1. The importance and way of lightning protection grounding Lightning protection and grounding are the top priority for building and personal life safety. When lightning strikes, there is a strong current passing through, generating mechanical force and thermal effect, destroying building (structure) and electrical equipment. However, in the process of supervision, construction or related professionals often pay insufficient attention to lightning protection and grounding. It is considered that its technicality is not strong, the process is relatively simple, and the scope is narrow. It often fails to operate or leak during construction. Arouse people's vigilance. Therefore, the construction acceptance of lightning protection and ground concealment projects is very important in the supervision work, and its construction quality directly affects the function, safety and service life of the entire building. 2, lightning protection grounding system construction quality common problems (1) replace the lightning rod (net) and its down conductor with structural steel, galvanized welding damage layer does not brush anti-rust paint. 3. Construction quality control points of lightning protection grounding system 3.1 Pre-control of lightning protection grounding Pre-control of lightning protection grounding construction is the first basic work. Supervisors must be familiar with the design drawings and electrical design instructions. Lightning protection grounding system. (3) For the equipotential welding and design, the parts to be repeatedly grounded, such as the grounding of the steel pipe of the household, the potential socket of the bathroom, and the equipotential floor area should be carefully checked. After the design requirements are met, the project is allowed to enter the next process. 4. Conclusion The current development of the construction market is still not perfect. The self-discipline of the enterprise is poor. The interests of the sub-contracting and subcontracting are driven by the interests. The construction unit management and technical personnel cannot fully perform their duties. Some of the construction workers have been transferred to the supervision, so Implementing the supervision system, exerting its professional superiority and improving the quality of supervision are crucial to the guarantee of project quality.
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There are usually three types of lightning damage: direct lightning strikes, inductive lightning and lightning strikes.
In the architectural design, it is stipulated that there should be a variety of lightning protection grounding requirements for building fortification. The basic methods of lightning protection are “discharge†and “resistanceâ€. On the one hand, it is necessary to use the grounded lightning protection facilities to vent the lightning to itself to weaken its power. On the other hand, various electrical equipment is required to have a certain level of insulation or to take other remedial measures to improve the ability to resist lightning damage. If the two can be properly combined and flexibly taken according to the specific conditions of the protection, it can prevent or reduce the lightning damage and achieve the purpose of ensuring safe power supply. At present, the lightning protection device commonly used in construction engineering consists of a lightning receptor, a down conductor and a grounding device.
(2) The length of the connection of the down conductor, the equalizing ring and the lightning protection belt is not enough, the flat steel is less than twice the width, the round steel is less than 6 times the diameter, the welding is not full, and the welding has slag inclusion, welding, and virtual Welding, biting meat and pores did not knock out defects such as welding slag.
(3) The lead wire of the grounding body is not treated with anti-corrosion treatment. When galvanized flat steel is used, the welding part of the lead wire is not brushed with anti-corrosion paint.
(4) When the grounding wire crosses the deformation joint of the building, no compensator is added, and the protective pipe is not applied when passing through the wall.
(5) Roofing metal objects, such as pipes, ladders, flagpoles and equipment casings, are not connected to the roof lightning protection system.
(6) The bolted connecting piece is untreated, the galvanized or tinned surface is incomplete, and the piece is not in close contact with the piece.
(7) The branch line of the grounding (zero) of the electrical equipment is not connected to the grounding trunk, and is connected in series or through the bracket and the foundation channel.
(8) The installation depth of the grounding body is not enough, and the height from the ground is less than 0.6m.
(9) The lightning protection belt is seriously deformed, the bracket is detached, the spacing between the lower points is too large, and the wiring outside the lower line is not reserved.
(10) Replace the PE wire and equipotential bonding with a metal pipe, and the diameter of the cross-ground wire of the bridge, metal pipe, electrical cabinet, box, door, etc. is insufficient.
(11) When the TN-S system is used in the multi-storey residential building, the incoming line is not repeatedly grounded at the main meter box, and the MEB is not used in the distribution room as required.
(12) The socket grounding wires are connected in series with each other, and the fixtures with a mounting height lower than 2.4 m can be close to the ungrounded metal conductors.
(1) Carefully review the design drawings. Not only must be familiar with the electrical diagram, but also carefully analyze the structure and equipment layout in the architectural design. It is necessary to fully understand the relevant descriptions in the design and discover the problems in the design. Nowadays, in many designs, the relevant professional design drawings are unclear, and the problems of not coordinating and coordinating according to regulations are widespread, which can easily lead to construction errors. If the construction unit is not experienced enough, it will be easy to cause construction errors due to improper cooperation of the work type (preface). The most common is the fault of the connection point of the grounded steel mesh, the leakage welding and the leakage of the embedded joint or the embedded part of the inspection point. In particular, the conversion layer of the building structure causes construction errors and omissions due to improper adjustment of the main steel bars in the structural column (wall) and improper coordination of the (prevention). The most common is the fault of the connection point of the grounded steel mesh, the leakage welding and the leakage of the embedded joint or the embedded part of the inspection point. In particular, the structural transformation layer of the building structure is more likely to occur due to the adjustment of the main steel bars in the structural column (wall) and the misconnection of the steel bars in the lightning protection and lowering line [5]. Another problem is that each professional pipeline and line collide with each other and contradict each other. Has become a multi-discipline of construction drawings.
(2) For some special construction project system, the supervisor should pay attention to the description in the design and do a good job in designing. Such as intelligent engineering, information communication, computer, monitoring, etc. in the weak current system, because these locations and settings are generally not clearly marked in the design plan paper, and are reserved for the construction standards according to the specification requirements. If the construction team's technical strength is insufficient, it is easy to ignore, the supervisor should pay attention to the design of the bottom, and should be written into the approval opinions for the problems that are easy to ignore and especially important in the construction, to remind the construction unit to implement.
