Erection of safety net and lightning protection of

2022-09-20
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Safe erection of scaffold and lightning protection

I. safe erection of scaffold

with the development of construction technology, most scaffold materials used in construction are φ forty-eight × 3.5 for steel pipes, only a small amount of wood and bamboo poles are used as scaffold materials in relatively remote areas (according to the requirements of the Ministry of construction, bamboo and wood scaffolds will be phased out - editor). In multi-storey and high-rise buildings, when using external scaffolding, it is necessary to erect safety, or when using internal scaffolding to build external walls, it is also necessary to erect safety. The safe erection should be gradually increased with the increase of floor construction. The inside and outside of high-rise construction should be fully hung with dense mesh safety from bottom to top. In addition, a safety level shall be set at every 4-6 floors. At present, most of the safety measures used in construction are φ Woven with 9mm hemp rope, palm rope or nylon rope, the specification is generally 6 × 3M, eye size 5 × 5cm。 When the inner scaffold is used to build the outer wall, a cross bar is placed in the window wall of the upper floor and bound firmly with the safe inner cross bar. The safe outer cross bar is connected with the upper end of the diagonal bar, and the lower end of the diagonal bar is connected with a cross bar and bound firmly with the cross bar in the lower window wall (as shown in Figure 1). For Gables without windows, vertical poles can be set up in the corner to erect safety, or "Ω" shaped reinforcement rings can be embedded in the wall to support the diagonal poles, or through wall steel pipes and rotary clips can be used to support the diagonal poles. The distance between safe inclined rods shall generally not be greater than 4m. However, this safe method of erection is troublesome and slow. Some construction units also use self-made or purchased steel suspenders to erect safety. In contrast, the latter has the advantages of simple manufacture, convenient transportation and use, light weight and fast construction speed. It includes self-made pin pieces, steel suspenders and diagonal rods. Its structure and construction method are as follows (see Figure 2):

Figure 1 safety of steel pipe erection

Figure 2 safety of tool steel suspenders erection

steel suspenders are usually used φ 12, with a length of 1560mm, bend a straight hook on the upper end of the suspender to hang on the pin embedded in the wall, and horizontally weld one on the other side of the right angle hook φ 12 hook is used to fasten the safety. A ring for pulling nylon rope is welded at the lower end of the hook. The lower end, such as bumper, fuel tank, steering wheel, interior decoration, etc., is welded with a movable hinge seat and wall support that can be installed with a diagonal bar. The wall support should be able to ensure the stability of the suspender and no rotation when subjected to the force of falling objects. Two diagonal rods 25 × The angle steel of 4 is welded into a square with a length of 2800mm, and one is welded at the top φ 12 the hook is used to hang the safety. A nylon rope ring is welded in the middle of the inclined rod, and the bottom end is connected with the hinge support of the bottom end of the suspender with M12 bolts. When installing this tool type structure, the inclination of the inclined rod can be adjusted by the length of the nylon rope hanging on the suspender and the inclined rod. The suspender is set along the outer wall of the building, and the spacing is generally 3~4m

for the construction of high-rise buildings, if the external scaffold is fully erected on the external wall, the experimental curve safety of changing the torque and changing the angle should be drawn by hanging a dense plotter along the outside of the external pole of the scaffold. The first step frame from bottom to top should be fully paved with scaffold boards. The scaffold boards of each working floor should be hung horizontally for safety, and the rest should be added with a layer of horizontal safety every 4-6 floors (as shown in Figure 3). If the hanging basket or hanging scaffold is used for construction, except for the top surface and the wall, the dense mesh safety shall be hung on all other surfaces, and the safety with a width of at least 4m shall be erected on the bottom layer, and the rest shall be picked out every 4-6 layers (as shown in Figure 4). If the cantilever scaffold is used for construction, when the cantilever scaffold is raised, the cantilever support is not removed, and the diagonal rod hook is tied for safety (as shown in Figure 5)

