Do you understand lightning protection and grounding? The construction techniques for lightning protection grounding are worth keeping

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Do you understand lightning protection and grounding? The construction techniques for lightning protection grounding are worth keeping. The installation process involves: installation of grounding electrodes → laying of grounding conductors → exposed installation of downconductors → concealed installation of lightning protection grids, lightning protection strips, or downconductors. Regarding the installation of grounding electrodes, artificial grounding electrodes (poles) should be installed in accordance with the following regulations: the minimum dimensions of such artificial grounding electrodes (poles) must meet the requirements specified in the standards. The burial depth of the grounding electrode should be no less than 0.6 m; the specific depth is adjusted according to the design requirements of each unit. The length of the vertically installed elements should not be less than 2.5 m, and the distance between them should generally be no less than 5 m. This project uses fire-clay welding; for lap welding, the welding length is as follows: for galvanized flat steel, it should be no less than 2 times its width, with welding carried out on three sides. (When the width of the flat steel varies, the lap length shall be based on the wider one.) Before installation, the flat steel must be straightened; the bends should not be too sharp, and there should be no noticeable bends in the straight sections. The welding length for galvanized round steel is 6 times its diameter, and welding should be performed on both sides (when the diameters differ, the lap length shall be based on the larger diameter). When connecting galvanized round steel and galvanized flat steel, its length should be 6 times the diameter of the round steel. When welding galvanized flat steel to galvanized steel pipes (or angle steel), to ensure a reliable connection, in addition to welding on both sides of the contact area, the flat steel itself should also be bent into an arc shape (or right angle) and welded directly to the steel pipe (or angle steel). When the grounding wire encounters a layer of white ash and slag that cannot be avoided, it should be fully protected with cement mortar. Processing for installing artificial grounding electrodes: The electrodes are fabricated according to the required quantity and material specifications; the materials typically used are steel pipes and angle iron, with a length of no less than 2.5 meters. If steel pipes are to be driven into the ground, they should be shaped appropriately according to the type of soil; in soft soil, they can be cut into an inclined shape. To prevent the tube from warping due to uneven forces during insertion, it can also be shaped into a flat pointed form ； When encountering very hard soil, the tip can be shaped into a cone. If angle steel is used, it should be of a size of at least 40mm×40mm×4mm, with a cutting length of not less than 2.5m; one end of the angle steel should be shaped into a pointed tip as specified. Process the materials strictly in accordance with the specific design requirements of each unit of the project. Ditch digging: In accordance with the requirements of the design drawings, measure and mark the lines that connect to the grounding electrode (grid). Dig a ditch along these lines that is 0.8–1 m deep and 0.5 m wide; the upper part of the ditch should be slightly wider, and any stones at the bottom should be removed. Install the grounding electrode: Once the trench is dug, the grounding electrode should be installed immediately along with the grounding flat steel, in order to prevent the soil from collapsing. First, place the grounding electrode on the center line of the trench and drive it into the ground; generally, a hand hammer is used for this purpose, with one person holding the grounding electrode while another person uses a sledgehammer to strike the top of it. To prevent the grounding pipe or angle steel from splitting, a protective sleeve can be fitted over the end of the grounding pipe; for angle steel grounding, a short piece of angle steel (about 10 cm long) can be welded to one of the corner pieces used for grounding. When hitting the grounding electrode with a hammer, do so gently and steadily; strike the exact center of the electrode without deviating from it, and ensure the hammer is perpendicular to the ground. Stop driving the electrode when its top is 600 mm above the ground. Laying of flat steel between grounding electrodes: Before laying the flat steel, it should be straightened first; then the steel is placed in the trench, and the flat steel is welded to the grounding electrodes one by one using welding (or gas welding). Flat steel should be placed on its side rather than flat; it has a lower dissipation resistance when placed on its side. The connection point between the flat steel and the steel pipe is located about 100 mm from the highest point of the grounding electrode. During welding, the flat steel should be straightened; after welding, the slag should be removed. Anti-rust paint should be applied first, followed by asphalt, as a means of corrosion protection. The grounding wire should also be led to the desired location, with enough connection length left for use. Inspection of grounding electrodes (wires): After the grounding electrodes are connected, it is necessary to promptly invite the quality inspection department and the supervision party to conduct hidden work inspections. The material, location, and welding quality of the grounding electrodes, as well as the cross-sectional dimensions of these electrodes (wires), must all meet the requirements specified in the design and construction acceptance standards. Records of these hidden works should also be kept. Backfilling can only be carried out after passing the inspection, and it should be compacted in layers. Finally, enter the measured grounding resistance value in the concealed work inspection record. For the installation of natural foundation grounding electrodes, the main rebar is used as the lightning down conductor: in the nitric acid unit, part of the main rebar is utilized as the roof lightning down conductor. The positions are marked according to the dimensions specified in the design drawings. It is necessary to ensure that the civil engineering team has welded the required connectors (connection plates) to the main rebar bars (no fewer than 2 bars). After that, the slag covering on these bars should be removed, and the two main rebar bars should be marked with colored paint to facilitate their identification and inspection. The quality inspection department should be consulted promptly for concealed inspections, and records of the concealed works should be kept. This task needs to be carried out in coordination with civil engineering. The installation of the grounding main shall comply with the following provisions: When the grounding main passes through a wall, it shall be protected by a sleeve; when it crosses expansion joints, it shall be bent to provide compensation. In