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Code for construction and acceptance of busbar installation of electric equipment installation engineering
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GB 50149-2010
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Basic data | Standard ID | GB 50149-2010 (GB50149-2010) | | Description (Translated English) | Code for construction and acceptance of busbar installation of electric equipment installation engineering | | Sector / Industry | National Standard | | Classification of Chinese Standard | P91 | | Word Count Estimation | 71,720 | | Date of Issue | 2010-11-03 | | Date of Implementation | 2011-10-01 | | Older Standard (superseded by this standard) | GB/T 149-1990 | | Quoted Standard | GB 50150; GB 50169; GB 50300; GB/T 772; GB/T 3669; GB/T 3670; GB/T 5273; GB/T 9460; GB/T 10858; DL/T 754 | | Regulation (derived from) | Bulletin of the Ministry of Housing and Urban No. 827 | | Issuing agency(ies) | Ministry of Housing and Urban-Rural Development of the People's Republic of China; General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China | | Summary | This Chinese standard applies to 750kV and below busbar equipment installation engineering construction and acceptance. | GB 50149-2010: Code for construction and acceptance of busbar installation of electric equipment installation engineering
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
1 General
1.0.1 This specification is formulated to ensure the installation quality of hard busbars, flexible busbars, metal-enclosed busbars, gas-insulated metal-enclosed busbars, insulators, fittings, wall bushings and other busbar devices, promote the progress of installation technology, and ensure the safe operation of equipment.
1.0.2 This code is applicable to the construction and acceptance of the installation project of 750kV and below busbar devices.
1.0.3 The installation of busbar devices shall be carried out according to the approved design documents.
1.0.4 The transportation and storage of equipment and equipment shall comply with the provisions of this specification. When the product has special requirements, it should still meet the requirements of product technical documents.
1.0.5 The storage period of equipment and equipment before installation should be one year. When long-term storage is required, the relevant requirements for storage of equipment and equipment in the product technical documents shall be met.
1.0.6 The equipment and equipment used shall comply with the current relevant national standards and shall have qualification certificates. The equipment should have a nameplate.
1.0.7 The equipment and equipment should be inspected in time after arriving at the site, and should comply with the following regulations.
1 The packaging and sealing should be good;
2 Open the box for inspection and inventory, the specifications should meet the design requirements, and the accessories and spare parts should be complete;
3 The technical documents of the product should be complete;
4 The visual inspection of the product should be in good condition.
1.0.8 The construction plan shall comply with this specification and the relevant current national safety technical standards and requirements of product technical documents.
1.0.9 The construction of construction projects related to the installation of busbar devices shall comply with the following regulations.
1 The engineering quality of buildings and structures related to the installation of busbar devices shall comply with the relevant provisions of the current national standard "Unified Standards for Construction and Quality Acceptance of Construction Engineering" GB 50300; when there are special requirements for design and equipment, they shall still meet the requirements of design and equipment requirements;
2 Before the busbar device is installed, the construction project shall meet the following conditions.
1) The foundation and structure meet the design requirements of electrical equipment;
2) After the construction of the roof and floor is completed, no leakage is allowed;
3) The construction of the indoor ground base is completed, and the level of troweling is marked on the wall;
4) The foundation and structure have reached the strength allowed for the installation of equipment, and the walkway boards, railings, ladders and platforms of the high-rise structure are complete and firm;
5) The decoration works that may damage the installed busbar device or the busbar device that cannot be carried out after the installation of the busbar device are all completed;
6) The doors and windows are installed, and the construction road is unobstructed;
7) The reserved holes and embedded parts for installing the busbar device meet the design requirements.
3 Before the busbar device is installed and put into operation, the construction project shall comply with the following regulations.
1) Embedded parts, openings, reaming and other modification works are completed;
2) Protective net doors, railings and all facilities isolated from power receiving parts are complete;
3) The projects that cannot be carried out after receiving power and affect the safety of operation have been completed;
4) The construction facilities have been dismantled and the site has been cleaned up.
1.0.10 The fasteners used for installation of busbar devices shall be galvanized or stainless steel products that meet the current national standards, and the fasteners used outdoors shall be hot-dip galvanized products.
1.0.11 Porcelain parts of insulators and wall bushings shall comply with the current national standard "Technical Conditions for Porcelain Parts of High-Voltage Insulators" GB/T 772 and the relevant technical requirements for electric porcelain products.
