Tower crane is one of the main construction machinery in the construction process of ancient Chinese industry and civil buildings. Because of its large radius of gyration, high lifting height, and easy operation, it is widely used in construction projects and brings great benefits to builders in terms of construction technology, quality, and progress. But at the same time, due to lax management, failure to keep up with normal maintenance, and different levels of operators, it will also bring serious safety hazards to the construction of the project. Aiming at the common safety problems in the use of tower cranes in construction projects, the solutions are proposed, hoping to play a positive role in the safety management of projects.
Common problem: severe water accumulation at the base.
Because the waste water on the construction site is highly corrosive, the material and welds of the foundation, anchor bolts, foundation joints or cross beams of the tower crane will be strongly corroded after the water accumulates. Temporary water accumulation will inevitably affect the safety of the tower crane. At the same time, the accumulated water is not conducive to the daily monitoring of the pretightening force of the tower crane anchor bolts, foundation joints and cross beam connecting bolts.
The correct way: Drainage ditches and water wells should be installed at the base of the tower crane, and at the same time ensure that the drainage is dredged or extracted in time.
2. The pretightening force of connecting bolts in standard joints
Common fault: the connecting bolts of the standard joints are loose or the pre-tightening force cannot meet the requirements.
The power transmission of the tower crane is mainly transmitted by the main chord. The transmission of the main chord force is accomplished by the pre-tightening force of the high-strength connecting bolts. The pretightening force does not meet the requirements, and the force can only be borne by the connecting bolts. The result is that the tower crane not only bears the tensile force but also bears the shear force during use. However, the high-strength connecting bolts have poor shear resistance, which may break the connecting bolts and cause tower collapse accidents.
The correct way: Use a special torque wrench to tighten the bolts so that the pre-tightening force meets the requirements (for example, the pre-tightening force of M30 bolts is 368kN, and the pre-tightening torque is 1800N?m). Do a good job of daily inspection, and tighten it in time if it is found to be loose. Here we need to remind you: after the high-strength connecting bolt pair is used, install it again and use it again, generally not more than twice. In addition, the bolts should be maintained and inspected, and flaw detection should be carried out when necessary, and they can be used only after they pass the test.
3. Opening pin setting of the pin shaft
Common faults: The non-standard setting of the opening pin mainly includes: 1) The opening pin is too small, 2) The opening pin is not opened or the opening degree is not enough, 3) The opening pin is replaced by iron wire or welding rod, 4) The opening pin is seriously corroded.
Since the strength of the opening pin or the strength of the substitute does not meet the requirements, the opening pin will often be sheared under the action of the axial force of the pin shaft. Opening pins without openings or insufficient openings are easy to fall off during use, and pin shafts without opening pins will disengage by themselves during use, which will cause serious accidents of arm folding. For example, a QTZ80 tower crane used in a Jiayuan construction site had a broken arm accident.
The correct way: the setting of the opening pin should be installed in strict accordance with the requirements of the manual, and it cannot be replaced by a smaller opening pin, iron wire or welding rod. Before installation, check the corrosion level and opening degree of the undismantled opening pin. To avoid the difficulty and safety risk of adding and changing after installation. After installation, the opening pin requires that the opening degree should be opened on both sides and reach 90°.
4. Safety limit installation
Common problems: 1) Safety limit installation does not work, 2) Safety limit installation is insensitive, 3) Artificial short circuit or removal.
Although there were no problems in advance, the safety limit installation did not work, burying serious safety hazards. Temporary overloading operations cause fatigue of the metal structure and affect the life of the tower crane.
The correct way: For tower cranes that have passed the inspection, the safety limit installation has basically passed the debugging, and operators and other personnel cannot stop dismantling and adjusting at will. At the same time, the daily inspection should also carefully check the safety limits.
5. The quality of the staff
Common faults: 1) The quality of the operators is not high (certified and competent), 2) Operating without a license.
Because the quality of the operator is not high, the sense of responsibility is not strong. Make tower crane operation accidents occur frequently.
The correct approach: special operations personnel must pass a special assessment, and can take up work only after passing the assessment. At the same time, it is necessary to strengthen the supervision of operators. Strictly follow the operating procedures to work, and put an end to working without a license.
The company has strong technical force, excellent equipment, advanced manufacturing technology, scientific and rigorous inspection and testing methods, the production of "Ming Tower" brand tower crane, construction hoist product series, more reasonable structure, more reliable performance, a variety of advanced technical parameters, won the love of the majority of construction colleagues, Ming Tower brand is known throughout the state, Ming Tower service is well-known in China.