Regarding the equipotential grounding of pipelines and flange bonding, which specific standards should be followed?

As a supplementary note: Which standards are used for acceptance in this regard? ?

For petrochemicals, use SH; for chemical industries, use HG. If neither is specified, follow GB

4.3 Pipeline System 4.3.1 Pipelines shall be grounded at the points where they enter and leave the plant area (including the production workshops) as well as at branching points. Long-distance unbranched pipes should be grounded every loom. 4.3.2 When the clear distance between parallel pipes is less than 100 mm, jumper wires should be installed every 20 m. When pipes intersect with a clear distance of less than 100 mm, bypass wires should be added. 4.3.3 When a metal flange is fastened with metal bolts or clamps, it is generally not necessary to install an additional electrostatic connection wire, but it must be ensured that there is good electrical contact between at least two of the bolts or clamps.

For a pipe with four bolts, is it necessary to use an electrostatic bonding wire for the flange? Which standard should be followed for inspection and acceptance?

First, it is necessary to check whether the design has such requirements; if grounding is required, then it is necessary to determine which standard the design follows, and installation and inspection should be carried out in accordance with that standard. Pipelines in different industries follow the standards of those industries, and their requirements also vary.

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 specific area, 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 whose maximum operating temperature is higher than or equal to its standard boiling point, or a liquid that is flammable, explosive, toxic, or corrosive. 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, bypass wires (between flanges or threaded joints) 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 installed. 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 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 Urban Gas\" (GB50028—2006) does not contain any explicit provisions regarding flange splices; instead, paragraph 3 of Article 10.8.5 states that the design of anti-static grounding systems for gas pipelines and equipment shall comply with the provisions of the current standard \"Technical Regulations for Anti-static Grounding 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. Paragraph 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 Preparation 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, jumper wires can be used in accordance with the requirements of the \"Regulations on Safety Inspection of Pressure Pipelines – Industrial Pipelines\" (TSG D0001‑2009). III. Bridging of petrochemical pipeline flanges: The petroleum industry has high requirements regarding static electricity prevention; are there stricter regulations for bridging pipeline flanges? 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. The \"Code for Design of Static Grounding in Petrochemical Industries\" (SH 3097-2000), as a corporate standard, is stricter than **national standards and industry standards. Paragraph 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 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 each section of the pipeline. 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 non-corrosive environments. Article 10.3.3 of the \"Code for Design and Construction of Automobile Fuel and Gas 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 hoses. When there are no fewer 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 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 petrochemical pipeline flanges need to be bridged depends on their resistance value or the number of bolts they have; it is not necessary to bridge them all. 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. It is determined whether a jumper is needed based on the flange fastening method or the number of metal bolts; it is applicable to gas pipelines and pipelines in petrochemical enterprises, but not suitable for common industrial pipelines. Article 6.12.1 of GB 50235-97 \"Code for Construction and Acceptance of Industrial Metal Piping\": For pipelines that require static grounding, there must be good electrical conductivity between each section 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 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 For pipelines that require static grounding, there must be good electrical conductivity between each section of the pipeline. 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 bridging 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 Grounding in Petrochemical Industries\": Article 4.3.1 Pipelines shall be grounded at the points where they enter and exit the plant area (including production workshops) as well as at branching points. Long-distance unbranched pipes should be grounded every 100 meters. Article 4.3.2 When the clear distance between parallel pipes is less than 100 mm, a bridging wire shall be installed every 20 meters. When pipes intersect with a clear distance of less than 100 mm, jumper wires should be added. Article 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 Industry Metal Piping\" are consistent with those in GB 50235-97 \"Code for Construction and Acceptance of Industrial Metal Piping\". Grounding wires – the lifeline of safety: In electrical engineering, establishing a good electrical connection between any part of an electrical system and the ground is referred to as grounding. Grounding is an important aspect of electrical fire safety technology. To ensure the safety of power system equipment and people in industrial production and daily life, various grounding measures must be taken, such as lightning protection grounding, anti-static grounding, protective grounding, and working grounding. Grounding is a simple and effective method to ensure the proper operation of equipment, prevent electric shock injuries, as well as avoid fires and explosions. The power plugs of household appliances such as air conditioners, washing machines, and microwave ovens are mostly three-pronged, and should be connected to the live wire, neutral wire, and ground wire respectively. For household appliances used under normal conditions, the ground wire seems redundant, but ignoring it is extremely dangerous; if the insulation around the wires inside the appliance is damaged and leakage occurs, an