the design of this project, the main structural reinforcement bars are used as lightning down conductors, while the embedded steel plates installed by the civil engineering team at a height of 0.5m above the ground are utilized as grounding resistance test plates. Use an 86-type cartridge, install a cover on it, and apply grounding marks. When the grounding main runs across a door, it should be installed concealed within the floor surface (buried before the floor is laid). When installed indoors, the grounding main should be at least 200 mm above the floor surface and at least 10 mm away from the wall surfaces. The supports should be made of flat steel with dimensions of 40 mm × 4 mm; their ends should be shaped like tails. The depth and width of the holes in which these supports are inserted should be 50 mm each, with a total length of 70 mm. The horizontal straight-distance between supports is generally 1 m, the vertical distance is 1.5 m, and the distance at turns is 0.5 m. Appropriate adjustments can be made according to the specific conditions on site. The grounding main wire should be laid straight; at corners, the bending radius of the grounding main wire must be no less than twice the thickness of the flat steel. The anti-corrosion paint on the grounding main trunk should be applied evenly without any omissions. For the installation of the outdoor grounding main wire, the wire is first straightened, positioned, drilled at the appropriate points, and bent as needed; thereafter, the connection clamps and grounding terminals are installed. Before laying, dig a trench at the dimensions and location specified in the design. Then lay the flat steel flat and embed it. The backfill soil should be compacted, but ramming is not required. The end of the grounding main wire should not protrude above the ground by more than 0.5m to facilitate the connection of the ground wire. Open-mounted indoor grounding main trunk: holes for installation and mounting supports – Holes for the grounding wires should be prepared at dimensions and locations specified in the design; the size of these holes should be at least 6 mm larger than the thickness and width of the grounding main trunk. There are three methods for this: a) During construction, a section of flat steel can be cut to the required dimensions and embedded in the wall; before the concrete sets, the flat steel can be pulled out so that it can be easily removed once the concrete has hardened. b Cover the flat steel with a layer of oil felt or several layers of kraft paper, then embed it in the wall; the distance between the holes in the dam and the wall surface should be 15–20 mm. c The protective cover can be made of iron sheet with a thickness of over 1 mm, in square or circular shape; its size should allow enough space of over 6 mm on each side when the grounding wire is inserted. Fixing of the supports: As per the design requirements, the positions of the coordinate axes are first determined on the brick wall (or aerated concrete wall, hollow brick wall). Then, square wooden templates measuring 50mm×50mm are placed inside the wall as it is being built. Once the wall is completed, these wooden templates are removed, and the supports are inserted into the holes. The holes are then wetted with water, and the supports are secured in place using cement mortar. They can be used after the mortar has set. For fixing brackets to cast-in-place concrete walls, first mark the positions according to the design requirements, drill holes, insert the brackets with their dovetail shapes into those holes, level them properly, and then secure them using cement mortar. The installation requirements for openly laid ground wires state that the laying location should not hinder the disassembly and maintenance of the equipment, and should facilitate inspection. The grounding wire should be laid horizontally or vertically, or it may also run in parallel along straight sections of the building’s inclined structure; there should be no undulations or bends. When the grounding wire is laid horizontally along the building walls, it should be kept at a distance of 200 mm from the ground as required by the design, and the gap between the grounding wire and the building walls should be no less than 10 mm. Installation of surface-mounted ground wire: Once the supports have been buried and the cement mortar has set, the ground wire on the wall can be installed. Lift the grounding flat bar along the wall, secure it at one end of the support using a clip, and pass it through the pre-made holes when passing behind partition walls; the connections to the main grounding wires should be welded firmly. The end reservations or connections shall meet the design requirements. Requirements for the fabrication and installation of lightning protection rods: Regulations require that all metal components be galvanized; the specific material shall be determined according to the design, and care must be taken to protect the galvanized layer during installation. When manufacturing the needle tip, the wall thickness must not be less than 3 mm. The lightning rod should be installed vertically and firmly, with an allowable deviation in verticality of 3/1000. For weld treatment, the flux should be removed and anti-rust paint applied. Lightning rods are generally made of round steel or steel pipes, and their diameter should not be less than the requirements specified in the standards. The angle steel supports for bracket installation should have a dovetail shape, with a burial depth of not less than 100 mm; flat steel and round steel supports should have a burial depth of not less than 80 mm. Specific requirements are detailed in the design drawings for each unit. All supports must be secure, with proper filling of mortar, and aligned horizontally and vertically. The tops of various supports for lightning protection devices should generally be 100 mm away from the building surface ； The top of the grounding main trunking support should be 20 mm away from the wall. The horizontal spacing between supports shall not exceed 1 m ； The vertical spacing shall not exceed 1.5 m. The spacing between them should be uniform, with an allowable deviation of 30 mm. The supports on either side of the corner are no more than 250 mm away from the center of the corner. The bracket should be straight. For levelness, the inspection section is 2m long, with an allowable deviation of 3/1000; for verticality, the inspection section is 3m long, with an allowable deviation of 2/1000 ； However, the total length deviation must not exceed 10 mm. Iron components such as brackets should be treated to prevent corrosion. The roof lightning protection strip is made of Φ12 round steel; first, a straight line is drawn between the supports at both ends with a horizontal spacing of 1.5 m, and then the other supports are leveled and straightened using mortar. The lightning protection mesh is secured using parapet wall brackets; when constructing the parapet wall, embedded metal parts (support clips) are prepared in accordance with the design specifications, and then round steel bars are fixed to these support clips to form the lightning protection mesh.