These standards determine whether a jumper is needed for metal pipe flanges

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I. Metal flange bridging for industrial pipelines: The Technical Code for Safety of Special Equipment, \"Regulations on the Safety Inspection of Pressure Pipelines – Industrial Pipelines\" (TSG D0001–2009), issued by the General Administration of Quality Supervision, Inspection and Quarantine on May 8, 2009, provides the following definition for industrial pipelines: These regulations apply to industrial pipelines that are part of process units, auxiliary units, as well as utility systems within a facility, provided that they meet all the conditions specified (hereinafter referred to as pipelines). (1) Those with a maximum operating pressure of 0.1 MPa or greater (gauge pressure, the same below) ； (2) Those with a nominal diameter (Note 1) greater than 25 mm ； (3) When the medium being transported is a gas, steam, liquefied gas, a liquid with a maximum operating temperature equal to or higher than its standard boiling point, or a flammable, explosive, toxic, or corrosive liquid. Most pressure pipes encountered during routine inspections fall under the category of industrial pipes mentioned above. Article 80 of the \"Regulations on Safety Inspection of Pressure Pipelines – Industrial Pipelines\" (TSG D0001–2009) specifies the following regarding anti-static measures using flange connections: For pipelines that require static electricity grounding, it is necessary to measure the resistance values between each connection joint as well as the resistance value of the pipeline system relative to the ground. When the stress exceeds the requirements specified in the \"Code for Pressure Piping – Industrial Piping\" (GB/T20801-2006) or in the design documents, bonding wires (between flanges or threaded connections) and grounding leads shall be installed. As can be seen from this clause, to determine whether a bypass wire is needed for the flanges, it is necessary to measure the resistance between them; if the resistance value exceeds the specified limit, a bypass wire must be used. Clause 10.12.1 of the \"Code for Pressure Piping – Industrial Piping, Part 4: Fabrication and Installation\" (GB/T20801.4-2006) stipulates that for pipelines requiring static grounding, good electrical conductivity must exist between various sections of such pipelines. When the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω, a wire bridge should be provided. In addition, Article 7.13.1 of the \"Code for Construction of Industrial Metal Piping Projects\" (GB 50235—2010) stipulates that for pipelines for which static electricity grounding is required, a bonding wire shall be installed when the resistance value between each pair of flanges or other joints exceeds 0.03 ohms. It can be seen from this that to determine whether industrial pipeline metal flanges need to be bridged, it is necessary to measure the resistance value between the flanges. When the resistance between the flanges exceeds 0.03Ω, a wire bridge should be installed. II. Flange bridging for gas pipelines is commonly used by enterprises that handle gas. What are the regulations regarding flange bridging for gas pipelines? The “Code for Design of Town Gas Systems” (GB50028—2006) contains no explicit provisions regarding flange bonding. However, Paragraph 3 of Article 10.8.5 stipulates that the design of anti-static grounding facilities for gas pipelines and equipment shall comply with the provisions of the current standard “Technical Regulations for Anti-Static Grounding Design in Chemical Enterprises” (HGJ28-90). The \"Technical Code for Static Grounding Design in Chemical Enterprises\" (HGJ28-90) has now been renumbered as HG/T20675-1990. Section 2.7.5 of this specification states that when metal flanges are fastened using metal bolts or clamps, it is generally not necessary to install additional electrostatic connection wires. Under corrosive conditions, it is necessary to ensure that there are at least two contact surfaces between the bolts or clamps; the surfaces should be descaled and degreased before installation, and anti-loosening nuts should be used during installation. The \"Explanations for the Compilation of Technical Specifications for Static Grounding Design in Chemical Enterprises\" provide the following explanation for clause 2.7.5: Based on the practical experience of many organizations, metal flanges connected by metal bolts possess sufficient static conductivity simply through the connection of those bolts. The installation requirements under corrosive conditions are intended to ensure conductivity. It can be seen from this that when metal flanges are fastened using metal bolts or clamps, it is not necessary to use a bridging wire for the gas pipeline flanges. Since most gas pipelines are industrial pipelines, if the flanges of such pipelines suffer severe corrosion and the resistance value exceeds 0.03Ω, bypass wires can be used in accordance with the requirements of the \"Regulations on Safety Supervision of Pressure Pipelines – Industrial Pipelines\" (TSG D0001–2009). 　　