Pipeline flanges require that metal pipe flanges that transport combustible, flammable and explosive substances should be crossed with wires to prevent electrostatic accidents. So, do metal pipe flanges need to be jumped, and under what circumstances do they need to be jumped?
1. Metal flange bridging of industrial pipelines
· Article 7.13.1 of GB 50235-2010 "Code for Construction of Industrial Metal Pipeline Engineering" stipulates that when the resistance value between each pair of flanges or other joints exceeds 0.03 ohms, a wire jumper shall be set up for pipelines designed with electrostatic grounding requirements. Clause 6.12.2 stipulates that when the resistance to ground of the piping system exceeds 100Ω, two grounding leads shall be provided. The grounding lead should be in the form of welding.
· GB 50184-2011 Code for Acceptance of Construction Quality of Industrial Metal Pipeline Engineering 7.13 Electrostatic Grounding Installation, 7.13.1 For pipelines with electrostatic grounding requirements, the resistance value between each pair of flanges or other joints shall be less than or equal to 0.03Ω.
· TSG D0001-2009 "Regulations for Technical Supervision of Pressure Pipeline Safety - Industrial Pipelines" has the following definitions for industrial pipelines: This regulation applies to process devices, auxiliary devices and industrial pipelines belonging to public works in the boundary area (hereinafter referred to as pipelines) that meet the following conditions at the same time.
(1) The maximum working pressure is greater than or equal to 0.1MPa (gauge pressure, the same below);
(2) The nominal diameter (Note 1) is greater than 25mm;
(3) The conveying medium is gas, steam, liquefied gas, liquid with a maximum working temperature higher than or equal to its standard boiling point, or flammable, explosive, toxic or corrosive liquid.
Most of the pressure pipes encountered in daily inspections belong to the above-mentioned industrial pipes. Article 80 of the Regulations for the Safety and Technical Supervision of Pressure Pipelines - Industrial Pipelines (TSG D0001-2009) has the following provisions on the anti-static of flange jumping: pipelines with electrostatic grounding requirements shall measure the resistance between the connecting joints and the ground resistance value of the pipeline system. When the value exceeds the provisions of the "Code for Pressure Piping - Industrial Piping" (GB/T20801-2006) or the design document, a jumper wire (between flanges or threaded joints) and a grounding lead wire shall be provided. It can be seen from this article whether the flange needs to be crossed over the wire, the resistance value between the flanges needs to be measured, and when the resistance value exceeds the specified value, it needs to be crossed.
· GB/T 20801.4-2006 "Code for Pressure Pipelines - Industrial Pipelines Part 4 Production and Installation" Article 10.12.1 stipulates that pipelines with electrostatic grounding requirements should have good conductivity between each section. When the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω, a wire jumper should be provided.
When the value exceeds the provisions of GB/T20801-2006 "Code for Pressure Pipelines - Industrial Pipelines" or design documents, jumper wires (between flanges or threaded joints) and grounding leads should be provided. It can be seen from this article whether the flange needs to be crossed over the wire, the resistance value between the flanges needs to be measured, and when the resistance value exceeds the specified value, it needs to be crossed. Article 10.12.1 stipulates that pipelines with electrostatic grounding requirements shall have good conductivity between each section. When the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω, a wire jumper should be provided.
· GB 50235-2010 "Code for Construction of Industrial Metal Pipeline Engineering" Article 7.13.1 stipulates that when the pipeline designed with electrostatic grounding requirements, when the resistance value between each pair of flanges or other joints exceeds 0.03 ohms, a wire span should be set. When the resistance value between the flanges exceeds 0.03Ω, the wire jumper should be set.
· GB 50944-2013 "Code for Construction and Quality Acceptance of Anti-static Engineering" 3.0.2 For new projects, anti-static grounding devices should be preset during civil construction· GB 50159-2013 "Code for the Design of Furnace Gas Station" 17.0.5 The gas pipeline shall be provided with a grounding device to dissipate static electricity.
· GB 12158-2006 "General Guidelines for the Prevention of Electrostatic Accidents" 6.4.10 The equipment for collecting and filtering powders shall be made of electrostatically conductive containers and filter materials and grounded.
As can be seen from the above provisions, the key is to guide the charge away through the grounding device, and whether the pipe flanges are crossed or according to the resistance value between the flanges.
2. Flange bridal connection of petrochemical pipelines
· Article 8.9.1 of GB 50517-2010 "Code for Construction Quality Acceptance of Petrochemical Metal Pipeline Engineering" stipulates that pipelines with electrostatic grounding requirements should be connected by wires when the resistance value between each pair of flanges or threaded joints is greater than 0.03Ω.
· GB 50074-2014 "Code for the Design of Petroleum Depots" Article 14.3.7 of Article 3: The rails, process pipelines, crane pipes, steel trestles, etc. of railway tank car loading and unloading facilities shall be equipotential bridging and grounding, and the distance between the two groups of jumper points shall not be greater than 20m, and the grounding resistance of each group shall not be greater than 10Ω.
