ANSI Pipe Marking Standards
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 hazardous materials they carry. The ANSI A13.1-1981
Scheme for Identification of Piping Systems addresses this concern by offering a common
labeling method for use in all facilities.
ANSI separates materials transported in above-ground 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.
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.
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. The following
table indicates ANSI-recommended letter height for various pipe sizes.
Outside Pipe Diameter Letter Height
|.75" to 1.25"||.5"|
|1.5" to 2"||.75"|
|2.5" to 6"||1.25"|
|8" to 10"||2.5"|
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 (see Illustration 1). 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
ANSI Pipe Marking Labeling Supplies
ANSI A13.1-1981 signs for liquid mixture pipes, steam pipes and low stage suction pipes can be hard to find. To make sure you
are up to date with the latest compliance rules in ANSI Z535.1-1991, for flow direction labeling, Low Temperature Recirculated Liquid and identifying Thermosyphon Supply pipes,
contact us today. We also sell compatible duralabel supplies, SafetyPro printers and TSC thermal transfer machines, which
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