In theprocess industry,chemical industry,manufacturing industry, and other commercial and industrial contexts,pipe marking is used to identify the contents, properties and flow direction of fluids in piping. It is typically carried out by markingpiping throughlabels andcolor codes. Pipe marking helps personnel and fire response teams identify the correct pipes for operational, maintenance or emergency response purposes.

Pipes are used extensively in commercial and industrial buildings and on industrial plant (e.g.oil refineries) to transfer fluids between items of plant and equipment.^[1] Positive identification assists operations personnel to correctly identify plant when carrying out routine or maintenance activities, and for emergency personnel when responding to emergencies. Pipe marking is particularly important for identification where pipes run alongpipe racks, through walls and bulkheads and through floors.^[2]

A range of corporate, national and international codes, standards and regulations are in use around the world.

Three ASME A13.1 pipe markers.

In theUnited States,Occupational Safety and Health Administration regulations recommend followingAmerican Society of Mechanical Engineers Standard A13.1-2015 - Scheme for the Identification of Piping Systems.^[3]

The standard states that labels should be placed where easily viewed by a person standing near the pipe at any of the following points:^[4]

2015 revisions added oxidizing materials to the existing 'Flammables' classification. The other major change allowed and encouraged labels to incorporate theGHS signal word,hazard pictograms, andhazard statements. This addition helped identify additional dangers when dealing with materials that fit into multiple categories, likehydrogen sulfide, which is both flammable and toxic.^[4]

In 2014, the International Institute of Ammonia Refrigeration introduced a specialized label design for use when marking pipes associated withrefrigeration systems usingammonia, including information such as thephysical state, pressure and purpose in the system.^[6]

TheNational Fire Protection Association have a special labeling system in the standard for Health Care Facilities, such as hospitals and dentistry offices. This standard puts more emphasis on gases found inMedical gas supply systems, which consist of bothoxidizing gases and gases thatdisplace oxygen.^[7]

In the United Kingdom there are three principal regulations that mandate the marking of equipment and piping:

• Classification, Labelling and Packaging of Chemicals(Amendments to Secondary Legislation) Regulations 2015,^[8]
• Health and Safety (Safety Signs and Signals) Regulations 1996,^[9]
• Provision and Use of Work Equipment Regulations 1998,^[1]

The regulations require that vessels containing hazardous substances together with the pipes containing or transporting such substances must be labelled or marked with the relevant hazard pictograms or pipe marking. The labels used on pipes must be positioned visibly in the vicinity of the most hazardous points, such as valves and joints; at both sides ofbulkheads and floor penetrations; and at reasonable intervals.

The regulations do not specify a specific marking system, but BS EN ISO 1710Graphical symbols — Safety colours and safety signs is often used.

A widely used British Standard (BS) for marking equipment is:

• BS 1710:2019Graphical symbols — Safety colours and safety signs — Registered safety signs

The Standard stipulates the colours to be used. These are as follows:^[2]

In addition to the basic colours, certain safety colours are used:

The arrangement of markings is for the safety colour to be between bands of the basic colour.^[2]

Firewater service would be:

The pipe contents must be identified adjacent to the banding.^[2] This can be done by giving either:

• The full name
• Abbreviation
• Chemical symbol
• Refrigerant number
• Coloured bands (user specified)

The direction of flow should also be identified near the banding.^[2]

Examples using this system are as shown.

The Indian Standard IS 2379 provides for a ground colour and a coloured band on piping to identify material.^[11]

Colour bands of 25 mm to 100 mm width are placed at locations such as battery limits, intersections, near valves, at walls, starting and terminating points. There is a large range of bands which define the contents of the line. For example, for oils.

Pipes, ducts and conduits are identification by the Australian Standard AS 1345—1995 “Identification of the contents of pipes, conduits and ducts”^[12]

Ships and marine facilities must conform to an international standard for piping systems identification. This is ISO 14726:2008Ships and marine technology — Identification colours for the content of piping systems.^[13]

This is a two-colour banded marking system. The main colour shows what the fluid is being used for. This is on either side of the secondary colour which indicates what the substance actually is. The main colours are as follows:^[13]

•   Black - Waste media
•   Blue - Fresh water
•   Brown - Fuel
•   Green – Sea water
•   Grey - Non-flammable gases
•   Maroon - Air and sounding pipes
•   Orange - Oils other than fuels
•   Silver - Steam
•   Red - Fire fighting
•   Violet -Acids, alkalis
•   White - Air in ventilation systems
•   Yellow - Flammable gases

International Standard ISO 20560-1:2020Safety information for the content of piping systems and tanks — Part 1: Piping systems was intended to replace the variety of regulations and standards across countries and regions. Basic identification colours and warning symbols identify the pipe contents and any hazards.^[14]

Pipe markers consists of 4 basic elements:

• Basic identification (background) colour, see table below, e.g. yellow for hazardous substance
• Name of the substance/content, e.g.NATURAL GAS
• Flow direction indicator arrows,⇒
• Warning symbols, e.g.GHS symbol

Colours and substances are typically as follows:^[14]

International Standard ISO 20560-2Safety information for the content of piping systems and tanks — Part 2: Tanks, provides a similar colour scheme for tanks.

RAL colour standard charts are used by architects, construction industry and road safety.^[15]

The pipe identification colours are as shown in the table.

Wikimedia Commons has media related toPipe marking.

• Piping
• American National Standards Institute
• American Society of Mechanical Engineers

• Piping
• Civil engineering
• Hazardous materials
• Chemical safety
• Color codes

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