accident can happen if it is not detected or addressed in time. Many people lost their lives due to the neglect of this ground wire. It is common to see cases in home appliance use where the ground wire is not used or not connected properly. Some people connect the ground wire to the water supply pipes, but in reality many of these water supply pipes are not grounded and therefore cannot form a circuit to direct any leakage current into the ground ； Some also use gas pipelines as grounding wires, which is strictly prohibited. Although gas pipelines are buried underground, they carry flammable gases; if a leak occurs and these gases mix with air to reach an explosive concentration, an explosion can happen when an electric spark generated by an electrical current comes into contact with them. Generally, grounding wires are left in place when a building is completed; one just needs to find their location and connect them properly. In industrial production, proper grounding not only prevents injuries and deaths caused by electric shocks but also stops fires and explosions from occurring. The metal parts of buildings in a factory, such as beams, columns, tracks, steel pipes for wiring, cables, and industrial pipes that pose no risk of combustion or explosion, can all be used as grounding wires. In pipes where flange gaskets provide insulation, it is necessary to connect the flanges or pipe joints using jumper wires. For grounding electrodes buried underground, aside from pipelines for flammable liquids and gases, various metal process pipelines and metal water pipes can also be used as grounding electrodes. In addition, the total resistance of the grounding system should also be taken into account; the lower the grounding resistance, the better for safety. Grounding facilities should be inspected regularly to ensure they remain in good condition and have a proper connection. Simply put, a ground wire is used to direct any electricity that leaks from the live wire into the ground, thereby ensuring at least the safety of people. After a leakage occurs, the conductive property of the wires allows electricity to be directed to the ground first, so it does not harm people; this is merely a safety measure. As opposed to the live wire, the wire that is charged among the two is the live wire, while the other one is the ground wire ； If it is three-phase, there is still only one live wire and two ground wires ； When the live wire and the ground wire are connected indirectly (through an electrical appliance), a current circuit is formed, which ensures safety ； Additionally, the ground wire can direct electrical charges to the ground, preventing accidental electric shocks. When flammable and explosive materials flow through pipes, friction against the pipe walls generates static electricity; this electric charge accumulates at the flanges, which is why jumper wires are used. Grounding wires, on the other hand, serve to prevent lightning strikes ； The codes for lightning protection and grounding in building design specify that flanges with more than 6 bolts do not require grounding. Regarding standard requirements: For pipelines that require static grounding, a wire bridge should be installed when the resistance value between each pair of flanges or threaded connections is greater than 0.03 ohms. However, many flanges were seen on site that were not bridged, and upon inquiry it was stated that metal gaskets were used. ②According to tests conducted by the relevant authorities, when the resistance value of the pipeline system relative to ground is less than 100 ohms, it is not necessary to use wires for bridging between the flanges; if there are 5 or more bolts used to connect the pipelines, bridging is not required either. Otherwise, a copper wire with a cross-sectional area of at least 6 mm2 must be used for connection. In cases where the current exceeds 500 mA, the provisions of the “Code for Design of Static Grounding in Petrochemical Industries” SH3097‑2000 (approved by the Petroleum and Chemical Industry Bureau on 2000‑06‑30 and implemented on 2000‑10‑01) apply. Excerpts from this code are as follows: 4.3 Pipeline Systems 4.3.1 Pipelines should be grounded at points where they enter or leave the plant area (including production workshops) as well as at branching points. Long-distance unbranched pipelines should be grounded every 100 meters. 4.3.2 When the clear distance between parallel pipes is less than 100 mm, a jumper wire should be installed every 20 m. When pipes intersect with a clear distance of less than 100 mm, jumper wires should be added. 4.3.3 When a metal flange is fastened with 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. 4.3.4 The heating tracing for process pipelines shall be equipotentially connected to the process pipelines at the steam inlet and return water outlet of the tracing. 4.3.5 When the protective covers for air ducts and insulation layers are made of thin metal sheets, they should be joined by overlapping edges and electrically bonded using bolts and other means for mechanical fixation. 4.3.6 For the non-conductive sections in between the metal pipes, in addition to requiring special anti-static treatment, the metal pipes at both ends should be connected to the grounding main line respectively, or bridged with copper-core flexible stranded wire having a cross-sectional area of not less than 6 mm2 and then grounded. 4.3.7 All metal components on non-conductive pipe sections shall be grounded. 4.3.8 Metal pipes buried directly underground may not require electrostatic grounding.

Article 6.12.1 of GB 50235-97 \"Code for Construction and Acceptance of Industrial Metal Piping\": For pipelines that require static grounding, there must be good electrical conductivity between each section of such pipelines. ...... SH3501-2002 \"Code for Construction and Acceptance of Toxic and Flammable Media in Petrochemical Industries\": Article 6.2.13 For pipelines that require static electricity grounding, there must be good electrical conductivity between each section of the pipeline. ...... HG 20225-95 \"Code for Construction and Acceptance of Chemical Industry Metal Piping\", Articles 6.11.1 to 6.11.5 are consistent with GB 50235-97 ...... Whether flanges on petrochemical pipelines need to be bonded depends on their resistance value or the number of bolts used; it is not mandatory to bond 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 can only be determined by measuring the resistance value,...