Painted markings on steel

Nitrogen pipes are painted yellow, industrial water pipes are painted gray-green, and fire protection pipes are painted red.

Table of Regulations for Coloring and Labeling Chemical Process Pipes Table of Regulations for Coloring and Labeling Chemical Process Pipes Serial Number Medium Name Painting Pipe Label Name Label Color Serial Number Medium Name Painting Pipe Label Name Label Color 1 Industrial water Green Supply water White 24 Instrument air Dark blue Instrument air White 2 Well water Green Well water White 25 Oxygen Sky blue Oxygen Black 3 Domestic water Green Domestic water White 26 Hydrogen Dark green Hydrogen Red 4 Filtered water Green Filtered water White 27 Nitrogen (low-pressure gas) Yellow Low-pressure nitrogen Black 5 Recirculated supply water Green Recirculated supply water White 28 Nitrogen (high-pressure gas) Yellow High-pressure nitrogen Black 6 Recirculated return water Green Recirculated return water White 29 Nitrogen for instruments Yellow Nitrogen for instruments Black 7 Softened water Green Softened water White 30 Nitrogen dioxide Black Nitrogen dioxide Yellow 8 Purified return water Green Purified water White 31 Vacuum White Vacuum Sky blue 9 Hot recirculation return water (upstream) Dark red Hot water (upstream) White 32 Ammonia Yellow Ammonia Black 10 Hot recirculation return water Dark red Hot water (return) White 33 Liquid ammonia Yellow Liquid ammonia Black 11 Fire-fighting water Green Fire-fighting water Red 34 Ammonium hydroxide Yellow Ammonium hydroxide Green 12 Fire foam Red Fire foam White 35 Chlorine Grass green Chlorine White 13 Chilled water (upstream) Light green Chilled water Red 36 Liquid ammonia Grass green Pure chlorine White 14 Chilled return water Light green Chilled return water Red 37 Soda ash Pink Soda ash White 15 Chilled brine (upstream) Light green Chilled brine (upstream) Red 38 Caustic soda Dark blue Caustic soda White 16 Chilled brine (return) Light green Chilled brine (return) Red 39 Alkali salt Gray Hydrochloric acid Yellow 17 Low-pressure steam Red Low-pressure steam White 40 Sulfuric acid Red Sulfuric acid White 18 Medium-pressure steam Red Medium-pressure steam White 41 Nitric acid Pipe natural color Nitric acid Blue 19 High-pressure steam Red High-pressure steam White 42 Acetic acid Pipe natural color Acetic acid Green 20 Superheated steam Dark red Superheated steam White 43 Combustible gases such as gas Purple Gas (combustible gas) White 21 Steam return water condensate Note: ① Heating systems must be painted silver with no labels. ②Ventilation ducts (except plastic pipes) must be painted gray. ③No coloring is applied to stainless steel pipes, non-ferrous metal pipes, glass pipes, plastic pipes, or when thin lead sheets are used for insulation. ④Pipes in outdoor trenches are not painted, but joints within manholes should be painted according to the medium. ⑤Anti-corrosion pipes coated with asphalt for heat preservation are not painted. Regulations on the Painting and Color Rings on the Surfaces of Equipment and Pipelines 1: General Provisions 1.1 These regulations are formulated in order to ensure safe production and avoid mistakes in operations and equipment maintenance, in accordance with the \"Safety Facilities Specification Manual for Power Generation Enterprises\" and the Chinese national industry standard \"Design Code for Insulation Paints in Thermal Power Plants\", taking into account the actual conditions of this plant. 2: Painting 2.1 External painting must be carried out in accordance with different requirements in the following situations: 2.1.1 Equipment, pipes, and their accessories that do not provide insulation ； 2.1.2 Insulation equipment, pipelines, and their accessories with a medium temperature below 120°C ； 2.1.3. Brackets, hangers, platform escalators, etc. (parts fabricated on-site). 