Definition and classification of pressure pipelines as well as identification of medium flow direction

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According to the Regulations on the Safety Supervision of Special Equipment (Decree No. 373 of 2003 issued by the State Council of the People’s Republic of China), a pressure pipeline refers to a tubular device that uses certain pressure to transport gases or liquids. It is defined as a pipeline in which the maximum operating pressure is greater than or equal to 0.1 MPa (gauge pressure), and which is used for transporting gas, liquefied gas, steam, or liquid media that are flammable, explosive, toxic, corrosive, and have a maximum operating temperature greater than or equal to their standard boiling point; such pipelines also have a nominal diameter of more than 25 mm. Classification of fluids transported under ANSI/ASME B31.3: The American standard ASME Code for Pressure Vessels, ANSI/ASME B31.3 (hereafter referred to as B31.3), classifies the fluids transported through pipelines in chemical plants and refineries into Category D, Category M, and a third category whose properties lie between those of the two previous categories, based on the properties of the fluids being transported and the consequences of any leaks. Class D fluids are non-flammable, non-toxic, and harmless to the human body under operating conditions ； The design pressure shall not exceed 150 lbf/in2 (1.05 MPa) ； Assume the design temperature is between -20°F (-29°C) and 366°F (186°C). Class M fluids are highly toxic; even a small amount of them leaking into the environment during transportation, and being inhaled or coming into contact with the human body, can cause severe and difficult-to-treat injuries, and no measures taken promptly can save the affected person. Once the fluid category is determined, the piping for that fluid can be designed, constructed, and inspected in accordance with the relevant provisions of ANSI/ASME B31.3. Classification of pressure pipelines: (Compiled according to TSG R1001-2008 \"Rules for Design Licensing of Pressure Vessels and Pressure Pipelines\") 1. GA category (long-distance pipelines). Long-distance (oil and gas) pipelines refer to those used for transporting commercial media between production sites, storage facilities, and user units; they are classified into GA1 level and GA2 level. 1) Long-distance pipelines that meet one of the following conditions are classified as GA1 grade: (1) Long-distance pipelines that transport toxic, flammable, or explosive gas media, with a maximum operating pressure of P > 4.0 MPa ； (2) Long-distance pipelines for transporting toxic, flammable, or explosive liquid media, with a maximum operating pressure of P ≥ 6.4 MPa, and a transportation distance (referring to the length of the pipelines used to transport such media between the source, storage location, and user) of ≥ 200 km ； 2) Long-distance (oil and gas) pipelines other than GA1 grade are classified as GA2 grade. GA1 grade is divided into GA1 Class A and GA1 Class B: 1. GA1 Class A (1) Pipelines for transporting toxic, flammable, or explosive gases or liquid media. (2) Pipelines for transporting toxic, flammable, or explosive gases or liquid media. 2. GA1 Class B: (1) Pipelines transporting toxic, flammable, or explosive gas media. (2) Pipelines for transporting toxic, flammable, and explosive liquid media. (3) Piping for transporting toxic, flammable, or explosive liquid or gas media. 2. GB category (public pipelines): Public pipelines refer to gas and heat pipelines used for public services or domestic purposes within cities or towns, and are classified into GB1 level and GB2 level. 1) GB1 level: Urban gas pipelines ； 2) GB2 level: Urban heating pipelines. 3) GC category (industrial pipelines): Industrial pipelines refer to those owned by enterprises and institutions and used for transporting process pipelines, utility pipelines, and other auxiliary pipelines; they are classified into GC1 level, GC2 level, and GC3 level. 1) Industrial pipelines that meet one of the following conditions are classified as GC1 grade: (1) Pipelines that transport media with an extreme hazard level as specified in GB5044‑85 \"Classification of Hazards from Occupational Exposure to Toxic Substances\", highly hazardous gaseous media, and highly hazardous liquid media whose operating temperature is above their standard boiling point ； (2) Pipelines that transport flammable gases of Class A or B, or flammable liquids of Class A (including liquefied hydrocarbons), as specified in GB50160-2008 \"Code for Fire Protection Design of Petrochemical Enterprises\" and GB50016-2014 \"Code for Fire Protection Design of Buildings\", and have a design pressure of P ≥ 4.0 MPa ； (3) Piping for transporting fluid media with a design pressure of P ≥ 10.0 MPa, or a design pressure of P ≥ 4.0 MPa and a design temperature of 400°C or higher ； 2) Pipes that are not GC3 grade as specified below, and those for which the toxicity level of the medium and the fire hazard (flammability), as well as the design pressure and design temperature, are lower than those specified for GC1 grade above, are classified as GC2 grade. 