1.0.12 The metal components and fittings for fixing the single-phase AC busbar shall not form a closed magnetic circuit.
1.0.13 The construction and acceptance of the busbar device installation project shall not only comply with this specification, but also comply with the current relevant national standards.
2 terms
2.0.1 metal-enclosed bus metal-enclosed bus
An assembly that encloses the conductor together with insulation, etc., with a metal casing.
2.0.2 isolated-phase bus
Each phase has a separate metal shell and there is a gap between the shells of each phase to isolate the metal-enclosed busbar.
2.0.3 noncontinuous enclosure type isolated-phase bus noncontinuous enclosure type isolated-phase bus
Each phase shell is divided into several sections, the sections are insulated, and each section has only one point of grounded isolated phase closed busbar.
2.0.4 Continuous enclosure type isolated-phase bus
Each phase enclosure is electrically connected, short-circuited and grounded at the beginning and end of the three-phase enclosure respectively.
2.0.5 micro-pressure air-charge isolated-phase bus micro-pressure air-charge isolated-phase bus
The phase-isolated closed bus is filled with slightly positive pressure gas in the bus housing.
2.0.6 Common enclosure bus common enclosure bus
A metal-enclosed busbar in which the conductors of the three-phase busbars are enclosed in the same metal casing.
2.0.7 Nonsegregated-phase common enclosure bus nonsegregated-phase common enclosure bus
The bus conductors of each phase are not separated by partitions.
2.0.8 segregated-phase common enclosure bus
The bus conductors of each phase bus are separated by partitions in a common box closed bus.
2.0.9 enclosure
The metal-enclosed busbar and a part of the gas-insulated metal-enclosed busbar, under the specified protection level, can protect the internal equipment from the influence of the outside world, and prevent the human body and foreign objects from approaching the live parts.
2.0.10 Compartment
In order to facilitate inspection, maintenance and avoid expansion of the scope of electrical accidents, the closed unit formed by isolating the gas-insulated closed busbar.
2.0.11 flex section
The elastic joints connected between two adjacent sections of the busbar have the function of compensating for dimensional changes caused by installation dimensional deviations, temperature changes, and uneven settlement of the foundation.
2.0.12 transport unit transportation unit
Part of a metal-enclosed busbar suitable for transport without disassembly.
2.0.13 Technical documentation of product
According to the technical part of the equipment contract, the manufacturer provides product manuals, installation and maintenance manuals, test reports, qualification certificates and installation drawings, etc.
2.0.14 Busway busways
Busbar Conductive equipment supported or isolated by insulating material in the wireway.
2.0.15 Gas-insulated metal-enclosed bus gas-insulated metal-enclosed bus
Metal-enclosed busbars with gases such as sulfur hexafluoride as the insulating medium.
3 busbar installation
3.1 General provisions
3.1.1 The equipment and equipment used in the busbar device shall be packed in anti-corrosive gas erosion and mechanical damage during transportation and storage.
3.1.2 The surface of the bus bar should be smooth and smooth, without cracks, wrinkles, inclusions, deformation and distortion.
3.1.3 Each section of the metal-enclosed busbar and busway supplied in a complete set shall be clearly marked, with complete accessories, the outer shell shall be free of deformation, and the interior shall be free of damage.
The overlapping surface of the bus bar connected by bolts should be flat, and the coating should be uniform, and there should be no pitting, peeling and uncovered parts.
3.1.4 The mounting screw holes of various metal components shall not be cut by gas welding or electric welding.
3.1.5 The anticorrosion treatment of metal components and busbars shall meet the following requirements.
1 The rust removal of metal components should be thorough, the anti-corrosion paint should be evenly applied, the adhesion should be firm, and there should be no defects such as peeling and wrinkling;
2 The paint on the busbar should be uniform, and there should be no defects such as layering and wrinkling;
3 Outdoor metal components should be hot-dip galvanized products;
4 In places with salt spray and corrosive gas, the busbar should be coated with anti-corrosion layer.
3.1.6 Non-charged metal components such as post insulator bases, bushing flanges, and protective nets (covers) shall be grounded in accordance with the relevant provisions of the current national standard "Code for Construction and Acceptance of Grounding Devices for Electrical Installation Engineering" GB 50169.The ground wires should be arranged neatly and connected reliably.