2.2 For equipment and pipelines that do not provide insulation, the paint to be used should be selected in accordance with the requirements of the anti-corrosion process and the properties of the paint. The type, color, and coating thickness of the paint to be used shall comply with the following specifications: 2.2.1 For equipment and pipelines installed indoors, it is advisable to apply 2 coats of rust-proof paint first, followed by 1–2 coats of oil-based finish paint ； For equipment and piping installed outdoors, it is advisable to apply 2 coats of epoxy primer first, followed by 2 coats of alkyd enamel or epoxy enamel ； For gas pipes installed outdoors, it is advisable to apply 2 coats of mica iron oxide phenolic primer first, followed by 2 coats of mica iron oxide topcoat. 2.2.2. On the outer surfaces of oil pipelines and equipment, it is advisable to apply 1–2 coats of alkyd primer first, followed by 1–2 coats of alkyd enamel ； For the interior walls of fuel tanks and oil containers, it is advisable to apply 2 coats of epoxy primer first, followed by 1–2 coats of aluminum powder acetal enamel or epoxy resistant paint. 2.2.3. For pipes in trenches, it is advisable to apply 2 coats of rust preventive paint first, followed by 2 coats of epoxy asphalt paint. 2.2.4. For equipment such as circulating water pipelines, industrial water pipelines, and industrial water tanks, it is advisable to apply 2 coats of rust-proof paint first, followed by 2 coats of asphalt paint ； The inner wall of large-diameter circulating water pipes should be coated with two coats of epoxy zinc-rich primer. 2.2.5. The exhaust pipeline should be coated with 1–2 coats of high-temperature resistant anti-rust paint. 2.2.6. For the equipment supplied by the manufacturer (such as water pumps, fans, containers, etc.) and supports, if the paint is damaged, it can be repainted with one coat of paint of the same color. 2.2.7. The paint colors for equipment and pipelines shall be as specified in the table below (Pipeline Paint Color Table). Pipeline Paint Color Table (excerpted from the Code for Design of Insulation Paints in Thermal Power Plants, DL/T 5072—1997) ； \"Code for Safety Facilities in Power Generation Enterprises\", May 1998) Serial Number, Pipe Name, Background Color, Color Ring: 1. Main steam and reheat steam pipes – No ring; 2. Extraction steam, backpressure steam, and heating pipes – Red; 3. Other steam pipes – Red; 4. Condensate water pipes (insulated) – Light green; 5. Condensate water pipes (uninsulated) – Light green, no ring; 6. Feedwater pipes – Green; 7. Desalinated water and chemical make-up water pipes – Light green, white; 8. Drainage and wastewater pipes – Green; 9. Hot water network pipes – Brown; 10. Circulating water, industrial water, jet water, and ash washing water pipes – Black, no ring; 11. Fire-fighting water pipes – Red, no ring; 12. Oil pipes – Yellow, no ring; 13. Cold air ducts – Light blue, no ring; 14. Hot air ducts and dust collector heating air ducts – Blue; 15. Flue ducts – No ring; 16. Raw coal pipes – Black, no ring; 17. Grinding and powder delivery pipes (insulated) – Black; 18. Powder delivery pipes (uninsulated) – Light gray, black; 19. Natural gas and blast furnace gas pipes – Blue, black; 20. Air pipes – Sky blue, no ring; 21. Oxygen pipes – Blue, red; 22. Hydrogen pipes – Orange, no ring; 23. Carbon dioxide and nitrogen pipes – Light gray, red; 24. Acetylene pipes – White, red; 25. Ferrous sulfate and aluminum sulfate pipes – Brown, no ring; 26. Salt water pipes – White, asphalt color; 27. Chlorine pipes – Dark green, white; 28. Ammonia pipes – Yellow, black; 29. Hydrazine – Orange-yellow, red; 30. Acidic liquids – Light gray, orange; 31. Alkaline liquids – Light gray, asphalt color; 32. Trisodium phosphate solution – Green, red; 33. Lime slurry – Light gray, white; 34. Filtered water – Light blue, no ring; 35. Buried pipes – Black, no ring; 36. Industrial water tanks – Black –; 37. Desalination water tanks and make-up water tanks – Light green –; 38. Supports and hangers – Silver gray –; 39. Platform escalators – Silver gray –. 2.3 The types of paint to be used and the degree of coating on insulated equipment and pipes shall comply with the following regulations: 2.3.1 When the temperature of the medium is below 120°C, the surfaces of equipment and pipes shall be coated with 2 coats of anti-rust paint. 