3) Pipes that transport non-toxic, non-flammable fluid media, with a design pressure of P≤1.0MPa, and a design temperature greater than -20°C but less than 185°C, are classified as GC3 grade. (1) GC1 grade: 1. Pipelines that transport highly hazardous gas media with an extremely high toxicity level, as well as highly hazardous liquid media whose operating temperature is above their standard boiling point; 2. Pipelines that transport flammable gases of categories A and B or flammable liquids of category A (including liquefied hydrocarbons), and whose design pressure is 4.0 Mpa or higher. 3. The design pressure of pipelines transporting flammable fluid media or toxic fluid media shall be ≥ 10.0 Mpa ； Or pipes with a design pressure of ≥4.0 Mpa and a design temperature of ≥400°C are classified as GC1 grade. (II) GC2 class 4: Industrial pipelines whose medium toxicity hazard level, fire hazard (flammability), design pressure, and design temperature are lower than those specified for GC1 class, except for pipelines of GC3 class, are classified as GC2 class pipelines. (III) GC3 class applies to industrial pipelines that transport non-toxic, non-flammable fluid media, with a design pressure of less than or equal to 1.0 Mpa, and a design temperature higher than -20°C but not exceeding 185°C. 3.GD category (power pipelines): Pipelines used in thermal power plants to transport steam and steam-water two-phase media, classified into GD1 grade and GD2 grade. (1) GD1 grade refers to pipes with a design pressure of P ≥ 6.3 MPa, or a design temperature of 400°C or higher ； (2) GD2 class refers to pipes with a design pressure of P < 6.3 MPa, or a design temperature of less than 400°C. All thermal pipelines are of GB2 grade. Thermal pipelines are divided into the following two categories: (1) Design pressure greater than 2.5 Mpa ； (2) Design pressure is less than or equal to 2.5 Mpa ； Summary table of design categories, grades, and types of pressure pipelines: In accordance with the Announcement issued by the General Administration of Quality Supervision, Inspection and Quarantine on October 30, 2014, regarding the revision of the “Catalogue of Special Equipment” (No. 114 of 2014), a pressure pipeline is defined as a tubular device that uses pressure to transport gases or liquids. It includes pipelines whose maximum operating pressure is 0.1 MPa (gauge pressure) or higher, whose medium is gas, liquefied gas, steam, or a liquid that is flammable, explosive, toxic, corrosive, and whose maximum operating temperature is equal to or higher than its standard boiling point; such pipelines also have a nominal diameter of 50 mm or greater. Except for pipes with a nominal diameter of less than 150 mm and a maximum operating pressure of less than 1.6 MPa (gauge pressure), as well as the pipes that form part of the equipment used for transporting non-toxic, non-flammable, and non-corrosive gases. Among them, the safety supervision and management of oil and gas pipelines shall also be carried out in accordance with laws and regulations such as the Work Safety Law and the Oil and Gas Pipeline Protection Law. Example: 1. A pipe with ammonia as the medium, a diameter of DN40, and a pressure of 0.3 Mpa does not fall under the category of pressure pipes, and therefore does not need to be classified as a GC2 pressure pipe ； (Denominative diameter less than 50 mm) 2. Pipelines with a medium of compressed air, diameter DN100, and pressure of 1.0 Mpa are not considered pressure pipelines, and therefore do not need to be classified as GC3 pressure pipelines ； (Nominal diameter less than 150 mm, operating pressure less than 1.6 MPa). Surface colors and marking colors for visual management of pipelines in the chemical industry: 1. The surface colors and marking colors shall be determined in accordance with the color codes specified in GSB05-1426-2001 \"Standard Color Cards for Paint Films\" ； 2. For stainless steel and galvanized pipes, unless otherwise specified, only color rings and markings shall be applied; no surface paint shall be used. Unified standards for easy management and identification: 1. Dimensions refer to the image on the left ； For the identification of the total length of pipelines (i.e., the color on the pipeline surface), refer to \"Surface Colors and Marking Colors for Visual Management of Pipelines\" ； 2. The minimum distance between the two markers should be 20m ； 3. The locations that need to be marked should include the starting and ending points of all pipes, intersection points, turns, both sides of valves and wall penetrations, points where pipes enter or exit the ground surface, areas where pipes cross the boundaries of installations, as well as other parts on the pipes, within system ducts and installation pipelines and their branches, at the inlets and outlets of equipment, multi-branch distribution pipes, boundary areas, and both sides of gantries. The exact locations should be determined in consultation with the on-site engineer before marking is carried out ； 4. When the routing of the pipelines in the internal pipe gallery of the facility remains unchanged, pipeline markings shall be applied every 3 spans ； Label the pipeline that has undergone a change in direction ； 5. If the flow of the substance in the pipe is bidirectional, it is indicated with a double arrow ； 6. The markings are arranged in a neat and aesthetically pleasing manner as a whole. 