3.1.7 When the bus bar is connected to the equipment terminal, the terminal should not be subjected to excessive lateral stress.
3.1.8 For overlapping connections between busbars and busbars, busbars and branch lines, and busbars and electrical terminals, the treatment of the overlapping surfaces shall comply with the following regulations.
1 The silver-plated lap surface can be directly connected;
2 The overlapping surface of copper and copper should be tinned outdoors, indoors with high temperature and humidity or corrosive gas to the busbar; it can be directly connected in a dry room;
3 The overlapping surfaces of aluminum and aluminum can be directly connected;
4 The overlapping surfaces of steel and steel shall not be connected directly, but shall be connected after tinning or galvanizing;
5 For the joint surface between copper and aluminum, the copper conductor should be tinned in a dry room; outdoors or indoors where the relative air humidity is close to 100%, a copper-aluminum transition plate should be used, and the copper end should be tinned;
6 The copper lap surface should be tinned, and the steel lap surface should be hot-dip galvanized;
7 The steel lap surface shall be hot-dip galvanized;
8.The metal-enclosed busbar bolt-fixed overlapping surface shall be silver-plated.
3.1.9 The phase sequence arrangement of the busbar shall comply with the following regulations when there is no requirement in the design.
1 When the top and bottom are arranged, the AC busbars should be arranged as A, B, and C phases from top to bottom, and the DC busbars should have positive poles on the top and negative poles on the bottom;
2.When arranged horizontally, the AC busbars should be arranged as A, B, and C phases from the back of the panel to the panel surface, and the DC busbars should be arranged from the back of the panel to the panel surface as positive and negative poles;
3 Looking from the back of the panel to the panel surface, the down conductors of the AC busbar should be arranged as phases A, B, and C from left to right, and the positive pole of the DC busbar should be on the left and the negative pole on the right.
3.1.10 The color of the bus bar identification shall meet the following requirements.
1 Three-phase AC bus, A corresponds to yellow, B corresponds to green, and C corresponds to red; single-phase AC bus should be the same color as the outgoing phase;
2 DC bus, the positive pole should be brown, and the negative pole should be blue;
3 The neutral wire or neutral wire of the three-phase circuit and the grounded neutral wire of the DC circuit should be light blue;
4 Metal-enclosed busbar, the outer surface of the busbar and the inner surface of the shell should be matte black, and the outer surface of the shell should be light-colored.
3.1.11 The phase and color identification of painted busbars shall meet the following requirements.
1 The outdoor flexible busbar, metal enclosed busbar shell, and tubular busbar should be marked with phase colors at both ends;
2 The visible surfaces of single-piece, multi-piece busbars and trough-shaped busbars should be painted with the same color;
3 The steel bus bar should be galvanized, and the visible surface should be painted with the same color;
4 The phase color painting should be uniform, not easy to fall off, without defects such as layering and wrinkling, and should be neat and consistent.
3.1.12 The busbar should not be painted with the same color in the following places.
1 The bolt connection and support point of the busbar, the connection between the busbar and the electrical appliance, and the places within 10mm from all the connections;
2 The contact surface for the connection of the portable ground wire, and the distance from the contact surface to the width or diameter of the busbar, and shall not be less than 50mm.
3.1.13 The AC and DC small bus bars in the panel should be installed through insulating tubes.
3.1.14 For busbar installation, the safe net distance of indoor power distribution devices shall comply with the regulations in Table 3.1.14-1, and the safe net distance of outdoor power distribution devices shall comply with the regulations in Table 3.1.14-2; when the actual voltage exceeds the 3.1.14-1 and Table 3.1.14-2 When the rated voltage of this level is used, the safe net distance of indoor and outdoor power distribution devices shall adopt the safe net distance value corresponding to the higher rated voltage.
3.2 Hard busbar processing
3.2.1 The bus bar should be straightened and the cut surface should be flat.
3.2.2 The overlapping connection of rectangular busbars shall comply with the provisions in Table 3.2.2; when the busbars are connected to equipment terminals, they shall comply with the relevant provisions of the current national standard "Terminals for transformers, high-voltage electrical appliances and bushings" GB/T 5273.
3.2.3 The main busbars, branch busbars, down conductors and equipment connection lines with the same layout should be symmetrical, horizontally flat and vertically neat and beautiful.
