Dangerous factors and preventive measures in the h

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Risk factors and preventive measures in tower crane hoisting operation

tower crane is the main equipment for vertical transportation of construction, and it is also an important symbol to measure the equipment strength of a construction enterprise. In today's increasingly competitive construction market, many construction enterprises have purchased tower cranes to meet the construction needs. With the widespread use of tower cranes in construction sites, there are more and more casualties caused by tower cranes, which have brought heavy losses to people's lives and property. According to the statistics of relevant domestic departments, the accident rate of tower cranes has reached 2.77%. Its safety is still one of the worries in construction. How to do a good job in the safe use and management of tower crane has become an important topic in front of safety management and equipment management personnel. Combined with my experience in equipment management and safety management of construction enterprises for many years, this paper focuses on the unsafe factors existing in the installation and disassembly of tower crane, and puts forward preventive measures. The purpose is to strengthen the safety management of tower crane, avoid accidents, and promote construction safety

1. The tower crane foundation is broken and the anchor bolt is loose; The verticality deviation of the tower body seriously exceeds the standard due to uneven foundation settlement; The concrete foundation can not meet the requirements of anti overturning stability, causing the tower crane overturning accident. The tower crane foundation must be constructed in strict accordance with the foundation design. The tower crane foundation must have reinforcement, concrete quality insurance, concrete test block report, concealed inspection sheet, and settlement observation. If the foundation has uneven settlement after the installation of the tower crane, the verticality deviation of the tower body exceeds 4 ‰, and it cannot be anchored with the building in advance, the problem of foundation settlement must be solved first, and the vertical correction of the tower crane must be carried out after the foundation is stable. If the foundation cannot be controlled and stabilized due to design problems, the tower crane shall be resolutely removed to avoid overturning accidents

2. The verticality deviation of the tower body is too large, and the whole center of gravity that has been curbed by the excessive growth momentum of the tower crane's production capacity has shifted too much. The result is to reduce the stability torque and increase the overturning torque, resulting in the destruction of the stability of the whole machine. Therefore, the verticality of the tower crane should be strictly controlled during installation. After installation, the verticality of the tower crane in two directions must be tested as required. Those with excessive deviation cannot be used. In the process of use, the verticality of the tower crane should be checked frequently. If it is found that the deviation is excessive, it should be corrected in time or anchored with the building in advance, and the verticality of the tower body should be adjusted with a brace when anchoring. Ensure that the verticality of the tower crane is within 3 ‰

3. Due to the narrow construction site and unreasonable construction layout, the support and leading role of key new material enterprises in the installation of tower crane is inappropriate, which is also one of the unsafe factors in the use of tower crane, and should be paid enough attention to. In 2002, many tower cranes were working at the same time at the construction site of Chongqing railway station, and two of them were too close, so that the boom of one of them hit the balance arm of the other when turning, which not only damaged the tower crane, but also broke the transmission line, causing a large area of power failure. Therefore, before installing the tower crane, you should understand the project overview, check the construction site and surrounding environment, and when selecting the installation location, you should consider the project needs, ground resistance, attached walls, space during disassembly, equipment entry and exit routes, the influence of surrounding buildings, whether there are high-voltage transmission lines around, etc. if some aspects cannot meet the requirements, you should take safety precautions to ensure the safe use of the tower crane. Determine the installation position of the tower crane to make it easy to install, and more importantly, how to measure the electronic tension machine so that it can be disassembled smoothly

4. Mixed loading of standard section and reinforced section: the tower body of the tower crane is usually divided into reinforced section and standard section. They are different in internal structure or size, and their stiffness and strength are different, so their installation positions are different. However, during the installation process, due to their unclear identification or failure to comply with the requirements of the instructions, mixed loading up and down is the cause of the accident that the tower body is broken during the use of the tower crane. It is necessary to strengthen the standardized management of the tower crane in and out of the warehouse and the warehouse, strictly strengthen the identification of section and standard section, and improve the technical quality and working spirit of all disassembly and assembly personnel

5. Violate the disassembly and assembly procedure of tower crane and fail to grasp the balance law. The most prominent thing is that when installing the tower crane, install the balance arm first, and then install 1 ~ 2 balance weights to make it have appropriate backward tilt torque, and then install the lifting boom. After installing the jib, the tower crane inclines forward, and finally install the counterweight, so that the tower crane has a backward inclination torque in the no-load state. Some people keep loading the counterweight as soon as they install it. If they don't grasp the appropriate backward tilting torque, they will cause the backward tipping tower. On the contrary, when dismantling the tower, it is necessary to dismantle the counterweight first, leaving at most 1-2 pieces, and then dismantle the boom, and finally dismantle the remaining counterweight and counterweight. However, some people do not remove the counterweight first before disassembling the jib. The backward tilting torque is too large, and as a result, the tower will fall down as soon as the jib is dismantled. These lessons are very important. In 1998, there was an accident that injured four people. It was because after the installation of the tower crane's balance arm, the installer hung all the balance weights at one time to save time, and installed the jib when the balance weight was full, causing the tower crane to fall backward. Therefore, the personnel participating in the installation and disassembly of tower cranes must undergo professional training, take up the post with valid operation certificate, and carry out the installation and disassembly in strict accordance with the relevant provisions and procedures in the installation and disassembly scheme and operation procedures of tower cranes

do you know the characteristics of ring stiffness testing machines? 6. In the process of tower crane jacking and section adding, the hydraulic jacking system suddenly malfunctioned, causing that the upper part cannot go up and the lower part cannot go down. The operators were inexperienced and could not be eliminated in time. They stayed too long and encountered strong wind load, causing tower collapse. Therefore, before work, check whether the hydraulic oil level meets the specified requirements and whether the oil is deteriorated, and add or replace it according to the specified requirements; At the same time, pay attention to whether the commissioning hydraulic system works normally; The jacking pressure shall not exceed the rated pressure, the overflow valve shall not be increased, and the balance valve shall have no oil leakage

7. The tower crane operated against rules during the jacking process, and the "empty stomach lifting" caused the overturning accident. For example, when a QTZ25 tower crane is removing the tower, first remove all the connecting bolts of the top standard section to be removed, and then move the luffing trolley to approach the jacking platform, causing the tower to collapse backward, causing 4 casualties. Another example is that two tower cranes overturned during jacking. After investigation, it was found that the accident was caused by illegal slewing boom during jacking. Therefore, in the work of installing (disassembling) the standard section of the tower crane, before the upper part of the tower crane is jacked up and connected firmly, the trolley must not be moved, let alone the slewing boom. The tower crane installation and disassembly personnel are required to keep in mind that there should be no carelessness in the work

8. When lifting, the pole beam (also known as the lifting beam) is not well built, and one end is only built a little, or only on the groove edge of the climbing claw. When the lifting reaches a certain height, one side falls off, causing the whole upper part to tilt, which is difficult to recover, and some will lead to tower collapse. High attention should be paid. Before starting the jacking oil cylinder every time, the personnel installing and disassembling the tower crane should check the overlap of the shoulder pole beam. If the lap joint is not good, it cannot be jacked

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