2.3.2. The inner walls of equipment such as deaerator tanks, drain tanks, expansion tanks, low-level tanks, and production return tanks should be painted with a high-temperature resistant paint applied in 2 coats; the anti-corrosion method for the inner walls of other equipment and containers should be determined based on the process requirements. 2.4 For support and hanger fixtures fabricated on-site, it is advisable to apply 2 coats of rust-proof paint first, followed by 1–2 coats of silver-gray colored paint. For indoor steel platform escalators, it is advisable to apply 2 coats of rust-proof paint first, followed by 1–2 coats of silver-gray colored paint ； For outdoor steel platform escalators, it is advisable to apply 2 coats of mica iron oxide phenolic primer first, followed by 2 coats of mica iron oxide topcoat. 2.5 For ease of identification, the color rings, names of the media, and arrows indicating the flow direction of the media on pipes shall comply with the following provisions: 2.5.1. Pipes covered with galvanized iron sheeting, pipe elbows, areas where pipes pass through walls, and locations where pipes are densely arranged and difficult to identify must be marked with color rings, names of the media, and arrows indicating the flow direction of the media. The medium name can be identified using its full name or chemical symbol, as shown in the figure below. The position and shape of the color rings on the pipes, the name of the medium, and the arrows indicating the direction of flow of the medium. 2.5.2. On the main steam and reheat steam pipes, at the welds that are under surveillance as well as at the points for measuring creep, a light blue ring should be placed outside the protective layer. 2.5.3. The color of the color rings on the pipes shall be painted according to the colors specified in the table below. Dimensions of the color rings on pipes, the names of the media, and the arrows indicating the flow direction of the media: 2.5.4. The position and shape of the color rings on pipes, the names of the media, and the arrows indicating the flow direction are as shown in the diagram titled “Position and Shape of Color Rings, Media Names, and Arrows Indicating Flow Direction”. The dimensional values are provided in the table titled “Dimensions of Color Rings, Media Names, and Arrows Indicating Flow Direction”; the tip angle of the arrows indicating the flow direction is 60 degrees. 2.5.5. When there are two possible directions of flow for the medium, flow arrows for both directions should be indicated. 2.5.6 The medium name and flow direction arrows can be painted in black or white paint. 2.5.7. For pipes with an outer diameter of less than 76 mm, when it is difficult to identify the name of the medium and the arrow indicating the flow direction by simply painting them on the pipe, signs can be installed at the areas where identification is needed. The name of the medium should be indicated on the label, with the pointed end of the label pointing in the direction of the medium flow. 2.5.8. For pipes such as main steam, saturated water (vapor), condensate water, industrial water, circulating water, ash flushing water, flue ducts, air ducts, and fire-fighting water, for which there is no requirement for color coding, the flow direction of the medium and the name of the pipe should be indicated. Arrows and fonts shall follow the standards. 2.6 Before painting, the metal surfaces of equipment and pipelines should be degreased and rust-removed. 2.7 Whenever new equipment is installed or the labels on existing equipment are updated, the size and format of the labels shall comply with the \"Specifications Manual for Safety Facilities in Power Generation Enterprises\" 1998. 5 standard implementation. 2.8 The valve labels at the production site shall comply with the following standards:
Name label: Length X Width (mm), Font (color), Background color
Valves of Dg50 and below: 90X60, Black font (red), Silver gray
Valves from Dg50 to Dg150: 100X70, Black font (red), Silver gray
Valves from Dg150 to Dg400: 120X80, Black font (red), Silver gray
All valves above Dg400: 140X90, Black font (red), Silver gray
Thermal instruments: 90X60, Black font (red), Silver gray