3.2.4 Rectangular busbars should be cold-bent and not hot-bend.
3.2.5 The bending of bus bars shall meet the following requirements (Figure 3.2.5).
1.The distance between the starting point of the busbar bend and the edge of the busbar supporting splint of the nearest insulator should not be greater than 0.25L, but not less than 50mm;
2.The distance between the bending point of the bus bar and the connection position of the bus bar should not be less than 50mm;
3 Rectangular busbars should reduce right-angle bends, and there should be no cracks or obvious wrinkles at the bends. The minimum bending radius of the busbars should meet the requirements in Table 3.2.5;
4 The curvature and spacing of multi-piece busbars should be consistent.
3.2.6 When the rectangular busbar is lapped by bolts, the distance between the joint and the edge of the support splint of the post insulator shall not be less than 50mm; the distance between the end of the upper piece of busbar and the start of flat bending of the lower piece of busbar shall not be less than 50mm (Figure 3.2.6).
3.2.7 When the rectangular bus bar is twisted by 90°, the length of the twisted part should be 2.5 to 5 times the width of the bus bar (Figure 3.2.7).
3.2.8 The diameter of the screw hole at the busbar connection should not be larger than the bolt diameter by 1mm; the screw hole should be vertical and not skewed, and the allowable deviation of the center distance is ±0.5mm.
3.2.9 The contact surface of the bus bar should be flat and free of oxide film. After processing, its section reduction value, the copper busbar should not exceed 3% of the original section; the aluminum busbar should not exceed 5% of the original section.
The lapping surfaces of busbars with silver plating shall not be filed.
3.2.10 The processing and fabrication of aluminum alloy tubular busbars shall meet the following requirements.
1 The cut nozzle should be flat and perpendicular to the axis;
2 The groove of the tubular busbar shall be machined, and the groove shall be smooth, uniform and free of burrs;
3 The distance between the butt joint of the busbar and the edge of the splint of the busbar supporter shall not be less than 50mm;
4 The bending degree of the aluminum alloy pipe supplied according to the manufacturing length shall not exceed the provisions in Table 3.2.10 of this code.
3.3 Hard bus installation
3.3.1 The connection of the hard busbar shall comply with the following regulations.
1 The connection of the hard busbar shall be welded, through-bolt connection or splint and clamping bolt lap connection;
2 The tubular and bar-shaped busbars shall be connected by special connecting fittings;
3 Pipe-shaped and bar-shaped bus bars shall not be connected by internal threaded pipe joints or soldering.
3.3.2 The connection of tubular and bar-shaped busbars shall comply with the following regulations.
1 Before installation, measure the size of the connecting fittings and the contact parts of the tubular and bar-shaped busbar conductors, and the error value should meet the requirements of the product technical documents;
2 The liner used in conjunction with the pipe bus connection fittings shall meet the requirements of the design and product technical documents;
3 Tightening torque of bolts for connecting fittings of tubular and bar-shaped busbars shall meet the requirements of product technical documents.
3.3.3 The connection between busbar and busbar or between busbar and equipment terminal should meet the following requirements.
1.The contact surfaces of the bus connection should be kept clean and coated with electric compound grease;
2 When the busbar is placed horizontally, the bolts should be passed from bottom to top, and the nuts should be on the top. In other cases, the nuts should be placed on the maintenance side, and the length of the bolts should expose 2 to 3 buttons of the nut;
3 There should be flat washers between the bolts and the fastening surface of the busbar. When the busbar is connected by multiple bolts, there should be a clear distance of more than 3mm between the adjacent bolt washers, and spring washers or lock nuts should be installed on the nut side;
4 The contact surface of the bus bar should be tightly connected, and the connecting bolts should be tightened with a torque wrench. The tightening torque value of steel bolts should meet the requirements in Table 3.3.3, and the tightening torque value of non-steel bolts should meet the requirements of product technical documents.
3.3.4 When the bus bar is connected to the screw-shaped terminal, the aperture of the bus bar should not be larger than the diameter of the screw-shaped terminal by 1mm. The oxide film of the screw thread should be removed, the contact surface of the nut should be flat, a copper tin-coated flat washer should be added between the nut and the busbar, and there should be a lock nut, but no spring washer.