Figure 3 safety of full scaffold erection on the outer wall

Figure 4 safety of basket scaffold erection

Figure 5 safety of scaffold erection after raising

when erection is safe, the safe extension width, if not required, should be at least 2m, and the lap should be firm. After erecting the safety scaffold, each piece of safety scaffold shall be able to bear at least 1.6kn impact load. During the construction process, the safety shall be checked and maintained frequently, and it is forbidden to throw debris inward to improve the quality of materials, so as to ensure safety

II. Lightning protection of scaffolds

for load scaffolds (including steel gantry, steel derrick, steel lifting frame, etc.) used in high-rise construction or construction on mining fields and hillsides, lightning protection measures should be taken in Thunderstorm seasons or lightning strike areas (see the scope specified in Table 1):

regulations on the installation of lightning protection devices at the construction site Table 1

see table

for scaffolds that need lightning protection devices, It is mainly about the correct selection and manufacture of Lightning Arresters (lightning rods) and grounding devices. Lightning arrester, generally selected φ 25~32mm galvanized steel pipe with wall thickness not less than 3mm or diameter not less than φ The length of 14mm galvanized steel bar shall be at least 1~2m according to the requirements of safety technology. The fabricated lightning arrester shall be installed on the scaffold pole at each corner of the building, and all the crossbars at the top layer shall be connected to form a lightning protection road. If the lightning arrester is installed on the gantry and other vertical transportation equipment frames, it is necessary to connect the middle pole on one side more than 2m above the top before installation. At the same time, the winch shell should be grounded. If the lightning arrester is installed on the most elevated floor and finally exits the site, its protection range can be calculated at 60 °, and other scaffolds and equipment within its protection range can not be equipped with lightning protection devices

grounding device includes grounding electrode, grounding wire and other connectors. The grounding device shall be designed according to the humidity and conductivity of soil and the limit value of grounding resistance before installation; The grounding position should be set at a place that people cannot go to, so as to avoid the harm of step voltage and mechanical damage to the grounding wire. The grounding electrode should be made of steel as far as possible. Angle steel, round steel or steel pipe should be used for the vertical grounding electrode, but threaded steel should not be used. When angle steel is used, it shall not be less than 50 × 5. The diameter of round steel is not less than 20mm, and the steel pipe is φ 25~50mm, wall thickness not less than 2.5mm. The length of vertical grounding stage is 1.5~2.5m. The length of horizontal grounding electrode shall not be less than 3m, and 25 can be used × 4~40 × 4mm Flat steel or φ Made of round steel above 8mm

generally, the continuous length of the scaffold should not exceed 50m for each grounding electrode, but if the transition resistance on the scaffold farthest from the grounding electrode reaches or is greater than 10 Ω, the spacing of grounding electrodes should be reduced. Generally, the grounding resistance shall not exceed 20 Ω. In areas where the soil resistivity is greater than 1000 Ω· m, it can be increased to 30 Ω; If this limit is exceeded, the number of vertical grounding electrodes shall be increased with a spacing of not less than 3m, and the length of horizontal grounding electrodes shall be increased. The buried depth of grounding electrode at the highest point buried underground shall not be less than 0.5m, and it cannot be set in dry soil layer. After the grounding electrode is buried, the new fill shall be compacted

the grounding wire should be selected as far as possible on the premise of ensuring reliability φ 8 round steel or flat steel with a thickness of more than 4mm shall be tightened in time; 5. Regularly check the transmission condition of the sprocket, but do not use aluminum conductor or underground grounding wire. The connection between the grounding wire and the grounding electrode should ensure reliable contact, and it is best to use welding. The length of welding shall be at least 6 times the diameter of grounding wire or 2 times the width of flat steel

III. electricity prevention of scaffold

see Table 2 for the minimum safe operation distance that must be maintained between the outer edge of the scaffold and the sideline of the external overhead line, and see Table 3 for the minimum vertical distance between the top surface of the scaffold and the lowest point of the cross external overhead line

Table 2 for the minimum safe distance between the outer edge of the scaffold and the outer empty line of the scaffold

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