(3) For the grounding of equipment in the building, it is necessary to pay attention to the mandatory standards and construction acceptance specifications to check whether the construction drawings meet the requirements of the specifications. If it is found that the requirements of the current construction regulations are not met or the practices are not appropriate, the lightning protection grounding materials selected should not be reported to the owner in time, and negotiate with the design unit to form a design document for implementation and filing.
3.2 Implementation of witness sampling, strict control of material quality control. The materials used for lightning protection grounding are angle steel, round steel and flat steel. The main control contents are: first, three materials for inspection; second, material specifications; third, inspection. Whether to use galvanized materials as specified in the design and specifications. During the construction supervision process, the operators often use the ordinary structure to weld the bars with ordinary steel bars, or replace the galvanized materials with ordinary steel. The fault of this wrong material must be strictly corrected.
3.3 Review of professional team qualifications and construction operators. The lightning protection grounding welding is always accompanied by the whole process of construction. The welding quality determines the quality of the project. Practice has shown that due to the lightning protection grounding of personnel who use welding technology, the lightning protection grounding of the project is not qualified. Therefore, the qualification level of the professional lightning protection grounding team should be strictly examined, and the technical team and class of the construction team should be Group) Long and the key personnel who lead the actual operation must hold the employment certificate.
3.4 Strengthening the quality control of key parts and processes of lightning protection grounding In the construction of several links that are prone to quality problems, set quality control points, formulate pre-control measures for supervision, and implement side-by-site supervision for key parts or key processes to prevent Mainly, dynamic follow-up supervision to ensure the quality of lightning protection grounding construction.
(1) Ground-based grounding welding is the first step in grounding construction. For the welding of the foundation ring beam or the welding of the pile foundation reinforcement and the foundation reinforcement, the welding of the foundation reinforcement and the column reinforcement, the foundation diagram and the grounding point shall be inspected one by one strictly, especially the cross-connection of the foundation reinforcement at the expansion joint is confirmed. . When the entire grounding grid is welded, use a resistance meter to test the grounding resistance value to confirm that it meets the design requirements.
When the resistance value does not meet the design requirements, check the welding quality again or make a manual grounding device according to the design requirements.
(2) For the grounding grid with the column bar as the upper line, the construction personnel are required to use each layer to mark the position of each column and the number of welded steel bars according to the axis to prevent the leakage or mis-welding position, and the welding length and quality are not satisfied. Design and specification requirements, etc. The supervisor should carefully inspect the welding quality of the lead point and the cross-bar, and require the positioning of the welding lead line to prevent the main layer from being welded to the upper layer, resulting in a grounding interruption error. Especially for the structural conversion layer, due to the adjustment of the column ribs, the lightning protection down conductor is easily misaligned and leaked by the main rib welding in the column, and repeated verification is required.
(4) For lightning rods and lightning protection nets, they are the only ones in the lightning protection system that are exposed on the roof of the building. Their construction quality reflects the level of electrical construction from one side, and also directly affects the reliability of lightning protection grounding. To increase the monitoring strength: First, we must pay attention to the specifications must meet the design requirements, the installation should be firm and reliable. Second, for all kinds of lightning rods that are imported, there must be a certificate of conformity, instructions for use and various technical materials. Third, the lightning protection net installed on the roof and the lightning rods and metal objects on the top of the building should be welded together. Fourth, the lead wire from the grounding body and the welding wire on the roof should be clearly marked. The fifth is to use the galvanized round steel of the specified diameter and the main ribs in the structural column as the lightning protection down conductor to ensure that the material specifications, welding spacing and welding quality are in compliance with the specifications.
3.5 According to the requirements of the specification, the lightning protection grounding project shall be checked and approved as a sub-division project. The sub-project shall be inspected and accepted according to the inspection batch during the construction process. The “three inspections†system for establishing the quality of the process at the time of acceptance: the operator should carry out the inspection between the procedures and the inspection of the full-time quality personnel on the basis of the self-inspection, and the inspection results should have a complete record, and then the supervision engineer Check and confirm, and make hidden acceptance in time. The quality of the inspection lot shall be checked and accepted according to the main control project and the general project. When the sub-project inspection batch does not meet the quality standard requirements, it shall be processed in time until it is qualified. After the construction is completed, the grounding resistance value should be shaken. Regardless of the natural grounding body or the artificial grounding body, as well as the glass curtain wall, lightning protection grid, lightning rod, etc., the grounding resistance value should be measured in time after the construction. In particular, after the construction of the grounding body or grounding grid is completed, the grounding resistance value should be confirmed in time to meet the design specifications. Because the grounding system with the pile foundation as the grounding body can not increase the construction of the artificial grounding body when the grounding resistance value meets the design requirements, the construction cost can be reduced. In addition, it can also avoid remediation after the completion of civil works, and conflict with other projects, resulting in repeated waste of manpower, material resources and financial resources. According to the provisions of GB50208-2002 "Construction Construction Quality Acceptance" appendix, and assess the construction level against the lightning protection grounding classification, as a necessary text for lightning protection grounding construction acceptance.
Of course, the problems found in the construction are diverse. The on-site supervision engineer should be good at summing up, strengthen the study of the new technology of lightning protection grounding, and put forward his own suggestions on the unreasonable or lack of lightning protection grounding design, familiar with the installation and acceptance specifications of lightning protection grounding construction. At the same time, it is necessary to strengthen on-site management and communication, coordinate work, organize professional meetings to explain construction technical requirements and precautions, check construction results, adhere to side station supervision, pay attention to process control, avoid common problems, and improve the quality of lightning protection grounding for construction projects. Will be guaranteed.