our definitions for what is "hazardous" has changed. Water, air or carbon dioxide, under certain situations (pressure, heat, mixture with other chemicals) are not always benign. How do we interpret, for example, materials that should be used for "fire quenching" that are also "hazardous"? Should we use the red or the yellow ANSI scheme? Or, how do we label a pipe that carries both the liquid (which should be green) and gas form of a chemical (which should be blue)?

Hazards, in other words, are not so easily defined. "Hazardous" may mean that the material is hazardous to a person nearby, or to the operation of the overall plant itself. Could "hazardous" mean that the materials flowing through the process piping, if not handled carefully, could contaminate the product. Or, if leaked into the atmosphere, could the chemical infect the environment or cause damage to employees after cumulative exposure over a period of years? Clearly, the ANSI standard was written for far simpler times.

* CHROMEL® and ALUMEL® are registered rademarks of Hoskins Manufacturing Company. PMC Corporation reserves the right to substitute equivalent product to CHROMEL® and ALUMEL® at any time.
For additional information see Bare Wire Data Sheet

Variations in color-coding standards are inevitable in our complex plant and pluralistic society. While laudable, harmonization of color-codes, then, will be very difficult to achieve. Many plants use other color-coding; for example, color-code each system (i.e. Lube Oil is brown, Condensate is green, etc.>) or color code by Unit (i.e. Unit 1 is yellow, Unit 2 is blue, etc.). For most plants, we recommend either the ANSI pipe marker color codes or simply black on yellow markers. For more complex plants, we recommend a color-coding by system. For all environments, we recommend the inclusion of RTK information on the valve or on the pipe.