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Tower cranes (hereinafter referred to as tower cranes), as the main construction machinery at construction sites, are widely used in construction sites due to their large lifting height and wide coverage, and are responsible for the main vertical transportation tasks. At the same time, because of its high center of gravity and high risk, safety accidents of one kind or another often occur, causing losses to people's lives and property. In serious cases, major accidents may even occur in which the aircraft is destroyed and people are killed or injured. Therefore, how to strengthen the safe use and management of tower cranes has attracted great attention from manufacturers, construction companies, and construction administrative departments. This article will briefly discuss the safe use and management of tower cranes from the following aspects, combined with my many years of experience in use, management and testing, in order to better do this work. 1. Data management The construction enterprise or tower crane owner should submit the tower crane's production license, product certificate, disassembly and assembly license, instruction manual, electrical schematic diagram, hydraulic system diagram, driver's operation certificate, tower crane basic diagram, geological survey data, tower crane disassembly and assembly plan, safety technical briefing, and main component warranty certificate (wire rope, high-strength connecting bolts, anchor bolts and main electrical components, etc.) to the tower crane testing center, and the tower crane testing center shall pass the inspection. Finally, obtain the safe use certificate, and handover records with the project management department after installation. At the same time, dynamic tracking and management of the tower crane must be strengthened in daily use, and shift records, inspection records, and maintenance records (including minor repairs, medium repairs, and overhauls) must be made and signed by relevant responsible persons. Materials and consumable parts replaced during the maintenance process must have certificates or quality assurance certificates, and the above materials must be archived in a timely manner to establish a one-machine-one-file ledger. 2. Disassembly and assembly management The disassembly and assembly of tower cranes is an accident-prone stage. Safety accidents caused by improper disassembly and assembly and substandard installation quality account for a large proportion. The disassembly and assembly of tower cranes must be carried out by qualified disassembly and assembly units, and the installation and disassembly must be carried out within the scope of qualifications. Disassembly and assembly personnel must undergo special business training, have certain disassembly and assembly experience and hold certificates to work. At the same time, they must have complete personnel of all types of work, clear positions, perform their duties, and obey unified instructions. During the debugging process, the technical level and sense of responsibility of professional electricians are very important. Electricians must hold electrician certificates and lifting work certificates. According to the statistics of a large amount of tower crane inspection data, it was found that a disassembly and assembly unit in our city has installed a total of 54 tower cranes so far this year, and 47 tower cranes have failed the first inspection. The first inspection pass rate is only 13%. Most of them are due to the poor installation technical level of the installation electricians, the disassembly and assembly unit's neglect of management, and the safety awareness needs to be further improved. Therefore, we have carried out special management to strengthen business training in this unit and achieved good results. In addition, because the disassembly and assembly costs in the disassembly and assembly market are not in accordance with the budgeted price, it even costs 400 to 500 yuan to install a tower crane, which is also an important reason for the decline in installation quality. A special disassembly and assembly plan must be prepared for disassembly and assembly. The plan must be reviewed and signed by the technical person in charge of the installation unit. The disassembly and assembly unit shall be provided with warning areas and cordons for disassembly and assembly. Special personnel shall be arranged to direct the area. Unrelated personnel are prohibited from entering. The operation shall be carried out in strict accordance with the disassembly and assembly procedures and instructions. When the wind force exceeds level 4, disassembly and assembly shall be stopped. When the wind force exceeds level 6, tower crane shall stop lifting operations. If special circumstances really require working at night, sufficient lighting must be provided. If special circumstances require working at night, full consultation and consensus must be reached with the truck crane driver on the disassembly and assembly procedures and precautions. 3. Tower crane foundation The tower crane foundation is the foundation of the tower crane. Practice has proved that many major safety accidents are caused by problems with the tower crane foundation. It is an important factor affecting the overall stability of the tower crane. Some accidents are caused by hasty installation at the construction site when the strength of the concrete is insufficient in order to rush for the construction period. Some accidents are caused by insufficient ground endurance. Some accidents are caused by excavation near the foundation, which may even lead to landslide displacement, or uneven settlement due to water accumulation, etc., etc., etc., all will cause serious safety accidents. We must pay great attention to it without being vague. The stability of the tower crane is the ability of the tower crane to resist overturning. The biggest accident of the tower crane is tipping and collapse. When making the tower crane foundation, be sure to ensure