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On the afternoon of April 24, 2019, a tower crane collapsed at a construction site near Teqin Road, Nanbaixiang Street, Ouhai District, Wenzhou City, Zhejiang Province. A pump truck was smashed at the construction site, causing considerable losses. The cause of the accident is suspected to be the frequent occurrence of strong convective weather that caused people to be trapped. The specific cause of the accident and casualties are subject to the on-site accident investigation report. Strong winds above level 6. The airflow speed of level 6 winds is between 10.8 m/s and 13.8 m/s. Such airflow speed is relatively fast, which is risky for tower crane operations. Therefore, such operations should not be carried out rashly when strong winds exceed level 6. Tower crane collapse accidents occur frequently. How to prevent them in 2019? Please refer to these three aspects - 1. Adhere to equipment age management, select famous brand products, and focus on avoiding safety risks caused by the use of old equipment. 1) The rental tower crane should try to use equipment that is less than 5 years old. The rental construction elevator, material hoist, and electric hanging basket should try to use equipment that is less than 3 years old. For equipment that has been used in the unit and the rental unit has strong maintenance capabilities, the service life can be appropriately relaxed. 2) Do not use QTZ40 and below tower cranes. If the main components of the equipment do not have production signs, or if the signs are painted with paint without authorization, they will be regarded as unqualified equipment and will be removed directly. Note: The above three items are drawn up from the perspective of the user unit and may infringe on the interests of the leasing unit. Factors such as rental price may also need to be taken into consideration during specific implementation. But the ultimate goal is to prevent some hidden dangers that cannot be rectified on-site from entering the hospital with diseases by selecting equipment with a brand name and a shorter age. Tower Crane Collapse 2. Subcontracting Selection and Equipment Check 1) Larger-scale units should formulate the company's selection methods and assessment systems for outstanding leasing subcontractors, and determine the unit's outstanding subcontractor team through comprehensive assessments from the perspectives of enterprise size, equipment quantity, registered capital, and maintenance team personnel construction. 2) Before the equipment enters the site, the machine administrator or mechanical management personnel must conduct an on-site inspection. Select qualified equipment and take photos and archives before allowing the equipment to enter the site. After entering the site, it will be inspected and confirmed again. Installation can only be carried out after passing the equipment. Installation acceptance is required after the installation is completed. This avoids the situation where diseased equipment enters the site and is difficult to exit. Many hidden dangers actually occur before entering the site. Once installed, it is difficult to rectify. 3) Contents that should be inspected and accepted before the equipment enters the site: 1. The rental unit is required to have a permanent workplace (need to be inspected). All rental tower cranes have their own property rights and are not affiliated. 2. Installation and disassembly capacity requirements: Companies with a fixed and own team of installation and dismantling workers will be given priority if they also have installation and dismantling qualifications. It is strictly prohibited to improvise installation and demolition personnel. 3. Maintenance ability: General tower crane failures are resolved within 4 hours, and major failures are resolved within 2 days. Monthly inspection and maintenance are required (the contract will stipulate that there will be corresponding penalties for failure). 4. Old equipment requires maintenance before entering the construction site. After entering the site, installation can only begin after passing the inspection again. It is strictly forbidden to mix the standard sections of tower cranes. All parts of a single brand of tower crane must be consistent and purchased from the original factory. 5. Requirements for tower crane structural components: There are no cracks, welds or serious deformations in the structural parts of the tower crane. All standard section bolts are required to be opened (including in the sleeve), and the rusted ones are required to be removed. All bolts used in the field must not be severely corroded, deformed, or worn. The structural parts of the tower crane must not be welded or modified without permission. All pins have cotter pins, bolts and nuts with three exposed threads, bolt washers, spring washers, nuts or washers, and double nuts. 6. Tower crane electrical limit requirements: The electrical circuit of the tower crane has no aging and cracking, the PE line is connected, and the limit cover is complete, sensitive and effective (especially the broken rope protection device must not be deformed). The wire rope has no broken wires, strands, burrs, etc. 7. Self-management status: Leasing units with manufacturer background will be given priority. The unit has a