III. Flange bridging for petrochemical pipelines: The petroleum industry places high demands on anti-static measures; are there stricter regulations regarding flange bridging? Article 8.9.1 of the \"Code for Acceptance of Construction Quality of Metal Piping in Petrochemical Projects\" (GB50517-2010) stipulates that for pipelines requiring static grounding, a wire bridge shall be provided when the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω. As an enterprise specification, the “Code for Design of Static Electricity Grounding in Petrochemical Industry” (SH 3097-2000) is stricter than **standards and industry standards. Section 4.3.3 of this standard specifies that in piping systems, when metal flanges are fastened using metal bolts or clamps, it is generally not necessary to install additional electrostatic connection wires; however, it is essential to ensure that there is good electrical contact between at least two of the bolts or clamps. Article 6.2.13 of the \"Code for Construction and Acceptance of Pipelines for Highly Toxic and Flammable Media in the Petrochemical Industry\" (SH 3501–2001) stipulates that for pipelines requiring static grounding, good electrical conductivity must exist between various sections of such pipelines. When the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω, a wire should be used for bridging. Article 14.2.14 of the \"Code for Design of Oil Depots\" (GB 50074-2002) stipulates that flange connections of oil (oil and gas) pipelines shall be bridged. When connected by no less than 5 bolts, bypass wiring is not required in a non-corrosive environment. Article 10.3.3 of the \"Code for Design and Construction of Automobile Fueling and Gas Refueling Stations\" (GB 50156—2002) stipulates that in areas prone to explosion, metal wires should be used for bonding at connections such as flanges on oil, liquefied petroleum gas, and natural gas pipelines, as well as at both ends of rubber hoses. When there are no less than 5 connection bolts on the flange, bypass wiring is not required in non-corrosive environments. As the industry standard for static electricity safety inspections, the \"Regulations for Static Electricity Safety Inspections in Chemical Enterprises\" (HG/T23002-92) stipulates in Section 5.1.2 that when metal equipment is connected to other metal equipment, or when pipes are connected to each other using metal flanges, it is not necessary to use additional bonding wires; however, there must be at least two bolts used for the connection. It can be seen from this that whether it is necessary to use bypass connections for petrochemical pipeline flanges depends on their resistance value or the number of bolts used; it is not mandatory to use bypass connections for all of them. IV. Conclusion In summary, it is not necessary to bridge all metal pipe flanges. Whether a bypass is needed depends on whether the design documents specify requirements for static electricity grounding. If the design documents are not available, it is necessary to determine the value by measuring the resistance; when the resistance between the flanges exceeds 0.03Ω, a wire must be used for bridging. Determining whether bridging is required based on the flange fastening method or the number of metal bolts; this applies to gas pipelines and pipelines in petrochemical plants, but not to common industrial pipelines. GB 50235-97 \"Code for Construction and Acceptance of Industrial Metal Piping\": Clause 6.12.1 Pipelines that require static grounding must have good electrical conductivity between their various sections. When the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω, a wire should be used for bridging. Article 6.12.2: When the earth resistance value of the piping system exceeds 100Ω, two grounding leads shall be provided. The grounding lead should be welded. SH3501-2002 \"Code for Construction and Acceptance of Toxic and Flammable Media in Petrochemical Industries\": Article 6.2.13 Pipes that require static grounding must have good electrical conductivity between their various sections. When the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω, a wire should be used for bridging. Article 6.2.16: For stainless steel pipes that require electrostatic grounding, the wire bonds or grounding leads shall be connected via stainless steel plates; they must not be connected directly to the stainless steel pipe. SH3097-2000 “Code for Design of Static Electricity Grounding in Petrochemical Industry”: Clause 4.3.1 states that pipelines shall be grounded at points where they enter or exit the plant area (including production workshop buildings) and at points where they branch off. Long-distance unbranched pipes should be grounded every 100 meters. Clause 4.3.2: When the minimum distance between parallel pipes is less than 100 mm, jumpers shall be installed every 20 meters. When pipes intersect with a clear distance of less than 100 mm, bypass wires should be added. Paragraph 4.3.3: When a metal flange is fastened using metal bolts or clamps, it is generally not necessary to install additional electrostatic connection wires, but it must be ensured that there is good electrical contact between at least two of the bolts or clamps. Articles 6.11.1 to 6.11.5 of HG 20225-95 “Code for Construction and Acceptance of Chemical Metal Piping” are identical to those in GB 50235-97 “Code for Construction and Acceptance of Industrial Metal Piping”