that the ground endurance meets the design requirements and that the strength of the reinforced concrete reaches at least 80% of the design value. Special treatment measures should be taken for the tower crane foundation of basement projects.: Some need to drive piles under the foundation, and the steel bars at the pile ends and the foundation bolts are firmly welded together. The bottom surface of the concrete foundation must be flat and compact, and the bottom of the foundation must not be shaped like a pot bottom. The dimensional error of foundation bolts must be constructed strictly in accordance with the requirements of the foundation drawing. The anchor bolts must maintain a sufficient length above the ground, and each anchor bolt must be pre-tightened by double nuts. Before installation, the foundation surface must be treated to ensure that the level of the foundation cannot exceed 1/1000. At the same time, the tower crane foundation must not accumulate water. Water accumulation will cause uneven settlement of the tower crane foundation. No digging or trenching is allowed near the foundation of the tower crane. 4. Safety distance When arranging tower cranes, a floor plan must be drawn, especially in real estate development communities with many residential buildings and tower cranes. The safety distance of adjacent tower cranes must also be considered. A safety distance of no less than 2m must be ensured in both horizontal and vertical directions. The tower body and boom of adjacent tower cranes must not interfere, and try to ensure that the tower crane can rotate freely when the wind is too strong. The safe distance between the rear arm of the tower crane and adjacent buildings should be no less than 50cm. The safety distance between the tower crane and the transmission line meets the requirements. If the safe distance between the tower crane and the transmission line is not enough as required in Table 1, a protective frame must be installed on the tower. In principle, the protective frame must be erected during a power outage. Metal materials are not allowed. Bamboo poles and other materials can be used. The distance between bamboo poles and power lines must be at least 1m and must have a certain degree of stability and strength to prevent them from being blown over by strong winds. In order to ensure that the above safety distances meet the regulatory requirements, especially during the construction of large residential areas, we have moved the focus of our work forward during daily safety inspections. When the project starts, we require the construction companies to reasonably arrange the overall layout of the construction machinery on site and report it to us. If it is difficult for different construction companies to coordinate with each other, we will notify the construction units to coordinate. For example, this year we have carried out special management of construction sites such as Xiangyi Real Estate Community, Xingtan Garden Community, and Yihe Garden Community in the urban area, and achieved good results. 5. Safety devices In order to ensure the normal and safe use of tower cranes, we mandate that tower cranes must have prescribed safety devices during installation. The main ones are:: Lifting moment limiter, lifting weight limiter, height limiter, amplitude limiter, rotation limiter, hook safety device, drum safety device, wind direction and anemometer, wire rope escapement safety, trolley rope-breaking device, trolley shaft-shaft prevention device and buffer, etc. These safety devices must ensure that it is intact, sensitive and reliable. If damage is found during use, it should be repaired and replaced in time. It is not allowed to lift or adjust arbitrarily without permission. On April 20, 2003, a tower crane driver at a construction site in Guanyun County, our city, removed the torque limiter without authorization. When overloaded, the standard angle steel of the tower crane cracked and the tower crane boom overturned. Fortunately, it was discovered in time and there were no casualties. Another example is the major tower crane overturning accident caused by Nantong No. 3 Construction Company's construction work in Beijing on July 16, which resulted in 2 deaths and 3 injuries. It was also caused by illegal adjustment of the torque limiter and overloading. These bloody lessons cannot help but cause us to attach great importance to the safety devices of tower cranes. 6. Stability The ratio between the height of the tower crane and the size of the bottom support is large, and the tower has a high center of gravity, large torque, frequent starting and braking, and large impact force. In order to increase its stability, we must analyze the main reasons for the tower crane tipping as follows:: 1. Overload. Different types of cranes usually use lifting torque as the main control. When the working range increases or the weight exceeds the corresponding rated load, the overturning moment of the weight exceeds its stable moment, which may cause the tower crane to collapse. 2. Oblique hanging. When a heavy object is lifted at an angle, its overturning moment will be increased, and horizontal and vertical components will be generated at the lifting point. An additional overturning moment will be generated at the bottom support point of the tower crane, thereby reducing the stability coefficient and causing the tower crane to collapse. 3. The foundation of the tower crane is uneven, the ground endurance is insufficient, and the verticality error is too large, which will also cause the overturning moment of the tower crane to increase and reduce the stability of the tower crane. Therefore, we must strictly inspect and check based on these key factors to prevent major equipment and personal safety accidents. 