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ANSI Color Codes

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.

Color Std Meaning Example
Red APWA Electric Power Lines, Cables, Conduit and Lighting Cables Buried High Voltage Line
Yellow APWA Gas, Oil, Steam, Petroleum or Gaseous Materials Natural Gas Distribution Line
Orange APWA Communication, Alarm or Signal Lines, Cables or Conduit Buried Fiber Optic Cable
Blue APWA Water, Irrigation and Slurry Lines Buried Water Line
Green APWA Sewers, Drain Line Buried Storm Sewer Line
Red Traffic Prohibition STOP, Yield
Orange Traffic Temporary Work Zone Construction Zone Ahead
Yellow Traffic Caution Merge Ahead, Slow
Blue Traffic Information Signs Hospital
Brown Traffic Historical or Park Picnic Area Ahead
Green Traffic Directional Signs Exit 1 Mile, Go
Red ANSI Sign Danger Signs, Highest Hazard Hazardous Voltage Will Cause Death
Orange ANSI Sign Warning Signs, Medium Hazard Hazardous Voltage May Cause Death
Yellow ANSI Sign Caution Signs, Lowest Hazard Turn Machine Off When Not In Use
Blue ANSI Sign Notice Signs Employees Only
Green ANSI Sign Safety First Signs Wear Ear Plugs
Red ANSI Pipe Fire Quenching Materials Fire Protection Water
Yellow ANSI Pipe Materials Inherently Hazardous Chlorine
Blue ANSI Pipe Materials of Inherently Low Hazard, Gas Compressed Air
Green ANSI Pipe Materials of Inherently Low Hazard, Liquid Storm Drain
Blue/Red/Yellow NFPA 701 Blue is used for Health Hazards, Red for Flammability and Yellow for reactivity


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.

ANSI Color Code for Thermocouple and Thermocouple Extension Wire
ANSI
Symbol
Wire Alloys Polarity Thermocouple Wire Color T/C Extension Wire Color
Individual Jacket Individual Jacket
J Iron
Constantan
(TM)
+JP
-JN
White
Red
Brown White
Red
Black
K CHROMEL®*
ALUMEL
®*
+KP
-KN
Yellow
Red
Brown Yellow
Red
Yellow
T Copper
Constantan
(TM)
+TP
-TN
Blue
Red
Brown Blue
Red
Blue
E CHROMEL®*
Constantan
(TM)
+EP
-EN
Purple
Red
Brown Purple
Red
Purple
N Nicrosil(TM)
Nisil
(TM)
+NP
-NN
Orange
Red
Brown Orange
Red
Orange
RSX Copper
Copper Alloy
+RSP
-RSN
- - Black
Red
Green
BX PCLW630/Copper
Copper
+BP
-BN
- - Grey
Red
Grey
W3X
W5X
Alloy 203; Alloy 405
Alloy 225; Alloy 426
+WP
-WN
- - White/Red
Red
White/Red

* 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

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