7. Material: Identification using galvanized iron plates; the galvanized plates are fixed to the pipes in accordance with the above standards (using straps and screws). 1. Materials such as non-ferrous metals, stainless steel, ceramics, and plastics (including fiberglass), as well as pipes coated with zinc, or those treated with enamel, zinc plating, alloy aluminum sheets, or asbestos cement; pipes covered with insulating materials, those that have been painted with color-changing paint, or those coated with thick fire-resistant paint – unless otherwise specified – shall only have color rings and markings applied to them, without any surface paint ； 2. Refer to the figure above for dimensions ； 3. The minimum distance between the two markers should be 20m ； 4. The locations that need to be marked should include the starting and ending points of all pipes, intersection points, turns, both sides of valves and wall penetrations, points where pipes enter or exit the ground surface, areas where pipes cross the boundaries of installations, as well as other areas on the pipes, within system ducts and installation pipelines and their branches, at the inlets and outlets of equipment, on multi-branch distribution pipes, at boundaries, and on both sides of gantries. It is necessary to confirm these locations with the on-site engineer before marking them ； 5. When the routing of the pipelines in the internal pipe gallery of the facility remains unchanged, pipeline markings shall be applied every 3 spans ； Label the pipeline that has undergone a change in direction ； 6. If the flow of the substance within the pipe is in both directions, it is indicated by a double arrow ； 8. The labels are arranged in a neat and aesthetically pleasing manner as a whole. 9. Material: Marking made of galvanized iron sheet; the galvanized sheet is fixed to the pipeline in accordance with the above standards (using straps or screws). No insulation: 1. All pipes in the plant’s pipe galleries must be managed using numbering systems; the rules for these numbering systems are to be established by the responsible department, and the font used for the numbers should be Calibri in bold. 2. The identification of the total length of the pipeline (i.e., the color on the pipeline surface) is specified in \"Surface Colors and Marking Colors for Visual Management of Pipelines in the Chemical Industry\" ； 3. Dimensions refer to the figure above ； 4. The material requirements are the same as those specified in the \"Requirements for Visual Management Labels on Pipes within Chemical Industry Plants\" ； Insulation is provided: 1. Pipeline corridor signs should be installed at the entrances and exits of the pipeline corridors, as well as at locations where straight ladders or walkways are present; at points where there are changes in the layout of pipelines within the main corridor; and at the junctions between the main corridor and branch corridors (signs should be installed on both the main corridor and the branch corridor at such junctions). These signs are hung vertically relative to the pipelines, and they come with dual-sided markings – meaning that whether one is standing in front of or behind the sign, the correct direction of the pipeline can be identified on both sides of the sign ； North-south pipelines are numbered from east to west, while east-west pipelines are numbered from south to north. Corresponding comprehensive pipeline identification signs are installed in the inspection passages of each layer of the overhead pipe gallery. 2. Above the signs in the above-ground pipe gallery, and next to the inspection passages for the gallery structures, pipe gallery signs should be hung; they must be easy to identify, and their hanging positions should be consistent. 3. The style of the pipe rack signs can refer to the image above. Production instructions: 1. First, measure the dimensions of the pipe ； 2. Calculate the dimensions of the arrows and label text based on the pipe size ； 3. Based on the calculated dimensions, find an advertising agency to create arrow templates or print the templates yourself ； 4. Paste the template onto the pipes on site in accordance with the standard requirements ； 5. Use paint in standard color codes for painting or spraying (be careful to prevent contamination) ； 6. The formwork can be removed 30 minutes after painting is completed ； 7. Re-verify the production quality and its compliance with standards.