7. Electrical safety In accordance with the requirements of the "Construction Safety Inspection Standard" (JGJ59-99), the special switch box for the tower crane must also meet the requirements of "one machine, one gate, one leakage box". The tripping rated operating current of the leakage protector should not be greater than 30mA, and the rated operating time should not exceed 0.1s. The switchboard in the driver's cab must not be left exposed. The electrical cabinet should be in good condition, with tight closing and complete door locks. The electrical components in the cabinet should be intact, the circuits should be clear, the operation control mechanism should be sensitive and reliable, and the limit switches should have good performance. Professional electricians should be regularly arranged for inspection and maintenance. 8. Wall-attached device When the tower crane exceeds its independent height, a wall-attached device must be erected to increase the stability of the tower crane. The wall-attached device must be erected in accordance with the requirements of the tower crane manual. The spacing between the attached walls and the free height above the wall-attached point cannot be arbitrarily long. Extra-long wall-attached supports should be designed separately and have a calculation sheet to check the strength and stability. The attachment frame should be kept horizontal and firmly fixed on the same horizontal plane as the attachment pole, and should be firmly connected to the building. After attachment, the verticality of the tower below the attachment point should not be greater than 2/1000, and the verticality above the attachment point should not be greater than 3/1000. The connection point with the building should be selected on concrete columns or concrete ring beams. Use embedded parts or wall bolts to effectively connect to the building structure. Some construction companies use expansion bolts instead of embedded parts, and cables and wind ropes instead of attached supports, which are very dangerous. 9. The key to safe operation of tower crane management is driver management. Operators must be in good health, understand the mechanical structure and working principles, be familiar with mechanical principles and maintenance rules, and hold a certificate to work. Drivers must perform maintenance work on the crane in accordance with regulations, have a high sense of responsibility, and carefully perform cleaning, lubrication, fastening, adjustment, anti-corrosion and other tasks. They are not allowed to operate under the influence of alcohol, illness or fatigue. They operate in strict accordance with the tower crane mechanical operating regulations and the "ten don'ts, ten don'ts" for tower cranes. They are not allowed to operate illegally or operate wildly, and have the right to refuse illegal orders. Sufficient lighting is required for night operations. The key to the daily safe use of tower cranes lies in the technical level and sense of responsibility of the operators, and the key to inspection and maintenance lies in the mechanical and electrical maintenance workers. We must firmly establish a people-oriented mentality. 10. Safety inspection The tower crane should be inspected before and after installation and during daily use. The metal structure welds must not crack, the metal structure must not plastically deform, the quality of the connecting bolts and pins meet the requirements, in order to prevent backing and loosening, the connecting bolts must be pre-tightened regularly, the wire rope must be well lubricated and maintained, the number of broken wires must not exceed the standard, strand breakage must not be allowed, plastic deformation is not allowed, the rope clamp joints meet the standards, the reduction box and cylinder must not leak oil, the hydraulic system pressure is normal, the brakes and limit insurance are sensitive and reliable, the transmission mechanism is well lubricated, the safety devices are complete and reliable, and the electrical control circuits are well insulated. In particular, tower crane drivers, maintenance electricians and mechanical maintenance workers must be urged to conduct frequent inspections, focusing on inspection of wearing parts such as wire ropes, hooks, various transmission parts, limit safety devices, etc., and deal with problems immediately if problems are found, so as to ensure that the personnel, time and measures are determined to strictly prevent the operation of machinery with diseases. 11.Exit mechanism * * The use of obsolete models must be resolutely prohibited, and tower cranes that have been in disrepair must be limited in load use after identification and repair. There is no unified standard for the service life of tower cranes. There are different opinions. Different regions have different regulations, all of which are within the concentration. In order to cater to the requirements of construction companies, expand sales, and occupy the market, some manufacturers increase the independent height and lengthen the boom to increase the coverage of the tower crane. This will inevitably reduce the stability of the tower crane, reduce the rated lifting capacity, and increase unsafe factors. There are also some privately modified tower cranes and tower cranes engaged in private assembly. These tower cranes are older, second-hand purchase prices are cheap, and they are unwilling to invest more money in repairs, so they have frequent failures. These should attract our great attention. We should be realistic, adapt to local conditions, and introduce relevant supporting policies to solve this problem based on extensive solicitation of opinions from all parties. Conclusion By strengthening the safety management of the above aspects of the tower crane, we can effectively prevent the occurrence of various accidents during the use of the tower crane, and achieve the purpose of nip in the bud. Practice has proved that as long as all construction companies, manufacturers, construction administrative departments, and tower crane inspection agencies can follow the above-mentioned links and strengthen special management of tower crane safety, they can effectively control the occurrence of major tower crane safety accidents. This post was last edited by limingshuguang on 2008-1-3 19:41 ]