3.3.5 When the busbar is fixed on the post insulator, the following requirements shall be met.
1 The fixing between the busbar fixing hardware and the post insulator should be flat and firm, and the busbar supported by it should not be subjected to additional stress;
2 The fixing fittings or other supporting fittings of the AC busbar shall not form a closed ferromagnetic circuit;
3 When the bus bar is placed horizontally, the upper pressure plate of the bus bar support splint should keep a gap of 1mm~1.5mm with the bus bar; when the bus bar is placed vertically, the upper pressure plate should keep a gap of 1.5mm~2mm with the bus bar;
4 The fixed dead point of the busbar on the post insulator should be set one for each section, and should be located at the full length or at the middle point of the expansion joint of the two busbars;
5 When the tubular busbar is installed on the sliding support, there should be a gap of 1mm to 2mm between the shaft seat of the supporter and the tubular busbar;
6 The busbar fixing device should be free from edges, corners and burrs.
3.3.6 Between multiple pieces of rectangular busbars, a gap not less than the thickness of the busbars should be maintained; the distance between the edges of adjacent spacers should be greater than 5mm.
3.3.7 There must be no cracks, broken strands and wrinkles in the busbar expansion joints; the total cross-section of the busbar expansion joints should not be less than 1.2 times the busbar cross-section.
3.3.8 The installation of the low-voltage busbar in the workshop with a tensioning device at the terminal or in the middle shall comply with the following regulations when there is no design requirement.
1.The terminal or intermediate tension fixing bracket should be equipped with a stay wire with an adjusting bolt, and the fixing point of the stay wire should be able to bear the tension of the stay wire;
2 Within the same span, the maximum deviation of the sag of each phase of the bus bar should be less than 10%.
3.3.9 When the length of the busbar exceeds 300m ~ 400m and needs to be transposed, the transposition should not be less than one cycle. The transposition section of the trough-shaped busbar can be connected by a rectangular busbar, and the bending degree of the busbars of each phase in the transposition section should be symmetrical and consistent.
3.3.10 The installation of plug-in busway shall meet the following requirements.
1 The hook of the suspended busway should have adjusting bolts, and the distance between the fixed points should not be greater than 3m;
2 The end of the bus duct should be equipped with a closed cover, and the cover of the lead-out hole should be complete;
3 The connection of the shells of each section of the busway should be detachable, there should be jumpers between the shells, and the grounding should be reliable.
3.3.11 The installation of heavy-duty busbars should meet the following requirements.
1 The connection between the busbar and the equipment should be softly connected, and the cross-section of the connecting line should not be smaller than the cross-section of the busbar;
2 For the fastening bolts of the busbar, the aluminum alloy bolts should be used for the aluminum busbar, and the copper bolts should be used for the copper busbar; a torque wrench should be used when tightening the bolts;
3 In places with high operating temperature, the bus bar should not have copper-aluminum transition joints;
4.There should be no jamming on the movable rolling rod of the busbar at the fixed point, and the mechanical strength and insulation resistance of the components should meet the design requirements.
3.3.12 The installation of aluminum alloy tubular busbars shall meet the following requirements.
1 The tubular busbar should be hoisted at multiple points, and the busbar should not be damaged;
2 The bus terminal should be installed with anti-corona device, and its surface should be smooth, without burrs or unevenness;
3 The axes of the same-phase pipe sections should be on a vertical plane, and the axes of the three-phase bus pipe sections should be parallel to each other;
4 For horizontally installed tubular busbars, pre-arching measures should be taken before installation.
3.4 Hard bus bar welding
3.4.1 Busbar welding should be carried out by welders who have passed the training and examination and obtained corresponding qualification certificates, and the welding quality should meet the relevant provisions of the current industry standard "Technical Regulations for Aluminum Busbar Welding" DL/T 754.
3.4.2 Before the formal welding, the welding procedure test shall be carried out first, and the performance of the welded joint shall meet the following requirements.
1 The surface and fracture should not have defects such as pores, slag inclusions, cracks, incomplete fusion and incomplete penetration;
2 The quality level of non-destructive testing shall comply with the provisions of non-destructive testing in the current industry standard "Technical Regulations for Aluminum Busbar Welding" DL/T 754;
3 The tensile strength of welded joints of aluminum and aluminum alloys should not be lower than the lower limit of the standard value of tensile strength of raw materials. For heat-treated aluminum alloys, the tensile strength of welded joints shall not be lower than 60% of the standard value of raw materials;
4 The DC resistance value of welded joints should not be greater than 1.05 times the DC resistance value of raw materials with the same specifications and sizes.
