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General Provisions 1 Scope 1.1 GB/T20801.1-2006 \"Code for pressure pipelines – Industrial pipelines\" specifies the basic safety requirements for industrial metal pressure pipelines. GB/T20801.1-2006 is Part 1 of the \"Code for pressure pipelines – Industrial pipelines\", which specifies the scope of application for industrial metal pipelines and the classification of such pipelines. 1.2 These specifications apply to pressure pipelines belonging to process units, auxiliary units, and utility systems within the boundary area. 1.3 “Pressure pipeline” refers to a pipeline with a maximum operating pressure of 0.1 MPa or higher for gaseous, liquefied gas, or steam media, or for liquid media that are flammable, toxic, or corrosive and have a maximum operating temperature of 0.1 MPa or higher at their standard boiling point, and whose nominal diameter is greater than 25 mm. Pressure pipelines for liquids with a nominal diameter of 25 mm or less, a maximum operating pressure of less than 0.1 MPa or in a vacuum state, and that are non-flammable, non-toxic, and non-corrosive may also follow these specifications; however, they are not subject to safety supervision and are not included in the pipeline classification system. 1.4 This specification does not address the applicability of modifying, inspecting, testing, maintaining, and repairing pipelines that are already in use. 1.5 The scope of application outside this specification is as follows: a) Piping with a nominal pressure of PN420 or higher ； b) Pipelines that can cause radioactive radiation in the event of an accident, such as those in nuclear industrial installations ； c) Pipelines for exploration and extraction equipment of oil, natural gas, geothermal energy, etc ； d) Pipes for smelting equipment in the steel industry ； e) Special ducts for electricity and telecommunications ； f) Pressure pipelines on mobile devices such as cars, ships, airplanes, etc ； g) Urban municipal utility pipelines ； h) Oil and gas transmission pipelines and internal gathering pipelines in oil and gas fields ； i) Internal pipes of fixed equipment such as pumps, compressors, and other devices for transporting or processing fluids, as well as the external connection ports of such equipment ； j) Pipes for heating and ventilation systems ； k) Special pressure pipes for hydropower stations, such as intake pipes and penstocks ； l) Steam and water pipelines in thermal power plants. 2 Normative reference documents The provisions in the following documents become provisions of this standard through reference to it. For reference documents with an indicated year, all subsequent amendment sheets (excluding corrections) or revised versions are not applicable to this specification. However, parties encouraged to reach an agreement under these specifications are advised to consider whether the latest versions of these documents can be used. For reference documents without an indicated year, their latest version applies to this specification. GBJ16－1987 Code for Fire Protection Design of Buildings; GB/T20801.2－2006 Code for Pressure Piping – Industrial Piping, Part 2: Materials; GB/T20801.3－2006 Code for Pressure Piping – Industrial Piping, Part 3: Design and Calculation; GB/T20801.4－2006 Code for Pressure Piping – Industrial Piping, Part 4: Fabrication and Installation; GB/T20801.5－2006 Code for Pressure Piping – Industrial Piping, Part 5: Inspection and Testing; GB/T20801.6－2006 Code for Pressure Piping – Industrial Piping, Part 6: Safety Protection; GB50160－1992 Code for Fire Protection Design of Petrochemical Enterprises; HG 20660－2000 Classification of Toxicity and Explosive Hazard of Chemical Media in Pressure Vessels. 3 Terms and Definitions 3.1 Piping: A set of pipe components used for transporting, distributing, mixing, separating, discharging, measuring, or stopping the flow of fluids. In addition to pipeline components, pipelines also include pipeline supports, but do not include supporting structures such as building frames, pipe racks, pipe tunnels, and bases (pipe piers or foundations). 3.2 Nominal Pressure (PN) is a pressure designation consisting of the letters PN and a dimensionless integer, which indicates the pressure class of pipe components. The number indicates the pressure rating of the pipeline components (equivalent to “bar”). Note 1: Other methods for indicating the pressure rating can also be used, such as CLASS150, etc. Note 2: Unless specified by the relevant standards, the digits following the letter PN do not represent measurement values. Note 3: The allowable operating pressure of pipeline components depends on their PN value, material, design, and operating temperature, and can be specified in the form of pressure-temperature ratings. Note 4: Except for the dimensionless number following PN, which represents pressure in ‘bars’, the units for pressure, stress, elastic modulus, etc. are MPa. 3.3 Nominal diameter (DN): The nominal diameter is a dimension designation composed of the letter DN and a dimensionless integer, which indicates the specifications of pipe components. The figure indicates the diameter of the connection ends of the pipeline components (in millimeters). Note 1: Other methods for identifying dimensions can also be used, such as NPS, outer diameter, inner diameter, pipe thread size, etc. Note 2: The numbers following the letter DN do not represent measurement values. 3.4 Pipe: A sealed, hollow, continuous structure used to transport fluids or transmit fluid pressure is called a pipe. Pipes used in pipelines are classified into two categories according to international conventions: a) Pipes, which are circular-section tubes manufactured in accordance with relevant standard specifications. Their dimensions are indicated by the \"nominal diameter.