complete management system and technical support capabilities (tower crane foundation construction, pre-embedding of attached walls, etc.). Broken tower crane 3. Process management equipment should be carefully inspected before entering the site and after installation and acceptance. Generally, there will be no major problems. However, new hidden dangers will arise due to environmental changes during use, and monthly maintenance and inspections are particularly important at this time. The monthly inspection of many projects is just filling in information and going through the motions. This is seriously irresponsible! During the monthly inspection, the special inspection of the leasing unit shall be carried out separately from the monthly inspection of the general contractor unit. The inspection status of the general contractor machinery management personnel shall be a review and supervision of the inspection status of the leasing unit. To sum up the reasons for the tower crane collapse accidents that occur all over the country all year round, there are only three major aspects:: One is the problem of tower crane installation and disassembly, the second is the problem of use, and the third is the quality problem of the tower crane itself. 1. Causes of accidents caused by installation and disassembly issues 1. The installation and disassembly team is unqualified and does not have a license to undertake disassembly and assembly tasks. The personnel, equipment, and technology of the installation and disassembly unit did not meet the required requirements, which was an important reason for the accident. 2. There is no plan or safety technical explanation for installation and disassembly, and it is based on experience. The disassembly and assembly unit did not prepare a disassembly and assembly plan, did not conduct safety technical briefings, and acted recklessly and illegally based on experience, which was the direct cause of the accident. 3. Violation of disassembly and assembly procedures during installation and disassembly. During the disassembly and assembly process, the disassembly and assembly unit did not follow the order of disassembly and assembly in the tower crane instruction manual, and did not operate according to the disassembly and assembly plan and safety technical disclosure requirements, in order to save trouble and rely on imagination. 4. Do not go through the disassembly and assembly application and acceptance procedures. The tower crane user unit and the disassembly and assembly unit do not handle the disassembly and assembly application and acceptance procedures in accordance with the regulations, and lose the * * Opportunities to be checked by competent authorities. 2. Reasons for accidents caused by usage problems 1. Operation and command personnel did not have certificates to work. Tower crane drivers and commanders have not received professional training and obtained qualification certificates as required to work, and do not have corresponding professional skills and knowledge. 2. Operation and command personnel operate and command in violation of regulations. Such as overload lifting, inclined lifting, using a tower crane to lift the concrete pump delivery pipe at the construction site to pump concrete and rotate it at will, etc. 3. The operators did not perform enough routine inspections and maintenance of the equipment, resulting in mechanical safety hazards for the tower crane. If the performance of the tower crane torque limiter is not fully understood and it is not clear whether it actually works, it may lead to misunderstanding that it is working normally and lead to accidents when it fails. Ignoring the human factors, such as to what extent and how much weight can be lifted, I have no bottom or no idea. 4. Insufficient education and training for operating and command personnel. Many units only provide pre-job training, but neglect the continuous training and improvement of operating skills and safety awareness of operators, and the continuous training of command personnel. 3. Reasons for accidents caused by quality problems of the tower crane product itself 1. Design problems. The design of the torque limiter is flawed and the sensitivity is poor ； The steel structure design is unreasonable in stress, the hydraulic system design is defective, etc. 2. Spare parts issues. Problems with the quality of the torque limiter components and problems with the steel materials used in the steel structure ； Hydraulic system component quality issues, etc. 3. Manufacturing issues 3.1 The welding of the steel structure does not meet the requirements. The height of the weld is not enough, and there are defects such as pores, slag inclusions and even false welds. In particular, there are welding quality problems in important connection parts on the tower cap, boom, balance arm and other components. 3.2 The geometric dimensions of the steel structure do not meet the requirements. The material is not cut according to the requirements, and the steel cross-section size does not meet the requirements. * * Standard regulations. 4. There is a problem with the factory certificate and instruction manual. If there is no factory certificate, it is a fake and shoddy product. There are no batch descriptions, and changes to the original design are not marked.