3.4.3 Reliable wind, rain, snow, freezing and fire prevention measures should be taken in the welding place.
3.4.4 Before welding, the brand name of the base metal should be confirmed, and the welding materials should be correctly selected and a reasonable welding process should be formulated.
3.4.5 The electrodes and wires used for busbar welding shall comply with the current national standards "Aluminum and Aluminum Alloy Electrodes" GB/T 3669, "Aluminum and Aluminum Alloy Welding Wires" GB/T 10858, "Copper and Copper Alloy Electrodes" GB/T 3670 And the relevant provisions of GB/T 9460 "Copper and Copper Alloy Welding Wire". Before welding, the electrode should be baked according to the regulations, and the surface oxide film, moisture, oil and other sundries should be removed from the welding wire.
3.4.6 Tubular busbars, trough busbars, metal-enclosed busbars and heavy-duty busbars made of aluminum and aluminum alloys shall be welded by argon arc welding.
3.4.7 Butt joints with a diameter greater than 300mm should adopt symmetrical welding.
3.4.8 Before welding, the surfaces on both sides of the groove of the busbar should be cleaned within a range of 30mm to 50mm, and there should be no oxide film, water and oil stains; the groove processing surface should be free of burrs and flashes.
3.4.9 The butt joint should be straight before welding, and its bending deviation should not be greater than 0.2% (Figure 3.4.9-1); when the butt joint is aligned, the root surface deviation should not be greater than 0.5mm (Figure 3.4.9-2).
3.4.10 Each weld should be welded continuously; before the weld is completely cooled, the bus bar must not move or be stressed.
3.4.11 For butt welding of aluminum and aluminum alloy hard busbars, the size of the weld joints shall comply with the requirements in Table 3.4.11.
3.4.12 The longitudinal axis of the reinforcing liner for the tubular busbar shall be located at the center of the weld, and the gap between the liner and the busbar shall be less than 0.5mm (Figure 3.4.12).
3.4.13 The location of the busbar butt welds shall meet the following requirements.
1 The welding seam should not be less than 100mm away from the edge of the supporting insulator bus splint;
2 Butt welds should be reduced for bus bars;
3 The staggered position of the butt welds on different pieces of the same-phase busbar shall not be less than 50mm.
3.4.14 The inspection standard after busbar welding shall meet the following requirements.
1 The butt weld of the busbar shall have a reinforcement height of 2mm to 4mm; the fillet size of the fillet weld shall be 2mm to 4mm larger than the wall thickness of the base metal on the thin-walled side. The welding seam of the hard bus bar with a voltage of 330kV and above should be arc-shaped, and there should be no burrs, uneven defects; when the down-conductor bus bar adopts lap welding, the length of the weld seam should not be less than twice the width of the bus bar;
2 There should be no visible cracks, incomplete fusion, pores, slag inclusions and other defects on the surface of welded joints;
3 The undercut depth shall not exceed 10% of the thickness of the busbar (tubular busbar is the wall thickness), and shall not be greater than 1mm, and its total length shall not exceed 20% of the total length of the weld;
4 In important conductive parts or main force-bearing parts, the butt welded joints shall pass the radiographic random inspection.
3.5 Soft bus erection
3.5.1 Conductors used for the first time should be tested, and the installation method and measures should be determined before full construction.
3.5.2 The flexible bus bar shall not have kinks, loose strands, broken strands, severe corrosion or other obvious damages; the enlarged wires shall not have obvious dents and deformations. The damage area at the same cross-section shall not exceed 5% of the total cross-sectional area of the conductive part.
3.5.3 In addition to quality certificates, the used fittings should also undergo the following inspections.
1 The specifications should be consistent, and the parts should be complete;
2 The surface should be smooth, free from defects such as cracks, burrs, scars, sand holes, rust, and sliding buckles, and the zinc layer should not peel off;
3.The contact surface between the boat-shaped pressure plate of the wire clamp and the wire should be smooth and flat, and the rotating part of the hanging wire clamp should be flexible.
3.5.4 The placement direction of the wire reel...
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