\" Tubes with the same nominal diameter can have different wall thicknesses, but they all have the same outer diameter; internationally, these are referred to as \"Pipes.\" b) Tubes that are not manufactured according to the above standards can be tubes with a circular cross-section or any other type of cross-section (such as rectangular, polygonal, etc.). The specifications of a circular tube are determined by two of the three parameters: outer diameter, inner diameter, and wall thickness; it is referred to internationally as a “Tube”. 3.5 The Process Unit is the area defined by the engineering design boundaries, where reactions, separations, and other processing operations take place. 3.6 Auxiliary Units: Auxiliary Units are facilities that serve the process units, such as loading and unloading stations, transfer stations, oil depots, batching workshops, tank farms, stockyards, and warehouses within the facility area. 3.7 Package Equipment refers to assemblies in which individual devices or components are installed together, with the pipes between them connected, and ports provided for connecting to external pipes. It can be installed on sliding plates or other movable frames before delivery. 3.8 Piping Components are mechanical elements used to connect or assemble pressure-sealed piping systems, including pipes, pipe fittings, flanges, gaskets, fasteners, valves, safety devices, as well as items such as expansion joints, flexible connectors, pressure-resistant hoses, filters, instruments in the piping system (such as orifice plates), and separators. 3.9 Piping Supporting Elements are components that transfer the loads on pipes – including the weight of the pipes themselves, the weight of the fluids being transported, loads resulting from operating pressures and temperature differences, as well as loads caused by vibration, wind forces, earthquakes, snow loads, impacts, and displacement strains – to the pipe support structure. It is divided into two categories: fixtures and structural accessories: a) Fixtures include suspension-type fixtures such as hangers, spring hangers, tie rods, counterweights, tension bolts, support rods, chains, guide rails, and mounting frames, as well as load-bearing fixtures such as saddles, bases, rollers, brackets, and sliding supports. b) Structural Attachments refer to components that are attached to pipes using welding, bolted connections, or clamping methods, such as lugs, pipe hangers, clamps, pipe clamps, U-clips, and splints. 3.10 Fittings: A category of pipe components that typically includes elbows, tees, reducers, pipe caps, flanged stubs, and union joints. 3.11 Pipe Support is a structure that supports pipes; the pipes transfer loads and thrusts to the pipe support through these supporting elements. The pipe rack is composed of columns, beams, or frames made of steel structures or reinforced concrete structures; it is fixed independently on a foundation, or it can also be fixed to equipment or walls. Classified by type, they include single-column, double-column, and cantilever types, etc. 3.12 The pipe rack is the main location where the pipes of large-scale installations are installed collectively; it consists of columns, beams, and frames made of steel structures or reinforced concrete structures. Classified by type, they include single-layer or multi-layer, passable or non-passable, etc. 3.13 Toxic media: According to GB50440 and HG20660, this term refers to a general designation for media that pose extreme, high, or moderate levels of hazard ； This standard classifies benzene as a highly hazardous medium. 3.14 Combustible Medium: According to GB50160 and GBJ16, it refers to fluids classified as Category A, B, or C based on their fire hazard level, as well as fluids whose operating temperature is higher than their flash point. 4 Pipeline Classification Industrial metal pressure pipelines are classified into three grades—GC1, GC2, and GC3—based on their safety levels. Among them, GC1 has the highest security level ； The GC3 security level is the lowest. 4.1 Industrial pressure pipelines that meet one of the following conditions are classified as GC1 grade: 4.1.1 Pipelines transporting media with toxicity levels as specified in GB5044 and HG20660, namely: a) Highly hazardous media (except benzene) ； b) Highly hazardous gas media (including benzene) ； c) Highly hazardous liquid media with working temperatures above the standard boiling point. 4.1.2 Pipelines that transport gases with the fire hazards specified in GB50160 and GBJ16 as listed below, and whose design pressure is 4.0 MPa or greater: a) Flammable gases of Class A and Class B ； b) Class A flammable liquids (including liquefied hydrocarbons). 4.1.3 Pipes that transport fluid media and have a design pressure of 10.0 MPa or higher, as well as pipes with a design pressure of 4.0 MPa or higher and a design temperature of 400°C or higher. 4.2 Industrial pressure pipelines that meet the following conditions are classified as GC2 grade: pipelines other than those of GC3 grade specified in clause 4.3, whose medium toxicity hazard level, fire risk (flammability), design pressure, and design temperature are lower than those specified in clause 4.1 (GC1 grade). 4.3 Industrial pressure pipelines that meet the following conditions are classified as GC3 grade: 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 +186°C. 4.4 When dealing with mixed media with different toxicity or flammability levels, consideration should be given to the medium with the highest level of toxicity or flammability hazard. When the concentration of a hazardous substance is extremely low, its toxicity or flammability category of the mixed substance should be determined by the owner or designer, taking into account both its degree of hazard and its concentration.