ANSI Pipe Marking Standards

Quick Tips #203

Hazardous materials flow through miles of piping in many industrial, commercial and institutional facilities. Just like hazardous materials in other situations, piping systems should be appropriately labeled to make people aware of the materials they carry. The older versions (1981 & 1996) of the ANSI (American National Standards Institute) A13.1 standard have merged into the ANSI/ASME (American Society of Testing and Materials) A13.1 Scheme for Identification of Piping Systems. This merged standard ANSI/ASME A13.1, addresses pipe marking by offering a common labeling method for use in all industrial, commercial, institutional facilities and in buildings used for public assembly. This ANSI pipe marking standard does not apply to buried pipelines or electrical conduit.

Label Requirements

Pipe marking labels must effectively communicate the contents of the pipes and give additional detail if special hazards (such as extreme temperatures or pressures) exist. The legend should be short in length and easy to understand. For example, the legend "Steam 100 PSIG" specifies the contents as well as the additional pressure hazard. An arrow should be used in conjunction with the legend to show which direction the material flows. If flow can be in both directions, arrows in both directions shall be displayed.

The older versions (1981 & 1996) of ANSI A13.1 pipe marking standard separated materials transported in aboveground piping systems into three categories:

  • High-hazard materials: Encompasses several hazard areas including corrosive and caustic materials; substances that are toxic or capable of creating toxic gases; explosive and flammable materials; radioactive substances; and materials that, if released, would be hazardous due to extreme pressures or temperatures.
  • Low-hazard materials: Materials that are not inherently hazardous and have a small chance of harming employees through mild temperatures and low pressures.
  • Fire suppression materials: Fire protection materials such as foam, carbon dioxide (CO2), Halon and water.

The three hazard classes have different color-coded labels associated with them. All high-hazard materials use black characters on a yellow background. The low-hazard material class is divided into two different color schemes: liquids or liquid mixtures use white characters on a green background; gases or gaseous mixtures use white characters on a blue background. The fire suppression class uses white letters on a red background. The letters on pipe labels should be a minimum of 1/2" high, and should increase in size as the pipe diameter increases-(Table 3).

The 2007 edition of the ANSI/ASME A13.1 changed the color scheme requirements for the labels. In this new edition of the pipe marking standard, there are 6 standard colors instead of 4 colors. The new label color requirements are based on the characteristic hazards of the contents. See Table 2 below for the new color requirements.

Label Placement

Labels should be positioned on the pipes so they can be easily read. Proper label placement is on the lower side of the pipe if the employee has to look up to the pipe, on the upper side of the pipe if the employee has to look down towards the pipe, or directly facing the employee if on the same level as the pipe. Labels should be located near valves, branches, where a change in direction occurs, on entry/re-entry points through walls or floors, and on straight segments with spacing between labels that allows for easy identification.

Exceptions to ANSI Pipe Marking Standard

Other pipe labeling systems are acceptable if they are put in writing and meet the basic ANSI requirements.

Commonly Asked Questions
Q.   Can I still use my current pipe marking system based on the older version of the standard or do I have to change my color scheme to meet ASME A13.1 2007?
A.   Existing schemes for identification shall be considered as meeting the requirements of the standard if the schemes are described in writing and employees are trained in the operation and hazards of the piping system.
Q.   What if I have a pipe smaller than 3/4" diameter?
A.   For pipes of less than 3/4" in diameter the use of a permanently legible tag is recommended.
Q.   Are particular shades of yellow, green, red and blue required for pipe labels?
A.   Yes, ANSI/ASME A13.1- recommends the color code featured in the ANSI Z53.1- Safety Color Code for Marking Physical Hazards. The color shades recommended are intended to give highest level of recognition to employees with both normal and color-deficient vision.
Q.   Has this ANSI pipe marking standard been adopted by OSHA?
A.   No, it is still considered an industry consensus standard, which is only a recommendation. Even though it has not been specifically adopted by OSHA, industry consensus standards may be evidence that a hazard is recognized and there is a feasible means of correcting such a hazard. If you do not follow a consensus standard, it is possible to be cited under the General Duty Clause.

ASME A13.1-2007 Scheme for the Identification of Piping Systems, American Society of Mechanical Engineers, New York, NY 10016.

ANSI A13.1-1981 Scheme for the Identification of Piping Systems, American National Standards Institute, New York, NY 10036.

ANSI Z53.1-1979 Safety Color Code for Marking Physical Hazards, American National Standards Institute, New York, NY 10036.

ANSI Z535.1-1991 Safety Color Code, American National Standards Institute, New York, NY 10036.

American National Standards Institute: 11 W. 42nd St. New York, NY 10036 (212) 642-4900.

(Rev. 1/2012)


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Please Note:
The content in this newsletter is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific compliance questions should refer to the cited regulation or consult with an attorney.

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