14.3.8 Automobile tankers or barrel filling facilities for Class A, B and C liquids shall be equipped with anti-static grounding devices that are connected to the tankers or barrels.
14.3.9 The loading and unloading dock for flammable and combustible liquids shall be equipped with an anti-static grounding device that crosses with the ship.
· Article 11.2.12 of GB 50156-2012 "Code for Design and Construction of Automobile Refueling and Gas Stations" explains: In the explosion hazard area, the flanges and hose connections at both ends of the oil, LPG, LNG and CNG pipelines should be crossed by metal wires, mainly to prevent static electricity or lightning sparks at the connections at both ends of the flange and hose due to poor connection (contact resistance greater than 0.03Ω), followed by explosion and fire accidents. There are no less than 5 bolted flanges, in a non-corrosive environment, the connection of the flange connection is good, so it can not be crossed by metal wires.
· SH 3501-2011 "Code for Construction and Acceptance of Petrochemical Toxic and Combustible Medium Steel Pipeline Engineering" Article 6.2.13 stipulates that the resistance value of the flange or threaded connection joint shall be determined for the pipeline with electrostatic grounding requirements in the design document. When the resistance value between the flange or threaded connection joint is greater than 0.03Ω, there should be wire jumper and comply with the relevant provisions of the current national standard SH3097 and design documents. The resistance value to the ground and the grounding position should meet the requirements of the design documents.
· SH/T 3097-2017 "Code for Electrostatic Grounding Design of Petrochemical Industry" 4.1.1 In the process of production, processing, storage and transportation, equipment, pipelines, operating tools and human body may generate and accumulate static electricity and cause electrostatic hazards, electrostatic grounding measures should be taken.
5.1.1 The shell of fixed equipment (towers, vessels, pumps, heat exchangers, filters, etc.) shall be electrostatically grounded. Covering equipment generally does not need to be electrostatically grounded.
· GB 50759-2012 Code for the Design of Oil and Gas Recovery Facilities in Oil Loading Systems 9.1.1 Oil pipelines, equipment and casings in oil and gas recovery facilities shall be provided with electrostatic grounding devices.
· GB 50684-2011 "Design Code for Sewage Treatment and Reuse in Chemical Industry" 5.3.10 The mechanical and electrical equipment of grease traps (tanks) shall take explosion-proof measures and shall be equipped with anti-static grounding facilities.
· SH 3097-2017 "Petrochemical Electrostatic Grounding Design Code" is a corporate specification that is stricter than national standards and industry standards. Article 4.3.3 of the code stipulates that in the pipeline system, when the metal flange is fastened by metal bolts or clips, it is generally not necessary to install additional electrostatic connecting wires, but it should be ensured that at least two bolts or clips have a good conductive contact surface. 4.3.1 The value of electrostatic grounding resistance of the electrostatic grounding system should not be greater than 106Ω. The resistance value to the ground of the special electrostatic grounding body should not be greater than 100Ω, and the resistance value to the ground should not be greater than 1000Ω in areas with high soil resistivity such as mountainous areas.
It can be seen from this that whether the flange of the petrochemical pipeline needs to be crossed depends on its resistance value or the number of bolts, and it is not necessary to force all of them.
3. Summary
· To sum up, to determine whether the metal pipe flange is crossed, we must first look at its design documents, and if so, it will be executed according to the design documents. If the design document does not require, whether the metal flange of the industrial pipeline is crossed, it is necessary to measure the resistance value between the flanges, when the resistance value between the flanges exceeds 0.03Ω, the wire jumper should be set, if the resistance value is less than 0.03Ω, there is no need to jump.
Therefore, whether the metal pipe flange of the pipe needs to be crossed can be determined according to the resistance value between the flanges (if the resistance value is less than 0.03Ω, the jumper is not required.) When the resistance value is greater than 0.03Ω, it should be crossed), which is relatively professional and practical, and should be based on national and industry standards, rather than some "experts" saying that it must be crossed or not connected.
For the electrostatic jumper of the pipe flange, the specific method is as follows, for reference only:
(1) Metal pipe flange + metal gasket + metal bolt + non-corrosive environment No electrostatic jumper is required
(2) Metal pipe flange + metal gasket + metal bolt + corrosive environment (more than 4 bolts) No electrostatic jumper is required
(3) Metal pipe flange + metal gasket + metal bolt + corrosive environment (less than 4 bolts) Electrostatic jumper
(4) Metal pipe flange + non-metallic gasket + metal bolt + non-corrosive environment (more than 4 bolts) No electrostatic jumper is required
(5) Metal pipe flange + non-metallic gasket + metal bolt + electrostatic jumper in corrosive environment
"Copper core wire or soft copper braided wire with a cross-sectional area of 6 mm2 or more"
