Classification and grading of pressure pipelines

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I. Definition of pressure pipelines In a broad sense, pressure pipelines refer to all pipes that are subjected to internal or external pressure, regardless of the medium contained within them. A pressure pipeline is a part of a piping system; pipelines are used to transport, distribute, mix, separate, discharge, measure, control, and stop the flow of fluids. They consist of pipes, fittings, flanges, connection bolts, gaskets, valves, other components, as well as pressure-bearing parts and supporting elements. Since the issuance of the Regulations on the Safety Management and Supervision of Pressure Pipelines in our country, “pressure pipeline” has become a specific term for pipelines subject to supervision. Article 2 of the Regulations on the Safety Management and Supervision of Pressure Pipelines defines pressure pipelines as: \"special equipment used in production and daily life that may pose significant risks such as fires, explosions, or poisoning.\" The Regulations on the Safety Supervision of Special Equipment, implemented on June 1, 2003, further define pressure pipelines as \"tubular devices that use a certain pressure to transport gases or liquids. These include pipelines in which the maximum working pressure is 0.1 MPa (gauge pressure) or higher for gases, liquefied gases, steam, or liquid media that are flammable, explosive, toxic, corrosive, and have a maximum working temperature equal to or above their standard boiling point, with a nominal diameter of more than 25 mm.\" In other words, the so-called \"pressure pipelines\" referred to today not only mean those that are subjected to a pressure of not less than 0.1 MPa inside them, but also those in which gases, liquefied gases, and steam, or liquids that may cause combustion, explosion, poisoning, or corrosion, are transported; furthermore, the nominal diameter of such pipelines must be greater than 25 mm. Pressure pipelines are pipelines with the following characteristics: (1) Pipelines that transport media with an extreme hazard level of toxicity as specified in GB 5044 \"Classification of Hazards from Occupational Exposure to Toxic Substances\". (2) Transporting pipelines for media with fire hazard categories A and B as specified in GB 50160 \"Code for Fire Protection Design of Petrochemical Enterprises\" and GB J16 \"Code for Fire Protection Design of Buildings\". (3) Pipelines with a maximum operating pressure of ≥0.1 MPa (gauge pressure, the same below), and whose transport medium is a gas or liquefied gas. (4) Maximum operating pressure ≥ 0.1 MPa; the medium transported is flammable, explosive, toxic, or corrosive, and the maximum operating temperature is equal to or higher than the standard boiling point – such as in liquid pipelines. (5) Pipeline auxiliary facilities and their safety protection devices corresponding to the first four items. As one of the five major modern transportation systems (road, rail, waterway, air, and pipeline), the pipeline transportation system is used in various fields of modern industrial production and urban construction; pressure pipelines are employed for almost all fluids throughout their production, processing, transportation, and use. Pressure pipeline projects are becoming increasingly complex, moving toward larger scale, integration, and automation. II. Classification of pressure pipelines To facilitate the implementation of the \"Regulations on Safety Supervision of Pressure Pipelines,\" it is advisable, just as with pressure vessels, to classify pressure pipelines according to their different operating conditions and uses, and to manage them separately. To this end, the **Quality and Technical Supervision Bureau issued the \"Regulations on the Qualification Certification and Management of Pressure Pipeline Design Units\" (hereinafter referred to as the \"Regulations\") via Document No. Guo Fa 272. The classification and grading method for pressure pipelines specified in these regulations is as follows: (1) Long-distance pipelines. Long-distance pipelines fall under Category GA, and are further classified into the following grades: ① GAI long-distance pipelines: Such pipelines are classified as GAI grade if they meet one of the following conditions: A. Pipelines that transport toxic, flammable, or explosive gas media, with a design pressure greater than 1.6 MPa; B. Pipelines that transport toxic, flammable, or explosive liquid media, over a distance of ≥200 meters and with a nominal diameter of DN ≥300 mm; C. Pipelines that transport slurry media, over a distance of ≥500 km, and with a nominal diameter of DN ≥150 mm. ②GA2 long-distance pipeline: A long-distance pipeline that meets one of the following conditions is classified as GA2 grade. A. Pipelines for transporting toxic, flammable, and explosive gas media, with a design pressure of P≤1.6MPa ； Long-distance pipelines outside the B.GAl② range ； Long-distance pipelines outside the C.GA1③ range. (2) Public pipelines Public pipelines are classified as GB category, with the following grades: ① GB1 public pipelines: Gas pipelines are classified as GB1 pipelines. ②GB2 utility pipelines: Thermal pipelines are GB2 pipelines. (3) Industrial pipelines Industrial pipelines are classified as GC-type pipelines, with the following grades: ① GC1 industrial pipelines: Industrial pipelines that meet one of the following conditions are classified as GC1 grade. A. Pipelines that transport media with an extreme toxicity level as defined in GB 5044 \"Classification of Hazards from Occupational Exposure to Toxic Substances\". B. Pipelines that transport flammable gases of Class A or B, or flammable liquids of Class A, as specified in GB 50160 \"Code for Fire Protection Design of Petrochemical Enterprises\" and GB J16 \"Code for Fire Protection Design of Buildings\", and whose design pressure is P≥4.0 MPa. C. Pipelines for transporting flammable fluid media or toxic fluid media, with a design pressure of P ≥ 4.0 MPa and a design temperature of ≥ 400°C. D. Pipelines for transporting fluid media with a design pressure of P ≥ 10 MPa. ②GC2 industrial pipes: Industrial pipes that meet one of the following conditions are classified as GC2 grade. A. Transporting flammable gases of Class A or B, or flammable liquids of Class A, as specified in GB 50160 \"Code for Fire Protection Design of Petrochemical Enterprises\" and GB J16 \"Code for Fire Protection Design of Buildings\", at a design pressure P